View source for Ocean

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{{Further|Seawater}}
[[File:Clouds over the Atlantic Ocean.jpg|thumb|275px|Surface of the [[Atlantic Ocean]] meeting the Earth's [[planetary boundary layer]] and [[troposphere]].]]
{{Five oceans}}

An '''ocean'''  ({{Etymology|grc|''{{linktext|Ὠκεανός}}, <small>[[romanization of Greek|transc.]]</small>''&nbsp;[[Oceanus|Okeanós]]}}, the [[sea]] of [[classical antiquity]]<ref name="tufts.pers">{{cite web |url=http://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.04.0057%3Aentry%3D*%29wkeano%2Fs |title=Ὠκεανός |work=[[Perseus Project|Perseus Digital Library]] |accessdate=May 17, 2012 }}</ref>) is a body of [[saline water]] that composes much of a [[planet]]'s [[hydrosphere]].<ref name="pri.ocean">{{cite web |url=http://wordnetweb.princeton.edu/perl/webwn?s=ocean |title=WordNet Search — ocean |publisher=Princeton University |accessdate=February 21, 2012 }}</ref> On [[Earth]], an ocean is one of the major conventional divisions of the World Ocean, which occupies two-thirds of the planet's surface. These are, in descending order by area, the [[Pacific Ocean|Pacific]], [[Atlantic Ocean|Atlantic]], [[Indian Ocean|Indian]], [[Southern Ocean|Southern]], and [[Arctic Ocean|Arctic]] Oceans.<ref name="oed.130201">{{cite web |url=http://www.oed.com/view/Entry/130201?redirectedFrom=ocean#eid |title=ocean, n |publisher=Oxford English Dictionary |accessdate=February 5, 2012 }}</ref><ref name="mw.ocean">{{cite web |url=http://www.merriam-webster.com/dictionary/ocean |title=ocean |publisher=Merriam-Webster |accessdate=February 6, 2012 }}</ref> The word ''[[sea]]'' is often used interchangeably with "ocean" in [[American English]] but, strictly speaking, a sea is a body of saline water (generally a division of the world ocean) partly or fully enclosed by land.<ref name="pri.sea">{{cite web |url=http://wordnetweb.princeton.edu/perl/webwn?s=sea |title=WordNet Search — sea |publisher=Princeton University |accessdate=February 21, 2012 }}</ref>

Saline water covers approximately 72% of the planet's surface (~3.6{{e|8}}&nbsp;km<sup>2</sup>) and is customarily divided into several principal oceans and smaller seas, with the ocean covering approximately 71% of the Earth's surface.<ref name="noaa.gov">{{cite web |title=NOAA – National Oceanic and Atmospheric Administration – Ocean |url=http://www.noaa.gov/ocean.html |publisher=Noaa.gov |accessdate=8-11-2012 }}</ref> The ocean contains 97% of the Earth's water, and [[Oceanography|oceanographers]] have stated that only 5% of the World Ocean has been explored.<ref name="noaa.gov" /> The total volume is approximately 1.3 billion cubic kilometers (310 million cu mi)<ref name="hypertextbook2003">{{cite web |last=Qadri |first=Syed |title=Volume of Earth's Oceans |work=The Physics Factbook |year=2003 |url=http://hypertextbook.com/facts/2001/SyedQadri.shtml |accessdate=2007-06-07 }}</ref> with an average depth of {{convert|3682|m|ft|sp=us}}.<ref name="Charette_Smith_Ocean-depth">{{cite journal |last=Charette |first=Matthew |last2=Smith |first2=Walter H. F. |title=The volume of Earth's ocean |journal=Oceanography |year=2010 |volume=23 |issue=2 |pages=112–114 |doi=10.5670/oceanog.2010.51 |url=http://www.tos.org/oceanography/archive/23-2_charette.html |accessdate=27 September 2012 }}</ref>

Because it is the principal component of Earth's hydrosphere, the world ocean is integral to [[Life on Earth|all known life]], forms part of the [[carbon cycle]], and influences [[climate]] and [[weather]] patterns.  It is the [[habitat]] of 230,000 known [[species]], although much of the oceans depths remain unexplored, and over two million [[Marine (ocean)|marine]] species are estimated to exist.<ref name="la.2009">{{cite news |title=Mapping an ocean of species |last=Drogin |first=Bob |url=http://articles.latimes.com/2009/aug/02/nation/na-fish2 |date=August 2, 2009 |accessdate=August 18, 2009 |work=Los Angeles Times }}</ref> The [[Origin of water on Earth|origin of Earth's oceans]] remains unknown; oceans are believed to have formed in the [[Hadean]] period and may have been the impetus for the [[Abiogenesis|emergence of life]].

