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{{Short description|Impacts of climate change on the Arctic}}
{{Use dmy dates|date=September 2012}}
{{Use dmy dates|date=October 2016}}
{{multiple image
| perrow = 2
| total_width = 350
| image1 = NASA NH decadal ice extent 2022.png
| alt1 = Average decadal extent and area of the Arctic Ocean sea ice since 1979.
| image2 = Greenland Meltdown 08072012 12072012.jpg
| alt2 = July 2012 melting event in Greenland
| image3 = Arctic amo 2020172.png
| alt3 = 2020 Siberia heatwave
| image4 = Permafrost coastal erosion USGS.png
| alt4 = Coastal erosion caused by permafrost thaw in Alaska
| height4 = 100
| footer = Arctic sea ice extent and area have declined every decade since the start of satellite observations in 1979: Greenland ice sheet had experienced a "massive melting event" in 2012, which reoccurred in 2019 and 2021; Satellite image of the extremely anomalous 2020 Siberian heatwave; Permafrost thaw is leading to severe [[erosion]], like in this coastal location in [[Alaska]]
}}


Due to '''climate change in the Arctic''', this polar region is expected to become "profoundly different" by 2050.<ref name="IPCC_AR6_WGII_Polar">{{cite journal |last1=Constable |first1=A.J. |last2=Harper |first2=S. |last3=Dawson |first3=J. |last4=Holsman |first4=K. |last5=Mustonen |first5=T. |last6=Piepenburg |first6=D. |last7=Rost |first7=B. |title=Cross-Chapter Paper 6: Polar Regions |journal=Climate Change 2022: Impacts, Adaptation and Vulnerability |year=2022 |volume=2021 |pages=2319–2367 |doi=10.1017/9781009325844.023 |bibcode=2021AGUFM.U13B..05K }}</ref>{{rp|2321}} The speed of change is "among the highest in the world",<ref name="IPCC_AR6_WGII_Polar" />{{rp|2321}} with the rate of warming being 3-4 times faster than the global average.<ref name="3X2021">{{cite web |date=2021-05-20 |title=Arctic warming three times faster than the planet, report warns |url=https://phys.org/news/2021-05-arctic-faster-planet.html |website=[[Phys.org]] |language=en |access-date=6 October 2022}}</ref><ref name="4X2021">{{cite web |date=2021-12-14 |title=The Arctic is warming four times faster than the rest of the world |url=https://www.science.org/content/article/arctic-warming-four-times-faster-rest-world |language=en |access-date=6 October 2022}}</ref><ref name="Rantanen2022">{{Cite journal |last1=Rantanen |first1=Mika |last2=Karpechko |first2=Alexey Yu |last3=Lipponen |first3=Antti |last4=Nordling |first4=Kalle |last5=Hyvärinen |first5=Otto |last6=Ruosteenoja |first6=Kimmo |last7=Vihma |first7=Timo |last8=Laaksonen |first8=Ari |date=11 August 2022 |title=The Arctic has warmed nearly four times faster than the globe since 1979 |journal=Communications Earth & Environment |language=en |volume=3 |issue=1 |pages=1–10 |doi=10.1038/s43247-022-00498-3 |s2cid=251498876 |issn=2662-4435|doi-access=free |bibcode=2022ComEE...3..168R |hdl=11250/3115996 |hdl-access=free }}</ref><ref name="Chylek2022">{{Cite journal |last1=Chylek |first1=Petr |last2=Folland |first2=Chris |last3=Klett |first3=James D. |last4=Wang |first4=Muyin |last5=Hengartner |first5=Nick |last6=Lesins |first6=Glen |last7=Dubey |first7=Manvendra K. |date=25 June 2022 |title=Annual Mean Arctic Amplification 1970–2020: Observed and Simulated by CMIP6 Climate Models |journal=Geophysical Research Letters |language=en |volume=49 |issue=13 |doi=10.1029/2022GL099371|s2cid=250097858 |doi-access=free |bibcode=2022GeoRL..4999371C }}</ref> This warming has already resulted in the profound [[Arctic sea ice decline]], the accelerating melting of the [[Greenland ice sheet]] and the thawing of the [[permafrost]] landscape.<ref name="IPCC_AR6_WGII_Polar" />{{rp|2321}}<ref name="Shepherd2020">{{Cite journal |last1=Shepherd |first1=Andrew |last2=Ivins |first2=Erik |last3=Rignot |first3=Eric |last4=Smith |first4=Ben |last5=van den Broeke |first5=Michiel |last6=Velicogna |first6=Isabella |author-link6=Isabella Velicogna |last7=Whitehouse |first7=Pippa |last8=Briggs |first8=Kate |last9=Joughin |first9=Ian |last10=Krinner |first10=Gerhard |last11=Nowicki |first11=Sophie |date=12 March 2020 |title=Mass balance of the Greenland Ice Sheet from 1992 to 2018 |journal=Nature |language=en |volume=579 |issue=7798 |pages=233–239 |doi=10.1038/s41586-019-1855-2 |pmid=31822019 |hdl=2268/242139 |s2cid=219146922 |issn=1476-4687 |url=https://orbi.uliege.be/handle/2268/242139 |access-date=23 October 2022 |archive-date=23 October 2022 |archive-url=https://web.archive.org/web/20221023151210/https://orbi.uliege.be/handle/2268/242139 |url-status=live }}</ref> These ongoing transformations are expected to be irreversible for centuries or even millennia.<ref name="IPCC_AR6_WGII_Polar" />{{rp|2321}}
[[File:ArcticYearlongTempAnom HR.jpg|thumb|The image above shows where average air temperatures (October 2010–September 2011) were up to 2 degrees Celsius above (red) or below (blue) the long-term average (1981–2010).]]
[[File:Arctic Sea Ice Minimum Comparison.png|thumb|The maps above compare the Arctic ice minimum extents from 2012 (top) and 1984 (bottom). In 1984 the sea ice extent was roughly the average of the minimum from 1979 to 2000, and so was a typical year. The minimum sea ice extent in 2012 was roughly half of that average.]]


Natural life in the Arctic is affected greatly. As the [[tundra]] warms, its soil becomes more hospitable to [[earthworm]]s and larger plants,<ref name="Lindsey2012">{{cite web |last=Lindsey |first=Rebecca |date=18 January 2012 |title=Shrub Takeover One Sign of Arctic Change |url=http://www.climatewatch.noaa.gov/article/2012/shrub-takeover-one-sign-of-arctic-change |url-status=dead |archive-url=https://web.archive.org/web/20130217095318/http://www.climatewatch.noaa.gov/article/2012/shrub-takeover-one-sign-of-arctic-change |archive-date=2013-02-17 |access-date=19 January 2012 |work=ClimateWatch Magazine |publisher=[[NOAA]]}}</ref> and the [[taiga|boreal forests]] spread to the north - yet this also makes the landscape more prone to [[wildfire]]s, which take longer to recover from than in the other regions. [[Beaver]]s also take advantage of this warming to colonize the Arctic rivers, and their [[beaver dam|dams]] contributing to [[atmospheric methane|methane]] emissions due to the increase in stagnant waters.<ref name="Clark2023" /> The [[Arctic Ocean]] has experienced a large increase in the [[marine primary production]] as warmer waters and less shade from sea ice benefit [[phytoplankton]].<ref name="IPCC_AR6_WGII_Polar" />{{rp|2326}}<ref name="NASAHansen2020" /> At the same time, it is already less alkaline than the rest of the global ocean, so [[ocean acidification]] caused by the increasing {{CO2}} concentrations is more severe, threatening some forms of [[zooplankton]] such as [[pteropod]]s.<ref name="IPCC_AR6_WGII_Polar" />{{rp|2328}}
The effects of '''global warming in the Arctic''' include rising temperatures, loss of [[sea ice]], and melting of the [[Greenland ice sheet]].<ref name="From 2 Satellites, the Big Picture on Ice Melt"/><ref name="nytimes"/><ref name="guardian"/> Potential [[Arctic MORTIMER METHANE GAS release|methane release]] from the region, especially through the thawing of [[permafrost]] and [[methane clathrates]], is also a concern. Because of the [[Polar amplification|amplified response of the Arctic]] to global warming, it is often seen as a leading indicator of [[global warming]].


The Arctic Ocean is expected to see its first ice-free events in the near future - most likely before 2050, and potentially in the late 2020s or early 2030s.<ref name="Jahn2024">{{cite journal |last1=Jahn |first1=Alexandra |last2=Holland |first2=Marika M. |last3=Kay |first3=Jennifer E. |title=Projections of an ice-free Arctic Ocean |journal=Nature Reviews Earth & Environment |date=5 March 2024 |volume=5 |issue=3 |pages=164–176 |doi=10.1038/s43017-023-00515-9 |bibcode=2024NRvEE...5..164J |url=https://www.nature.com/articles/s43017-023-00515-9 }}</ref> This would have no precedent in the last 700,000 years.<ref name="Overpeck2005">{{cite journal |last1=Overpeck |first1=Jonathan T. |title=Arctic System on Trajectory to New, Seasonally Ice-Free State |journal=[[Eos (journal)|Eos, Transactions, American Geophysical Union]] |volume=86 |issue=34 |pages=309–316 |date=23 August 2005 |doi=10.1029/2005EO340001 |display-authors=3 |last2=Sturm |first2=Matthew |last3=Francis |first3=Jennifer A. |last4=Perovich |first4=Donald K. |last5=Serreze |first5=Mark C. |last6=Benner |first6=Ronald |last7=Carmack |first7=Eddy C. |last8=Chapin |first8=F. Stuart |last9=Gerlach |first9=S. Craig |bibcode=2005EOSTr..86..309O |df=dmy-all |doi-access=free }}</ref><ref name="Ottera">{{cite journal | last = Butt | first = F. A. | author2 = H. Drange | author3 = A. Elverhoi | author4 = O. H. Ottera | author5 = A. Solheim | url = http://www.nersc.no/~oddho/Thesis/chapter3.pdf | title = The Sensitivity of the North Atlantic Arctic Climate System to Isostatic Elevation Changes, Freshwater and Solar Forcings | journal = Quaternary Science Reviews | volume = 21 | pages = 1643–1660 | year = 2002 | oclc = 108566094 | issue = 14–15 | doi = 10.1016/S0277-3791(02)00018-5 | url-status = dead | archive-url = https://web.archive.org/web/20080910213953/http://www.nersc.no/~oddho/Thesis/chapter3.pdf | archive-date = 10 September 2008 | df = dmy-all }}</ref> Some sea ice regrows every Arctic winter, but such events are expected to occur more and more frequently as the warming increases. This has great implications for the [[fauna]] species which are dependent on sea ice, such as [[polar bear]]s. For humans, trade routes across the ocean will become more convenient. Yet, multiple countries have [[infrastructure]] in the Arctic which is worth billions of dollars, and it is threatened with collapse as the underlying permafrost thaws. The Arctic's indigenous people have a long relationship with its icy conditions, and face the loss of their cultural heritage.
==Rising temperatures==
According to the [[Intergovernmental Panel on Climate Change]], "warming in the Arctic, as indicated by daily maximum and minimum temperatures, has been as great as in any other part of the world."<ref name="tar_wg2"/> The period of 1995-2005 was the warmest decade in the Arctic since at least the 17th century, with temperatures {{convert|2|C-change|1}} above the 1951-1990 average.<ref name="Przybylak 2007">{{cite journal | last1 = Przybylak | first1 = Rajmund | year = 2007 | title = Recent air-temperature changes in the Arctic | url = http://www.igsoc.org/annals/46/a46a005.pdf | format = PDF | journal = Annals of Glaciology | volume = 46 | issue = | pages = 316–324 | doi=10.3189/172756407782871666}}</ref> Some regions within the Arctic have warmed even more rapidly, with [[Alaska]] and western Canada's temperature rising by {{convert|3|to|4|C-change|2}}.<ref name="ACIA 2004">Arctic Climate Impact Assessment (2004): ''Arctic Climate Impact Assessment''. Cambridge University Press, ISBN 0-521-61778-2, siehe [http://www.acia.uaf.edu/pages/scientific.html online]</ref> This warming has been caused not only by the rise in [[greenhouse gas]] concentration, but also the deposition of [[soot]] on Arctic ice.<ref name="Quinn et al. 2007">Quinn, P.K., T. S. Bates, E. Baum et al. (2007): ''Short-lived pollutants in the Arctic: their climate impact and possible mitigation strategies'', in: Atmospheric Chemistry and Physics, Vol. 7, S. 15669–15692, siehe [http://www.atmos-chem-phys-discuss.net/7/15669/2007/acpd-7-15669-2007.html online]</ref> A 2013 article published in [[Geophysical Research Letters]] has shown that temperatures in the region haven't been as high as they currently are since at least 44,000 years ago and perhaps as long as 120,000 years ago. The authors conclude that "anthropogenic increases in greenhouse gases have led to unprecedented regional warmth."<ref>[http://www.livescience.com/40676-arctic-temperatures-record-high.html Arctic Temperatures Highest in at Least 44,000 Years], Livescience, Oct 24, 2013</ref><ref>{{Cite journal | last1 = Miller | first1 = G. H. | last2 = Lehman | first2 = S. J. | last3 = Refsnider | first3 = K. A. | last4 = Southon | first4 = J. R. | last5 = Zhong | first5 = Y. | title = Unprecedented recent summer warmth in Arctic Canada | doi = 10.1002/2013GL057188 | journal = Geophysical Research Letters | volume = 40 | issue = 21 | pages = 5745 | year = 2013 | pmid = | pmc = }}</ref>


Further, there are numerous implications which go beyond the Arctic region. Sea ice loss not only enhances warming in the Arctic but also adds to global temperature increase through the [[ice-albedo feedback]]. Permafrost thaw results in emissions of {{CO2}} and methane that are comparable to those of major countries. Greenland melting is a significant contributor to global [[sea level rise]]. If the warming exceeds - or thereabouts, there is a significant risk of the entire ice sheet being lost over an estimated 10,000 years, adding up to global sea levels. Warming in the Arctic may affect the stability of the [[jet stream]], and thus the extreme weather events in [[midlatitude]] regions, but there is only "low confidence" in that hypothesis.
===Arctic amplification===
{{main|Arctic amplification}}
The poles of the planet are more sensitive to any change in the planet's climate than the rest of the planet. In the face of ongoing global warming, the poles are warming faster than lower latitudes. The primary cause of this phenomenon is [[ice-albedo feedback]], whereby melting ice uncovers darker land or ocean beneath, which then absorbs more sunlight, causing more heating.<ref name="RCAmp">[http://www.realclimate.org/index.php/archives/2006/01/polar-amplification/ Cecilia Bitz (2006): ''Polar Amplification'', in: RealClimate.org]</ref><ref name="nature09051"/><ref name="Black"/> The loss of the Arctic sea ice may represent a [[tipping point (climatology)|tipping point]] in global warming, when [[runaway climate change|'runaway' climate change]] starts,<ref name="2005gl025080"/><ref name="2004gc000854"/> but on this point the science is not yet settled.<ref name="Arctic summer sea ice loss may not 'tip' over the edge"/><ref name="Eisenman2009"/>


{{TOC limit|3}}
==Decline of sea ice==
{{See also|Arctic sea ice decline}}


== Impacts on the physical environment ==
Sea ice is currently in decline in area, extent, and volume and may cease to exist sometime during the 21st century. Sea ice area refers to the total area covered by ice, whereas sea ice extent is the area of ocean with at least 15% sea ice, while the volume is the total amount of ice in the Arctic.<ref>{{cite web|title=Daily Updated Time series of Arctic sea ice area and extent derived from SSMI data provided by NERSC|url=http://arctic-roos.org/observations/satellite-data/sea-ice/|accessdate=14 September 2013}}</ref>
=== Warming ===
[[File: ArcticYearlongTempAnom HR.jpg|thumb|The image above shows where average air temperatures (October 2010 – September 2011) were up to 2 degrees Celsius above (red) or below (blue) the long-term average (1981–2010).]]


The period of 1995–2005 was the warmest decade in the Arctic since at least the 17th century, with temperatures {{convert|2|C-change|1}} above the 1951–1990 average.<ref name="Przybylak2007">{{cite journal |last1=Przybylak |first1=Rajmund | year = 2007 | title = Recent air-temperature changes in the Arctic | journal = Annals of Glaciology | volume = 46 | issue = 1 | pages = 316–324 | doi = 10.3189/172756407782871666 | bibcode = 2007AnGla..46..316P | s2cid = 129155170 | doi-access = free }}</ref> Alaska and western Canada's temperature rose by {{convert|3|to|4|C-change|2}} during that period.<ref name="ACIA 2004">Arctic Climate Impact Assessment (2004): ''Arctic Climate Impact Assessment''. Cambridge University Press, {{ISBN|0-521-61778-2}}, siehe [http://www.acia.uaf.edu/pages/scientific.html online] {{Webarchive|url=https://web.archive.org/web/20130628144322/http://www.acia.uaf.edu/pages/scientific.html |date=28 June 2013 }}</ref> 2013 research has shown that temperatures in the region haven't been as high as they currently are since at least 44,000 years ago and perhaps as long as 120,000 years ago.<ref>[http://www.livescience.com/40676-arctic-temperatures-record-high.html Arctic Temperatures Highest in at Least 44,000 Years], Livescience, 24 October 2013</ref><ref>{{Cite journal | last1 = Miller | first1 = G. H. | last2 = Lehman | first2 = S. J. | last3 = Refsnider | first3 = K. A. | last4 = Southon | first4 = J. R. | last5 = Zhong | first5 = Y. | title = Unprecedented recent summer warmth in Arctic Canada | doi = 10.1002/2013GL057188 | journal = Geophysical Research Letters | volume = 40 | issue = 21 | pages = 5745–5751 | year = 2013 | bibcode = 2013GeoRL..40.5745M | s2cid = 128849141 }}</ref> Since 2013, Arctic annual mean surface air temperature (SAT) has been at least {{convert|1|C-change|1}} warmer than the 1981-2010 mean.
===Changes in extent and area===
[[File:Seaice-1870-part-2009.png|thumb|1870–2009 Northern Hemisphere [[Measurement of sea ice#Sea ice extent|sea ice extent]] in million square kilometers. Blue shading indicates the pre-satellite era; data then is less reliable. In particular, the near-constant level extent in autumn up to 1940 reflects lack of data rather than a real lack of variation.]]


In 2016, there were extreme anomalies from January to February with the temperature in the Arctic being estimated to be between {{convert|4-5.8|C-change|1}} more than it was between 1981 and 2010.<ref>{{cite journal |last1=Yu |first1=Yining |last2=Xiao |first2=Wanxin |last3=Zhang |first3=Zhilun |last4=Cheng |first4=Xiao |last5=Hui |first5=Fengming |last6=Zhao |first6=Jiechen |title=Evaluation of 2-m Air Temperature and Surface Temperature from ERA5 and ERA-I Using Buoy Observations in the Arctic during 2010–2020|journal=Remote Sensing |date=17 July 2021 |volume=13 |issue=Polar Sea Ice: Detection, Monitoring and Modeling|page=2813 |doi=10.3390/rs13142813 |bibcode=2021RemS...13.2813Y |doi-access=free }}</ref> In 2020, mean SAT was {{convert|1.9|C-change|1}} warmer than the 1981–2010 average.<ref>{{Cite web|title=Surface Air Temperature|url=https://arctic.noaa.gov/Report-Card/Report-Card-2020/ArtMID/7975/ArticleID/878/Surface-Air-Temperature|access-date=2021-05-18|website=Arctic Program|date=October 2020 |language=en-US}}</ref> On 20 June 2020, for the first time, a temperature measurement was made inside the Arctic Circle of 38&nbsp;°C, more than 100&nbsp;°F. This kind of weather was expected in the region only by 2100. In March, April and May the average temperature in the Arctic was {{convert|10|C-change|1}} higher than normal.<ref>{{cite news |last1=Rosane |first1=Olivia |title=A Siberian Town Just Hit 100 F Degrees |url=https://www.ecowatch.com/siberia-100-degrees-2646222137.html |access-date=23 June 2020 |agency=Ecowatch |date=22 June 2020}}</ref><ref>{{cite news |last1=King |first1=Simon |last2=Rowlatt |first2=Justin |title=Arctic Circle sees 'highest-ever' recorded temperatures |url=https://www.bbc.com/news/science-environment-53140069 |access-date=23 June 2020 |agency=BBC |date=22 June 2020}}</ref> This heat wave, without human – induced warming, could happen only one time in 80,000 years, according to an attribution study published in July 2020. It is the strongest link of a weather event to anthropogenic climate change that had been ever found, for now.<ref name="RowlattBBC2020">{{cite news |last1=Rowlatt |first1=Justin |title=Climate change: Siberian heatwave 'clear evidence' of warming |url=https://www.bbc.com/news/science-environment-53415297 |access-date=17 July 2020 |agency=BBC |date=15 July 2020}}</ref>
Reliable [[measurement of sea ice]] edges began with the satellite era in the late 1970s. Before this time, sea ice area and extent were monitored less precisely by a combination of ships, buoys and aircraft.<ref name="Whither Arctic sea ice? A clear signal of decline regionally, seasonally and extending beyond the satellite record"/> The data show a long-term negative trend in recent years, attributed to global warming, although there is also a considerable amount of variation from year to year.<ref name="NASASeesArcticOcean"/> Some of this variation may be related to effects such as the [[arctic oscillation]], which may itself be related to global warming<ref name="The Arctic and Antarctic Oscillations and their Projected Changes Under Global Warming"/> and some of the variation is essentially random "weather noise".