Extra-terrestrial oceans may be composed of water or other [[Chemical element|element]]s and [[Chemical compound|compounds]]. The only confirmed large stable bodies of [[wikt:extraterrestrial|extraterrestrial]] surface liquids are the [[lakes of Titan]], although there is evidence for the existence of oceans elsewhere in the [[Solar System]]. Early in their geologic histories, [[Mars]] and [[Venus]] are theorized to have had large water oceans. The [[Mars ocean hypothesis]] suggests that nearly a third of the surface of Mars was once covered by water, and a [[runaway greenhouse effect]] may have boiled away the global ocean of Venus. Compounds such as [[Salt (chemistry)|salts]] and [[ammonia]] dissolved in water lower its freezing point, so that water might exist in large quantities in extraterrestrial environments as brine or convecting [[ice]]. Unconfirmed oceans are speculated beneath the surface of many dwarf planets and natural satellites; notably, the ocean of [[Europa (moon)|Europa]] is believed to have over twice the water volume of Earth. The Solar System's [[gas giant]] planets are also believed to possess liquid [[atmospheric]] layers of yet to be confirmed compositions. Oceans may also exist on [[exoplanet]]s and [[exomoon]]s, including surface oceans of liquid water within a [[circumstellar habitable zone]]. [[Ocean planet]]s are a hypothetical type of planet with a surface completely covered with liquid.<ref name="mindblowingscience">{{cite web |title=Titan Likely To Have Huge Underground Ocean {{!}} Mind Blowing Science |url=http://mindblowingscience.com/latest-news/titan-likely-to-have-huge-underground-ocean/ |publisher=Mindblowingscience.com |accessdate=8-11-2012 }}</ref><ref name="sciencedaily">{{cite web |title=Ocean-bearing Planets: Looking For Extraterrestrial Life In All The Right Places |url=http://www.sciencedaily.com/releases/2008/12/081215091011.htm |publisher=Sciencedaily.com |accessdate=8-11-2012 }}</ref>

== Earth's global ocean ==

=== Global divisions ===
{{further|Borders of the oceans}}
[[Image:World ocean map.gif|right|thumb|240px|Various ways to divide the World Ocean |alt=Rotating series of maps showing alternate divisions of the oceans]]

Though generally described as several separate oceans, these waters comprise one global, interconnected body of salt water sometimes referred to as the [[World Ocean]] or global ocean.<ref name="autogenerated1">{{cite web |title=Ocean |url=http://www.sciencedaily.com/articles/o/ocean.htm |publisher=Sciencedaily.com |accessdate=8-11-2012 }}</ref><ref
name="UNAoO">"{{cite web |url=http://www.oceansatlas.com/unatlas/about/physicalandchemicalproperties/background/seemore1.html |title=Distribution of land and water on the planet |work=[http://www.oceansatlas.com/ UN Atlas of the Oceans] |publisher= |date= }}</ref> This concept of a continuous body of water with relatively free interchange among its parts is of fundamental importance to [[oceanography]].<ref name="spil.42">{{cite journal |last=Spilhaus |first=Athelstan F. |date=July 1942 |title=Maps of the whole world ocean |publisher=[[American Geographical Society]] |volume=32 (3) |pages=431–5 }}</ref>

The major oceanic divisions are defined in part by the [[continent]]s, various [[archipelago]]s, and other criteria. See the table below for more information; note that the table is in descending order in terms of size.<ref name="sciencedaily" /><ref name="ceoe">{{cite web |title=Pacific Ocean – University of Delaware |url=http://www.ceoe.udel.edu/extreme2004/mission/divelocation/pacific.html |publisher=Ceoe.udel.edu |accessdate=8-11-2012 }}</ref>

{| class="wikitable"
|-
! Rank !! Ocean !! Notes
|-
| 1 || [[Pacific Ocean|Pacific]] || The peaceful sea west of the [[Magellan Strait]],<ref name=oedpac>''Oxford English Dictionary'', {{nowrap|3rd ed.}} "Pacific, ''adj.''<sup>2</sup> and ''n.''<sup>2</sup>" Oxford University Press (Oxford), 2005.</ref> officially separated into the [[North Pacific Ocean|North]] and [[South Pacific Ocean|South Pacific]] (divided by the [[Equator]]<ref>Apart from the [[Galapagos Islands|Galapagos]] and [[Gilbert Islands]], whose surroundings waters are formally included in the South Pacific, even where they lie north of the Equator.</ref> and containing the waters between the southernmost points of [[South East Cape|Tasmania]] and [[Cape Horn|Terra del Fuego]] (and including the waters of the [[Magellan Strait]]) but limited by the borders of the [[Tasman Sea|Tasman]], [[Coral Sea|Coral]], [[Solomon Sea|Solomon]], and [[Bismark Sea]]s, the [[East Indian Archipelago]], the [[Philippine Sea|Philippine]], [[Japan Sea|Japan]], [[Sea of Okhotsk|Okhotsk]], and [[Bering Sea]]s, the [[Gulf of Alaska]], the coastal waters of [[Alaska Panhandle|southeast Alaska]] and [[British Columbia]], and the [[Gulf of California]].<ref name="IHO"/>
|-
| 2 || [[Atlantic Ocean|Atlantic]] || The sea beyond the [[Atlas Mountains]],<ref name=oedatl>''Oxford English Dictionary'', {{nowrap|1st ed.}} "Atlantic, ''adj.'' and ''n.''" Oxford University Press (Oxford), 1885.</ref><ref>[[Herodotus]]. {{lang|grc|Ἱστορίαι}} [''[[Histories (Herodotus)|The Histories]]''], I.202. c. 420 BC. {{grc icon}}</ref> officially separated into the [[North Atlantic Ocean|North]] and [[South Atlantic Ocean|South Atlantic]] (divided by the [[Equator]]) and containing the waters between the southernmost points of [[Cape Horn|Tierra del Fuego]] and [[Cape Agulhas|Africa]] but limited by the borders of the [[Rio de la Plata]], the [[Caribbean Sea]], the [[Gulf of Mexico]], the [[Bay of Fundy]], the [[Gulf of St. Lawrence]], the [[Davis Strait]], the [[Greenland Sea|Greenland]], [[Norwegian Sea|Norwegian]], [[North Sea|North]], [[Inner Seas off the West Coast of Scotland|Scottish]], and [[Irish Sea]]s, the [[Bristol Channel|Bristol]] and [[English Channel]]s, the [[Bay of Biscay]], the [[Mediterranean Sea]], and the [[Gulf of Guinea]],<ref name="IHO"/> although now often considered to end north of the [[Antarctic Convergence]].
|-
| 3 || [[Indian Ocean|Indian]] || The sea south of [[India]], officially containing the waters between the southernmost points of [[Cape Agulhas|Africa]] and [[South East Cape|Tasmania]], bounded on the north by the [[Arabian Sea|Arabian]] and [[Laccadive Sea]]s, the [[Bay of Bengal]], the [[East Indian Archipelago]], and the [[Great Australian Bight]] and on the south by [[Antarctica]],<ref name="IHO"/> although now often considered to end north of the [[Antarctic Convergence]].
|-
| 4 || [[Southern Ocean|Southern]]<br>or<br>Antarctic || Still officially considered an extension of the Pacific, Atlantic and Indian Oceans by the [[International Hydrographic Organization|IHO]],<ref name="sciencedaily" /><ref name="IHO">{{cite web |url=http://www.iho-ohi.net/iho_pubs/standard/S-23/S23_1953.pdf |format=PDF |title=Limits of Oceans and Seas, 3rd edition |year=1953 |publisher=International Hydrographic Organization |accessdate=7 February 2010 }}</ref> it is distinguished by the [[Antarctic Convergence|convergence]] which encircles [[Antarctica]].
|-
| 5 || [[Arctic Ocean|Arctic]] || The sea around the [[North Pole]], officially containing the waters north of the [[Greenland Sea]], then a line east along [[80°N]] to the [[Barentsz Sea|Barentsz]], [[Kara Sea|Kara]], [[Laptev Sea|Laptev]], [[East Siberian Sea|East Siberian]], [[Chuckchi Sea|Chuckchi]], and [[Beaufort Sea]]s.<ref name="IHO"/> Sometimes{{when|date=November 2014}} itself considered{{by who|date=November 2014}} a sea of the Atlantic.
|}

These adjacent regions&mdash;whether [[list of seas|seas]], [[List of gulfs|gulfs]], [[bay]]s, [[bight (geography)|bight]]s, or [[strait]]s&mdash;are very often included as part of the nearest ocean.

=== Physical properties ===
{{further|Seawater}}
<!-- Image with unknown copyright status removed: [[Image:EarthSeaVolumeCompare.jpg|right|thumb|350px|Global water and air volume]] -->

The total mass of the [[hydrosphere]] is about {{convert|1400000000000000000|metric ton|short ton}} or 1.4×10<sup>21</sup> kg, which is about 0.023 percent of the Earth's total mass. Less than 3 percent is [[freshwater]]; the rest is [[seawater|saltwater]], mostly in the ocean. The area of the World Ocean is 361 million square kilometers (139 million square miles),<ref name="encarta">{{cite encyclopedia |publisher=Encarta |title=The World's Oceans and Seas |url=http://encarta.msn.com/media_461547746/The_World's_Oceans_and_Seas.html }}</ref> and its volume is approximately 1.3 billion cubic kilometers (310 million cu mi).<ref name="hypertextbook2003" /> This can be thought of as a cube of water with an edge length of {{convert|1111|km|mi|sp=us}}. Its average depth is {{convert|3790|m|ft|sp=us}}, and its maximum depth is {{convert|10923|m|mi|sp=us}}.<ref name="encarta" /> Nearly half of the world's marine waters are over {{convert|3000|m|ft|sp=us}} deep.<ref name="UNAoO" /> The vast expanses of deep ocean (anything below {{convert|200|m|ft|sp=us}}) cover about 66% of the Earth's surface.<ref name="drazen">{{cite web |last=Drazen |first=Jeffrey C. |title=Deep-Sea Fishes |publisher=School of Ocean and Earth Science and Technology, the [[University of Hawaiʻi at Mānoa]] |url=http://www.soest.hawaii.edu/oceanography/faculty/drazen/fishes.htm |accessdate=2007-06-07 }}</ref> This does not include seas not connected to the World Ocean, such as the [[Caspian Sea]].