====Arctic amplification====
The Arctic sea ice September minimum extent (i.e., area with at least 15% sea ice coverage) reached new record lows in 2002, 2005, 2007, and 2012.<ref>{{cite web|url= http://www.metoffice.gov.uk/news/releases/archive/2012/sea-ice-minimum|title= Record Arctic sea ice minimum confirmed by NSIDC}}</ref> The 2007 melt season let to a minimum 39% below the 1979-2000 average, and for the first time in human memory, the fabled [[Northwest Passage]] opened completely.<ref name="nsidc"/> The dramatic 2007 melting surprised and concerned scientists.<ref name="Remarkable"/><ref name="NASA - Monitoring Sea Ice"/>
[[File:Wunderling_2020_regional_impact.jpg|thumb|Potential regional warming caused by the loss of all land ice outside of East Antarctica, and by the disappearance of Arctic sea ice every year starting from June. While plausible, consistent sea ice loss would likely require relatively high warming, and the loss of all ice in Greenland would require multiple millennia.]]
{{excerpt|Ice–albedo feedback#Current role|file=no}}
{{excerpt|Polar amplification#Recent Arctic amplification|paragraphs=2-3}}


=== Precipitation ===
[[File:Oldest Arctic Sea Ice is Disappearing.png|left|thumb|Sea ice coverage in 1980 (bottom) and 2012 (top), as observed by passive microwave sensors on NASA’s Nimbus-7 satellite and by the Special Sensor Microwave Imager/Sounder (SSMIS) from the Defense Meteorological Satellite Program (DMSP). Multi-year ice is shown in bright white, while average sea ice cover is shown in light blue to milky white. The data shows the ice cover for the period of 1 November through 31 January in their respective years.]]
An observed impact of climate change is a strong increase in the number of lightnings in the Arctic. Lightnings increase the risk for wildfires.<ref>{{cite news |last1=Chao-Fong |first1=Léonie |title='Drastic' rise in high Arctic lightning has scientists worried |url=https://www.theguardian.com/environment/2022/jan/07/lightning-high-arctic-rise-scientists-worried |access-date=30 January 2022 |agency=The Guardian |date=7 January 2021}}</ref> Some research suggests that globally, a warming greater than {{convert|1.5|C-change|1}} over the preindustrial level could change the type of precipitation in the Arctic from snow to rain in summer and autumn.<ref name="Druckenmiller_20211214"/>


=== Cryosphere loss ===
From 2008 to 2011, Arctic sea ice minimum extent was higher than 2007, but it did not return to the levels of previous years.<ref name="nsidc1"/><ref name="Arcticseaiceextent"/> In 2012 however, the 2007 record low was broken in late August with 3 weeks still left in the melt season.<ref name="nsidc2"/> It continued to fall, bottoming out on 16 September 2012 at 3.41 million square kilometers (1.32 million square miles), or 760,000 square kilometers (293,000 square miles) below the previous low set on 18 September 2007 and 50% below the 1979-2000 average.<ref name="nsidc3"/><ref name=" Record Arctic sea ice minimum confirmed by NSIDC ">Record Arctic sea ice minimum confirmed by NSIDC</ref>
[[File:Slater 2021 global ice loss.png|thumb|On average, climate change has lowered the thickness of land ice with every year, and reduced the extent of sea ice cover.<ref name="Slater2021">{{cite journal |last1=Slater |first1=Thomas |last2=Lawrence |first2=Isobel R. |last3=Otosaka |first3=Inès N. |last4=Shepherd |first4=Andrew |last5=Gourmelen |first5=Noel |last6=Jakob |first6=Livia |last7=Tepes |first7=Paul |last8=Gilbert |first8=Lin |last9=Nienow |first9=Peter |title=Review article: Earth's ice imbalance |journal=The Cryosphere |date=25 Jan 2021 |doi=10.5194/tc-15-233-2021 |doi-access=free |volume=15 |issue=1 |pages=233–246 [[File:CC-BY icon.svg|50px]] Material was copied from this source, which is available under a [https://creativecommons.org/licenses/by/4.0/ Creative Commons Attribution 4.0 International License]|bibcode=2021TCry...15..233S |hdl=20.500.11820/df343a4d-6b66-4eae-ac3f-f5a35bdeef04 |hdl-access=free }}</ref>]]
==== Sea ice ====
[[File:Seaice-1870-part-2009.png|thumb|1870–2009 Northern Hemisphere [[Measurement of sea ice#Sea ice extent|sea ice extent]] in million square kilometers. Blue shading indicates the pre-satellite era; data then is less reliable.]]{{excerpt|Arctic sea ice decline|paragraphs=1-2|file=no}}
<!-- Reliable [[measurement of sea ice]] edges began with the satellite era in the late 1970s. Before this time, sea ice area and extent were monitored less precisely by a combination of ships, [[Ice mass balance buoy|buoys]] and aircraft.<ref name="2005gl025080">{{Cite journal|last1=Lawrence|first1=D. M.|last2=Slater|first2=A.|year=2005|title=A projection of severe near-surface permafrost degradation during the 21st century|journal=[[Geophysical Research Letters]]|volume=32|issue=24|pages=L24401|bibcode=2005GeoRL..3224401L|doi=10.1029/2005GL025080|s2cid=128425266}}</ref> The data show a long-term negative trend in recent years, attributed to global warming, although there is also a considerable amount of variation from year to year.<ref name="2007gl029703">{{Cite journal|last1=Stroeve|first1=J.|last2=Holland|first2=M. M.|author-link2=Marika Holland|last3=Meier|first3=W.|last4=Scambos|first4=T.|last5=Serreze|first5=M.|year=2007|title=Arctic sea ice decline: Faster than forecast|journal=Geophysical Research Letters|volume=34|issue=9|pages=L09501|bibcode=2007GeoRL..34.9501S|doi=10.1029/2007GL029703|doi-access=free}}</ref> Some of this variation may be related to effects such as the [[Arctic oscillation]], which may itself be related to global warming.<ref name="Accelerated decline in Arctic sea ice cover">{{cite journal|author1=Comiso, Josefino C.|author2=Parkinson, Claire L.|author3=Gersten, Robert|author4=Stock, Larry|year=2008|title=Accelerated decline in Arctic sea ice cover|journal=Geophysical Research Letters|volume=35|issue=1|pages=L01703|bibcode=2008GeoRL..35.1703C|doi=10.1029/2007GL031972|s2cid=129445545}}</ref>


[[File:Oldest Arctic Sea Ice is Disappearing.png|thumb|Sea ice coverage in 1980 (bottom) and 2012 (top), as observed by passive microwave sensors from NASA. Multi-year ice is shown in bright white, while average sea ice cover is shown in light blue to milky white.]]
The rate of the decline in entire arctic ice coverage is accelerating. From 1979–1996, the average per decade decline in entire ice coverage was a 2.2% decline in ice extent and a 3% decline in ice area. For the decade ending 2008, these values have risen to 10.1% and 10.7%, respectively. These are comparable to the September to September loss rates in year-round ice (i.e., perennial ice, which survives throughout the year), which averaged a retreat of 10.2% and 11.4% per decade, respectively, for the period 1979–2007.<ref name="Accelerated decline in Arctic sea ice cover"/>


The rate of the decline in entire Arctic ice coverage is accelerating. From 1979 to 1996, the average per decade decline in entire ice coverage was a 2.2% decline in ice extent and a 3% decline in ice area. For the decade ending 2008, these values have risen to 10.1% and 10.7%, respectively. These are comparable to the September to September loss rates in year-round ice (i.e., perennial ice, which survives throughout the year), which averaged a retreat of 10.2% and 11.4% per decade, respectively, for the period 1979–2007.<ref>{{Cite journal|last1=Comiso|first1=Josefino C.|last2=Parkinson|first2=Claire L.|last3=Gersten|first3=Robert|last4=Stock|first4=Larry|date=2008-01-03|title=Accelerated decline in the Arctic sea ice cover|url=http://dx.doi.org/10.1029/2007gl031972|journal=Geophysical Research Letters|volume=35|issue=1|pages=L01703|doi=10.1029/2007gl031972|bibcode=2008GeoRL..35.1703C|s2cid=129445545|issn=0094-8276}}</ref>
===Changes in volume===
[[File:Plot arctic sea ice volume.svg|thumb|Seasonal variation and long term decrease of Arctic sea ice volume as determined by measurement backed numerical modelling.<ref name="zhangrothrock1"/>]]
The sea ice thickness field, and accordingly the ice volume and mass, is much more difficult to determine than the extension. Exact measurements can be made only at a limited number of points. Because of large variations in ice and snow thickness and consistency air- and spaceborne-measurements have to be evaluated carefully. Nevertheless, the studies made support the assumption of a dramatic decline in ice age and thickness.<ref name="Arcticseaiceextent" /> While the arctic ice area and extent show an accelerating downward trend, arctic ice volume shows an even sharper decline than the ice coverage. Since 1979, the ice volume has shrunk by 80% and in just the past decade the volume declined by 36% in the autumn and 9% in the winter.<ref>{{cite news|last=Masters|first=Jeff|title=Arctic sea ice volume now one-fifth its 1979 level|url=http://www.wunderground.com/blog/JeffMasters/article.html?entrynum=2352|work=weather underground|date=19 February 2013|accessdate=14 September 2013}}</ref>


The Arctic sea ice September minimum extent (SIE) (i.e., area with at least 15% sea ice coverage) reached new record lows in 2002, 2005, 2007, 2012 (5.32 million km2), 2016 and 2019 (5.65 million km2).<ref>{{cite web|url= http://www.metoffice.gov.uk/news/releases/archive/2012/sea-ice-minimum|title= Record Arctic sea ice minimum confirmed by NSIDC|url-status= dead|archive-url= https://web.archive.org/web/20130729155912/http://www.metoffice.gov.uk/news/releases/archive/2012/sea-ice-minimum|archive-date= 29 July 2013|df= dmy-all}}</ref><ref>{{Cite journal|last1=Petty|first1=Alek A.|last2=Stroeve|first2=Julienne C.|last3=Holland|first3=Paul R.|last4=Boisvert|first4=Linette N.|last5=Bliss|first5=Angela C.|last6=Kimura|first6=Noriaki|last7=Meier|first7=Walter N.|date=2018-02-06|title=The Arctic sea ice cover of 2016: a year of record-low highs and higher-than-expected lows|journal=The Cryosphere|volume=12|issue=2|pages=433–452|doi=10.5194/tc-12-433-2018|bibcode=2018TCry...12..433P|issn=1994-0424 |doi-access=free }}</ref><ref name=":3">{{Cite journal|last1=Yadav|first1=Juhi|last2=Kumar|first2=Avinash|last3=Mohan|first3=Rahul|date=2020-05-21|title=Dramatic decline of Arctic sea ice linked to global warming|url=http://dx.doi.org/10.1007/s11069-020-04064-y|journal=Natural Hazards|volume=103|issue=2|pages=2617–2621|doi=10.1007/s11069-020-04064-y|s2cid=218762126|issn=0921-030X}}</ref> The 2007 melt season let to a minimum 39% below the 1979–2000 average, and for the first time in human memory, the fabled [[Northwest Passage]] opened completely.<ref name="Arctic summer sea ice loss may not 'tip' over the edge">{{cite web|date=30 January 2009|title=Arctic summer sea ice loss may not 'tip' over the edge|url=http://environmentalresearchweb.org/cws/article/research/37591|url-status=dead|archive-url=https://web.archive.org/web/20090202155122/http://environmentalresearchweb.org/cws/article/research/37591|archive-date=2 February 2009|access-date=26 July 2010|publisher=environmentalresearchweb|df=dmy-all}}</ref> During July 2019 the warmest month in the Arctic was recorded, reaching the lowest SIE (7.5 million km2) and sea ice volume (8900 km3). Setting a decadal trend of SIE decline of −13%.<ref name=":3" /> As for now, the SIE has shrink by 50% since the 1970s.<ref name=":2">{{Cite journal|last1=Senftleben|first1=Daniel|last2=Lauer|first2=Axel|last3=Karpechko|first3=Alexey|date=2020-02-15|title=Constraining Uncertainties in CMIP5 Projections of September Arctic Sea Ice Extent with Observations|url=http://dx.doi.org/10.1175/jcli-d-19-0075.1|journal=Journal of Climate|volume=33|issue=4|pages=1487–1503|doi=10.1175/jcli-d-19-0075.1|bibcode=2020JCli...33.1487S|s2cid=210273007|issn=0894-8755}}</ref>
===An end to summer sea ice?===


From 2008 to 2011, Arctic sea ice minimum extent was higher than 2007, but it did not return to the levels of previous years.<ref name="Arcticseaiceextent">{{cite web|date=6 October 2009|title=Arctic sea ice extent remains low; 2009 sees third-lowest mark|url=http://nsidc.org/news/press/20091005_minimumpr.html|access-date=26 July 2010|publisher=NSIDC|archive-date=26 December 2012|archive-url=https://web.archive.org/web/20121226072828/http://nsidc.org/news/press/20091005_minimumpr.html|url-status=dead}}</ref><ref name="Black">{{cite news|last=Black|first=Richard|date=18 May 2007|title=Earth – melting in the heat?|work=BBC News|url=http://news.bbc.co.uk/2/hi/science/nature/4315968.stm|access-date=3 January 2008}}</ref> In 2012 however, the 2007 record low was broken in late August with three weeks still left in the melt season.<ref name="Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Chapter 10">{{cite book|last=Meehl|first=G.A.|url=http://archive.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-chapter10.pdf|title=Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Chapter 10|publisher=[[Cambridge University Press]]|year=2007|location=New York|display-authors=etal}}</ref> It continued to fall, bottoming out on 16 September 2012 at 3.42 million square kilometers (1.32 million square miles), or 760,000 square kilometers (293,000 square miles) below the previous low set on 18 September 2007 and 50% below the 1979–2000 average.<ref name="Climatology: threatened loss of the Greenland ice-sheet">{{cite journal|author1=Gregory JM|author-link=Jonathan M. Gregory|author2=Huybrechts P|author3=Raper SC|date=April 2004|title=Climatology: threatened loss of the Greenland ice-sheet|url=http://homepages.vub.ac.be/~phuybrec/pdf/Nature.Green.2004.pdf|journal=[[Nature (journal)|Nature]]|volume=428|issue=6983|page=616|bibcode=2004Natur.428..616G|doi=10.1038/428616a|pmid=15071587|quote=The Greenland ice-sheet would melt faster in a warmer climate and is likely to be eliminated — except for residual glaciers in the mountains — if the annual average temperature in [[Greenland]] increases by more than about 3 [[°C]]. This would raise the global average sea-level by 7 metres over a period of 1000 years or more. We show here that concentrations of greenhouse gasses will probably have reached levels before the year 2100 that are sufficient to raise the temperature past this warming threshold.|s2cid=4421590|access-date=5 April 2008|archive-date=9 August 2017|archive-url=https://web.archive.org/web/20170809085231/http://homepages.vub.ac.be/~phuybrec/pdf/Nature.Green.2004.pdf|url-status=dead}}</ref><ref name="Record Arctic sea ice minimum confirmed by NSIDC">Record Arctic sea ice minimum confirmed by NSIDC</ref>
The IPCC's Fourth Assessment Report in 2007 summarized the current state of sea ice projections: "the projected reduction <nowiki>[in global sea ice cover]</nowiki> is accelerated in the Arctic, where some models project summer sea ice cover to disappear entirely in the high-emission A2 scenario in the latter part of the 21st century.″ <ref name="Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Chapter 10"/> However, current [[climate model]]s frequently underestimate the rate of sea ice retreat.<ref name="2007gl029703"/> A summertime ice-free arctic would be unprecedented in recent geologic history, as currently [[scientific evidence]] does not indicate an ice-free polar sea anytime in the last 700,000 years.<ref name="overpeck"/><ref name="Ottera"/>


[[File:Plot arctic sea ice volume.svg|thumb|Seasonal variation and long-term decrease of Arctic sea ice volume as determined by measurement backed numerical modelling.<ref name="zhangrothrock1">{{cite journal|author1=Zhang, Jinlun |author2=D.A. Rothrock|title=Modeling global sea ice with a thickness and enthalpy distribution model in generalized curvilinear coordinates|journal=Mon. Wea. Rev.|volume=131|issue=5|pages=681–697|year=2003|doi=10.1175/1520-0493(2003)131<0845:MGSIWA>2.0.CO;2|citeseerx=10.1.1.167.1046|bibcode=2003MWRv..131..845Z}}</ref>]]
The [[Arctic ocean]] will likely be free of summer [[sea ice]] before the year 2100, but many different dates have been projected. One study suggests 2060–2080,<ref name="ngeo467"/> another 2030,<ref name="Arctic Largely Ice Free in Summer Within Ten Years?"/><ref>{{cite journal|author= Richard A. Kerr |title= Ice-Free Arctic Sea May be Years, Not Decades, Away |journal=Science|pages= 1591 |volume= 337 |date= 28 September 2012|bibcode = 2012Sci...337.1591K |doi=10.1126/science.337.6102.1591}}</ref> and, yet another, 2016.<ref name="planetsave"/><ref name="New warning on Arctic sea ice melt"/> A 2013 study showed that simply extending summertime ice melting trends into the future in a straight line predicts an ice-free summertime Arctic as early as by 2020.<ref>{{cite journal|doi=10.1002/grl.50316 | volume=40 | title=When will the summer Arctic be nearly sea ice free? | journal=Geophysical Research Letters | pages=2097–2101}}</ref><ref>[http://www.usatoday.com/story/tech/sciencefair/2013/04/12/arctic-summer-ice/2077579/ ''Arctic summers may be ice free sooner than predicted''] April 12, 2013 [[USA Today]]</ref>
The sea ice thickness field and accordingly the ice volume and mass, is much more difficult to determine than the extension. Exact measurements can be made only at a limited number of points. Because of large variations in ice and snow thickness and consistency air- and spaceborne-measurements have to be evaluated carefully. Nevertheless, the studies made support the assumption of a dramatic decline in ice age and thickness.<ref name="Arcticseaiceextent" /> While the Arctic ice area and extent show an accelerating downward trend, arctic ice volume shows an even sharper decline than the ice coverage. Since 1979, the ice volume has shrunk by 80% and in just the past decade the volume declined by 36% in the autumn and 9% in the winter.<ref>{{cite news|last=Masters|first=Jeff|title=Arctic sea ice volume now one-fifth its 1979 level|url=http://www.wunderground.com/blog/JeffMasters/article.html?entrynum=2352|work=weather underground|date=19 February 2013|access-date=14 September 2013|url-status=dead|archive-url=https://web.archive.org/web/20131219012233/http://www.wunderground.com/blog/JeffMasters/article.html?entrynum=2352|archive-date=19 December 2013|df=dmy-all}}</ref> And currently, 70% of the winter sea ice has turned into seasonal ice.<ref name=":2" />


The [[Arctic Ocean]] will likely be free of summer [[sea ice]] before the year 2100, but many different dates have been projected, with models showing near-complete to complete loss in September from 2035 to some time around 2067.<ref>{{Cite web|last=Reich|first=Katharine|date=2019-11-15|title=Arctic Ocean could be ice-free for part of the year as soon as 2044|url=https://phys.org/news/2019-11-arctic-ocean-ice-free-year.html|access-date=2020-09-03|website=phys.org|language=en}}</ref><ref>{{Cite web|last=Kirby|first=Alex|date=2020-08-11|title=End of Arctic sea ice by 2035 possible, study finds|url=https://climatenewsnetwork.net/end-of-arctic-sea-ice-by-2035-possible-study-finds/|access-date=2020-09-03|website=Climate News Network|language=en-GB}}</ref> -->
==Permafrost thaw==
[[File:Beaufort Permafrost1.JPG|thumb|right|Rapidly thawing Arctic permafrost and coastal erosion on the Beaufort Sea, Arctic Ocean, near Point Lonely, AK. Photo Taken in August, 2013]]
{{Main|Arctic methane release}}
This century, thawing of the various forms of Arctic permafrost could release large amounts of carbon into the atmosphere. It has been estimated that about two-thirds of released carbon escapes to the atmosphere as carbon dioxide, originating primarily from ancient ice deposits along the ~7,000 kilometer long coastline of the East Siberian Arctic Shelf (ESAS) and shallow subsea permafrost. Following thaw, collapse and erosion of coastline and seafloor deposits may accelerate with Arctic amplification of climate warming.<ref>{{cite journal|authors=J. E. Vonk, L. Sánchez-García, B. E. van Dongen, V. Alling, D. Kosmach, A. Charkin, I. P. Semiletov, O. V. Dudarev, N. Shakhova, P. Roos, T. I. Eglinton, A. Andersson & Ö. Gustafsson|title=Activation of old carbon by erosion of coastal and subsea permafrost in Arctic Siberia|journal=Nature|date= August 29, 2012|doi=10.1038/nature11392|url=http://www.nature.com/nature/journal/v489/n7414/full/nature11392.html|accessdate= April 12, 2014|volume=489|pages=137–140}}</ref>


==== Greenland ice sheet ====
Climate models suggest that during periods of rapid sea-ice loss, temperatures could increase as far as {{convert|1450|km|abbr=on}} inland, accelerating the rate of terrestrial permafrost thaw, with consequential effects on carbon and methane release.<ref name="yale"/><ref name="ucar.edu"/>
[[File:Beckmann 2023 Greenland 2300 RCP85 extent.png|thumb|2023 projections of how much the Greenland ice sheet may shrink from its present extent by the year 2300 under the worst possible climate change scenario (upper half) and of how much faster its remaining ice will be flowing in that case (lower half)]]
{{excerpt|Greenland ice sheet|paragraphs=2-4|file=no}}


== Biological environment ==
===Subsea permafrost===
===Impacts on Arctic flora===
{{Main|Clathrate gun hypothesis}}
Subsea permafrost occurs beneath the seabed and exists in the continental shelves of the polar regions.<ref>{{cite web|authors=IPCC AR4|title=Climate Change 2007: Working Group I: The Physical Science Basis|date= 2007|url=http://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch4s4-7-2-4.html|accessdate= April 12, 2014}}</ref> This source of methane is different from methane clathrates, but contributes to the overall outcome and feedbacks.

[[Sea ice]] serves to stabilise methane deposits on and near the shoreline,<ref name="2005gl022751"/> preventing the [[clathrate]] breaking down and venting into the water column and eventually reaching the atmosphere. From sonar measurements in recent years researchers quantified the density of bubbles emanating from the subsea permafrost into the Ocean (a process called ebullition), and found that 100–630&nbsp;mg methane per square meters is emitted daily along the East Siberian Shelf, into the water column. They also found that during storms, methane levels in the water column drop dramatically, when wind driven air-sea gas exchange accelerates the ebullition process into the atmosphere. This observed pathway suggest that methane from seabed permafrost will progress rather slowly, instead of abrupt changes. However, Arctic cyclones, fueled by [[global warming]] and further accumulation of greenhouse gases in the atmosphere could contribute to more release from this methane source.<ref>{{cite journal|authors=Natalia Shakhova, Igor Semiletov, Ira Leifer, Valentin Sergienko, Anatoly Salyuk, Denis Kosmach, Denis Chernykh, Chris Stubbs, Dmitry Nicolsky, Vladimir Tumskoy & Örjan Gustafsson|title=Ebullition and storm-induced methane release from the East Siberian Arctic Shelf|journal=Nature|date= November 24, 2013|doi=10.1038/ngeo2007|url=[http://www.nature.com/ngeo/journal/v7/n1/full/ngeo2007.html Nature news] [http://www.see.ed.ac.uk/~shs/Methane/Shakhova%202013.pdf PDF]|accessdate= April 12, 2014|volume=7|pages=64–70}}</ref>

==Changes in vegetation==
[[File:Arctic Vegetation Index Trend (WH).png|right|thumb|Western Hemisphere Arctic Vegetation Index Trend]]
[[File:Arctic Vegetation Index Trend (WH).png|right|thumb|Western Hemisphere Arctic Vegetation Index Trend]]
[[File:Arctic Vegetation Index Trend (EH).png|right|thumb|Eastern Hemisphere Vegetation Index Trend]]
[[File:Arctic Vegetation Index Trend (EH).png|right|thumb|Eastern Hemisphere Vegetation Index Trend]]
Climate change is expected to have a strong effect on the Arctic's flora, some of which is already being seen.<ref>{{Cite journal|last1=Bjorkman|first1=Anne D.|last2=García Criado|first2=Mariana|last3=Myers-Smith|first3=Isla H.|last4=Ravolainen|first4=Virve|last5=Jónsdóttir|first5=Ingibjörg Svala|last6=Westergaard|first6=Kristine Bakke|last7=Lawler|first7=James P.|last8=Aronsson|first8=Mora|last9=Bennett|first9=Bruce|last10=Gardfjell|first10=Hans|last11=Heiðmarsson|first11=Starri|date=2019-03-30|title=Status and trends in Arctic vegetation: Evidence from experimental warming and long-term monitoring|url=http://dx.doi.org/10.1007/s13280-019-01161-6|journal=Ambio|volume=49|issue=3|pages=678–692|doi=10.1007/s13280-019-01161-6|issn=0044-7447|pmc=6989703|pmid=30929249}}</ref> NASA and NOAA have continuously monitored Arctic vegetation with satellite instruments such as [[Moderate Resolution Imaging Spectroradiometer]] (MODIS) and [[Advanced very-high-resolution radiometer]] (AVHRR).<ref>{{Cite journal|last=Gutman|first=G.Garik|date=February 1991|title=Vegetation indices from AVHRR: An update and future prospects|url=http://dx.doi.org/10.1016/0034-4257(91)90005-q|journal=Remote Sensing of Environment|volume=35|issue=2–3|pages=121–136|bibcode=1991RSEnv..35..121G|doi=10.1016/0034-4257(91)90005-q|issn=0034-4257}}</ref> Their data allows scientists to calculate so-called "Arctic greening" and "Arctic browning".<ref name=":7">{{Cite book|last=Sonja|first=Myers-Smith, Isla H. Kerby, Jeffrey T. Phoenix, Gareth K. Bjerke, Jarle W. Epstein, Howard E. Assmann, Jakob J. John, Christian Andreu-Hayles, Laia Angers-Blondin, Sandra Beck, Pieter S. A. Berner, Logan T. Bhatt, Uma S. Bjorkman, Anne D. Blok, Daan Bryn, Anders Christiansen, Casper T. Cornelissen, J. Hans C. Cunliffe, Andrew M. Elmendorf, Sarah C. Forbes, Bruce C. Goetz, Scott J. Hollister, Robert D. de Jong, Rogier Loranty, Michael M. Macias-Fauria, Marc Maseyk, Kadmiel Normand, Signe Olofsson, Johan Parker, Thomas C. Parmentier, Frans-Jan W. Post, Eric Schaepman-Strub, Gabriela Stordal, Frode Sullivan, Patrick F. Thomas, Haydn J. D. Tommervik, Hans Treharne, Rachael Tweedie, Craig E. Walker, Donald A. Wilmking, Martin Wipf|url=http://worldcat.org/oclc/1234747430|title=Complexity revealed in the greening of the Arctic|date=2020|publisher=Umeå universitet, Institutionen för ekologi, miljö och geovetenskap|oclc=1234747430}}</ref> From 1985 to 2016, greening has occurred in 37.3% of all sites sampled in the tundra, whereas browning was observed only in 4.7% of the sites - typically the ones that were still experiencing cooling and drying, as opposed to warming and wettening for the rest.<ref name="Berner2020">{{Cite journal|last1=Berner|first1=Logan T.|last2=Massey|first2=Richard|last3=Jantz|first3=Patrick|last4=Forbes|first4=Bruce C.|last5=Macias-Fauria|first5=Marc|last6=Myers-Smith|first6=Isla|last7=Kumpula|first7=Timo|last8=Gauthier|first8=Gilles|last9=Andreu-Hayles|first9=Laia|last10=Gaglioti|first10=Benjamin V.|last11=Burns|first11=Patrick|date=December 2020|title=Summer warming explains widespread but not uniform greening in the Arctic tundra biome|journal=Nature Communications|language=en|volume=11|issue=1|pages=4621|bibcode=2020NatCo..11.4621B|doi=10.1038/s41467-020-18479-5|issn=2041-1723|pmc=7509805|pmid=32963240}}</ref>
Changes in vegetation are associated with the increases in landscape scale CH4 emissions.<ref name="Methane is a greenhouse gas">{{Cite journal| title = Thawing sub-arctic permafrost: Effects on vegetation and methane emissions | first8 = B. H.| first7 = P.| first6 = T.| journal = Geophysical Research Letters| volume = 31| last8 = Svensson| doi = 10.1029/2003GL018680| year = 2004| pages = L04501| first1 = T. R.| first5 = N.| first3 = H.| last3 = Jonas Åkerman| last2 = Johansson| last1 = Christensen| last5 = Malmer| last7 = Crill| last6 = Friborg| last4 = Mastepanov | first4 = M. | first2 = T. Ö.| issue = 4 | bibcode=2004GeoRL..3104501C}}</ref>


This expansion of vegetation in the Arctic is not equivalent across types of vegetation. A major trend has been from [[shrub]]-type plants taking over areas previously dominated by moss and lichens. This change contributes to the consideration that the tundra biome is currently experiencing the most rapid change of any terrestrial biomes on the planet.<ref>{{Cite journal|last1=Martin|first1=Andrew|last2=Petrokofsky|first2=Gillian|date=2018-05-24|title=Shrub growth and expansion in the Arctic tundra: an assessment of controlling factors using an evidence-based approach.|url=http://dx.doi.org/10.17011/conference/eccb2018/108642|journal=Proceedings of the 5th European Congress of Conservation Biology|location=Jyväskylä|publisher=Jyvaskyla University Open Science Centre|doi=10.17011/conference/eccb2018/108642|s2cid=134164370 }}</ref><ref>{{Cite journal|last1=Myers-Smith|first1=Isla H.|last2=Hik|first2=David S.|date=2017-09-25|title=Climate warming as a driver of tundra shrubline advance|url=http://dx.doi.org/10.1111/1365-2745.12817|journal=Journal of Ecology|volume=106|issue=2|pages=547–560|doi=10.1111/1365-2745.12817|issn=0022-0477|hdl=20.500.11820/f12e7d9d-1c24-4b5f-ad86-96715e071c7b|s2cid=90390767}}</ref> The direct impact on mosses and lichens is unclear as there exist very few studies at species level, but climate change is more likely to cause increased fluctuation and more frequent extreme events.<ref>{{Cite journal|last1=Alatalo|first1=Juha M.|last2=Jägerbrand|first2=Annika K.|last3=Molau|first3=Ulf|date=2014-08-14|title=Climate change and climatic events: community-, functional- and species-level responses of bryophytes and lichens to constant, stepwise, and pulse experimental warming in an alpine tundra|url=http://dx.doi.org/10.1007/s00035-014-0133-z|journal=Alpine Botany|volume=124|issue=2|pages=81–91|doi=10.1007/s00035-014-0133-z|bibcode=2014AlBot.124...81A |issn=1664-2201|s2cid=6665119}}</ref> While shrubs may increase in range and biomass, warming may also cause a decline in [[cushion plant]]s such as moss campion, and since [[cushion plants]] act as facilitator species across [[trophic level]]s and fill important ecological niches in several environments, this could cause cascading effects in these ecosystems that could severely affect the way in which they function and are structured.<ref>{{Cite journal|last1=Alatalo|first1=Juha M|last2=Little|first2=Chelsea J|date=2014-03-22|title=Simulated global change: contrasting short and medium term growth and reproductive responses of a common alpine/Arctic cushion plant to experimental warming and nutrient enhancement|journal=SpringerPlus|volume=3|issue=1|page=157|doi=10.1186/2193-1801-3-157|issn=2193-1801|pmc=4000594|pmid=24790813 |doi-access=free }}</ref>
The growing season has lengthened in the far northern latitudes, bringing major changes to plant communities in tundra and boreal (also known as taiga) ecosystems.


The expansion of these shrubs can also have strong effects on other important ecological dynamics, such as the [[Albedo|albedo effect]].<ref>{{Cite journal|last1=Loranty|first1=Michael M|last2=Goetz|first2=Scott J|last3=Beck|first3=Pieter S A|date=2011-04-01|title=Tundra vegetation effects on pan-Arctic albedo|url=http://dx.doi.org/10.1088/1748-9326/6/2/024014|journal=Environmental Research Letters|volume=6|issue=2|pages=024014|bibcode=2011ERL.....6b4014L|doi=10.1088/1748-9326/6/2/024014|s2cid=250681995 |issn=1748-9326}}</ref> These shrubs change the winter surface of the tundra from undisturbed, uniform snow to mixed surface with protruding branches disrupting the snow cover,<ref name=":9">{{Cite journal|last1=Belke-Brea|first1=M.|last2=Domine|first2=F.|last3=Barrere|first3=M.|last4=Picard|first4=G.|last5=Arnaud|first5=L.|date=2020-01-15|title=Impact of Shrubs on Winter Surface Albedo and Snow Specific Surface Area at a Low Arctic Site: In Situ Measurements and Simulations|url=http://dx.doi.org/10.1175/jcli-d-19-0318.1|journal=Journal of Climate|volume=33|issue=2|pages=597–609|bibcode=2020JCli...33..597B|doi=10.1175/jcli-d-19-0318.1|s2cid=210295151|issn=0894-8755}}</ref> this type of snow cover has a lower albedo effect, with reductions of up to 55%, which contributes to a positive feedback loop on regional and global climate warming.<ref name=":9" /> This reduction of the albedo effect means that more radiation is absorbed by plants, and thus, surface temperatures increase, which could disrupt current surface-atmosphere energy exchanges and affect thermal regimes of permafrost.<ref name=":9" /> Carbon cycling is also being affected by these changes in vegetation, as parts of the tundra increase their shrub cover, they behave more like boreal forests in terms of carbon cycling.<ref name=":10">{{Cite journal|last1=Jeong|first1=Su-Jong|last2=Bloom|first2=A. Anthony|last3=Schimel|first3=David|last4=Sweeney|first4=Colm|last5=Parazoo|first5=Nicholas C.|last6=Medvigy|first6=David|last7=Schaepman-Strub|first7=Gabriela|last8=Zheng|first8=Chunmiao|last9=Schwalm|first9=Christopher R.|last10=Huntzinger|first10=Deborah N.|last11=Michalak|first11=Anna M.|date=July 2018|title=Accelerating rates of Arctic carbon cycling revealed by long-term atmospheric CO 2 measurements|url=http://dx.doi.org/10.1126/sciadv.aao1167|journal=Science Advances|volume=4|issue=7|pages=eaao1167|bibcode=2018SciA....4.1167J|doi=10.1126/sciadv.aao1167|issn=2375-2548|pmc=6040845|pmid=30009255}}</ref> This is speeding up the carbon cycle, as warmer temperatures lead to increased permafrost thawing and carbon release, but also carbon capturing from plants that have increased growth.<ref name=":10" /> It is not certain whether this balance will go in one direction or the other, but studies have found that it is more likely that this will eventually lead to increased {{CO2}} in the atmosphere.<ref name=":10" />
For decades, NASA and NOAA satellites have continuously monitored vegetation from space. The Moderate Resolution Imaging Spectroradiometer (MODIS) and Advanced Very High Resolution Radiometer (AVHRR) instruments measure the intensity of visible and near-infrared light reflecting off of plant leaves. Scientists use the information to calculate the Normalized Difference Vegetation Index (NDVI), an indicator of photosynthetic activity or “greenness” of the landscape.


However, boreal forests, particularly those in North America, showed a different response to warming. Many boreal forests greened, but the trend was not as strong as it was for tundra of the circumpolar Arctic, mostly characterized by shrub expansion and increased growth.<ref>{{Cite journal|last1=Martin|first1=Andrew C.|last2=Jeffers|first2=Elizabeth S.|last3=Petrokofsky|first3=Gillian|last4=Myers-Smith|first4=Isla|last5=Macias-Fauria|first5=Marc|date=August 2017|title= Shrub growth and expansion in the Arctic tundra: An assessment of controlling factors using an evidence-based approach|url=https://iopscience.iop.org/article/10.1088/1748-9326/aa7989|journal=Environmental Research Letters|language=en|volume=12|issue=8|page=085007|doi=10.1088/1748-9326/aa7989|bibcode=2017ERL....12h5007M|s2cid=134164370 }}</ref> In North America, some boreal forests actually experienced browning over the study period. Droughts, increased forest fire activity, animal behavior, industrial pollution, and a number of other factors may have contributed to browning.<ref name=":7" />
The maps above show the Arctic Vegetation Index Trend between July 1982 and December 2011 in the [[Arctic Circle]]. Shades of green depict areas where plant productivity and abundance increased; shades of brown show where photosynthetic activity declined. The maps show a ring of greening in the treeless tundra ecosystems of the circumpolar Arctic—the northernmost parts of Canada, Russia, and Scandinavia. Tall shrubs and trees started to grow in areas that were previously dominated by tundra grasses. The researchers concluded that plant growth had increased by 7 to 10 percent overall.
<!-- The expansion of shrubs could affect permafrost dynamics, but the picture is quite unclear at the moment. In the winter, shrubs trap more snow, which insulates the permafrost from extreme cold spells, but in the summer they shade the ground from direct sunlight, how these two effects counter and balance each other is not yet well understood.<ref>{{Cite journal|last1=TAPE|first1=KEN|last2=STURM|first2=MATTHEW|last3=RACINE|first3=CHARLES|date=2006-03-24|title=The evidence for shrub expansion in Northern Alaska and the Pan-Arctic|url=http://dx.doi.org/10.1111/j.1365-2486.2006.01128.x|journal=Global Change Biology|volume=12|issue=4|pages=686–702|bibcode=2006GCBio..12..686T|doi=10.1111/j.1365-2486.2006.01128.x|s2cid=86278724|issn=1354-1013}}</ref> -->


===Impacts on terrestrial fauna===
However, boreal forests, particularly those in North America, showed a different response to warming. Many boreal forests greened, but the trend was not as strong as it was for tundra of the circumpolar Arctic. In North America, some boreal forests actually experienced “browning” (less photosynthetic activity) over the study period. Droughts, forest fire activity, animal and insect behavior, industrial pollution, and a number of other factors may have contributed to the browning.
[[File:Polar Bear Habitat.png|thumb|Projected change in polar bear habitat from 2001–2010 to 2041–2050]]
Arctic warming negatively affects the foraging and breeding ecology of native Arctic mammals, such as [[Arctic fox]]es or [[Arctic reindeer]].<ref name="Descamps2016">{{Cite journal|last1=Descamps|first1=Sébastien|last2=Aars|first2=Jon|last3=Fuglei|first3=Eva|last4=Kovacs|first4=Kit M.|last5=Lydersen|first5=Christian|last6=Pavlova|first6=Olga|last7=Pedersen|first7=Åshild Ø.|last8=Ravolainen|first8=Virve|last9=Strøm|first9=Hallvard|date=2016-06-28|title=Climate change impacts on wildlife in a High Arctic archipelago – Svalbard, Norway|url=http://dx.doi.org/10.1111/gcb.13381|journal=Global Change Biology|volume=23|issue=2|pages=490–502|doi=10.1111/gcb.13381|issn=1354-1013|pmid=27250039|s2cid=34897286}}</ref> In July 2019, 200 [[Svalbard reindeer]] were found starved to death apparently due to low precipitation related to climate change.<ref>[https://www.livescience.com/66047-200-dead-reindeer-norway.html More Than 200 Reindeer Found Dead in Norway, Starved by Climate Change] By Mindy Weisberger. Live Science, 29 July 2019</ref> This was only one episode in the long-term decline of the species.<ref name="IPCC_AR6_WGII_Polar" />{{rp|2327}} [[United States Geological Survey]] research suggests that the shrinkage of Arctic sea ice would eventually extirpate polar bears from [[Alaska]], but leave some of their [[habitat]] in the [[Canadian Arctic Archipelago]] and areas off the northern Greenland coast.<ref>{{cite web|last=DeWeaver|first=Eric|author2=U.S. Geological Survey|year=2007|title=Uncertainty in Climate Model Projections of Arctic Sea Ice Decline: An Evaluation Relevant to Polar Bears|url=http://www.usgs.gov/newsroom/special/polar_bears/docs/USGS_PolarBear_DeWeaver_GCM-Uncertainty.pdf|url-status=dead|archive-url=https://web.archive.org/web/20090509072101/http://www.usgs.gov/newsroom/special/polar_bears/docs/USGS_PolarBear_DeWeaver_GCM-Uncertainty.pdf|archive-date=9 May 2009|publisher=[[United States Department of the Interior]]|oclc=183412441|df=dmy-all}}</ref><ref>{{cite news|last=Broder|first=John|author2=Revkin, Andrew C.|date=8 July 2007|title=Warming Is Seen as Wiping Out Most Polar Bears|work=The New York Times|url=https://www.nytimes.com/2007/09/08/science/earth/08polar.html?_r=1&hp=&adxnnl=1&oref=slogin&adxnnlx=1190574637-aS0VOr2klykTSNwK91tiDg|access-date=23 September 2007}}</ref>


As the pure [[Arctic climate]] is gradually replaced by the [[subarctic climate]], animals adapted to those conditions spread to the north.<ref name="IPCC_AR6_WGII_Polar" />{{rp|2325}} For instance, [[beaver]]s have been actively colonizing Arctic regions, and as they create [[beaver dam|dam]]s, they flood areas which used to be permafrost, contributing to its thaw and methane emissions from it.<ref name="Clark2023">{{Cite journal |last1=Clark |first1=Jason A |last2=Tape |first2=Ken D |last3=Baskaran |first3=Latha |last4=Elder |first4=Clayton |last5=Miller |first5=Charles |last6=Miner |first6=Kimberley |last7=O'Donnell |first7=Jonathan A |last8=Jones |first8=Benjamin M |date=3 July 2023 |title=Do beaver ponds increase methane emissions along Arctic tundra streams? |journal=Environmental Research Letters |language=en |volume=18 |issue=7 |doi=10.1088/1748-9326/acde8e |bibcode=2023ERL....18g5004C }}</ref> These colonizing species can outright replace native species, and they may also interbreed with their southern relations, like in the case of the [[Grizzly–polar bear hybrid]]. This usually has the effect of reducing the [[genetic diversity]] of the [[genus]]. [[Infection|Infectious diseases]], such as [[brucellosis]] or [[phocine distemper virus]], may spread to populations previously separated by the cold, or, in case of the [[marine mammal]]s, the sea ice.<ref>{{cite web|last=Struzik|first=Ed|date=14 February 2011|title=Arctic Roamers: The Move of Southern Species into Far North|url=http://e360.yale.edu/feature/arctic_roamers_the_move_of_southern_species_into_far_north/2370/|access-date=19 July 2016|website=Environment360|publisher=Yale University|quote=Grizzly bears mating with polar bears. Red foxes out-competing Arctic foxes. Exotic diseases making their way into once-isolated polar realms. These are just some of the worrisome phenomena now occurring as Arctic temperatures soar and the Arctic Ocean, a once-impermeable barrier, melts.}}</ref>
“Satellite data identify areas in the boreal zone that are warmer and drier and other areas that are warmer and wetter,” explained co-author Ramakrishna Nemani of NASA’s Ames Research Center. “Only the warmer and wetter areas support more growth.”


=== Marine ecosystems ===
“We found more plant growth in the boreal zone from 1982 to 1992 than from 1992 to 2011, because water limitations were encountered in the later two decades of our study,” added co-author Sangram Ganguly of the Bay Area Environmental Research Institute and NASA Ames.
[[File:NASA Arctic chlorophyll increase.png|thumb|The observed increase in phytoplankton biomass in the Arctic since 1998<ref name="NASAHansen2020">{{cite web |last=Hansen |first=Kathryn |date=26 July 2020 |title=Phytoplankton Surge in Arctic Waters |url=https://earthobservatory.nasa.gov/images/147049/phytoplankton-surge-in-arctic-waters |website=[[NASA]] Earth Observatory |language=en |access-date=25 May 2024 }}</ref>]]
<ref name="The Greening Arctic">{{cite web | url = http://earthobservatory.nasa.gov/IOTD/view.php?id=80637 | title = The Greening Arctic, NASA Image of the Day | accessdate = 2013-03-16}}</ref>
The reduction of sea ice has brought more sunlight to the [[phytoplankton]] and increased the annual [[marine primary production]] in the Arctic by over 30% between 1998 and 2020.<ref name="IPCC_AR6_WGII_Polar" />{{rp|2327}} As the result, the Arctic Ocean became a stronger [[carbon sink]] over this period;<ref>{{Cite journal |last1=Yasunaka |first1=Sayaka |last2=Manizza |first2=Manfredi |last3=Terhaar |first3=Jens |last4=Olsen |first4=Are |last5=Yamaguchi |first5=Ryohei |last6=Landschützer |first6=Peter |last7=Watanabe |first7=Eiji |last8=Carroll |first8=Dustin |last9=Adiwira |first9=Hanani |last10=Müller |first10=Jens Daniel |last11=Hauck |first11=Judith |date=10 November 2023 |title=An Assessment of CO2 Uptake in the Arctic Ocean From 1985 to 2018 |journal=Global Biogeochemical Cycles |volume=37 |issue=11 |page=e2023GB007806 |doi=10.1029/2023GB007806 }}</ref> yet, it still accounts for only 5% to 14% of the total ocean carbon sink, although it is expected to play a larger role in the future.<ref>{{cite journal |last1=Richaud |first1=Benjamin |last2=Fennel |first2=Katja |last3=Oliver |first3=Eric C. J. |last4=DeGrandpre |first4=Michael D. |last5=Bourgeois |first5=Timothée |last6=Hu |first6=Xianmin |last7=Lu |first7=Youyu |title=Underestimation of oceanic carbon uptake in the Arctic Ocean: ice melt as predictor of the sea ice carbon pump |date=11 July 2023 |journal=The Cryosphere |volume=17 |issue=7 |pages=2665–2680 |doi=10.5194/tc-17-2665-2023 |doi-access=free |bibcode=2023TCry...17.2665R }}</ref> By 2100, phytoplankton [[biomass]] in the Arctic Ocean is generally expected to increase by ~20% relative to 2000 under the low-emission scenario, and by 30-40% under the high-emission scenario.<ref name="IPCC_AR6_WGII_Polar" />{{rp|2329}}


[[Atlantic cod]] have been able to move deeper into the Arctic due to the warming waters, while the [[Polar cod]] and local [[marine mammal]]s have been losing habitat.<ref name="IPCC_AR6_WGII_Polar" />{{rp|2327}} Many [[copepod]] species appear to be declining, which is also likely to reduce the numbers of fish which prey on them, such as [[walleye pollock]] or the [[arrowtooth flounder]].<ref name="IPCC_AR6_WGII_Polar" />{{rp|2327}} This also affects Arctic [[shorebird]]s. For instance, around 9000 [[puffin]]s and other shorebirds in Alaska died of starvation in 2016, because too many fish have moved to the north.<ref>{{Cite web|date=30 May 2019 |author=Helen Briggs|title=Climate change link to puffin deaths |url=https://www.bbc.com/news/science-environment-48447394|access-date=25 June 2023|website=[[BBC News]]|language=en}}</ref> While the shorebirds also appear to nest more successfully due to the observed warming,<ref>{{cite journal|author1=Weiser, E.L.|author2=Brown, S.C.|author3=Lanctot, R.B.|author4=River Gates, H.|author5=Abraham, K.F.|author6=Bentzen, R.L.|author7=Bêty, J.|author8=Boldenow, M.L.|author9=Brook, R.W.|author10=Donnelly, T.F.|author11=English, W.B.|display-authors=5|year=2018|title=Effects of environmental conditions on reproductive effort and nest success of Arctic-breeding shorebirds|journal=Ibis|volume=160|issue=3|pages=608–623|doi=10.1111/ibi.12571|hdl-access=free|author20=Kwon, E.|author35=Solovyeva, D.|hdl=10919/99313|author12=Flemming, S.A.|author13=Franks, S.E.|author14=Gilchrist, H.G.|author15=Giroux, M.|author16=Johnson, A.|author17=Kendall, S.|author18=Kennedy, L.V.|s2cid=53514207|author38=Sandercock, B.K.|author37=Woodard, P.F.|author36=Ward, D.H.|author34=Soloviev, M.|author21=Lamarre, J.|author33=Smith, P.A.|author32=Senner, N.R.|author31=Saalfeld, S.T.|author30=Robards, M.|author29=Rausch, J.|author28=Perz, J.|author27=Nol, E.|author26=McKinnon, L.|author25=Liebezeit, J.R.|author19=Koloski, L.|author23=Latty, C.J.|author22=Lank, D.B.|author24=Lecomte, N.}}</ref> this benefit may be more than offset by [[phenological mismatch]] between shorebirds' and other species' life cycles.<ref name="Saalfeld2021">{{Cite journal|last1=Saalfeld|first1=Sarah T.|last2=Hill|first2=Brooke L. |last3=Hunter|first3=Christine M. |last4=Frost|first4=Charles J.|last5=Lanctot|first5=Richard B.|date=27 July 2021|title=Warming Arctic summers unlikely to increase productivity of shorebirds through renesting|journal=Scientific Reports|volume=11|issue=1 |page=15277 |doi=10.1038/s41598-021-94788-z |pmid=34315998 |pmc=8316457 |doi-access=free|bibcode=2021NatSR..1115277S }}</ref> Marine mammals such as [[ringed seal]]s and [[walrus]]es are also being negatively affected by the warming.<ref name="Descamps2016" /><ref>{{Cite web|title=Walruses in a Time of Climate Change|url=https://www.arctic.noaa.gov/Report-Card/Report-Card-2015/ArtMID/5037/ArticleID/226/Walruses-in-a-Time-of-Climate-Change|access-date=2021-05-19|website=Arctic Program|date=14 July 2016 |language=en-US}}</ref>
The less severe winters in tundra areas allow [[shrubs]] such as [[alder]]s and dwarf birch to replace [[moss]] and [[lichen]]s. The impact on mosses and lichens is however unclear as there exist very few studies at species level, also climate change is more likely to cause increased fluctuation and more frequent extreme events.<ref>{{cite journal | last1 = Alatalo | first1 = J.M. | last2 = Jägerbrand | first2 = A.K. | last3 = Molau | first3 = U. | year = 2014 | title = Climate change and climatic events: community-, functional- and species level responses of bryophytes and lichens to constant, stepwise and pulse experimental warming in an alpine tundra | url = | journal = Alpine Botany | volume = 124 | issue = | pages = 81–91 | doi = 10.1007/s00035-014-0133-z }}</ref> The feedback effect of shrubs on the tundra's permafrost is unclear, however. In the winter they trap more snow which insulates the permafrost from extreme cold spells, but in the summer they shade the ground from direct sunlight.<ref name="Shrub Takeover One Sign of Arctic Change"/> The warming is likely to cause changes in the plant communities.<ref>{{cite journal | last1 = Alatalo | first1 = JM | last2 = Little | first2 = CJ | last3 = Jägerbrand | first3 = AK | last4 = Molau | first4 = U | year = 2014 | title = Dominance hierarchies, diversity and species richness of vascular plants in an alpine meadow: contrasting short and medium term responses to simulated global change | url = | journal = PeerJ | volume = 2 | issue = | page = e406 | doi = 10.7717/peerj.406 }}</ref> Except for an increase in shurbs, warming may also cause a decline in cushion plants such as moss campion. As cushion plants act as facilitator species across trophic level and fill important roles in severe environments this could cause cascading effects in the ecosystems.<ref>{{cite journal | last1 = Alatalo | first1 = J.M. | last2 = Little | first2 = C.J. | year = 2014 | title = Simulated global change: contrasting short and medium term growth and reproductive responses of a common alpine/Arctic cushion plant to experimental warming and nutrient enhancement | url = | journal = SpringerPlus | volume = 3 | issue = | page = 157 | doi = 10.1186/2193-1801-3-157 }}</ref> Rising summer temperature melts on Canada's Baffin Island have revealed moss previously covered which hasn't seen daylight in 44,000 years.<ref>[http://www.nytimes.com/interactive/2014/09/22/science/on-the-cusp-of-climate-change.html ''On the Cusp of Climate Change''] 22.September.2014 New York Times</ref>