The bluish [[color of water]] is a composite of several contributing agents. Prominent contributors include dissolved organic matter and [[chlorophyll]].<ref name="Coble">{{cite journal |first=Paula G. |last=Coble |title=Marine Optical Biogeochemistry:  The Chemistry of Ocean Color |journal=Chemical Reviews |year=2007 |volume=107 |pages=402–418 |doi=10.1021/cr050350 }}</ref>

[[Sailors]] and other mariners have reported that the ocean often emits a visible glow, or luminescence, which extends for miles at night. In 2005, scientists announced that for the first time, they had obtained photographic evidence of this glow.<ref name="ls.051004">{{cite web |url=http://www.livescience.com/strangenews/051004_sea_glow.html |title=Mystery Ocean Glow Confirmed in Satellite Photos |first=Robert Roy |last=Britt |date=October 4, 2005 }}</ref> It is most likely caused by [[bioluminescence]].<ref name="usa.2005">{{cite web |url=http://www.usatoday.com/tech/columnist/aprilholladay/2005-11-21-glowing-sea-algae_x.htm |title=A glowing sea, courtesy of algae |date=November 21, 2005 |last=Holladay |first=April |work=[[USA Today]] }}</ref><ref name="ns.18825195">{{cite web |url=http://www.newscientist.com/article.ns?id=mg18825195.600&feedId;=earth_rss20 |title=Sea's eerie glow seen from space |date=October 5, 2005 |work=[[New Scientist]] }}</ref><ref name="nasa.algae">{{cite web |url=http://earthobservatory.nasa.gov/Study/glowingalgae/ |title=The Incredible Glowing Algae |last=Casey |first=Amy |work=[[NASA Earth Observatory]] |publisher=[[NASA]] |date=August 8, 2003 }}</ref>

=== Zones with depth ===
[[Image:Oceanic divisions.svg|400px|thumb|The major oceanic divisions |alt=Drawing showing divisions according to depth and distance from shore]]

Oceanographers divide the ocean into different [[Oceanic zone|zones]] by physical and biological conditions. The [[pelagic zone]] includes all open ocean regions, and can be divided into further regions categorized by depth and light abundance. The [[photic zone]] includes the oceans from the surface to a depth of 200&nbsp;m; it is the region where photosynthesis can occur and is, therefore, the most [[biodiverse]]. Since plants require [[photosynthesis]], life found deeper than the photic zone must either rely on material sinking from above (see [[marine snow]]) or find another energy source. [[Hydrothermal vents]] are the primary source of energy in what is known as the [[aphotic zone]] (depths exceeding 200&nbsp;m). The pelagic part of the photic zone is known as the [[epipelagic]].

The pelagic part of the aphotic zone can be further divided into vertical regions according to temperature.
The [[mesopelagic]] is the uppermost region. Its lowermost boundary is at a [[thermocline]] of {{convert|12|C|F}}, which, in the tropics generally lies at {{convert|700|-|1000|m|ft|sp=us}}. Next is the [[bathypelagic]] lying between {{convert|10|and|4|C|F}}, typically between {{convert|700|-|1000|m|ft|sp=us}} and {{convert|2000|-|4000|m|ft|sp=us}} Lying along the top of the [[abyssal plain]] is the [[abyssal zone|abyssopelagic]], whose lower boundary lies at about {{convert|6000|m|ft|sp=us}}. The last zone includes the deep [[oceanic trench]], and is known as the [[hadal zone|hadalpelagic]]. This lies between {{convert|6000|-|11000|m|ft|sp=us}} and is the deepest oceanic zone.

The [[benthic]] zones are aphotic and correspond to the three deepest zones of the [[deep-sea]]. The [[bathyal zone]] covers the continental slope down to about {{convert|4000|m|ft|sp=us}}. The abyssal zone covers the abyssal plains between 4,000 and 6,000&nbsp;m. Lastly, the [[hadal]] zone corresponds to the hadalpelagic zone, which is found in oceanic trenches.

The pelagic zone can be further subdivided into two subregions: the [[neritic zone]] and the [[oceanic zone]]. The neritic zone encompasses the water mass directly above the [[continental shelves]] whereas the oceanic zone includes all the completely open water.

In contrast, the [[littoral zone]] covers the region between low and high tide and represents the transitional area between marine and terrestrial conditions. It is also known as the [[intertidal]] zone because it is the area where tide level affects the conditions of the region.

The ocean can be divided into three density zones: the surface zone, the [[pycnocline]], and the [[deep sea|deep zone]]. The surface zone, also called the mixed layer, refers to the uppermost density zone of the ocean. Temperature and salinity are relatively constant with depth in this zone due to currents and wave action. The surface zone contains ocean water that is in contact with the atmosphere and within the photic zone. The surface zone has the ocean's least dense water and represents approximately 2% of the total volume of ocean water. The surface zone usually ranges between depths of 500 feet to 3,300 feet below ocean surface, but this can vary a great deal. In some cases, the surface zone can be entirely non-existent. The surface zone is typically thicker in the tropics than in regions of higher latitude. The transition to colder, denser water is more abrupt in the tropics than in regions of higher latitudes. The pycnocline refers to a zone wherein density substantially increases with depth due primarily to decreases in temperature. The pycnocline effectively separates the lower-density surface zone above from the higher-density deep zone below. The pycnocline represents approximately 18% of the total volume of ocean water. The deep zone refers to the lowermost density zone of the ocean. The deep zone usually begins at depths below 3,300 feet in mid-latitudes. The deep zone undergoes negligible changes in water density with depth. The deep zone represents 84% of the total volume of ocean water. The deep zone contains relatively colder and stable water.