== Greenhouse gas emissions from the Arctic ==
The reduction of sea ice has boosted the productivity of [[phytoplankton]] by about twenty percent over the past thirty years. However, the effect on [[marine ecosystem]]s is unclear, since the larger types of phytoplankton, which are the preferred food source of most marine animals, do not appear to have increased as much as the smaller types. So far, arctic phytoplankton have not had a significant impact on the global carbon cycle.<ref name="Sea Ice Declines Boost Arctic Phytoplankton Productivity"/> In summer, the melt ponds on young and thin ice have allowed sunlight to penetrate the ice, in turn allowing phytoplankton to bloom in unexpected concentrations, although it is unknown just how long this phenomenon has been occurring.<ref name="Unprecedented Blooms of Ocean Plant Life"/>
{{See also|Arctic methane emissions}}
In 2024, the Arctic has transformed from a carbon sink to a carbon source due to the impacts of climate change, mainly rising temperatures and wildfires.<ref>{{cite web |title=Arctic tundra becoming source of carbon dioxide emissions |url=https://www.noaa.gov/news-release/arctic-tundra-becoming-source-of-carbon-dioxide-emissions |website=NOAA logo National Oceanic and Atmospheric Administration |access-date=22 December 2024}}</ref>
=== Permafrost thaw ===
[[File:Permafrost thaw ponds in Hudson Bay Canada near Greenland.jpg|thumb|Permafrost thaw ponds on [[Baffin Island]]]]
[[Permafrost]] is an important component of hydrological systems and ecosystems within the Arctic landscape.<ref>{{Cite web|title=Terrestrial Permafrost|url=https://arctic.noaa.gov/Report-Card/Report-Card-2017/ArtMID/7798/ArticleID/694/Terrestrial-Permafrost|access-date=2021-05-18|website=Arctic Program|date=24 October 2017 |language=en-US}}</ref> In the Northern Hemisphere the terrestrial permafrost domain comprises around 18 million km<sup>2</sup>.<ref name=":4">{{Cite journal|last1=Sayedi|first1=Sayedeh Sara|last2=Abbott|first2=Benjamin W|last3=Thornton|first3=Brett F|last4=Frederick|first4=Jennifer M|last5=Vonk|first5=Jorien E|last6=Overduin|first6=Paul|last7=Schädel|first7=Christina|last8=Schuur|first8=Edward A G|last9=Bourbonnais|first9=Annie|last10=Demidov|first10=Nikita|last11=Gavrilov|first11=Anatoly|date=2020-12-01|title=Subsea permafrost carbon stocks and climate change sensitivity estimated by expert assessment|url=http://dx.doi.org/10.1088/1748-9326/abcc29|journal=Environmental Research Letters|volume=15|issue=12|pages=B027-08|doi=10.1088/1748-9326/abcc29|bibcode=2020AGUFMB027...08S|s2cid=234515282|issn=1748-9326}}</ref> Within this permafrost region, the total soil organic carbon (SOC) stock is estimated to be 1,460-1,600 Pg (where 1 Pg = 1 billion tons), which constitutes double the amount of carbon currently contained in the atmosphere.<ref>{{Cite journal|last1=Hugelius|first1=G.|last2=Strauss|first2=J.|last3=Zubrzycki|first3=S.|last4=Harden|first4=J. W.|author-link4=Jennifer Harden|last5=Schuur|first5=E. A. G.|last6=Ping|first6=C.-L.|last7=Schirrmeister|first7=L.|last8=Grosse|first8=G.|last9=Michaelson|first9=G. J.|last10=Koven|first10=C. D.|last11=O'Donnell|first11=J. A.|date=2014-12-01|title=Estimated stocks of circumpolar permafrost carbon with quantified uncertainty ranges and identified data gaps|journal=Biogeosciences|volume=11|issue=23|pages=6573–6593|doi=10.5194/bg-11-6573-2014|bibcode=2014BGeo...11.6573H|s2cid=14158339 |issn=1726-4189 |doi-access=free }}</ref><ref>{{Cite web|title=Permafrost and the Global Carbon Cycle|url=https://arctic.noaa.gov/Report-Card/Report-Card-2019/ArtMID/7916/ArticleID/844/Permafrost-and-the-Global-Carbon-Cycle|access-date=2021-05-18|website=Arctic Program|date=31 October 2019 |language=en-US}}</ref>


{{excerpt|Permafrost#Climate change feedback|paragraphs=1-2|file=no}}
==Changes for animals==
{{excerpt|Permafrost#Impact on global temperatures|hat=no}}


=== Black carbon ===
[[File:Polar Bear Habitat.png|thumb|left|Projected change in polar bear habitat from 2001–2010 to 2041–2050]]
[[File:Winiger 2016 black carbon.jpg|thumb|Black carbon emissions from fire and human activities around the Arctic in the year 2012, as measured from a research station in [[Abisko]]<ref name="Winiger2016">{{Cite journal|last1=Winiger |first1=P |last2=Andersson |first2=A |last3=Stohl |first3=A |last4=Gustafsson |first4=Ö. |date= 15 September 2016 |title=The sources of atmospheric black carbon at a European gateway to the Arctic |journal=Nature Communications |volume=7 |issue=1 |page=12776 |doi=10.1038/ncomms12776 |bibcode=2016NatCo...712776W }}</ref> ]]
3 April 2007, the [[National Wildlife Federation]] urged the [[United States Congress]] to place [[polar bear]]s under the [[Endangered Species Act]].<ref name="Protection For Polar Bears Urged By National Wildlife Federation"/>
{{Main|Black carbon}}
Four months later, the [[United States Geological Survey]] completed a year-long study<ref name="Uncertainty in Climate Model Projections of Arctic Sea Ice Decline: An Evaluation Relevant to Polar Bears"/> which concluded in part that the floating [[Arctic sea ice]] will continue its rapid shrinkage over the next 50 years, consequently wiping out much of the polar bear [[habitat]]. The bears would disappear from Alaska, but would continue to exist in the [[Canadian Arctic Archipelago]] and areas off the northern Greenland coast.<ref name="Warming Is Seen as Wiping Out Most Polar Bears"/> Secondary ecological effects are also resultant from the shrinkage of sea ice; for example, [[polar bear]]s are denied their historic length of seal hunting season due to late formation and early thaw of [[pack ice]].
[[Black carbon]] deposits (from the combustion of heavy fuel oil (HFO) of Arctic shipping) absorb solar radiation in the atmosphere and strongly reduce the albedo when deposited on snow and ice, thus accelerating the effect of the melting of snow and sea ice.<ref name="Qi2019">{{Cite journal|last1=Qi|first1=Ling|last2=Wang|first2=Shuxiao|date=November 2019|title=Sources of black carbon in the atmosphere and in snow in the Arctic|url=http://dx.doi.org/10.1016/j.scitotenv.2019.07.073|journal=Science of the Total Environment|volume=691|pages=442–454|doi=10.1016/j.scitotenv.2019.07.073|pmid=31323589|bibcode=2019ScTEn.691..442Q|s2cid=198135020|issn=0048-9697}}</ref> A 2013 study quantified that [[gas flaring]] at petroleum extraction sites contributed over 40% of the black carbon deposited in the Arctic.<ref>{{Citation |author=Stohl, A. |author2=Klimont, Z. |author3=Eckhardt, S. |author4=Kupiainen, K. |author5=Chevchenko, V.P. |author6=Kopeikin, V.M. |author7=Novigatsky, A.N. |title=Black carbon in the Arctic: the underestimated role of gas flaring and residential combustion emissions |journal=Atmos. Chem. Phys. |volume=13 |issue=17 |pages=8833–8855 |year=2013 |doi=10.5194/acp-13-8833-2013 |bibcode=2013ACP....13.8833S |doi-access=free }}</ref><ref>{{Cite web |url=https://arctic-council.org/images/PDF_attachments/COP24_2018/2018-11-10-COP24-Stanley-flaring-World-Bank-BC.pdf |title=Gas flaring: An industry practice faces increasing global attention |first=Michael |last=Stanley |publisher=World Bank |date=2018-12-10 |access-date=2020-01-20 |archive-date=15 February 2019 |archive-url=https://web.archive.org/web/20190215231453/https://www.arctic-council.org/images/PDF_attachments/COP24_2018/2018-11-10-COP24-Stanley-flaring-World-Bank-BC.pdf |url-status=dead }}</ref> 2019 research attributed the majority (56%) of Arctic surface black carbon to emissions from Russia, followed by European emissions, and Asia also being a large source.<ref>{{Cite journal|last1=Zhu|first1=Chunmao|last2=Kanaya|first2=Yugo|last3=Takigawa|first3=Masayuki|last4=Ikeda|first4=Kohei|last5=Tanimoto|first5=Hiroshi|last6=Taketani|first6=Fumikazu|last7=Miyakawa|first7=Takuma|last8=Kobayashi|first8=Hideki|last9=Pisso|first9=Ignacio|title=Flexpart v10.1 simulation of source contributions to Arctic black carbon|date=2019-09-24|journal=Atmospheric Chemistry and Physics |doi=10.5194/acp-2019-590|s2cid=204117555 |doi-access=free }}</ref><ref name="Qi2019" /> In 2015, research suggested that reducing black carbon emissions and short-lived greenhouse gases by roughly 60 percent by 2050 could cool the Arctic up to 0.2&nbsp;°C.<ref>{{cite web|url=http://www.climatecentral.org/news/race-to-understand-black-carbons-climate-impact-21458|title=The Race to Understand Black Carbon's Climate Impact|publisher=ClimateCentral|year=2017|access-date=21 May 2017|archive-date=22 November 2017|archive-url=https://web.archive.org/web/20171122113008/http://www.climatecentral.org/news/race-to-understand-black-carbons-climate-impact-21458|url-status=dead}}</ref> However, a 2019 study indicates that "Black carbon emissions will continuously rise due to increased shipping activities", specifically fishing vessels.<ref>{{Cite journal|last1=Zhang|first1=Qiang|last2=Wan|first2=Zheng|last3=Hemmings|first3=Bill|last4=Abbasov|first4=Faig|date=December 2019|title=Reducing black carbon emissions from Arctic shipping: Solutions and policy implications|url=http://dx.doi.org/10.1016/j.jclepro.2019.118261|journal=Journal of Cleaner Production|volume=241|pages=118261|doi=10.1016/j.jclepro.2019.118261|bibcode=2019JCPro.24118261Z |s2cid=203303955|issn=0959-6526}}</ref>


The number of wildfires in the Arctic Circle has increased. In 2020, Arctic wildfire {{CO2}} emissions broke a new record, peaking at 244 megatonnes of carbon dioxide emitted.<ref name=":11">{{Cite journal|last=Witze|first=Alexandra|date=2020-09-10|title=The Arctic is burning like never before — and that's bad news for climate change|url=http://dx.doi.org/10.1038/d41586-020-02568-y|journal=Nature|volume=585|issue=7825|pages=336–337|bibcode=2020Natur.585..336W|doi=10.1038/d41586-020-02568-y|issn=0028-0836|pmid=32913318|s2cid=221625701}}</ref>  This is due to the burning of peatlands, carbon-rich soils that originate from the accumulation of waterlogged plants which are mostly found at Arctic latitudes.<ref name=":11" /> These peatlands are becoming more likely to burn as temperatures increase, but their own burning and releasing of {{CO2}} contributes to their own likelihood of burning in a positive feedback loop.<ref name=":11" />The smoke from wildfires defined as "[[brown carbon]]" also increases arctic warming, with its warming effect is around 30% that of black carbon. As wildfires increases with warming this creates a [[positive feedback loop]].<ref name="McGrath_20220319"/>
==Melting of the Greenland Ice Sheet==
[[File:Greenland Albedo Change.png|left|thumb|Albedo Change on Greenland]]
[[File:Greenland Ice Mass Trend.jpg|thumb|[[Greenland Ice Sheet]] Mass Trend 2003-2005]]
Models predict a sea-level contribution of about {{convert|5|cm|in|0}} from melting in Greenland during the 21st century.<ref name="ipcc"/> It is also predicted that Greenland will become warm enough by 2100 to begin an almost complete melt during the next 1,000 years or more.<ref name="Climatology: threatened loss of the Greenland ice-sheet"/><ref name="Regional Sea Level Change"/> In early July 2012, 97% percent of the Ice Sheet experienced some form of surface melt including the summits.<ref name="nasa"/>


===Methane clathrate deposits ===
Ice thickness measurements from the [[Gravity Recovery and Climate Experiment|GRACE]] satellite indicate that ice mass loss is accelerating. For the period 2002–2009, the rate of loss increased from −137 Gt/yr to −286 Gt/yr, with an acceleration of −30 gigatonnes per year per year.<ref name="Increasing rates of ice mass loss from the Greenland and Antarctic ice sheets revealed by GRACE"/>
{{excerpt|Clathrate gun hypothesis|paragraphs=1}}
{{excerpt|Clathrate gun hypothesis#Current outlook|paragraphs=2-3|hat=no}}


==Effect on ocean circulation==
==Effects on other parts of the world==
===On ocean circulation===
{{See also|Shutdown of thermohaline circulation|Ocean anoxic event}}
[[File:Sgubin2017 spg amoc collapse.jpg|thumb|Modelled 21st century warming under the "intermediate" global warming scenario (top). The potential [[North Atlantic Current#Climate change|collapse of the subpolar gyre]] in this scenario (middle). The collapse of the entire Atlantic Meriditional Overturning Circulation (bottom).]]
{{excerpt|Atlantic meridional overturning circulation|paragraph=1|file=no}}
{{excerpt|Atlantic meridional overturning circulation#Stability and vulnerability|paragraph=1|file=no|hat=no}}
{{excerpt|Atlantic meridional overturning circulation|paragraph=4|file=no|hat=no}}
{{excerpt|Atlantic meridional overturning circulation#Major review studies|paragraphs=2-3|file=no|hat=no}}


===On mid-latitude weather===
Although this is now thought unlikely in the near future, it has also been suggested that there could be a [[shutdown of thermohaline circulation]], similar to that which is believed to have driven the [[Younger Dryas]], an [[abrupt climate change]] event. There is also potentially a possibility of a more general disruption of [[ocean circulation]], which may lead to an [[ocean anoxic event]], although these are believed to be much more common in the distant past. It is unclear whether the appropriate pre-conditions for such an event exist today.
{{excerpt|Jet stream#Longer-term climatic changes|paragraphs=1,2,6,7|file=yes}}


== Impacts on people ==
==Territorial claims==
===Territorial claims===
{{Main|Territorial claims in the Arctic}}
{{Main|Territorial claims in the Arctic}}
Growing evidence that global warming is shrinking polar ice has added to the urgency of several nations' [[Territorial claims in the Arctic|Arctic territorial claims]] in hopes of establishing resource development and new shipping lanes, in addition to protecting sovereign rights.<ref name="WashPost"/>
Growing evidence that global warming is shrinking polar ice has added to the urgency of several nations' [[Territorial claims in the Arctic|Arctic territorial claims]] in hopes of establishing resource development and [[Arctic shipping routes|new shipping lanes]], in addition to protecting sovereign rights.<ref name="WashPost">{{cite news | first = Mike | last = Eckel | title = Russia: Tests Show Arctic Ridge Is Ours | url = https://www.washingtonpost.com/wp-dyn/content/article/2007/09/20/AR2007092001703.html |agency=Associated Press | newspaper = The Washington Post | date = 20 September 2007 | access-date = 21 September 2007}}{{dead link|date=June 2021|bot=medic}}{{cbignore|bot=medic}}</ref>


As ice sea coverage decreases more and more, year on year, Arctic countries (Russia, Canada, Finland, Iceland, Norway, Sweden, the United States and Denmark representing Greenland) are making moves on the geopolitical stage to ensure access to potential [[Arctic shipping routes|new shipping lanes]], oil and gas reserves, leading to overlapping claims across the region.<ref name=":13">{{Cite web|title=Territorial Claims in the Arctic Circle: An Explainer|url=https://theobserver-qiaa.org/territorial-claims-in-the-arctic-circle-an-explainer|access-date=2021-05-19|website=The Observer|language=en-US}}</ref>
Danish Foreign Minister [[Per Stig Møller]] and Greenland's Premier [[Hans Enoksen]] invited [[foreign minister]]s from Canada, Norway, Russia and the United States to [[Ilulissat|Ilulissat, Greenland]] for a summit in May 2008 to discuss how to divide borders in the changing Arctic region, and a discussion on more cooperation against climate change affecting the Arctic.<ref name="EUX"/> At the [[Arctic Ocean Conference]], Foreign Ministers and other officials representing the five countries announced the [[Ilulissat Declaration]] on 28 May 2008.<ref name="Conference in Ilulissat, Greenland: Landmark political declaration on the future of the Arctic"/><ref name="The Ilulissat Declaration"/>


There is more activity in terms of maritime boundaries between countries, where overlapping claims for [[internal waters]], [[Territorial waters|territorial seas]] and particularly [[Exclusive economic zone|Exclusive Economic Zones]] (EEZs) can cause frictions between nations. Currently, official maritime borders have an unclaimed triangle of international waters lying between them, that is at the centerpoint of international disputes.<ref name=":13" />
==Social impacts==
People are affecting the geographic space of the Arctic and the Arctic is affecting the population. Much of the climate change in the Arctic can be attributed to humans influences on the atmosphere, such as an increased [[greenhouse effect]] caused by the increase in CO2 due to the burning of [[fossil fuels]].<ref name="greenhouse effect">http://www.ciesin.org/docs/003-074/003-074.html</ref> Climate change is having a direct impact on the people that live in the Arctic, as well as other societies around the world.<ref name="ClimateImpactAssessment">{{cite book|last=Hassol|first=Arctic Climate Impact Assessment ; [author, Susan Joy|title=Impacts of a warming Arctic|year=2004|publisher=Cambridge University Press|location=Cambridge, U.K.|isbn=978-0-521-61778-9|edition=Reprinted.}}</ref>


This unclaimed land can be obtainable by submitting a claim to the [[United Nations Convention on the Law of the Sea]], these claims can be based on geological evidence that continental shelves extend beyond their current maritime borders and into international waters.<ref name=":13" />
The warming environment presents challenges to local communities such as the [[Inuit]]. Hunting, which is a major way of survival for some small communities, will be changed with increasing temperatures.<ref name="adapting">http://www.ecology.ethz.ch/education/Resilience_Stuff/Berkes_and_Jolly_2001.pdf</ref> The reduction of [[sea ice]] will cause certain species populations to decline or even become extinct.<ref name="ClimateImpactAssessment" /> In good years, some communities are fully employed by the commercial harvest of certain animals.<ref name="adapting" /> The harvest of different animals fluctuates each year and with the rise of temperatures it is likely to continue changing and creating issues for Inuit hunters. Unsuspected changes in river and snow conditions will cause herds of animals, including reindeer, to change migration patterns, [[calving]] grounds, and [[forage]] availability.<ref name="ClimateImpactAssessment" />


Some overlapping claims are still pending resolution by international bodies, such as a large portion containing the [[North Pole|north pole]] that is both claimed by Denmark and Russia, with some parts of it also contested by Canada.<ref name=":13" /> Another example is that of the [[Northwest Passage]], globally recognized as international waters, but technically in Canadian waters.<ref name=":13" /> This has led to Canada wanting to limit the number of ships that can go through for environmental reasons but the United States disputes that they have the authority to do so, favouring unlimited passage of vessels.<ref name=":13" />
Governments and private industry have shown a growing interest in the Arctic.<ref>[http://www.popsci.com/science/article/2013-01/energy-development-arctic ''As The Earth Warms, The Lure Of The Arctic's Natural Resources Grows; Under the thawing Arctic ice lies bounty that could fill mouths, and pockets, around the world''] 02.01.2013 [[Popular Science]]</ref> Major new shipping lanes are opening up: [[Northern Sea Route|the northern sea route]] route had 34 passages in 2011 while the [[Northwest Passage]] had 22 traverses, more than any time in history.<ref name="beyers">http://www.aljazeera.com/indepth/opinion/2011/12/2011121913304370977.html</ref> Shipping companies may benefit from the shortened distance of these northern routes. Access to natural resources will increase, including valuable minerals and offshore oil and gas.<ref name="ClimateImpactAssessment" /><ref name="beyers" /> Finding and controlling these resources will be difficult with the continually moving ice.<ref name="ClimateImpactAssessment" /> Tourism may also increase as less sea ice will improve safety and accessibility to the Arctic.<ref name="ClimateImpactAssessment" />


===Navigation===
Other forms of transportation in the Arctic have seen negative impacts from the current warming, with some transportation routes and pipelines on land being disrupted by the melting of ice.<ref name="ClimateImpactAssessment" /> Many Arctic communities rely on frozen roadways to transport supplies and travel from area to area.<ref name="ClimateImpactAssessment" /> The changing landscape and unpredictability of weather is creating new challenges in the Arctic.<ref name="uofa">{{cite journal|last=Nuttall|first=Mark |author2=Pierre-André Forest |author3=Svein D. Mathiesen|title=Adaptation to Climate Change in The Arctic|journal=University of the Arctic|date=February 2008|pages=1–5|url=http://www.uarctic.org/Adaptation_to_Climate_Change_in_the_Arctic_FIN...}}</ref>
The [[Transpolar Sea Route]] is a future Arctic shipping lane running from the Atlantic Ocean to the Pacific Ocean across the center of the Arctic Ocean. The route is also sometimes called Trans-Arctic Route. In contrast to the [[Northeast Passage]] (including the [[Northern Sea Route]]) and the [[North-West Passage]] it largely avoids the territorial waters of Arctic states and lies in international high seas.<ref>{{cite journal|last1=Humpert|first1=Malte|last2=Raspotnik|first2=Andreas|title=The Future of Shipping Along the Transpolar Sea Route|journal=The Arctic Yearbook|year=2012|volume=1|issue=1|pages=281–307|url=http://www.arcticyearbook.com/images/Articles_2012/Humpert_and_Raspotnik.pdf|access-date=18 November 2015|archive-url=https://web.archive.org/web/20160121203700/http://www.arcticyearbook.com/images/Articles_2012/Humpert_and_Raspotnik.pdf|archive-date=21 January 2016|url-status=dead|df=dmy-all}}</ref>


Governments and private industry have shown a growing interest in the Arctic.<ref>{{cite web|url=http://www.popsci.com/science/article/2013-01/energy-development-arctic|title=As The Earth Warms, The Lure Of The Arctic's Natural Resources Grows|date=18 March 2019}}</ref> Major new shipping lanes are opening up: [[Northern Sea Route|the northern sea route]] had 34 passages in 2011 while the [[Northwest Passage]] had 22 traverses, more than any time in history.<ref>{{cite web|url=http://www.aljazeera.com/indepth/opinion/2011/12/2011121913304370977.html|title=Melting Arctic brings new opportunities|first=Michael|last=Byers|website=aljazeera.com}}</ref> Shipping companies may benefit from the shortened distance of these northern routes. Access to natural resources will increase, including valuable minerals and offshore oil and gas.<ref name="ClimateImpactAssessment" /> Finding and controlling these resources will be difficult with the continually moving ice.<ref name="ClimateImpactAssessment" /> Tourism may also increase as less sea ice will improve safety and accessibility to the Arctic.<ref name="ClimateImpactAssessment" />
==Research==


The melting of Arctic ice caps is likely to increase traffic in and the commercial viability of the Northern Sea Route. One study, for instance, projects, "remarkable shifts in trade flows between Asia and Europe, diversion of trade within Europe, heavy shipping traffic in the Arctic and a substantial drop in Suez traffic. Projected shifts in trade also imply substantial pressure on an already threatened Arctic ecosystem."<ref>{{Cite journal|last1=Bekkers|first1=Eddy|last2=Francois|first2=Joseph F.|last3=Rojas-Romagosa|first3=Hugo|date=2016-12-01|title=Melting Ice Caps and the Economic Impact of Opening the Northern Sea Route|journal=The Economic Journal|volume=128|issue=610|language=en|pages=1095–1127|doi=10.1111/ecoj.12460|s2cid=55162828|issn=1468-0297|url=https://boris.unibe.ch/89212/1/Melting%20Ice%20Caps.pdf}}</ref>
===National===
Individual countries within the Arctic zone, [[Canada]], [[Denmark]] ([[Greenland]]), [[Finland]], [[Iceland]], [[Norway]], [[Russia]], [[Sweden]], and the [[United States]] ([[Alaska]]) conduct independent research through a variety of organizations and agencies, public and private, such as Russia's [[Arctic and Antarctic Research Institute]]. Countries who do not have Arctic claims, but are close neighbors, conduct Arctic research as well, such as the [[Chinese Arctic and Antarctic Administration]] (CAA). The United States's [[National Oceanic and Atmospheric Administration]] (NOAA) produces an [[Arctic Report Card]] annually, containing [[Peer review|peer-review]]ed information on recent observations of environmental conditions in the Arctic relative to historical records.


===International===
=== Infrastructure ===
[[File:Hjort_2018_permafrost_infrastructure.png|thumb|Map of likely risk to infrastructure from permafrost thaw expected to occur by 2050.]]
International cooperative research between nations has become increasingly important:
{{excerpt|Permafrost#Infrastructure|paragraphs=1-4|file=no}}

=== Toxic pollution ===
{{excerpt|Permafrost#Release of toxic pollutants}}
{{excerpt|Greenland ice sheet#Geophysical and biochemical role of Greenland's meltwater|paragraph=3|file=no}}

=== Impacts on indigenous peoples ===
As climate change speeds up, it is having more and more of a direct impact on societies around the world. This is particularly true of people that live in the Arctic, where increases in temperature are occurring at faster rates than at other latitudes in the world, and where traditional ways of living, deeply connected with the natural arctic environment are at particular risk of environmental disruption caused by these changes.<ref name="ClimateImpactAssessment">{{cite book |last=Hassol |first=Susan Joy |url=https://archive.org/details/impactsofwarming0000hass |title=Impacts of a warming Arctic |publisher=Cambridge University Press |year=2004 |isbn=978-0-521-61778-9 |edition=Reprinted |location=Cambridge, UK |author-link=Susan Joy Hassol |url-access=registration}}</ref>

The warming of the atmosphere and ecological changes that come alongside it presents challenges to local communities such as the [[Inuit]]. Hunting, which is a major way of survival for some small communities, will be changed with increasing temperatures.<ref name="ethz.ch">{{cite journal |last1=Berkes |first1=Fikret |last2=Jolly |first2=Dyanna |title=Adapting to climate change: social-ecological resilience in a Canadian western Arctic community |url=https://www.ecologyandsociety.org/vol5/iss2/art18/print.pdf |journal=Conservation Ecology |volume=5 |issue=2 |date=2001}}</ref> The reduction of sea ice will cause certain species populations to decline or even become extinct.<ref name="ClimateImpactAssessment" /> Inuit communities are deeply reliant on seal hunting, which is dependent on sea ice flats, where seals are hunted.<ref name=":15">{{Cite journal|last=Farquhar|first=Samantha D.|date=2020-03-18|title=Inuit Seal Hunting in Canada: Emerging Narratives in an Old Controversy|url=http://dx.doi.org/10.14430/arctic69833|journal=Arctic|volume=73|issue=1|pages=13–19|doi=10.14430/arctic69833|s2cid=216308832|issn=1923-1245}}</ref>

Unsuspected changes in river and snow conditions will cause herds of animals, including reindeer, to change migration patterns, [[Birth#Cattle|calving]] grounds, and [[forage]] availability.<ref name="ClimateImpactAssessment" /> In good years, some communities are fully employed by the commercial harvest of certain animals.<ref name="ethz.ch" /> The harvest of different animals fluctuates each year and with the rise of temperatures it is likely to continue changing and creating issues for Inuit hunters, as unpredictability and disruption of ecological cycles further complicate life in these communities, which already face significant problems, such as Inuit communities being the poorest and most unemployed of North America.<ref name=":15" />

Other forms of transportation in the Arctic have seen negative impacts from the current warming, with some transportation routes and pipelines on land being disrupted by the melting of ice.<ref name="ClimateImpactAssessment" /> Many Arctic communities rely on frozen roadways to transport supplies and travel from area to area.<ref name="ClimateImpactAssessment" /> The changing landscape and unpredictability of weather is creating new challenges in the Arctic.<ref>{{Cite journal|last=Timonin|first=Andrey|date=2021|title=Climate Change in the Arctic and Future Directions for Adaptation: Views From Non-Arctic States|url=http://dx.doi.org/10.2139/ssrn.3802303|journal=SSRN Electronic Journal|doi=10.2139/ssrn.3802303|s2cid=233756936|issn=1556-5068}}</ref> Researchers have documented historical and current trails created by the Inuit in the [[Pan Inuit Trails Atlas]], finding that the change in sea ice formation and breakup has resulted in changes to the routes of trails created by the Inuit.<ref>{{Cite web |last=Rogers |first=Sarah |date=2014-06-13 |title=New online atlas tracks Nunavut's centuries-old Inuit trails |url=https://nunatsiaq.com/stories/article/65674new_online_atlas_tracks_centuries-old_inuit_trails/ |access-date=2021-05-19 |website=Nunatsiaq News |language=en}}</ref>

== Adaptation ==
=== Research ===
Individual countries within the Arctic zone, [[Canada]], Denmark (Greenland), [[Finland]], [[Iceland]], [[Norway]], [[Russia]], [[Sweden]], and the [[United States]] ([[Alaska]]) conduct independent research through a variety of organizations and agencies, public and private, such as Russia's [[Arctic and Antarctic Research Institute]]. Countries who do not have Arctic claims, but are close neighbors, conduct Arctic research as well, such as the [[Chinese Arctic and Antarctic Administration]] (CAA). The United States's [[National Oceanic and Atmospheric Administration]] (NOAA) produces an [[Arctic Report Card]] annually, containing [[Peer review|peer-review]]ed information on recent observations of environmental conditions in the Arctic relative to historical records.<ref name="Freedman_2017"/><ref name="ARC_2017"/> International cooperative research between nations has also become increasingly important:
* Arctic [[climate change]] is summarized by the [[Intergovernmental Panel on Climate Change]] (IPCC) in its series of [[IPCC#Assessment reports|Assessment Reports]] and the [[Arctic Climate Impact Assessment]].
* Arctic [[climate change]] is summarized by the [[Intergovernmental Panel on Climate Change]] (IPCC) in its series of [[IPCC#Assessment reports|Assessment Reports]] and the [[Arctic Climate Impact Assessment]].
* [[European Space Agency]] (ESA) launched [[CryoSat#CryoSat II|CryoSat-2]] on 8 April 2010. It provides satellite data on Arctic ice cover change rates.<ref name="esa">{{cite web | url = http://www.esa.int/esaLP/ESAOMH1VMOC_LPcryosat_0.html | title = ESA's ice mission CryoSat-2 | date = 11 September 2008 | publisher = esa.int | access-date = 15 June 2009}}</ref>
* [http://www.damocles-eu.org/about_damocles.shtml DAMOCLES] (Developing Arctic Modeling and Observing Capabilities for Long-term Environmental Studies): European integrated project "specifically concerned with the potential for a significantly reduced sea ice cover, and the impacts this might have on the environment and on human activities, both regionally and globally".
* [[European Space Agency]] (ESA) launched [[CryoSat#CryoSat II|CryoSat-2]] on 8 April 2010. It provides satellite data on Arctic ice cover change rates.<ref name="esa"/>
* [[International Arctic Buoy Program]]: deploys and maintains buoys that provide real-time position, pressure, temperature, and interpolated ice velocity data
* [[International Arctic Buoy Program]]: deploys and maintains buoys that provide real-time position, pressure, temperature, and interpolated ice velocity data
* [[International Arctic Research Center]]: Main participants are the United States and [[Japan]].
* [[International Arctic Research Center]]: Main participants are the United States and [[Japan]].
* [[International Arctic Science Committee]]: [[non-governmental]] [[organization]] (NGO) with diverse membership, including 18 countries from 3 continents.
* [[International Arctic Science Committee]]: [[non-governmental]] [[organization]] (NGO) with diverse membership, including 23 countries from 3 continents.
* 'Role of the Arctic Region', in conjunction with the [[International Polar Year]], was the focus of the second international conference on Global Change Research, held in [[Nynäshamn]], [[Sweden]], October 2007.<ref name="Global Environmental Change The Role of the Arctic Region"/><ref name="E SF, VR, FORMAS sign MOU to promote Global Environmental Change Research"/>
* 'Role of the Arctic Region', in conjunction with the [[International Polar Year]], was the focus of the second international conference on Global Change Research, held in [[Nynäshamn]], [[Sweden]], October 2007.<ref name="E SF, VR, FORMAS sign MOU to promote Global Environmental Change Research">{{cite web | first = Corinne | last = Wininger | url = http://www.innovations-report.com/html/reports/environment_sciences/report-93680.html | title = E SF, VR, FORMAS sign MOU to promote Global Environmental Change Research | publisher = innovations-report.de | date = 26 October 2007 | access-date = 26 November 2007}}</ref>
* SEARCH ([[Study of Environmental Arctic Change]]): Supported by the [[Arctic Research Office]], a division of the United States' [[National Oceanic and Atmospheric Administration]] (NOAA), and the [[Russian Academy of Sciences]].
* SEARCH ([[Study of Environmental Arctic Change]]): A research framework originally promoted by several US agencies; an international extension is ISAC (the International Study of Arctic Change<ref>{{cite web|url=http://www.arcticchange.org/|title=Arctic Change|website=International Study of Arctic Change}}</ref>).

The 2021 [[Arctic Monitoring and Assessment Programme]] (AMAP) report by an international team of more than 60 experts, scientists, and indigenous knowledge keepers from Arctic communities, was prepared from 2019 to 2021.<ref name="AMAP_2021">{{cite report |title=AMAP Arctic Climate Change Update 2021: Key Trends and Impacts |pages=viii + 148 |work=[[Arctic Monitoring and Assessment Programme]] (AMAP) |date=2021 |location= [[Tromsø, Norway]] |isbn=978-82-7971-201-5 }}</ref>{{rp|vii}} It is a follow-up report of the 2017 assessment, "Snow, Water, Ice and Permafrost in the Arctic" (SWIPA).<ref name="AMAP_2021"/>{{rp|vii}} The 2021 IPCC AR6 WG1 Technical Report confirmed that "[o]bserved and projected warming" were ""strongest in the Arctic".<ref name="IPCC_AR6_WG1_2021">{{Cite book |chapter= Technical Summary |last1=Arias |first1=Paola A. |last2 = Bellouin |first2= Nicolas |last3 = Coppola |first3 = Erika |last4 = Jones |first4 = Richard G. |last5 = Krinner |first5 = Gerhard |display-authors=4 |chapter-url= https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_TS.pdf |year= 2021 |title= IPCC AR6 WG1 |pages=76 }}</ref>{{rp|29}} According to an 11 August 2022 article published in ''[[Nature (journal)|Nature]]'', there have been numerous reports that the Arctic is warming from twice to three times as fast as the global average since 1979, but the co-authors cautioned that the recent report of the "four-fold Arctic warming ratio" was potentially an "extremely unlikely event".<ref name="Rantanen_Karpechko_20220811">{{Cite journal |last1=Rantanen |first1=Mika |last2=Karpechko |first2=Alexey Yu |last3=Lipponen |first3=Antti |last4=Nordling |first4=Kalle |last5=Hyvärinen |first5=Otto |last6=Ruosteenoja |first6=Kimmo |last7=Vihma |first7=Timo |last8=Laaksonen |first8=Ari |date=11 August 2022 |title=The Arctic has warmed nearly four times faster than the globe since 1979 |url=https://www.nature.com/articles/s43247-022-00498-3 |journal=Communications Earth & Environment |language=en |volume=3 |issue=1 |page=168 |doi=10.1038/s43247-022-00498-3 |bibcode=2022ComEE...3..168R |s2cid=251498876 |issn=2662-4435}}</ref> The annual mean Arctic Amplification (AA) index had "reached values exceeding four" from c. 2002 through 2022, according to a July 2022 article in ''[[Geophysical Research Letters]]''.<ref name="Chylek_20220716">{{cite journal |last1=Chylek |first1=Petr |last2=Folland |first2=Chris |last3=Klett |first3=James D. |last4=Wang |first4=Muyin |last5=Hengartner |first5=Nick |last6=Lesins |first6=Glen |last7=Dubey |first7=Manvendra K. |title=Annual Mean Arctic Amplification 1970–2020: Observed and Simulated by CMIP6 Climate Models |journal=Geophysical Research Letters |date=16 July 2022 |volume=49 |issue=13 |doi=10.1029/2022GL099371 |bibcode=2022GeoRL..4999371C |s2cid=250097858 |language=en |issn=0094-8276 }} via [[Wikipedia Library]] and EBSCOhost</ref>{{rp|1}}<ref name="LANL_202207">{{cite news |title=Arctic temperatures are increasing four times faster than global warming |url=https://phys.org/news/2022-07-arctic-temperatures-faster-global.html |access-date=18 July 2022 |work=Los Alamos National Laboratory |language=en}}</ref>

The 14 December 2021 16th Arctic Report Card produced by the United States's [[National Oceanic and Atmospheric Administration]] (NOAA) and released annually, examined the "interconnected physical, ecological and human components" of the circumpolar Arctic.<ref name="ARC_2021">{{cite report |url=http://www.arctic.noaa.gov/Report-Card/Report-Card-2021 |series=Arctic Report Card: Update for 2021 |title=Rapid and pronounced warming continues to drive the evolution of the Arctic environment |publisher=[[NOAA]]}}</ref><ref name="Druckenmiller_20211214">{{cite news |last1=Druckenmiller |first1=Matthew |last2=Thoman |first2=Rick |last3=Moon |first3=Twila |author-link3=Twila Moon |title=2021 Arctic Report Card reveals a (human) story of cascading disruptions, extreme events and global connections |url=https://theconversation.com/2021-arctic-report-card-reveals-a-human-story-of-cascading-disruptions-extreme-events-and-global-connections-172136 |access-date=30 January 2022 |agency=The Conversation |date=14 December 2021}}</ref> The report said that the 12 months between October 2020 and September 2021 were the "seventh warmest over Arctic land since the record began in 1900".<ref name="ARC_2021"/> The 2017 report said that the melting ice in the warming Arctic was unprecedented in the past 1500 years.<ref name="Freedman_2017">{{cite web |url=https://mashable.com/2017/12/12/arctic-ice-melt-warming-unprecedented-1500-years-report-card |title=Arctic warming, ice melt 'unprecedented' in at least the past 1,500 years |first=Andrew |last=Freedman |date=12 December 2017 |work=Mashable |access-date=13 December 2017}}</ref><ref name="ARC_2017">{{cite web |url=https://www.arctic.noaa.gov/Report-Card/Report-Card-2017 |title=Arctic Report Card: Update for 2017; Arctic shows no sign of returning to reliably frozen region of recent past decades |work=NOAA |access-date=13 December 2017}}</ref> NOAA's State of the Arctic Reports, starting in 2006, updates some of the records of the original 2004 and 2005 [[Arctic Climate Impact Assessment]] (ACIA) reports by the intergovernmental [[Arctic Council]] and the non-governmental [[International Arctic Science Committee]].<ref name="ACIA_20041015">{{cite report |work=[[Arctic Climate Impact Assessment]] (ACIA) |date=15 October 2004 |title=Impacts of a Warming Arctic: Arctic Climate Impact Assessment |isbn=0-521-61778-2 |series= Overview report |publisher=Cambridge University Press |pages=140}}</ref>

A 2022 [[United Nations Environment Programme]] (UNEP) report "Spreading Like Wildfire: The Rising Threat Of Extraordinary Landscape Fires" said that smoke from wildfires around the world created a [[positive feedback loop]] that is a contributing factor to Arctic melting.<ref name="UNEP_2022">{{cite report |work=United Nations Environment Programme (UNEP) |date=2022 |title=Spreading like Wildfire – The Rising Threat of Extraordinary Landscape Fires |series=A UNEP Rapid Response Assessment |location=[[Nairobi, Kenya]] |pages=122}}</ref><ref name="McGrath_20220319">{{cite news |last1=McGrath |first1=Matt |title=Climate change: Wildfire smoke linked to Arctic melting |url=https://www.bbc.com/news/science-environment-60782084 |access-date=20 March 2022 |agency=BBC |date=19 March 2022}}</ref> The [[List of heat waves|2020 Siberian heatwave]] was "associated with extensive burning in the Arctic Circle".<ref name="UNEP_2022"/>{{rp|36}} Report authors said that this extreme heat event was the first to demonstrate that it would have been "almost impossible" without anthropogenic emissions and climate change.<ref name="Ciavarella_2021">{{cite journal |last1=Ciavarella |first1=A. |last2=Cotterill |first2=D. |last3=Stott |first3=P. |title=Prolonged Siberian heat of 2020 almost impossible without human influence |journal=Climatic Change |volume=166 |number=9 |date=2021 |page=9 |doi=10.1007/s10584-021-03052-w|pmid=34720262 |pmc=8550097 |bibcode=2021ClCh..166....9C |s2cid=233875870 }}</ref><ref name="UNEP_2022"/>{{rp|36}}


==See also==
==See also==
{{portal|Global warming|Ecology|Environment}}
{{portal|Climate change|Ecology|Environment}}
{{div col}}
* [[Arctic Climate Impact Assessment]]
* [[Arctic Cooperation and Politics]]
* [[Arctic cooperation and politics]]
* [[Arctic haze]]
* [[Arctic haze]]
* [[Arctic sea ice ecology and history]]
* [[Arctic sea ice ecology and history]]
* [[Atlantification of the Arctic]]
* [[Atmospheric Brown Cloud]]
* [[Climate of the Arctic]]
* [[Climate of the Arctic]]
* [[Climate and vegetation interactions in the Arctic]]
* [[Long-term effects of global warming]]
* [[Northern Sea Route]]
* [[Northern Sea Route]]
*[[Climate change in Antarctica]]
* [[Ozone depletion and climate change]]
* [[Save the Arctic]]
{{div col end}}


==References==
==References==
{{reflist|30em|refs=
{{reflist|30em}}
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<ref name="abcnews">Borenstein, Seth. [http://abcnews.go.com/Technology/GlobalWarming/wireStory?id=7295178 "Obama Looking at Cooling Air to Fight Warming"], Associated Press via ABC News. (9 April 2009).</ref>
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<ref name="Arctic Largely Ice Free in Summer Within Ten Years?">{{cite web | url = http://news.nationalgeographic.com/news/2009/10/091015-arctic-ice-free-gone-global-warming.html | title = Arctic Largely Ice Free in Summer Within Ten Years? |author=Roach, John | date = 2009-10-15 | work = National Geographic News | accessdate = 2010-10-02 }}</ref>
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<ref name="bf00144504">{{cite journal|doi=10.1007/BF00144504 | volume=16 | title=Role of methane clathrates in past and future climates | year=1990 | journal=Climatic Change | pages=247–281 | last1 = MacDonald | first1 = Gordon J. | bibcode=1990ClCh...16..247M}}</ref>
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<ref name="catlinarcticsurvey">{{cite web|url=http://www.catlinarcticsurvey.com/science/sea-ice-thickness-2009/|title=Sea Ice Loss (2009) &#124; Catlin Arctic Survey|access-date=4 November 2012|archive-url=https://web.archive.org/web/20121026174904/http://www.catlinarcticsurvey.com/science/sea-ice-thickness-2009/|archive-date=26 October 2012|url-status=dead|df=dmy-all}}</ref>
<ref name="Arcticseaiceextent">{{cite web | url = http://nsidc.org/news/press/20091005_minimumpr.html | title = Arctic sea ice extent remains low; 2009 sees third-lowest mark | date = 2009-10-06 | publisher = NSIDC | accessdate = 2010-07-26}}</ref>


<ref name="Black">{{cite news | last = Black | first = Richard | url = http://news.bbc.co.uk/2/hi/science/nature/4315968.stm | title = Earth melting in the heat? | publisher = BBC News | date = 2007-05-18 | accessdate = 2008-01-03}}</ref>
<ref name="Cryosphere">{{cite web | url = http://nsidc.org/sotc/sea_ice.html | title = State of the Cryosphere, Is the Cryosphere sending signals about climate change? | date = 18 February 2010 | publisher = National Snow and Ice Data Center | access-date = 26 July 2010}}</ref>


<ref name="Geoengineering: a critical review">{{cite web | url = http://www.cosis.net/abstracts/EGU2008/09934/EGU2008-A-09934.pdf?PHPSESSID= | title = Geoengineering: a critical review | last = Lenton | first = T |author2=N. Vaughan | access-date = 23 February 2009}}</ref>
<ref name="Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Chapter 10">{{cite book | first = G.A., and others | last = Meehl | coauthors = Intergovernmental Panel on Climate Change Working Group I. | title = Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Chapter 10 | url = http://www.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-chapter10.pdf | publisher = [[Cambridge University Press]] | location = New York | year = 2007}}</ref>


<ref name="Global Outlook for Ice and Snow, Chapter 5: Ice in the Sea">{{cite web | url=http://www.unep.org/geo/geo_ice/PDF/GEO_C5_LowRes.pdf | title=Global Outlook for Ice and Snow, Chapter 5: Ice in the Sea | pages=75–76 | publisher=United Nations Environment Programme}}</ref>
<ref name="Climatology: threatened loss of the Greenland ice-sheet">{{cite journal |author1=Gregory JM |authorlink=Jonathan M. Gregory |author2=Huybrechts P |author3=Raper SC | title = Climatology: threatened loss of the Greenland ice-sheet | journal = [[Nature (journal)|Nature]] | volume = 428 | issue = 6983 | page = 616 |date=April 2004 | pmid = 15071587 | doi = 10.1038/428616a | url = http://homepages.vub.ac.be/~phuybrec/pdf/Nature.Green.2004.pdf |quote=The Greenland ice-sheet would melt faster in a warmer climate and is likely to be eliminated — except for residual glaciers in the mountains — if the annual average temperature in [[Greenland]] increases by more than about 3 [[°C]]. This would raise the global average sea-level by 7 metres over a period of 1000 years or more. We show here that concentrations of greenhouse gasses will probably have reached levels before the year 2100 that are sufficient to raise the temperature past this warming threshold.|bibcode = 2004Natur.428..616G }}</ref>


<ref name="greenhouse effect">{{cite web |url=http://www.ciesin.org/docs/003-074/003-074.html |title=Greenhouse Effect |access-date=4 November 2012}}</ref>
<ref name="Conference in Ilulissat, Greenland: Landmark political declaration on the future of the Arctic">{{cite news | title = Conference in Ilulissat, Greenland: Landmark political declaration on the future of the Arctic | url = http://www.um.dk/en/servicemenu/News/ConferenceInIlulissatGreenlandLandmarkPoliticalDeclarationOnTheFutureOfTheArctic.htm | publisher = Ministry of Foreign Affairs of Denmark | date = 2008-05-28 | accessdate = 2008-06-06 |archiveurl = http://web.archive.org/web/20080615022625/http://www.um.dk/en/servicemenu/News/ConferenceInIlulissatGreenlandLandmarkPoliticalDeclarationOnTheFutureOfTheArctic.htm <!-- Bot retrieved archive --> |archivedate = 2008-06-15}}</ref>


<ref name="Nature Geoscience">{{cite journal|doi=10.1038/ngeo338 | volume=1 | title=Attribution of polar warming to human influence | year=2008 | journal=Nature Geoscience | pages=750–754 | last1 = Gillett | first1 = Nathan P. | bibcode=2008NatGe...1..750G}}</ref>
<ref name="E SF, VR, FORMAS sign MOU to promote Global Environmental Change Research">{{cite web | first = Corinne | last = Wininger | url = http://www.innovations-report.com/html/reports/environment_sciences/report-93680.html | title = E SF, VR, FORMAS sign MOU to promote Global Environmental Change Research | publisher = innovations-report.de | date = 2007-10-26 | accessdate = 2007-11-26}}</ref>


<ref name="New warning on Arctic sea ice melt">{{cite news|title=New warning on Arctic sea ice melt|url=http://www.bbc.co.uk/news/science-environment-13002706 | first=Jonathan|last=Amos|date=8 April 2011|work=BBC News Online}}</ref>
<ref name="Eisenman2009">{{cite journal | last = Eisenman | first = Ian |author2=Wettlaufer, J.S. | year = 2009 | title = Nonlinear threshold behavior during the loss of Arctic sea ice | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 106 | issue = 1 | pages = 28–32 | doi = 10.1073/pnas.0806887106 | url = http://pantheon.yale.edu/%7Ejw378/articles/E&W_Bif_PNAS.pdf | pmid = 19109440 | pmc = 2629232 | bibcode = 2009PNAS..106...28E|arxiv = 0812.4777 }}</ref>
<ref name="NSIDC Sea Ice">{{cite web | publisher=NSIDC | url=http://www.nsidc.org/seaice/intro.html | title=All About Sea Ice | access-date=10 January 2009 | archive-url=https://web.archive.org/web/20090105023919/http://nsidc.org/seaice/intro.html | archive-date=5 January 2009 | url-status=dead | df=dmy-all }}</ref>


<ref name="esa">{{cite web | url = http://www.esa.int/esaLP/ESAOMH1VMOC_LPcryosat_0.html | title = ESA's ice mission CryoSat-2 | date = 2008-09-11 | publisher = esa.int | accessdate = 2009-06-15}}</ref>
<ref name="nsidc4">{{cite web |url=http://nsidc.org/data/seaice_index/images/daily_images/N_stddev_timeseries.png |title=Arctic Sea Ice Extent |access-date=4 November 2012}}</ref>


<ref name="On the reliability of simulated Arctic sea ice in Global Climate Models">{{cite journal | last = Eisenman | first = Ian | author2 = Untersteiner, Norbert | author3 = Wettlaufer, J.S. | year = 2007 | title = On the reliability of simulated Arctic sea ice in Global Climate Models | journal = [[Geophysical Research Letters]] | volume = 34 | issue = 10 | pages = L10501 | doi = 10.1029/2007GL029914 | url = http://pantheon.yale.edu/%7Ejw378/articles/EUW_revised_2007.pdf | bibcode = 2007GeoRL..3410501E }}{{Dead link|date=April 2019 |bot=InternetArchiveBot |fix-attempted=yes }} This is due to high sea ice thickness sensitivity to variations in downward thermal radiation, which are not reflected in outcomes of different models but seem to have been compensated by adaption of other parameters like albedo, short wave irradiation or ocean heat flux.</ref>
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<ref name="From 2 Satellites, the Big Picture on Ice Melt">{{cite news| url=http://green.blogs.nytimes.com/2012/02/08/from-2-satellites-the-big-picture-on-ice-melt/ | work=The New York Times | first=Joanna M. | last=Foster | title=From 2 Satellites, the Big Picture on Ice Melt | date=2012-02-08}}</ref>
<ref name="planetsave">{{cite web|url=http://planetsave.com/2012/09/21/arctic-sea-ice-may-disappear-within-4-years-according-to-one-of-the-worlds-leading-sea-ice-researchers|title=Arctic Sea Ice May Disappear Within 4 Years, According To One Of The World's Leading Sea Ice Researchers PlanetSave|date=21 September 2012}}</ref>


<ref name="Global Environmental Change The Role of the Arctic Region">{{cite web | first = Annakarin | last = Svenningsson | title = Global Environmental Change The Role of the Arctic Region | url = http://www.innovations-report.de/html/berichte/veranstaltungen/bericht-92741.html | publisher = innovations-report.de | date = 2007-10-14 | accessdate = 2007-10-16}}</ref>
<ref name="Sea Ice Declines Boost Arctic Phytoplankton Productivity">{{cite web| last = Kennedy| first = Caitlyn| title = Sea Ice Declines Boost Arctic Phytoplankton Productivity| work = ClimateWatch Magazine| publisher = [[NOAA]]| date = 1 December 2011| url = http://www.climatewatch.noaa.gov/article/2011/sea-ice-declines-boost-arctic-phytoplankton-productivity| access-date = 20 January 2012}}</ref>