If a zone undergoes dramatic changes in temperature with depth, it contains a [[thermocline]]. The tropical thermocline is typically deeper than the thermocline at higher latitudes. Polar waters, which receive relatively little solar energy, are not stratified by temperature and generally lack a thermocline since surface water at polar latitudes are nearly as cold as water at greater depths. Below the thermocline, water is very cold, ranging from −1&nbsp;°C to 3&nbsp;°C. Since this deep and cold layer contains the bulk of ocean water, the average temperature of the world ocean is 3.9&nbsp;°C
If a zone undergoes dramatic changes in salinity with depth, it contains a [[halocline]]. If a zone undergoes a strong, vertical chemistry gradient with depth, it contains a [[chemocline]].

The halocline often coincides with the thermocline, and the combination produces a pronounced pycnocline.

=== Exploration ===
[[Image:Ocean gravity map.gif|right|thumb|350px|Map of large underwater features (1995, [[NOAA]])|alt=False color photo]]

Ocean travel by boat dates back to prehistoric times, but only in modern times has extensive underwater travel become possible.

The deepest point in the ocean is the [[Mariana Trench]], located in the Pacific Ocean near the [[Northern Mariana Islands]]. Its maximum depth has been estimated to be {{convert|10971|m|ft|sp=us}} (plus or minus 11 meters; see the [[Mariana Trench]] article for discussion of the various estimates of the maximum depth.) The British naval vessel, ''Challenger II'' surveyed the trench in 1951 and named the deepest part of the trench, the "[[Challenger Deep]]". In 1960, the [[Bathyscaphe Trieste|Trieste]] successfully reached the bottom of the trench, manned by a crew of two men.

=== Climate ===
[[Image:Thermohaline Circulation 2.png|A map of the global thermohaline circulation; blue represent deep-water currents, while red represent surface currents|thumb|200px|left |alt=World map with colored, directed lines showing how water moves through the oceans. Cold deep water rises and warms in the central Pacific and in the Indian, while warm water sinks and cools near Greenland in the North Atlantic and near Antarctica in the South Atlantic.]]

[[Ocean current]]s greatly affect the Earth's [[climate]] by transferring heat from the tropics to the polar regions.  Transferring warm or cold air and precipitation to coastal regions, where winds may carry them inland. Surface heat and freshwater [[flux]]es create global [[density gradient]]s that drive the [[thermohaline circulation]] part of large-scale ocean circulation. It plays an important role in supplying heat to the polar regions, and thus in sea ice regulation. Changes in the thermohaline circulation are thought to have significant impacts on the Earth's radiation budget. In so far as the thermohaline circulation governs the rate at which deep waters reach the surface, it may also significantly influence atmospheric carbon dioxide concentrations.

For a discussion of the possibilities of changes to the thermohaline circulation under [[global warming]], see [[shutdown of thermohaline circulation]].

It is often stated that the thermohaline circulation is the primary reason that the climate of Western Europe is so temperate. An alternate hypothesis claims that this is largely incorrect, and that Europe is warm mostly because it lies downwind of an ocean basin, and because [[atmospheric waves]] bring warm air north from the [[subtropics]].<ref name="sea.2006">{{cite doi|10.1511/2006.60.999 }}</ref><ref name="rc.2003">{{cite journal |year=2003 |url=http://www.realclimate.org/Rhines_hakkinen_2003.pdf |format=PDF |title=Is the Oceanic Heat Transport in the North Atlantic Irrelevant to the Climate in Europe? |journal=ASOF Newsletter |last=Rhines |last2=Hakkinen }}</ref>

The [[Antarctic Circumpolar Current]] encircles that continent, influencing the area's climate and connecting currents in several oceans.

One of the most dramatic forms of [[weather]] occurs over the oceans: [[tropical cyclone]]s (also called "typhoons" and "hurricanes" depending upon where the system forms).