<ref name="Shrub Takeover One Sign of Arctic Change">{{cite web| last = Lindsey| first = Rebecca| title = Shrub Takeover One Sign of Arctic Change| work = ClimateWatch Magazine| publisher = [[NOAA]]| date = 18 January 2012| url = http://www.climatewatch.noaa.gov/article/2012/shrub-takeover-one-sign-of-arctic-change| access-date = 19 January 2012}}</ref>
<ref name="guardian">{{cite news|author=Goldenberg S|date=2012-07-24 |url=http://www.guardian.co.uk/environment/2012/jul/24/greenland-ice-sheet-thaw-nasa |title=Greenland ice sheet melted at unprecedented rate during July &#124; Environment &#124; |publisher=The Guardian |format= |work= |accessdate=2012-11-04 |location=London}}</ref>


<ref name="smh">{{cite news| url=http://www.smh.com.au/environment/climate-change/staggering-arctic-ice-loss-smashes-melt-records-20120917-260zu.html | work=The Sydney Morning Herald | title='Staggering' Arctic ice loss smashes melt records}}</ref>
<ref name="Increasing rates of ice mass loss from the Greenland and Antarctic ice sheets revealed by GRACE">{{cite journal |author=Velicogna, I. |title=Increasing rates of ice mass loss from the Greenland and Antarctic ice sheets revealed by GRACE |journal=Geophysical Research Letters |volume=36 |pages=L19503 |year=2009 |doi=10.1029/2009GL040222 |bibcode = 2009GeoRL..3619503V }}</ref>


<ref name="Study: Circulation Shift May Be Melting Arctic Sea Ice">{{cite news | url = https://www.foxnews.com/story/study-circulation-shift-may-be-melting-arctic-sea-ice | title = Study: Circulation Shift May Be Melting Arctic Sea Ice | date = 24 November 2007 | publisher = Fox News | access-date = 27 November 2007}}</ref>
<ref name="ipcc">[[Intergovernmental Panel on Climate Change|IPCC]] [[AR4]] chapter 10 [http://www.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-chapter10.pdf] Table 10.7</ref>


<ref name="Thinning and volume loss of Arctic sea ice: 2003–2008">{{cite journal |author1=Kwok, R. |author2=Cunningham, G.F. |author3=Wensnahan, M. |author4=Rigor, I. |author5=Zwally, H.J. |author6=Yi D. |title=Thinning and volume loss of Arctic sea ice: 2003–2008 |journal=Journal of Geophysical Research |volume=114 |pages=C07005 |year=2009 |doi=10.1029/2009JC005312 |bibcode = 2009JGRC..11407005K }}</ref>
<ref name="NASA - Monitoring Sea Ice">{{cite web | url = http://earthobservatory.nasa.gov/Features/SeaIce/page2.php | title = Monitoring Sea Ice | date = 2010-07-25 | work = NASA Earth Observatory | publisher = NASA | accessdate = 2010-07-26}}</ref>


<ref name="Winds from Siberia reduce Arctic sea ice cover">{{cite news | url = http://www.forskningsradet.no/en/Newsarticle/Winds_from_Siberia_reduce_Arctic_sea_ice_cover/1253955174381 | title = Winds from Siberia reduce Arctic sea ice cover | date = 27 April 2010 | publisher = The [[Research Council of Norway]] | access-date = 27 April 2010}}</ref>
<ref name="nasa">{{cite web |url=http://www.nasa.gov/topics/earth/features/greenland-melt.html |title=NASA - Satellites See Unprecedented Greenland Ice Sheet Surface Melt |work= |accessdate=2012-11-04}}</ref>


<ref name="uofa">{{cite journal|last=Nuttall|first=Mark |author2=Pierre-André Forest |author3=Svein D. Mathiesen|title=Adaptation to Climate Change in The Arctic|journal=University of the Arctic|date=February 2008|pages=1–5|url=http://www.uarctic.org/Adaptation_to_Climate_Change_in_the_Arctic_FIN…|access-date=5 November 2012}}</ref>
<ref name="NASASeesArcticOcean">{{cite news | url = http://www.jpl.nasa.gov/news/news.cfm?release=2007-131 | title = NASA Sees Arctic Ocean Circulation Do an About-Face | date = 2007-11-13 | work = JPL News | publisher = JPL/[[California Institute of Technology]] | accessdate = 2010-07-26 | location = Pasadena}}</ref>
-->


===Works cited===
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|year= 2021

|title= Climate Change 2021: The Physical Science Basis
<ref name="ngeo467">{{Cite journal| first1 = J.| last2 = Hall| first2 = A.| first3 = X. | title = September sea-ice cover in the Arctic Ocean projected to vanish by 2100| journal = [[Nature Geoscience ]]| volume = 2| last3 = Qu | pages = 341| last1 = Boé| year = 2009 | doi = 10.1038/ngeo467|bibcode = 2009NatGe...2..341B | issue=5}}</ref>
|series= Contribution of Working Group I to the [[IPCC Sixth Assessment Report|Sixth Assessment Report]] of the Intergovernmental Panel on Climate Change

|display-editors= 4
<ref name="nsidc">{{cite web |url=http://nsidc.org/news/press/2007_seaiceminimum/20071001_pressrelease.html+ |title=NSIDC Arctic Sea Ice News Fall 2007 |format= |work= |accessdate=2012-11-04}}</ref>
|editor1-first= V. |editor1-last= Masson-Delmotte

|editor2-first= P. |editor2-last= Zhai
<ref name="nsidc1">{{cite web |url=http://nsidc.org/arcticseaicenews/2011/10/summer-2011-arctic-sea-ice-near-record-lows/ |title=Summer 2011: Arctic sea ice near record lows &#124; Arctic Sea Ice News and Analysis |format= |work= |accessdate=2012-11-04}}</ref>
|editor3-first= A. |editor3-last= Pirani

|editor4-first= S. L. |editor4-last= Connors
<ref name="nsidc2">{{cite web |url=http://nsidc.org/arcticseaicenews/2012/08/arctic-sea-ice-breaks-2007-record-extent/ |title=Arctic sea ice extent breaks 2007 record low &#124; Arctic Sea Ice News and Analysis |format= |work= |accessdate=2012-11-04}}</ref>
|editor5-first= C. |editor5-last= Péan

|editor6-first= S. |editor6-last= Berger
<ref name="nsidc3">{{cite web |url=http://nsidc.org/arcticseaicenews/ |title=Arctic Sea Ice News and Analysis &#124; Sea ice data updated daily with one-day lag |format= |work= |accessdate=2012-11-04}}</ref>
|editor7-first= N. |editor7-last= Caud

|editor8-first= Y. |editor8-last= Chen
<ref name="nytimes">{{cite news |author=Slivka K|url=http://www.nytimes.com/2012/07/25/science/earth/rare-burst-of-melting-seen-in-greenland-ice-sheet.html |title=Rare Burst of Melting Seen in Greenland Ice Sheet|date=2012-07-25|publisher=NYTimes.com |work= |accessdate=2012-11-04}}</ref>
|editor9-first= L. |editor9-last= Goldfarb

|editor10-first= M. I. |editor10-last= Gomis
<ref name="Ottera">{{cite journal | last = Butt | first = F. A. |author2=H. Drange |author3=A. Elverhoi |author4=O. H. Ottera |author5=A. Solheim | url = http://www.nersc.no/~oddho/Thesis/chapter3.pdf | title = The Sensitivity of the North Atlantic Arctic Climate System to Isostatic Elevation Changes, Freshwater and Solar Forcings | publisher = Quaternary Science Reviews | volume = 21 | pages = 1643–1660 | year = 2002 | oclc = 108566094 | issue = 14–15}}</ref>
|publisher= Cambridge University Press (In Press)

|place=
<ref name="overpeck">{{cite journal | last = Overpeck | first = Jonathan T. | url = http://atoc.colorado.edu/~dcn/reprints/Overpeck_etal_EOS2005.pdf | format = PDF | title = Arctic System on Trajectory to New, Seasonally Ice-Free State | journal = [[Eos (journal)|Eos, Transactions, American Geophysical Union]] | volume = 86 | issue = 34 | pages = 309–316 | date = 2005-08-23 | accessdate = 2007-12-24 | doi = 10.1029/2005EO340001 |displayauthors=3 |last2=Sturm |first2=Matthew |last3=Francis |first3=Jennifer A. |last4=Perovich |first4=Donald K. |last5=Serreze |first5=Mark C. |last6=Benner |first6=Ronald |last7=Carmack |first7=Eddy C. |last8=Chapin |first8=F. Stuart |last9=Gerlach |first9=S. Craig|bibcode = 2005EOSTr..86..309O }}</ref>
|isbn=

|url= https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_Full_Report.pdf
<ref name="planetsave">[http://planetsave.com/2012/09/21/arctic-sea-ice-may-disappear-within-4-years-according-to-one-of-the-worlds-leading-sea-ice-researchers Arctic Sea Ice May Disappear Within 4 Years, According To One Of The World’s Leading Sea Ice Researchers]</ref>
}}

** {{Cite book
<ref name="Protection For Polar Bears Urged By National Wildlife Federation">{{cite news | url = http://www.sciencedaily.com/releases/2008/04/080402210456.htm | title = Protection For Polar Bears Urged By National Wildlife Federation | date = 2008-04-03 | publisher = [[Science Daily]] | accessdate = 2008-04-03}}</ref>
|ref= {{harvid|IPCC AR6 WG1 Ch9|2021}}

|chapter=Chapter 9: Ocean, cryosphere, and sea level change
<ref name="Regional Sea Level Change">{{cite web | publisher = Intergovernmental Panel on Climate Change | url = http://www.grida.no/climate/ipcc_tar/wg1/432.htm#fig1116 | title = Regional Sea Level Change | format = Figure 11.16}}</ref>
| last1 = Fox-Kemper| first1 = Baylor| last2 = Hewitt| first2 = Helene T.| last3 = Xiao| first3 = Cunde| last4 = Aðalgeirsdóttir| first4 = Guðfinna| last5 = Drijfhout| first5 = Sybren S.| last6 = Edwards| first6 = Tamsin L.| last7 = Golledge| first7 = Nicholas R.

|chapter-url= https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_Chapter_09.pdf
<ref name="Remarkable">{{cite web | url = http://www.nasa.gov/vision/earth/environment/arctic_minimum.html | title = 'Remarkable' Drop in Arctic Sea Ice Raises Questions | last = Cole | first = Stephen | date = 2007-09-25 | publisher = [[NASA]] | accessdate = 2010-07-26}}</ref>
|display-authors=4

|title= {{Harvnb|IPCC AR6 WG1|2021}}
<ref name="Sea Ice Declines Boost Arctic Phytoplankton Productivity">{{cite web| last = Kennedy| first = Caitlyn| title = Sea Ice Declines Boost Arctic Phytoplankton Productivity| work = ClimateWatch Magazine| publisher = [[NOAA]]| date = 1 December 2011| url = http://www.climatewatch.noaa.gov/article/2011/sea-ice-declines-boost-arctic-phytoplankton-productivity| accessdate = 20 January 2012}}</ref>
|year=2021

<ref name="Shrub Takeover One Sign of Arctic Change">{{cite web| last = Lindsey| first = Rebecca| title = Shrub Takeover One Sign of Arctic Change| work = ClimateWatch Magazine| publisher = [[NOAA]]| date = 18 January 2012| url = http://www.climatewatch.noaa.gov/article/2012/shrub-takeover-one-sign-of-arctic-change| accessdate = 19 January 2012}}</ref>

<ref name="tar_wg2">{{cite book | first = James J. | last = McCarthy | coauthors = Intergovernmental Panel on Climate Change Working Group II. | title = Climate Change 2001: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Third Assessment Report of the Intergovernmental Panel on Climate Change | url = http://www.grida.no/climate/ipcc_tar/wg2/597.htm#16131 | publisher = [[Cambridge University Press]] | location = New York | isbn = 0-521-80768-9 | year = 2001 | accessdate = 2007-12-24}}</ref>

<ref name="The Arctic and Antarctic Oscillations and their Projected Changes Under Global Warming">{{cite journal | last = Fyfe | first = J.C |author2=G.J. Boer |author3=G.M. Flato | date = 1999-06-01 | title = The Arctic and Antarctic Oscillations and their Projected Changes Under Global Warming | journal = Geophysical Research Letters | volume = 26 | issue = 11 | pages = 1601–4 | doi = 10.1029/1999GL900317 | bibcode = 1999GeoRL..26.1601F}}</ref>

<ref name="The Ilulissat Declaration">{{cite web | url = http://www.um.dk/NR/rdonlyres/BE00B850-D278-4489-A6BE-6AE230415546/0/ArcticOceanConference.pdf | title = The Ilulissat Declaration | date = 2008-05-28 | publisher = [[Ministry of Foreign Affairs (Denmark)]] | accessdate = 2008-06-06}}</ref>

<ref name="ucar.edu">{{cite web | url = http://www.ucar.edu/news/releases/2008/permafrost.jsp | title = Permafrost Threatened by Rapid Retreat of Arctic Sea Ice, NCAR Study Finds – News Release | publisher = Ucar.edu | accessdate = 2010-07-26}}</ref>

<ref name="Uncertainty in Climate Model Projections of Arctic Sea Ice Decline: An Evaluation Relevant to Polar Bears">{{cite web | first = Eric | last = DeWeaver |author2=U.S. Geological Survey | url = http://www.usgs.gov/newsroom/special/polar_bears/docs/USGS_PolarBear_DeWeaver_GCM-Uncertainty.pdf | format = PDF | title = Uncertainty in Climate Model Projections of Arctic Sea Ice Decline: An Evaluation Relevant to Polar Bears | publisher = [[United States Department of the Interior]] | oclc = 183412441 | year = 2007}}</ref>

<ref name="Unprecedented Blooms of Ocean Plant Life">{{cite web| title =Unprecedented Blooms of Ocean Plant Life| work =NASA Science News| date =8 June 2012| url =http://science.nasa.gov/science-news/science-at-nasa/2012/08jun_arcticbloom/| accessdate = 12 June 2012}}</ref>

<ref name="Warming Is Seen as Wiping Out Most Polar Bears">{{cite news | first = John | last = Broder |author2=Revkin, Andrew C. | title = Warming Is Seen as Wiping Out Most Polar Bears | url = http://www.nytimes.com/2007/09/08/science/earth/08polar.html?_r=1&hp=&adxnnl=1&oref=slogin&adxnnlx=1190574637-aS0VOr2klykTSNwK91tiDg | publisher = The New York Times | date = 2007-07-08 | accessdate = 2007-09-23}}</ref>

<ref name="WashPost">{{cite news | first = Mike | last = Eckel | title = Russia: Tests Show Arctic Ridge Is Ours | url = http://www.washingtonpost.com/wp-dyn/content/article/2007/09/20/AR2007092001703.html |agency=Associated Press | publisher = The Washington Post | date = 2007-09-20 | accessdate = 2007-09-21}} {{Dead link | date = October 2010|bot=H3llBot}}</ref>

<ref name="Whither Arctic sea ice? A clear signal of decline regionally, seasonally and extending beyond the satellite record">{{cite journal | doi = 10.3189/172756407782871170 | last = Meier | first = W.N. |author2=J.C. Stroeve |author3=F. Fetterer | year = 2007 | title = Whither Arctic sea ice? A clear signal of decline regionally, seasonally and extending beyond the satellite record | journal = Annals of Glaciology | volume = 46 | pages = 428–434 | url = http://www.igsoc.org/annals/46/a46a251.pdf|bibcode = 2007AnGla..46..428M }}</ref>

<ref name="yale">{{cite web | first = Susan Q. | last = Stranahan | url = http://e360.yale.edu/content/feature.msp?id=2081 | title = Melting Arctic Ocean Raises Threat of ‘Methane Time Bomb’ | publisher = E360.yale.edu | accessdate = 2010-07-26}}</ref>

<ref name="zhangrothrock1">{{cite journal|author=Zhang, Jinlun and D.A. Rothrock|title=Modeling global sea ice with a thickness and enthalpy distribution model in generalized curvilinear coordinates|journal=Mon. Wea. Rev.|volume=131|issue=5|pages=681–697|year=2003|doi=10.1175/1520-0493(2003)131<0845:MGSIWA>2.0.CO;2}}</ref>

<ref name="greenhouse effect">{{cite web |url=http://www.ciesin.org/docs/003-074/003-074.html |title=Greenhouse Effect |work= |accessdate=2012-11-04}}</ref>

<ref name="ClimateImpactAssessment">{{cite book|last=Hassol]|first=Arctic Climate Impact Assessment ; author, Susan Joy|title=Impacts of a warming Arctic|year=2004|publisher=Cambridge University Press|location=Cambridge, U.K.|isbn=978-0-521-61778-9|edition=Reprinted.}}</ref>

<ref name="adapting">{{cite journal|title=Adapting to Climate Change: Social-Ecological Resilience in a Canadian Western Arctic Community|author=Berkes F, Jolly D |url=http://www.ecology.ethz.ch/education/Resilience_Stuff/Berkes_and_Jolly_2001.pdf|format=pdf |accessdate=2012-11-05|journal=Conservation Ecology|volume=5 |issue=2|pages=18|year=2001}}</ref>

<ref name="beyers">{{cite web |url=http://www.aljazeera.com/indepth/opinion/2011/12/2011121913304370977.html |title=Melting Arctic brings new opportunities - Opinion - Al Jazeera English |work= |accessdate=2012-11-04}}</ref>

<ref name="uofa">{{cite journal|last=Nuttall|first=Mark |author2=Pierre-André Forest |author3=Svein D. Mathiesen|title=Adaptation to Climate Change in The Arctic|journal=University of the Arctic|date=February 2008|pages=1–5|url=http://www.uarctic.org/Adaptation_to_Climate_Change_in_the_Arctic_FIN…|accessdate=2012-11-05}}</ref>
}}
}}
* {{citation
| year=2013
| author=IPCC AR5 WG1
| editor=Stocker, T.F.| title=Climate Change 2013: The Physical Science Basis. Working Group 1 (WG1) Contribution to the Intergovernmental Panel on Climate Change (IPCC) 5th Assessment Report (AR5)
| url=http://archive.ipcc.ch/report/ar5/wg1/
| publisher=Cambridge University Press
|display-editors=etal}}. [http://www.climatechange2013.org/ Climate Change 2013 Working Group 1 website.]


==Further reading==
<!-- UNUSED REFS


*{{cite web | title=Black Carbon and Methane | website=Arctic Council | date=9 Jul 2018 | url=https://arctic-council.org/about/task-expert/egbcm/ | access-date=6 Nov 2023}} <!--quote: Despite generating just ten percent of global black carbon emissions, Arctic States are responsible for 30% of black carbon’s warming effects in the Arctic, due to the greater warming impact of local emission sources ... In developing recommendations for its Summary Reports, the Expert Group sought to identify a focused menu of priority actions from which Arctic States could select – based on their national circumstances and recognizing the need for economic development of Arctic communities. These priority actions include recommendations on how to reduce emissions from: mobile and stationary diesel-powered sources; oil and gas methane leakage, venting and flaring; residential combustion; solid waste disposal; agriculture and animal husbandry; management of wildfires.-->
<ref name="abcnews">Borenstein, Seth. [http://abcnews.go.com/Technology/GlobalWarming/wireStory?id=7295178 "Obama Looking at Cooling Air to Fight Warming"], Associated Press via ABC News. (2009-04-09).</ref>
*{{cite web | last=Hersher | first=Rebecca | title=The Arctic is heating up nearly four times faster than the whole planet, study finds | website=NPR | date=11 Aug 2022 | url=https://www.npr.org/2022/08/11/1116608415/the-arctic-is-heating-up-nearly-four-times-faster-than-the-rest-of-earth-study-f | access-date=6 Nov 2023}}

<ref name="BBCNews">{{cite news | last = Black | first = Richard | title = 'Drastic' shrinkage in Arctic ice | url = http://news.bbc.co.uk/2/hi/science/nature/5344208.stm | publisher = BBC News | work = Science/Nature | date = 2006-09-14 | accessdate = 2007-09-16}}</ref>

<ref name="bf00144504">{{cite doi|10.1007/BF00144504}}</ref>

<ref name="catlinarcticsurvey">{{cite web |url=http://www.catlinarcticsurvey.com/science/sea-ice-thickness-2009/ |title=Sea Ice Loss (2009) &#124; Catlin Arctic Survey |format= |work= |accessdate=2012-11-04}}</ref>

<ref name="Cryosphere">{{cite web | url = http://nsidc.org/sotc/sea_ice.html | title = State of the Cryosphere, Is the Cryosphere sending signals about climate change? | date = 2010-02-18 | publisher = National Snow and Ice Data Center | accessdate = 2010-07-26}}</ref>

<ref name="Geoengineering: a critical review">{{cite web | url = http://www.cosis.net/abstracts/EGU2008/09934/EGU2008-A-09934.pdf?PHPSESSID= | title = Geoengineering: a critical review | last = Lenton | first = T |author2=N. Vaughan | accessdate = 2009-02-23}}</ref>

<ref name="Global Outlook for Ice and Snow, Chapter 5: Ice in the Sea">{{cite web | url=http://www.unep.org/geo/geo_ice/PDF/GEO_C5_LowRes.pdf | title=Global Outlook for Ice and Snow, Chapter 5: Ice in the Sea | pages=75–76 | publisher=United Nations Environment Programme}}</ref>

<ref name="Nature Geoscience">{{cite doi|10.1038/ngeo338}}</ref>

<ref name="NSIDC Sea Ice">{{cite web | publisher=NSIDC | url=http://www.nsidc.org/seaice/intro.html | title=All About Sea Ice | accessdate=2009-01-10}}</ref>

<ref name="nsidc4">{{cite web |url=http://nsidc.org/data/seaice_index/images/daily_images/N_stddev_timeseries.png |title=Arctic Sea Ice Extent |format= |work= |accessdate=2012-11-04}}</ref>

<ref name="On the reliability of simulated Arctic sea ice in Global Climate Models">{{cite journal | last = Eisenman | first = Ian |author2=Untersteiner, Norbert |author3=Wettlaufer, J.S.| year = 2007 | title = On the reliability of simulated Arctic sea ice in Global Climate Models | journal = [[Geophysical Research Letters]] | volume = 34 | issue = 10 | pages = L10501 | doi = 10.1029/2007GL029914 | url = http://pantheon.yale.edu/%7Ejw378/articles/EUW_revised_2007.pdf | bibcode = 2007GeoRL..3410501E }} This is due to high sea ice thickness sensitivity to variations in downward thermal radiation, which are not reflected in outcomes of different models but seem to have been compensated by adaption of other parameters like albedo, short wave irradiation or ocean heat flux.</ref>

<ref name="smh">{{cite news| url=http://www.smh.com.au/environment/climate-change/staggering-arctic-ice-loss-smashes-melt-records-20120917-260zu.html | work=The Sydney Morning Herald | title='Staggering' Arctic ice loss smashes melt records}}</ref>

<ref name="Study: Circulation Shift May Be Melting Arctic Sea Ice">{{cite news | url = http://www.foxnews.com/story/0,2933,311753,00.html | title = Study: Circulation Shift May Be Melting Arctic Sea Ice | date = 2007-11-24 | publisher = Fox News | accessdate = 2007-11-27}}</ref>

<ref name="Thinning and volume loss of Arctic sea ice: 2003–2008">{{cite journal |author=Kwok, R.; Cunningham, G.F.; Wensnahan, M.; Rigor, I.; Zwally, H.J.; Yi D. |title=Thinning and volume loss of Arctic sea ice: 2003–2008 |journal=Journal of Geophysical Research |volume=114 |pages=C07005 |year=2009 |doi=10.1029/2009JC005312 |bibcode = 2009JGRC..11407005K }}</ref>

<ref name="Winds from Siberia reduce Arctic sea ice cover">{{cite news | url = http://www.forskningsradet.no/en/Newsarticle/Winds_from_Siberia_reduce_Arctic_sea_ice_cover/1253955174381 | title = Winds from Siberia reduce Arctic sea ice cover | date = 2010-04-27 | publisher = The [[Research Council of Norway]] | accessdate = 2010-04-27}}</ref>