=== Biology ===
{{further|Marine biology}}

The ocean has a significant effect on the [[biosphere]]. Oceanic [[evaporation]], as a phase of the [[water cycle]], is the source of most rainfall, and ocean temperatures determine [[climate]] and [[wind]] patterns that affect life on land. Life within the ocean [[evolution|evolved]] 3 billion years prior to life on land. Both the depth and the distance from shore strongly influence the [[biodiversity]] of the plants and animals present in each region.<ref name="bcc.34">{{cite book |title=Biology: Concepts & Connections |chapter=Chapter 34: The Biosphere: An Introduction to Earth's Diverse Environment |at=section 34.7 |last= |first= |publisher= |date= |url=http://wps.aw.com/bc_campbell_concepts_7_oa/215/55135/14114612.cw/-/t/index.html}}</ref>

Lifeforms native to the ocean include:
* [[Fish]];
* [[Radiata]], such as [[jellyfish]] ([[Cnidaria]]);
* [[Cetacea]], such as [[whale]]s, [[dolphin]]s, and [[porpoise]]s;
* [[Cephalopod]]s, such as [[octopus]] and [[squid]];
* [[Crustacean]]s, such as [[lobster]]s, [[clam]]s, [[shrimp]], and [[krill]];
* [[Marine worm]]s;
* [[Plankton]]; and
* [[Echinoderms]], such as [[brittle star]]s, [[starfish]], [[sea cucumber]]s, and [[sand dollar]]s.

In addition, many land animals have adapted to living a major part of their life on the oceans. For instance, [[seabirds]] are a diverse group of birds that have adapted to a life mainly on the oceans.  They feed on marine animals and spend most of their lifetime on water, many only going on land for breeding.  Other birds that have adapted to oceans as their living space are [[penguin]]s, [[Gull|seagulls]] and [[Pelecaniformes|pelicans]].  Seven species of turtles, the [[sea turtle]]s, also spend most of their time in the oceans.

=== Gases ===
{| class="wikitable" cellpadding="5" style="margin:auto;"
|+Characteristics of Oceanic Gases <ref name="soest.OCN623">{{cite web |url=http://www.soest.hawaii.edu/oceanography/courses/OCN623/Spring2012/Non_CO2_gases.pdf |format=PDF |title=Dissolved Gases other than Carbon Dioxide in Seawater |format=PPT |publisher=soest.hawaii.edu|accessdate=2014-05-05 }}</ref><ref name="uiuc.L23">{{cite web |url=http://butane.chem.uiuc.edu/pshapley/GenChem1/L23/web-L23.pdf |format=PDF |title= Dissolved Oxygen and Carbon Dioxide|work= |publisher= chem.uiuc.edu|date= }}</ref><ref name="sea.water">{{cite web |first=Floor |last=Anthoni |url=http://www.seafriends.org.nz/oceano/seawater.htm |title=Composition of seawater |publisher=Seafriends.org.nz |date= |accessdate=2014-05-05 }}</ref>
|-
! Gas !! Concentration of Seawater, by Mass (in parts per million), for whole Ocean !! % Dissolved Gas, by Volume, in Seawater at Ocean Surface
|-
| '''Carbon dioxide (CO<sub>2</sub>)''' || 64 to 107 || 15%
|-
| '''Nitrogen (N<sub>2</sub>)''' || 10 to 18 || 48% 
|-
| '''Oxygen (O<sub>2</sub>)''' || 0 to 13 || 36% 
|}
{| class="wikitable" 
|+ '''Solubility of Oceanic Gases (in terms of mL/L) with Temperature at salinity of 33‰ and atmospheric pressure'''<ref name="mit.12.742">{{cite web |url=http://ocw.mit.edu/courses/earth-atmospheric-and-planetary-sciences/12-742-marine-chemistry-fall-2006/lecture-notes/lec_11_gas_exch.pdf |format=PDF |title=12.742. Marine Chemistry. Lecture 8. Dissolved Gases and Air-sea exchange|date= |accessdate=2014-05-05 }}</ref>
|-
! Temperature  !! O<sub>2</sub> !! CO<sub>2</sub> !! N<sub>2</sub> 
|-
| '''0&nbsp;°C''' || 8.14 || 8,700 || 14.47
|-
| '''10&nbsp;°C''' || 6.42 || 8,030 || 11.59 
|-
| '''20&nbsp;°C''' || 5.26 || 7,350 || 9.65
|- 
| '''30&nbsp;°C''' || 4.41 || 6,600 || 8.26 
|}