-->

==Further reading==
{{refbegin}}
* {{cite journal | title = International – The Arctic – Drawing lines in melting ice | journal = [[The Economist]] | volume = 384 | year = 2007 | page = 47 | oclc = 166288931 | issue = 8542 | url = http://www.economist.com/world/international/displaystory.cfm?story_id=9660012}}
* {{cite journal | author=Harriss R|title=The Arctic: Past or Prologue?|journal=Environment: Science and Policy for Sustainable Development|year=2012|url=http://www.environmentmagazine.org/Archives/Back%20Issues/2012/September-October%202012/arctic_full.html|accessdate=2012-10-15}}
* {{cite journal | last = Miller | first = PA |author2=SW Laxon |author3=DL Feltham | year = 2007 | title = Consistent and Contrasting Decadal Arctic Sea Ice Thickness Predictions from a Highly Optimized Sea Ice Model | journal = Journal of Geophysical Research | volume = 112 | pages = C07020–2 | doi = 10.1029/2006JC003855 | oclc = 170040287 | issue = C7 | bibcode = 2007JGRC..11207020M}}
* {{cite journal | last = Oyugi | first = JO |author2=H Qiu |author3=D. Safronetz | year = 2007 | title = Global Warming and the Emergence of Ancient Pathogens in Canada's Arctic Regions | journal = Medical Hypotheses | volume = 68 | page = 709 | oclc = 110702580 | doi = 10.1016/j.mehy.2006.09.006 | pmid = 17064851 | issue = 3}}
* {{cite journal | last = Schiermeier | first = Q | year = 2007 | title = Polar Research: the New Face of the Arctic | journal = Nature | volume = 446 | pages = 133–135 | oclc = 110702580 | doi = 10.1038/446133a | pmid = 17344829 | issue = 7132|bibcode = 2007Natur.446..133S }}
* {{cite journal | last = Stroeve | first = J |author2=MM Holland |author3=W Meier |author4=T Scambos |author5=M Serreze | year = 2007 | title = The Cryosphere – L09501 – Arctic Sea Ice Decline: Faster Than Forecast | journal = Geophysical Research Letters | volume = 34 | pages = n.p. | doi = 10.1029/2007GL029703 | oclc = 110702580 | issue = 9 | bibcode = 2007GeoRL..3409501S}}
* {{cite journal | last = Xu | first = J |author2=G Wang |author3=B Zhang | year = 2007 | title = Climate Change Comparison between Arctic and Other Areas in the Northern Hemisphere Since the Last Interstade | journal = Journal of Geographical Sciences | volume = 17 | pages = 43–50 | oclc = 91622949 | doi = 10.1007/s11442-007-0043-8 | issue = 1}}
{{refend}}


==External links==
==External links==
* [http://www.arctic.noaa.gov/detect/ Arctic Change website, in near-realtime]
* [http://www.arctic.noaa.gov/ Arctic Change website, in near-realtime]
* [http://iabp.apl.washington.edu/ International Arctic Buoy Programme]
* [http://www.iarc.uaf.edu/ International Arctic Research Center]
* [http://www.arcticportal.org/iasc/ International Arctic Science Committee]
* [http://www.panda.org/about_wwf/where_we_work/europe/what_we_do/arctic/index.cfm World Wildlife Foundation's International Arctic Programme]
* [http://instaar.colorado.edu/meetings/AW2008/index.html 38th Annual International Arctic Workshop 2008]
* [http://www.geus.dk/publications/bull/nr10/nr10_p61-64.pdf Radical past climatic changes in the Arctic Ocean and a geophysical signature of the Lomonosov Ridge north of Greenland]
* [http://nsidc.org/arcticseaicenews/ Arctic Sea Ice News & Analysis]
* [http://nsidc.org/arcticseaicenews/ Arctic Sea Ice News & Analysis]
* {{Cite news |last=Smith |first=Duane |date=2007 |title=Climate Change In The Arctic: An Inuit Reality |work=[[UN Chronicle]] |url=https://www.un.org/en/chronicle/article/climate-change-arctic-inuit-reality}}
* [http://www.arctic.io/satellite The Arctic ice sheet], satellite map with daily updates.
* [http://www.arctic.io/#home The Arctic ice sheet], satellite map with daily updates.
* [[NOAA]]: [http://www.arctic.noaa.gov Arctic Theme Page] – A comprehensive resource focused on the Arctic
* [[NOAA]]: [http://www.arctic.noaa.gov Arctic Theme Page] – A comprehensive resource focused on the Arctic
* {{cite report |url=http://www.arctic.noaa.gov/Report-Card/Report-Card-2016 |series=Arctic Report Card: Update for 2016 |title=Persistent warming trend and loss of sea ice are triggering extensive Arctic changes |publisher=[[NOAA]]}}
* [[NOAA]]: [http://www.arctic.noaa.gov/future The Future of Arctic Climate and Global Impacts]
* {{cite report |url=http://www.arctic.noaa.gov/Report-Card/Report-Card-2021 |series=Arctic Report Card: Update for 2021 |title=Rapid and pronounced warming continues to drive the evolution of the Arctic environment |publisher=[[NOAA]]}}
*[https://origins.osu.edu/article/pollution-climate-change-killing-arctic?language_content_entity=en Killing the Arctic] Origins: Current Events in Historical Perspective (October 2020), by John McCannon


{{Arctic topics}}
{{Arctic topics}}
{{Climate change regions|state=expanded}}
{{Global warming}}


{{DEFAULTSORT:Arctic Shrinkage}}
[[Category:Arctic Ocean|G]]
[[Category:Arctic Ocean]]
[[Category:Arctic research]]
[[Category:Shipping routes]]
[[Category:Effects of climate change]]
[[Category:Effects of global warming]]
[[Category:Environment of the Arctic]]
[[Category:Environment of the Arctic]]
[[Category:Sea ice]]
[[Category:Sea ice|Arctic Sea, Global warming]]
[[Category:Sea lanes|Arctic Sea, Global warming]]
[[Category:Regional effects of climate change]]
[[Category:Climate change by country and region|Arctic]]

Latest revision as of 09:55, 22 December 2024

Average decadal extent and area of the Arctic Ocean sea ice since 1979.
July 2012 melting event in Greenland
2020 Siberia heatwave
Coastal erosion caused by permafrost thaw in Alaska
Arctic sea ice extent and area have declined every decade since the start of satellite observations in 1979: Greenland ice sheet had experienced a "massive melting event" in 2012, which reoccurred in 2019 and 2021; Satellite image of the extremely anomalous 2020 Siberian heatwave; Permafrost thaw is leading to severe erosion, like in this coastal location in Alaska

Due to climate change in the Arctic, this polar region is expected to become "profoundly different" by 2050.[1]: 2321  The speed of change is "among the highest in the world",[1]: 2321  with the rate of warming being 3-4 times faster than the global average.[2][3][4][5] This warming has already resulted in the profound Arctic sea ice decline, the accelerating melting of the Greenland ice sheet and the thawing of the permafrost landscape.[1]: 2321 [6] These ongoing transformations are expected to be irreversible for centuries or even millennia.[1]: 2321 

Natural life in the Arctic is affected greatly. As the tundra warms, its soil becomes more hospitable to earthworms and larger plants,[7] and the boreal forests spread to the north - yet this also makes the landscape more prone to wildfires, which take longer to recover from than in the other regions. Beavers also take advantage of this warming to colonize the Arctic rivers, and their dams contributing to methane emissions due to the increase in stagnant waters.[8] The Arctic Ocean has experienced a large increase in the marine primary production as warmer waters and less shade from sea ice benefit phytoplankton.[1]: 2326 [9] At the same time, it is already less alkaline than the rest of the global ocean, so ocean acidification caused by the increasing CO2 concentrations is more severe, threatening some forms of zooplankton such as pteropods.[1]: 2328 

The Arctic Ocean is expected to see its first ice-free events in the near future - most likely before 2050, and potentially in the late 2020s or early 2030s.[10] This would have no precedent in the last 700,000 years.[11][12] Some sea ice regrows every Arctic winter, but such events are expected to occur more and more frequently as the warming increases. This has great implications for the fauna species which are dependent on sea ice, such as polar bears. For humans, trade routes across the ocean will become more convenient. Yet, multiple countries have infrastructure in the Arctic which is worth billions of dollars, and it is threatened with collapse as the underlying permafrost thaws. The Arctic's indigenous people have a long relationship with its icy conditions, and face the loss of their cultural heritage.

Further, there are numerous implications which go beyond the Arctic region. Sea ice loss not only enhances warming in the Arctic but also adds to global temperature increase through the ice-albedo feedback. Permafrost thaw results in emissions of CO2 and methane that are comparable to those of major countries. Greenland melting is a significant contributor to global sea level rise. If the warming exceeds - or thereabouts, there is a significant risk of the entire ice sheet being lost over an estimated 10,000 years, adding up to global sea levels. Warming in the Arctic may affect the stability of the jet stream, and thus the extreme weather events in midlatitude regions, but there is only "low confidence" in that hypothesis.

Impacts on the physical environment

[edit]

Warming

[edit]
The image above shows where average air temperatures (October 2010 – September 2011) were up to 2 degrees Celsius above (red) or below (blue) the long-term average (1981–2010).

The period of 1995–2005 was the warmest decade in the Arctic since at least the 17th century, with temperatures 2 °C (3.6 °F) above the 1951–1990 average.[13] Alaska and western Canada's temperature rose by 3 to 4 °C (5.40 to 7.20 °F) during that period.[14] 2013 research has shown that temperatures in the region haven't been as high as they currently are since at least 44,000 years ago and perhaps as long as 120,000 years ago.[15][16] Since 2013, Arctic annual mean surface air temperature (SAT) has been at least 1 °C (1.8 °F) warmer than the 1981-2010 mean.

In 2016, there were extreme anomalies from January to February with the temperature in the Arctic being estimated to be between 4–5.8 °C (7.2–10.4 °F) more than it was between 1981 and 2010.[17] In 2020, mean SAT was 1.9 °C (3.4 °F) warmer than the 1981–2010 average.[18] On 20 June 2020, for the first time, a temperature measurement was made inside the Arctic Circle of 38 °C, more than 100 °F. This kind of weather was expected in the region only by 2100. In March, April and May the average temperature in the Arctic was 10 °C (18.0 °F) higher than normal.[19][20] This heat wave, without human – induced warming, could happen only one time in 80,000 years, according to an attribution study published in July 2020. It is the strongest link of a weather event to anthropogenic climate change that had been ever found, for now.[21]

Arctic amplification

[edit]
Potential regional warming caused by the loss of all land ice outside of East Antarctica, and by the disappearance of Arctic sea ice every year starting from June. While plausible, consistent sea ice loss would likely require relatively high warming, and the loss of all ice in Greenland would require multiple millennia.

Snow– and ice–albedo feedback have a substantial effect on regional temperatures. In particular, the presence of ice cover and sea ice makes the North Pole and the South Pole colder than they would have been without it.[22] Consequently, recent Arctic sea ice decline is one of the primary factors behind the Arctic warming nearly four times faster than the global average since 1979 (the year when continuous satellite readings of the Arctic sea ice began), in a phenomenon known as Arctic amplification.[23]

Modelling studies show that strong Arctic amplification only occurs during the months when significant sea ice loss occurs, and that it largely disappears when the simulated ice cover is held fixed.[24] Conversely, the high stability of ice cover in Antarctica, where the thickness of the East Antarctic ice sheet allows it to rise nearly 4 km above the sea level, means that this continent has experienced very little net warming over the past seven decades, most of which was concentrated in West Antarctica.[25][26][27] Ice loss in the Antarctic and its contribution to sea level rise is instead driven overwhelmingly by the warming of the Southern Ocean, which had absorbed 35–43% of the total heat taken up by all oceans between 1970 and 2017.[28]

Ice–albedo feedback also has a smaller, but still notable effect on the global temperatures. Arctic sea ice decline between 1979 and 2011 is estimated to have been responsible for 0.21 watts per square meter (W/m2) of radiative forcing, which is equivalent to a quarter of radiative forcing from CO2[29] increases over the same period. When compared to cumulative increases in greenhouse gas radiative forcing since the start of the Industrial Revolution, it is equivalent to the estimated 2019 radiative forcing from nitrous oxide (0.21 W/m2), nearly half of 2019 radiative forcing from methane (0.54 W/m2) and 10% of the cumulative CO2 increase (2.16 W/m2).[30] Between 1992 and 2015, this effect was partly offset by the growth in sea ice cover around Antarctica, which produced cooling of about 0.06 W/m2 per decade. However, Antarctic sea ice had also begun to decline afterwards, and the combined role of changes in ice cover between 1992 and 2018 is equivalent to 10% of all the anthropogenic greenhouse gas emissions.[31]
The dark ocean surface reflects only 6 percent of incoming solar radiation, while sea ice reflects 50 to 70 percent.[32]

The Arctic was historically described as warming twice as fast as the global average,[33] but this estimate was based on older observations which missed the more recent acceleration. By 2021, enough data was available to show that the Arctic had warmed three times as fast as the globe - 3.1°C between 1971 and 2019, as opposed to the global warming of 1°C over the same period.[34] Moreover, this estimate defines the Arctic as everything above 60th parallel north, or a full third of the Northern Hemisphere: in 2021–2022, it was found that since 1979, the warming within the Arctic Circle itself (above the 66th parallel) has been nearly four times faster than the global average.[35][36] Within the Arctic Circle itself, even greater Arctic amplification occurs in the Barents Sea area, with hotspots around West Spitsbergen Current: weather stations located on its path record decadal warming up to seven times faster than the global average.[37][38] This has fuelled concerns that unlike the rest of the Arctic sea ice, ice cover in the Barents Sea may permanently disappear even around 1.5 degrees of global warming.[39][40]

The acceleration of Arctic amplification has not been linear: a 2022 analysis found that it occurred in two sharp steps, with the former around 1986, and the latter after 2000.[41] The first acceleration is attributed to the increase in anthropogenic radiative forcing in the region, which is in turn likely connected to the reductions in stratospheric sulfur aerosols pollution in Europe in the 1980s in order to combat acid rain. Since sulphate aerosols have a cooling effect, their absence is likely to have increased Arctic temperatures by up to 0.5 degrees Celsius.[42][43] The second acceleration has no known cause,[34] which is why it did not show up in any climate models. It is likely to be an example of multi-decadal natural variability, like the suggested link between Arctic temperatures and Atlantic Multi-decadal Oscillation (AMO),[44] in which case it can be expected to reverse in the future. However, even the first increase in Arctic amplification was only accurately simulated by a fraction of the current CMIP6 models.[41]

Precipitation

[edit]

An observed impact of climate change is a strong increase in the number of lightnings in the Arctic. Lightnings increase the risk for wildfires.[45] Some research suggests that globally, a warming greater than 1.5 °C (2.7 °F) over the preindustrial level could change the type of precipitation in the Arctic from snow to rain in summer and autumn.[46]

Cryosphere loss

[edit]
On average, climate change has lowered the thickness of land ice with every year, and reduced the extent of sea ice cover.[47]

Sea ice

[edit]
1870–2009 Northern Hemisphere sea ice extent in million square kilometers. Blue shading indicates the pre-satellite era; data then is less reliable.

Sea ice in the Arctic region has declined in recent decades in area and volume due to climate change. It has been melting more in summer than it refreezes in winter. Global warming, caused by greenhouse gas forcing is responsible for the decline in Arctic sea ice. The decline of sea ice in the Arctic has been accelerating during the early twenty-first century, with a decline rate of 4.7% per decade (it has declined over 50% since the first satellite records).[48][49][50] Summertime sea ice will likely cease to exist sometime during the 21st century.[51]

The region is at its warmest in at least 4,000 years.[52] Furthermore, the Arctic-wide melt season has lengthened at a rate of five days per decade (from 1979 to 2013), dominated by a later autumn freeze-up.[53] The IPCC Sixth Assessment Report (2021) stated that Arctic sea ice area will likely drop below 1 million km2 in at least some Septembers before 2050.[54]: 1249  In September 2020, the US National Snow and Ice Data Center reported that the Arctic sea ice in 2020 had melted to an extent of 3.74 million km2, its second-smallest extent since records began in 1979.[55] Earth lost 28 trillion tonnes of ice between 1994 and 2017, with Arctic sea ice accounting for 7.6 trillion tonnes of this loss. The rate of ice loss has risen by 57% since the 1990s.[56]

Greenland ice sheet

[edit]
2023 projections of how much the Greenland ice sheet may shrink from its present extent by the year 2300 under the worst possible climate change scenario (upper half) and of how much faster its remaining ice will be flowing in that case (lower half)

Greenland has had major glaciers and ice caps for at least 18 million years,[57] but a single ice sheet first covered most of the island some 2.6 million years ago.[58] Since then, it has both grown[59][60] and contracted significantly.[61][62][63] The oldest known ice on Greenland is about 1 million years old.[64] Due to anthropogenic greenhouse gas emissions, the ice sheet is now the warmest it has been in the past 1000 years,[65] and is losing ice at the fastest rate in at least the past 12,000 years.[66]

Every summer, parts of the surface melt and ice cliffs calve into the sea. Normally the ice sheet would be replenished by winter snowfall,[67] but due to global warming the ice sheet is melting two to five times faster than before 1850,[68] and snowfall has not kept up since 1996.[69] If the Paris Agreement goal of staying below 2 °C (3.6 °F) is achieved, melting of Greenland ice alone would still add around 6 cm (2+12 in) to global sea level rise by the end of the century. If there are no reductions in emissions, melting would add around 13 cm (5 in) by 2100,[70]: 1302  with a worst-case of about 33 cm (13 in).[71] For comparison, melting has so far contributed 1.4 cm (12 in) since 1972,[72] while sea level rise from all sources was 15–25 cm (6–10 in) between 1901 and 2018.[73]: 5 

If all 2,900,000 cubic kilometres (696,000 cu mi) of the ice sheet were to melt, it would increase global sea levels by ~7.4 m (24 ft).[74] Global warming between 1.7 °C (3.1 °F) and 2.3 °C (4.1 °F) would likely make this melting inevitable.[75] However, 1.5 °C (2.7 °F) would still cause ice loss equivalent to 1.4 m (4+12 ft) of sea level rise,[76] and more ice will be lost if the temperatures exceed that level before declining.[75] If global temperatures continue to rise, the ice sheet will likely disappear within 10,000 years.[77][78] At very high warming, its future lifetime goes down to around 1,000 years.[71]

Biological environment

[edit]

Impacts on Arctic flora

[edit]
Western Hemisphere Arctic Vegetation Index Trend
Eastern Hemisphere Vegetation Index Trend

Climate change is expected to have a strong effect on the Arctic's flora, some of which is already being seen.[79] NASA and NOAA have continuously monitored Arctic vegetation with satellite instruments such as Moderate Resolution Imaging Spectroradiometer (MODIS) and Advanced very-high-resolution radiometer (AVHRR).[80] Their data allows scientists to calculate so-called "Arctic greening" and "Arctic browning".[81] From 1985 to 2016, greening has occurred in 37.3% of all sites sampled in the tundra, whereas browning was observed only in 4.7% of the sites - typically the ones that were still experiencing cooling and drying, as opposed to warming and wettening for the rest.[82]

This expansion of vegetation in the Arctic is not equivalent across types of vegetation. A major trend has been from shrub-type plants taking over areas previously dominated by moss and lichens. This change contributes to the consideration that the tundra biome is currently experiencing the most rapid change of any terrestrial biomes on the planet.[83][84] The direct impact on mosses and lichens is unclear as there exist very few studies at species level, but climate change is more likely to cause increased fluctuation and more frequent extreme events.[85] While shrubs may increase in range and biomass, warming may also cause a decline in cushion plants such as moss campion, and since cushion plants act as facilitator species across trophic levels and fill important ecological niches in several environments, this could cause cascading effects in these ecosystems that could severely affect the way in which they function and are structured.[86]

The expansion of these shrubs can also have strong effects on other important ecological dynamics, such as the albedo effect.[87] These shrubs change the winter surface of the tundra from undisturbed, uniform snow to mixed surface with protruding branches disrupting the snow cover,[88] this type of snow cover has a lower albedo effect, with reductions of up to 55%, which contributes to a positive feedback loop on regional and global climate warming.[88] This reduction of the albedo effect means that more radiation is absorbed by plants, and thus, surface temperatures increase, which could disrupt current surface-atmosphere energy exchanges and affect thermal regimes of permafrost.[88] Carbon cycling is also being affected by these changes in vegetation, as parts of the tundra increase their shrub cover, they behave more like boreal forests in terms of carbon cycling.[89] This is speeding up the carbon cycle, as warmer temperatures lead to increased permafrost thawing and carbon release, but also carbon capturing from plants that have increased growth.[89] It is not certain whether this balance will go in one direction or the other, but studies have found that it is more likely that this will eventually lead to increased CO2 in the atmosphere.[89]

However, boreal forests, particularly those in North America, showed a different response to warming. Many boreal forests greened, but the trend was not as strong as it was for tundra of the circumpolar Arctic, mostly characterized by shrub expansion and increased growth.[90] In North America, some boreal forests actually experienced browning over the study period. Droughts, increased forest fire activity, animal behavior, industrial pollution, and a number of other factors may have contributed to browning.[81]

Impacts on terrestrial fauna

[edit]
Projected change in polar bear habitat from 2001–2010 to 2041–2050

Arctic warming negatively affects the foraging and breeding ecology of native Arctic mammals, such as Arctic foxes or Arctic reindeer.[91] In July 2019, 200 Svalbard reindeer were found starved to death apparently due to low precipitation related to climate change.[92] This was only one episode in the long-term decline of the species.[1]: 2327  United States Geological Survey research suggests that the shrinkage of Arctic sea ice would eventually extirpate polar bears from Alaska, but leave some of their habitat in the Canadian Arctic Archipelago and areas off the northern Greenland coast.[93][94]

As the pure Arctic climate is gradually replaced by the subarctic climate, animals adapted to those conditions spread to the north.[1]: 2325  For instance, beavers have been actively colonizing Arctic regions, and as they create dams, they flood areas which used to be permafrost, contributing to its thaw and methane emissions from it.[8] These colonizing species can outright replace native species, and they may also interbreed with their southern relations, like in the case of the Grizzly–polar bear hybrid. This usually has the effect of reducing the genetic diversity of the genus. Infectious diseases, such as brucellosis or phocine distemper virus, may spread to populations previously separated by the cold, or, in case of the marine mammals, the sea ice.[95]

Marine ecosystems

[edit]
The observed increase in phytoplankton biomass in the Arctic since 1998[9]

The reduction of sea ice has brought more sunlight to the phytoplankton and increased the annual marine primary production in the Arctic by over 30% between 1998 and 2020.[1]: 2327  As the result, the Arctic Ocean became a stronger carbon sink over this period;[96] yet, it still accounts for only 5% to 14% of the total ocean carbon sink, although it is expected to play a larger role in the future.[97] By 2100, phytoplankton biomass in the Arctic Ocean is generally expected to increase by ~20% relative to 2000 under the low-emission scenario, and by 30-40% under the high-emission scenario.[1]: 2329 

Atlantic cod have been able to move deeper into the Arctic due to the warming waters, while the Polar cod and local marine mammals have been losing habitat.[1]: 2327  Many copepod species appear to be declining, which is also likely to reduce the numbers of fish which prey on them, such as walleye pollock or the arrowtooth flounder.[1]: 2327  This also affects Arctic shorebirds. For instance, around 9000 puffins and other shorebirds in Alaska died of starvation in 2016, because too many fish have moved to the north.[98] While the shorebirds also appear to nest more successfully due to the observed warming,[99] this benefit may be more than offset by phenological mismatch between shorebirds' and other species' life cycles.[100] Marine mammals such as ringed seals and walruses are also being negatively affected by the warming.[91][101]

Greenhouse gas emissions from the Arctic

[edit]

In 2024, the Arctic has transformed from a carbon sink to a carbon source due to the impacts of climate change, mainly rising temperatures and wildfires.[102]

Permafrost thaw

[edit]
Permafrost thaw ponds on Baffin Island

Permafrost is an important component of hydrological systems and ecosystems within the Arctic landscape.[103] In the Northern Hemisphere the terrestrial permafrost domain comprises around 18 million km2.[104] Within this permafrost region, the total soil organic carbon (SOC) stock is estimated to be 1,460-1,600 Pg (where 1 Pg = 1 billion tons), which constitutes double the amount of carbon currently contained in the atmosphere.[105][106]

As recent warming deepens the active layer subject to permafrost thaw, this exposes formerly stored carbon to biogenic processes which facilitate its entrance into the atmosphere as carbon dioxide and methane.[107] Because carbon emissions from permafrost thaw contribute to the same warming which facilitates the thaw, it is a well-known example of a positive climate change feedback.[108] Permafrost thaw is sometimes included as one of the major tipping points in the climate system due to the exhibition of local thresholds and its effective irreversibility.[109] However, while there are self-perpetuating processes that apply on the local or regional scale, it is debated as to whether it meets the strict definition of a global tipping point as in aggregate permafrost thaw is gradual with warming.[110]

In the northern circumpolar region, permafrost contains organic matter equivalent to 1400–1650 billion tons of pure carbon, which was built up over thousands of years. This amount equals almost half of all organic material in all soils,[111][107] and it is about twice the carbon content of the atmosphere, or around four times larger than the human emissions of carbon between the start of the Industrial Revolution and 2011.[112] Further, most of this carbon (~1,035 billion tons) is stored in what is defined as the near-surface permafrost, no deeper than 3 metres (9.8 ft) below the surface.[111][107] However, only a fraction of this stored carbon is expected to enter the atmosphere.[113] In general, the volume of permafrost in the upper 3 m of ground is expected to decrease by about 25% per 1 °C (1.8 °F) of global warming,[114]: 1283  yet even under the RCP8.5 scenario associated with over 4 °C (7.2 °F) of global warming by the end of the 21st century,[115] about 5% to 15% of permafrost carbon is expected to be lost "over decades and centuries".[107]
Nine probable scenarios of greenhouse gas emissions from permafrost thaw during the 21st century, which show a limited, moderate and intense CO2 and CH4 emission response to low, medium and high-emission Representative Concentration Pathways. The vertical bar uses emissions of selected large countries as a comparison: the right-hand side of the scale shows their cumulative emissions since the start of the Industrial Revolution, while the left-hand side shows each country's cumulative emissions for the rest of the 21st century if they remained unchanged from their 2019 levels.[107]

Altogether, it is expected that cumulative greenhouse gas emissions from permafrost thaw will be smaller than the cumulative anthropogenic emissions, yet still substantial on a global scale, with some experts comparing them to emissions caused by deforestation.[107] The IPCC Sixth Assessment Report estimates that carbon dioxide and methane released from permafrost could amount to the equivalent of 14–175 billion tonnes of carbon dioxide per 1 °C (1.8 °F) of warming.[114]: 1237  For comparison, by 2019, annual anthropogenic emissions of carbon dioxide alone stood around 40 billion tonnes.[114]: 1237  A major review published in the year 2022 concluded that if the goal of preventing 2 °C (3.6 °F) of warming was realized, then the average annual permafrost emissions throughout the 21st century would be equivalent to the year 2019 annual emissions of Russia. Under RCP4.5, a scenario considered close to the current trajectory and where the warming stays slightly below 3 °C (5.4 °F), annual permafrost emissions would be comparable to year 2019 emissions of Western Europe or the United States, while under the scenario of high global warming and worst-case permafrost feedback response, they would approach year 2019 emissions of China.[107]

Fewer studies have attempted to describe the impact directly in terms of warming. A 2018 paper estimated that if global warming was limited to 2 °C (3.6 °F), gradual permafrost thaw would add around 0.09 °C (0.16 °F) to global temperatures by 2100,[116] while a 2022 review concluded that every 1 °C (1.8 °F) of global warming would cause 0.04 °C (0.072 °F) and 0.11 °C (0.20 °F) from abrupt thaw by the year 2100 and 2300. Around 4 °C (7.2 °F) of global warming, abrupt (around 50 years) and widespread collapse of permafrost areas could occur, resulting in an additional warming of 0.2–0.4 °C (0.36–0.72 °F).[109][117]

Black carbon

[edit]
Black carbon emissions from fire and human activities around the Arctic in the year 2012, as measured from a research station in Abisko[118]

Black carbon deposits (from the combustion of heavy fuel oil (HFO) of Arctic shipping) absorb solar radiation in the atmosphere and strongly reduce the albedo when deposited on snow and ice, thus accelerating the effect of the melting of snow and sea ice.[119] A 2013 study quantified that gas flaring at petroleum extraction sites contributed over 40% of the black carbon deposited in the Arctic.[120][121] 2019 research attributed the majority (56%) of Arctic surface black carbon to emissions from Russia, followed by European emissions, and Asia also being a large source.[122][119] In 2015, research suggested that reducing black carbon emissions and short-lived greenhouse gases by roughly 60 percent by 2050 could cool the Arctic up to 0.2 °C.[123] However, a 2019 study indicates that "Black carbon emissions will continuously rise due to increased shipping activities", specifically fishing vessels.[124]

The number of wildfires in the Arctic Circle has increased. In 2020, Arctic wildfire CO2 emissions broke a new record, peaking at 244 megatonnes of carbon dioxide emitted.[125]  This is due to the burning of peatlands, carbon-rich soils that originate from the accumulation of waterlogged plants which are mostly found at Arctic latitudes.[125] These peatlands are becoming more likely to burn as temperatures increase, but their own burning and releasing of CO2 contributes to their own likelihood of burning in a positive feedback loop.[125]The smoke from wildfires defined as "brown carbon" also increases arctic warming, with its warming effect is around 30% that of black carbon. As wildfires increases with warming this creates a positive feedback loop.[126]

Methane clathrate deposits

[edit]
Methane clathrate is released as gas into the surrounding water column or soils when ambient temperature increases.
The clathrate gun hypothesis is a proposed explanation for the periods of rapid warming during the Quaternary. The hypothesis is that changes in fluxes in upper intermediate waters in the ocean caused temperature fluctuations that alternately accumulated and occasionally released methane clathrate on upper continental slopes. This would have had an immediate impact on the global temperature, as methane is a much more powerful greenhouse gas than carbon dioxide. Despite its atmospheric lifetime of around 12 years, methane's global warming potential is 72 times greater than that of carbon dioxide over 20 years, and 25 times over 100 years (33 when accounting for aerosol interactions).[127] It is further proposed that these warming events caused the Bond cycles and individual interstadial events, such as the Dansgaard–Oeschger interstadials.[128]
In 2018, a perspective piece devoted to tipping points in the climate system suggested that the climate change contribution from methane hydrates would be "negligible" by the end of the century, but could amount to 0.4–0.5 °C (0.72–0.90 °F) on the millennial timescales.[129] In 2021, the IPCC Sixth Assessment Report no longer included methane hydrates in the list of potential tipping points, and says that "it is very unlikely that CH4 emissions from clathrates will substantially warm the climate system over the next few centuries."[130] The report had also linked terrestrial hydrate deposits to gas emission craters discovered in the Yamal Peninsula in Siberia, Russia beginning in July 2014,[131] but noted that since terrestrial gas hydrates predominantly form at a depth below 200 meters, a substantial response within the next few centuries can be ruled out.[130] Likewise, a 2022 assessment of tipping points described methane hydrates as a "threshold-free feedback" rather than a tipping point.[132][133]

Effects on other parts of the world

[edit]

On ocean circulation

[edit]
Modelled 21st century warming under the "intermediate" global warming scenario (top). The potential collapse of the subpolar gyre in this scenario (middle). The collapse of the entire Atlantic Meriditional Overturning Circulation (bottom).
The Atlantic meridional overturning circulation (AMOC) is the main ocean current system in the Atlantic Ocean.[134]: 2238  It is a component of Earth's ocean circulation system and plays an important role in the climate system. The AMOC includes Atlantic currents at the surface and at great depths that are driven by changes in weather, temperature and salinity. Those currents comprise half of the global thermohaline circulation that includes the flow of major ocean currents, the other half being the Southern Ocean overturning circulation.[135]
The AMOC has not always existed; for much of Earth's history, overturning circulation in the northern hemisphere occurred in the North Pacific. Paleoclimate evidence shows the shift of overturning circulation from the Pacific to the Atlantic occurred 34 million years ago at the Eocene-Oligocene transition, when the Arctic-Atlantic gateway had closed.[136] This closure fundamentally changed the thermohaline circulation structure; some researchers have suggested climate change may eventually reverse this shift and re-establish the Pacific circulation after the AMOC shuts down.[137][138] Climate change affects the AMOC by making surface water warmer as a consequence of Earth's energy imbalance and by making surface water less saline due to the addition of large quantities of fresh water from melting ice – mainly from Greenland – and through increasing precipitation over the North Atlantic. Both of these causes would increase the difference between the surface and deep layers, thus making the upwelling and downwelling that drives the circulation more difficult.[139]
Severe weakening of the AMOC may lead to a collapse of the circulation, which would not be easily reversible and thus constitutes one of the tipping points in the climate system.[140] A collapse would substantially lower the average temperature and amount of rain and snowfall in Europe.[141][142] It may also raise the frequency of extreme weather events and have other severe effects.[143][144]

In 2021, the IPCC Sixth Assessment Report again said the AMOC is "very likely" to decline within the 21st century and that there was a "high confidence" changes to it would be reversible within centuries if warming was reversed.[145]: 19  Unlike the Fifth Assessment Report, it had only "medium confidence" rather than "high confidence" in the AMOC avoiding a collapse before the end of the 21st century. This reduction in confidence was likely influenced by several review studies that draw attention to the circulation stability bias within general circulation models,[146][147] and simplified ocean-modelling studies suggesting the AMOC may be more vulnerable to abrupt change than larger-scale models suggest.[148]

The synthesis report of the IPCC Sixth Assessment Report summarized the scientific consensus as follows: "The Atlantic Meridional Overturning Circulation is very likely to weaken over the 21st century for all considered scenarios (high confidence), however an abrupt collapse is not expected before 2100 (medium confidence). If such a low probability event were to occur, it would very likely cause abrupt shifts in regional weather patterns and water cycle, such as a southward shift in the tropical rain belt, and large impacts on ecosystems and human activities."[149]

On mid-latitude weather

[edit]

Since the early 2000s, climate models have consistently identified that global warming will gradually push jet streams poleward. In 2008, this was confirmed by observational evidence, which proved that from 1979 to 2001, the northern jet stream moved northward at an average rate of 2.01 kilometres (1.25 mi) per year, with a similar trend in the southern hemisphere jet stream.[150][151] Climate scientists have hypothesized that the jet stream will also gradually weaken as a result of global warming. Trends such as Arctic sea ice decline, reduced snow cover, evapotranspiration patterns, and other weather anomalies have caused the Arctic to heat up faster than other parts of the globe, in what is known as the Arctic amplification. In 2021–2022, it was found that since 1979, the warming within the Arctic Circle has been nearly four times faster than the global average,[152][153] and some hotspots in the Barents Sea area warmed up to seven times faster than the global average.[154][155] While the Arctic remains one of the coldest places on Earth today, the temperature gradient between it and the warmer parts of the globe will continue to diminish with every decade of global warming as the result of this amplification. If this gradient has a strong influence on the jet stream, then it will eventually become weaker and more variable in its course, which would allow more cold air from the polar vortex to leak mid-latitudes and slow the progression of Rossby waves, leading to more persistent and more extreme weather.[156]

The hypothesis above is closely associated with Jennifer Francis, who had first proposed it in a 2012 paper co-authored by Stephen J. Vavrus.[156] While some paleoclimate reconstructions have suggested that the polar vortex becomes more variable and causes more unstable weather during periods of warming back in 1997,[157] this was contradicted by climate modelling, with PMIP2 simulations finding in 2010 that the Arctic Oscillation (AO) was much weaker and more negative during the Last Glacial Maximum, and suggesting that warmer periods have stronger positive phase AO, and thus less frequent leaks of the polar vortex air.[158] However, a 2012 review in the Journal of the Atmospheric Sciences noted that "there [has been] a significant change in the vortex mean state over the twenty-first century, resulting in a weaker, more disturbed vortex.",[159] which contradicted the modelling results but fit the Francis-Vavrus hypothesis. Additionally, a 2013 study noted that the then-current CMIP5 tended to strongly underestimate winter blocking trends,[160] and other 2012 research had suggested a connection between declining Arctic sea ice and heavy snowfall during midlatitude winters.[161]

However, because the specific observations are considered short-term observations, there is considerable uncertainty in the conclusions. Climatology observations require several decades to definitively distinguish various forms of natural variability from climate trends.[162] This point was stressed by reviews in 2013[163] and in 2017.[164] A study in 2014 concluded that Arctic amplification significantly decreased cold-season temperature variability over the northern hemisphere in recent decades. Cold Arctic air intrudes into the warmer lower latitudes more rapidly today during autumn and winter, a trend projected to continue in the future except during summer, thus calling into question whether winters will bring more cold extremes.[165] A 2019 analysis of a data set collected from 35 182 weather stations worldwide, including 9116 whose records go beyond 50 years, found a sharp decrease in northern midlatitude cold waves since the 1980s.[166]

Moreover, a range of long-term observational data collected during the 2010s and published in 2020 suggests that the intensification of Arctic amplification since the early 2010s was not linked to significant changes on mid-latitude atmospheric patterns.[167][168] State-of-the-art modelling research of PAMIP (Polar Amplification Model Intercomparison Project) improved upon the 2010 findings of PMIP2; it found that sea ice decline would weaken the jet stream and increase the probability of atmospheric blocking, but the connection was very minor, and typically insignificant next to interannual variability.[169][170] In 2022, a follow-up study found that while the PAMIP average had likely underestimated the weakening caused by sea ice decline by 1.2 to 3 times, even the corrected connection still amounts to only 10% of the jet stream's natural variability.[171]

Impacts on people

[edit]

Territorial claims

[edit]

Growing evidence that global warming is shrinking polar ice has added to the urgency of several nations' Arctic territorial claims in hopes of establishing resource development and new shipping lanes, in addition to protecting sovereign rights.[172]

As ice sea coverage decreases more and more, year on year, Arctic countries (Russia, Canada, Finland, Iceland, Norway, Sweden, the United States and Denmark representing Greenland) are making moves on the geopolitical stage to ensure access to potential new shipping lanes, oil and gas reserves, leading to overlapping claims across the region.[173]

There is more activity in terms of maritime boundaries between countries, where overlapping claims for internal waters, territorial seas and particularly Exclusive Economic Zones (EEZs) can cause frictions between nations. Currently, official maritime borders have an unclaimed triangle of international waters lying between them, that is at the centerpoint of international disputes.[173]

This unclaimed land can be obtainable by submitting a claim to the United Nations Convention on the Law of the Sea, these claims can be based on geological evidence that continental shelves extend beyond their current maritime borders and into international waters.[173]

Some overlapping claims are still pending resolution by international bodies, such as a large portion containing the north pole that is both claimed by Denmark and Russia, with some parts of it also contested by Canada.[173] Another example is that of the Northwest Passage, globally recognized as international waters, but technically in Canadian waters.[173] This has led to Canada wanting to limit the number of ships that can go through for environmental reasons but the United States disputes that they have the authority to do so, favouring unlimited passage of vessels.[173]

[edit]

The Transpolar Sea Route is a future Arctic shipping lane running from the Atlantic Ocean to the Pacific Ocean across the center of the Arctic Ocean. The route is also sometimes called Trans-Arctic Route. In contrast to the Northeast Passage (including the Northern Sea Route) and the North-West Passage it largely avoids the territorial waters of Arctic states and lies in international high seas.[174]

Governments and private industry have shown a growing interest in the Arctic.[175] Major new shipping lanes are opening up: the northern sea route had 34 passages in 2011 while the Northwest Passage had 22 traverses, more than any time in history.[176] Shipping companies may benefit from the shortened distance of these northern routes. Access to natural resources will increase, including valuable minerals and offshore oil and gas.[177] Finding and controlling these resources will be difficult with the continually moving ice.[177] Tourism may also increase as less sea ice will improve safety and accessibility to the Arctic.[177]

The melting of Arctic ice caps is likely to increase traffic in and the commercial viability of the Northern Sea Route. One study, for instance, projects, "remarkable shifts in trade flows between Asia and Europe, diversion of trade within Europe, heavy shipping traffic in the Arctic and a substantial drop in Suez traffic. Projected shifts in trade also imply substantial pressure on an already threatened Arctic ecosystem."[178]

Infrastructure

[edit]
Map of likely risk to infrastructure from permafrost thaw expected to occur by 2050.

As of 2021, there are 1162 settlements located directly atop the Arctic permafrost, which host an estimated 5 million people. By 2050, permafrost layer below 42% of these settlements is expected to thaw, affecting all their inhabitants (currently 3.3 million people).[179] Consequently, a wide range of infrastructure in permafrost areas is threatened by the thaw.[180][181]: 236  By 2050, it's estimated that nearly 70% of global infrastructure located in the permafrost areas would be at high risk of permafrost thaw, including 30–50% of "critical" infrastructure. The associated costs could reach tens of billions of dollars by the second half of the century.[182] Reducing greenhouse gas emissions in line with the Paris Agreement is projected to stabilize the risk after mid-century; otherwise, it'll continue to worsen.[183]

In Alaska alone, damages to infrastructure by the end of the century would amount to $4.6 billion (at 2015 dollar value) if RCP8.5, the high-emission climate change scenario, were realized. Over half stems from the damage to buildings ($2.8 billion), but there's also damage to roads ($700 million), railroads ($620 million), airports ($360 million) and pipelines ($170 million).[184] Similar estimates were done for RCP4.5, a less intense scenario which leads to around 2.5 °C (4.5 °F) by 2100, a level of warming similar to the current projections.[185] In that case, total damages from permafrost thaw are reduced to $3 billion, while damages to roads and railroads are lessened by approximately two-thirds (from $700 and $620 million to $190 and $220 million) and damages to pipelines are reduced more than ten-fold, from $170 million to $16 million. Unlike the other costs stemming from climate change in Alaska, such as damages from increased precipitation and flooding, climate change adaptation is not a viable way to reduce damages from permafrost thaw, as it would cost more than the damage incurred under either scenario.[184]

In Canada, Northwest Territories have a population of only 45,000 people in 33 communities, yet permafrost thaw is expected to cost them $1.3 billion over 75 years, or around $51 million a year. In 2006, the cost of adapting Inuvialuit homes to permafrost thaw was estimated at $208/m2 if they were built at pile foundations, and $1,000/m2 if they didn't. At the time, the average area of a residential building in the territory was around 100 m2. Thaw-induced damage is also unlikely to be covered by home insurance, and to address this reality, territorial government currently funds Contributing Assistance for Repairs and Enhancements (CARE) and Securing Assistance for Emergencies (SAFE) programs, which provide long- and short-term forgivable loans to help homeowners adapt. It is possible that in the future, mandatory relocation would instead take place as the cheaper option. However, it would effectively tear the local Inuit away from their ancestral homelands. Right now, their average personal income is only half that of the median NWT resident, meaning that adaptation costs are already disproportionate for them.[186]

By 2022, up to 80% of buildings in some Northern Russia cities had already experienced damage.[182] By 2050, the damage to residential infrastructure may reach $15 billion, while total public infrastructure damages could amount to 132 billion.[187] This includes oil and gas extraction facilities, of which 45% are believed to be at risk.[183]

Toxic pollution

[edit]
Graphical representation of leaks from various toxic hazards caused by the thaw of formerly stable permafrost.[188]

For much of the 20th century, it was believed that permafrost would "indefinitely" preserve anything buried there, and this made deep permafrost areas popular locations for hazardous waste disposal. In places like Canada's Prudhoe Bay oil field, procedures were developed documenting the "appropriate" way to inject waste beneath the permafrost. This means that as of 2023, there are ~4500 industrial facilities in the Arctic permafrost areas which either actively process or store hazardous chemicals. Additionally, there are between 13,000 and 20,000 sites which have been heavily contaminated, 70% of them in Russia, and their pollution is currently trapped in the permafrost.[citation needed]

About a fifth of both the industrial and the polluted sites (1000 and 2200–4800) are expected to start thawing in the future even if the warming does not increase from its 2020 levels. Only about 3% more sites would start thawing between now and 2050 under the climate change scenario consistent with the Paris Agreement goals, RCP2.6, but by 2100, about 1100 more industrial facilities and 3500 to 5200 contaminated sites are expected to start thawing even then. Under the very high emission scenario RCP8.5, 46% of industrial and contaminated sites would start thawing by 2050, and virtually all of them would be affected by the thaw by 2100.[188]

Organochlorines and other persistent organic pollutants are of a particular concern, due to their potential to repeatedly reach local communities after their re-release through biomagnification in fish. At worst, future generations born in the Arctic would enter life with weakened immune systems due to pollutants accumulating across generations.[189]

Distribution of toxic substances currently located at various permafrost sites in Alaska, by sector. The number of fish skeletons represents the toxicity of each substance.[188]

A notable example of pollution risks associated with permafrost was the 2020 Norilsk oil spill, caused by the collapse of diesel fuel storage tank at Norilsk-Taimyr Energy's thermal power plant No. 3. It spilled 6,000 tonnes of fuel into the land and 15,000 into the water, polluting Ambarnaya, Daldykan and many smaller rivers on Taimyr Peninsula, even reaching lake Pyasino, which is a crucial water source in the area. State of emergency at the federal level was declared.[190][191] The event has been described as the second-largest oil spill in modern Russian history.[192][193]

Another issue associated with permafrost thaw is the release of natural mercury deposits. An estimated 800,000 tons of mercury are frozen in the permafrost soil. According to observations, around 70% of it is simply taken up by vegetation after the thaw.[189] However, if the warming continues under RCP8.5, then permafrost emissions of mercury into the atmosphere would match the current global emissions from all human activities by 2200. Mercury-rich soils also pose a much greater threat to humans and the environment if they thaw near rivers. Under RCP8.5, enough mercury will enter the Yukon River basin by 2050 to make its fish unsafe to eat under the EPA guidelines. By 2100, mercury concentrations in the river will double. Contrastingly, even if mitigation is limited to RCP4.5 scenario, mercury levels will increase by about 14% by 2100, and will not breach the EPA guidelines even by 2300.[194]
The impact of meltwater from Greenland goes beyond nutrient transport. For instance, meltwater also contains dissolved organic carbon, which comes from the microbial activity on the ice sheet's surface, and, to a lesser extent, from the remnants of ancient soil and vegetation beneath the ice.[195] There is about 0.5-27 billion tonnes of pure carbon underneath the entire ice sheet, and much less within it.[196] This is much less than the 1400–1650 billion tonnes contained within the Arctic permafrost,[197] or the annual anthropogenic emissions of around 40 billion tonnes of CO2.[70]: 1237 ) Yet, the release of this carbon through meltwater can still act as a climate change feedback if it increases overall carbon dioxide emissions.[198]

Impacts on indigenous peoples

[edit]

As climate change speeds up, it is having more and more of a direct impact on societies around the world. This is particularly true of people that live in the Arctic, where increases in temperature are occurring at faster rates than at other latitudes in the world, and where traditional ways of living, deeply connected with the natural arctic environment are at particular risk of environmental disruption caused by these changes.[177]

The warming of the atmosphere and ecological changes that come alongside it presents challenges to local communities such as the Inuit. Hunting, which is a major way of survival for some small communities, will be changed with increasing temperatures.[199] The reduction of sea ice will cause certain species populations to decline or even become extinct.[177] Inuit communities are deeply reliant on seal hunting, which is dependent on sea ice flats, where seals are hunted.[200]

Unsuspected changes in river and snow conditions will cause herds of animals, including reindeer, to change migration patterns, calving grounds, and forage availability.[177] In good years, some communities are fully employed by the commercial harvest of certain animals.[199] The harvest of different animals fluctuates each year and with the rise of temperatures it is likely to continue changing and creating issues for Inuit hunters, as unpredictability and disruption of ecological cycles further complicate life in these communities, which already face significant problems, such as Inuit communities being the poorest and most unemployed of North America.[200]

Other forms of transportation in the Arctic have seen negative impacts from the current warming, with some transportation routes and pipelines on land being disrupted by the melting of ice.[177] Many Arctic communities rely on frozen roadways to transport supplies and travel from area to area.[177] The changing landscape and unpredictability of weather is creating new challenges in the Arctic.[201] Researchers have documented historical and current trails created by the Inuit in the Pan Inuit Trails Atlas, finding that the change in sea ice formation and breakup has resulted in changes to the routes of trails created by the Inuit.[202]

Adaptation

[edit]

Research

[edit]

Individual countries within the Arctic zone, Canada, Denmark (Greenland), Finland, Iceland, Norway, Russia, Sweden, and the United States (Alaska) conduct independent research through a variety of organizations and agencies, public and private, such as Russia's Arctic and Antarctic Research Institute. Countries who do not have Arctic claims, but are close neighbors, conduct Arctic research as well, such as the Chinese Arctic and Antarctic Administration (CAA). The United States's National Oceanic and Atmospheric Administration (NOAA) produces an Arctic Report Card annually, containing peer-reviewed information on recent observations of environmental conditions in the Arctic relative to historical records.[203][204] International cooperative research between nations has also become increasingly important:

The 2021 Arctic Monitoring and Assessment Programme (AMAP) report by an international team of more than 60 experts, scientists, and indigenous knowledge keepers from Arctic communities, was prepared from 2019 to 2021.[208]: vii  It is a follow-up report of the 2017 assessment, "Snow, Water, Ice and Permafrost in the Arctic" (SWIPA).[208]: vii  The 2021 IPCC AR6 WG1 Technical Report confirmed that "[o]bserved and projected warming" were ""strongest in the Arctic".[209]: 29  According to an 11 August 2022 article published in Nature, there have been numerous reports that the Arctic is warming from twice to three times as fast as the global average since 1979, but the co-authors cautioned that the recent report of the "four-fold Arctic warming ratio" was potentially an "extremely unlikely event".[210] The annual mean Arctic Amplification (AA) index had "reached values exceeding four" from c. 2002 through 2022, according to a July 2022 article in Geophysical Research Letters.[211]: 1 [212]

The 14 December 2021 16th Arctic Report Card produced by the United States's National Oceanic and Atmospheric Administration (NOAA) and released annually, examined the "interconnected physical, ecological and human components" of the circumpolar Arctic.[213][46] The report said that the 12 months between October 2020 and September 2021 were the "seventh warmest over Arctic land since the record began in 1900".[213] The 2017 report said that the melting ice in the warming Arctic was unprecedented in the past 1500 years.[203][204] NOAA's State of the Arctic Reports, starting in 2006, updates some of the records of the original 2004 and 2005 Arctic Climate Impact Assessment (ACIA) reports by the intergovernmental Arctic Council and the non-governmental International Arctic Science Committee.[214]

A 2022 United Nations Environment Programme (UNEP) report "Spreading Like Wildfire: The Rising Threat Of Extraordinary Landscape Fires" said that smoke from wildfires around the world created a positive feedback loop that is a contributing factor to Arctic melting.[215][126] The 2020 Siberian heatwave was "associated with extensive burning in the Arctic Circle".[215]: 36  Report authors said that this extreme heat event was the first to demonstrate that it would have been "almost impossible" without anthropogenic emissions and climate change.[216][215]: 36 

See also

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Works cited

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Further reading

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