=== Ocean Surface ===
{| class="wikitable" cellpadding="5" style="margin:auto;"
|+Generalized Characteristics of Ocean Surface by Latitude <ref name="ipcc.556">{{cite web |url=http://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch5s5-6.html |title=5.6 Synthesis – AR4 WGI Chapter 5: Observations: Oceanic Climate Change and Sea Level |publisher=Ipcc.ch |date= |accessdate=2014-05-05 }}</ref><ref name="ecmwf.era40">{{cite web |url=http://www.ecmwf.int/research/era/ERA-40/ERA-40_Atlas/docs/section_B/charts/B12_LL_YEA.html |title=Evaporation minus precipitation, Latitude-Longitude, Annual mean |work=ERA-40 Atlas |publisher=ECMWF |date= |deadurl=yes |archivedate=2014-02-02 |archiveurl=http://web.archive.org/web/20140202152523/http://www.ecmwf.int/research/era/ERA-40/ERA-40_Atlas/docs/section_B/charts/B12_LL_YEA.html }}</ref><ref name="Atmosphere, Weather, and Climate">{{cite web |title=Atmosphere, Weather, and Climate |publisher=[Routledge] |first=Roger Graham |last=Barry |first2=Richard J. |last2=Chorley |date=2003 |page=68 }}</ref><ref name="ssec.strat">{{cite web |url=http://eesc.columbia.edu/courses/ees/climate/lectures/o_strat.html |title=Ocean Stratification |publisher=Eesc.columbia.edu |date= |accessdate=2014-05-05 }}</ref><ref name="Ocean Circulation: Wind-Driven and Thermohaline Processes">{{cite web |title=Ocean Circulation: Wind-Driven and Thermohaline Processes |publisher=[Cambridge University Press] |first=Rui Xin |last=Huang |date=2010 }}</ref><ref name="ucar.10">{{cite doi|10.1146/annurev-marine-120408-151453}}</ref><ref name="tamu.0603">{{cite web |url=http://oceanworld.tamu.edu/resources/ocng_textbook/chapter06/chapter06_03.htm |work=Introduction to Physical Oceanography : |title=Chapter 6 – Temperature, Salinity, and Density – Geographical Distribution of Surface Temperature and Salinity |publisher=Oceanworld.tamu.edu |date=2009-03-23 |accessdate=2014-05-05 }}</ref>
|-
! Characteristic !!  Oceanic Waters in Polar regions !! Oceanic Waters in Temperate regions !! Oceanic Waters in Tropical regions
|-
| '''[[Precipitation]] vs. [[evaporation]]''' || P > E || P > E || E > P
|-
| '''[[Sea surface temperature|Sea Surface Temperature]] in Winter''' || −2&nbsp;°C || 5 to 20&nbsp;°C || 20 to 25&nbsp;°C
|-
| '''Average [[Salinity]]''' || 28‰ to 32‰ || 35‰ || 35‰ to 37‰ 
|-
| '''Annual Variation of Air [[Temperature]]''' || ≤ 40ªC || 10&nbsp;°C || < 5&nbsp;°C
|-
| '''Annual Variation of Water [[Temperature]]''' || < 5ªC || 10&nbsp;°C || < 5&nbsp;°C 
|}

=== Mixing Time ===
Residence Time=The amount of the element in the ocean ÷ The rate at which that element is added to (or removed from) the ocean

The mean oceanic mixing time ([[residence time]]) is thought to be approximately 1,600 years. If a given element in the ocean stays in the ocean, on average, longer than the oceanic mixing time, then that element is assumed to be homogeneously spread throughout the ocean. As a result, since the major salts have a residence time that is longer than 1,600 years, the ratio of major salts is thought to be unchanging across the ocean. This constant ratio is often referred to as Forchhammer's principle or the principle of constant proportions.

{| class="wikitable" cellpadding="5" style="margin:auto;"
|+Mean Oceanic Residence Times for specific Constituents <ref name="uga.3030">{{cite web |url=http://www.gly.uga.edu/railsback/3030/3030Tres.pdf |format=PDF |title= Calculation of residence times in seawater of some important solutes|work= |publisher=gly.uga.edu |date= }}</ref><ref name="Chester Marine Geochem">{{cite book |last=Chester, Jickells |first=Roy, Tim |title=Marine Geochemistry |date=2012 |publisher=Blackwell Publishing |isbn=978-1-118-34907-6 |pages=225–230 }}</ref> 
|-
! Constituent !! Residence Time (in years)
|-
| Iron (Fe) || 200
|-
| Aluminum (Al) || 600
|-
| Manganese (Mn) || 1,300
|-
| Water (H<sub>2</sub>O) || 4,100
|-
| Silicon (Si) || 20,000
|-
| Carbonate (CO<sub>3</sub><sup>2-</sup>) || 110,000
|-
| Calcium (Ca<sup>2+</sup>) || 1,000,000
|-
| Sulfate (SO<sub>4</sub><sup>2-</sup>) || 11,000,000
|-
| Potassium (K<sup>+</sup>)|| 12,000,000
|-
| Magnesium (Mg<sup>2+</sup>) || 13,000,000
|-
| Sodium (Na<sup>+</sup>) || 68,000,000
|-
| Chloride (Cl<sup>-</sup>) || 100,000,000
|}

=== Salinity ===
A zone of rapid salinity increase with depth is called a [[halocline]]. The temperature of maximum density of [[Salinity#Seawater|seawater]] decreases as its salt content increases. Freezing temperature of water decreases with salinity, and boiling temperature of water increases with [[salinity]]. Typical seawater freezes at around −1.9&nbsp;°C at atmospheric pressure. If precipitation exceeds evaporation, as is the case in polar and temperate regions, salinity will be lower. If evaporation exceeds precipitation, as is the case in tropical regions, salinity will be higher. Thus, oceanic waters in polar regions have lower salinity content than oceanic waters in temperate and tropical regions.<ref name="autogenerated2">{{cite book |last=Chester, Jickells |first=Roy, Tim |title=Marine Geochemistry |date=2012 |publisher=Blackwell Publishing |isbn=978-1-118-34907-6 }}</ref>

Salinity can be calculated using the chlorinity, which is a measure of the total mass of halogen ions (includes fluorine, chlorine, bromine, and iodine) in seawater. By international agreement, the following formula is used to determine salinity:

'''Salinity (in ‰)=1.80655 x Chlorinity (in ‰)'''

The average chlorinity is about 19.2‰, and, thus, the average salinity is around 34.7‰ <ref name="autogenerated2" />

=== Absorption of light ===
{| class="wikitable" cellpadding="5" style="margin:auto;"
|+Absorption of Light in Different Wavelengths by Ocean <ref name="autogenerated2" />
|-
! Color: Wavelength (nm) !! Depth wherein 99 percent of wavelength is absorbed (in meters) !! Percent absorbed in 1 meter of water
|-
| '''Ultraviolet (UV)''': 310 || 31 || 14.0
|-
| '''Violet (V)''': 400 || 107 || 4.2
|-
| '''Blue (B)''': 475 || 254 || 1.8
|-
| '''Green (G)''': 525 || 113 || 4.0
|-
| '''Yellow (Y)''': 575 || 51 || 8.7
|-
| '''Orange (O)''': 600 || 25 || 16.7 
|-
| '''Red (R)''': 725 || 4 || 71.0 
|-
| '''Infrared (IR)''': 800 || 3 || 82.0
|}

=== Economic value ===

The oceans are essential to transportation. This is because most of the world's goods move by [[ship]] between the world's [[seaport]]s. Oceans are also the major supply source for the [[fishing industry]]. Some of the more major ones are [[shrimp]], [[fish]], [[crabs]], and [[lobster]].<ref name="noaa.gov" />

=== Waves ===
{{Further|Wind wave}}
The motions of the ocean surface, known as undulations or ''[[waves]]'', are the partial and alternate rising and falling of the ocean surface.

== Extraterrestrial oceans ==
{{Further|Extraterrestrial liquid water}}
[[File:PIA18071-SaturnMoonEnceladus-WaterOcean-20140403.jpg|thumb|right|Artist's conception of subsurface ocean of Enceladus confirmed April 3, 2014.<ref name="NASA-20140403" /><ref name="SCI-20140404">{{cite journal |last1=Iess |first1=L. |last2=Stevenson |first2=D.J. |last3=Parisi |first3=M. |last4=Hemingway |first4=D. |last5=Jacobson |first5=R.A. |last6=Lunine |first6=J.I. |last7=Nimmo |first7=F. |last8=Armstrong |first8=J.w. |last9=Asmar |first9=S.w. |last10=Ducci |first10=M. |last11=Tortora |first11=P. |title=The Gravity Field and Interior Structure of Enceladus |url=http://www.sciencemag.org/content/344/6179/78 |date=4 April 2014 |journal=[[Science (journal)|Science]] |volume=344 |number=6179 |pages=78–80 |doi=10.1126/science.1250551 |accessdate=3 April 2014 }}</ref>]]
[[Image:EuropaInterior1.jpg|thumb|right|Two models for the composition of Europa predict a large subsurface ocean of liquid water. Similar models have been proposed for other celestial bodies in the Solar System]]

Although Earth is the only known [[planet]] with large stable bodies of liquid water on its surface and the only one in the [[Solar System]], other celestial bodies are believed to possess large oceans.

=== Planets ===

The [[gas giant]]s, [[Jupiter]] and [[Saturn]], are thought to lack surfaces and instead have a stratum of [[liquid hydrogen]], however their [[planetary geology]] is not well understood.  The possibility of [[Uranus]] and [[Neptune]] possessing hot, highly compressed, supercritical water<!-- {{efn |name=pressures}} --> under their thick atmospheres has been hypothesised. Although their composition is still not fully understood, a 2006 study by Wiktorowicz et al. ruled out the possibility of such a water "ocean" existing on Neptune,<ref name="WiktorowiczIngersoll2007">{{cite journal |last1=Wiktorowicz |first1=Sloane J. |last2=Ingersoll |first2=Andrew P. |title=Liquid water oceans in ice giants |journal=Icarus |volume=186 |issue=2 |year=2007 |pages=436–447 |issn=00191035 |doi=10.1016/j.icarus.2006.09.003 |arxiv=astro-ph/0609723 |bibcode=2007Icar..186..436W }}</ref> though some studies have suggested that exotic oceans of liquid diamond are possible.<ref name="Silvera2010">{{cite journal |last1=Silvera |first1=Isaac |title=Diamond: Molten under pressure |journal=Nature Physics |volume=6 |issue=1 |year=2010 |pages=9–10 |issn=1745-2473 |doi=10.1038/nphys1491 |bibcode=2010NatPh...6....9S }}</ref>

The Mars ocean hypothesis suggests that nearly a third of the surface of Mars was once covered by water, though the water on Mars is no longer oceanic. The possibility continues to be studied along with reasons for their apparent disappearance. Astronomers believe that [[Atmosphere of Venus|Venus]] had liquid water and perhaps oceans in its very early history. If they existed, all later vanished via [[Geology of Venus|resurfacing]].

=== Natural satellites ===

A global layer of liquid water thick enough to decouple the crust from the mantle is believed to be present on [[Titan (moon)|Titan]], [[Europa (moon)|Europa]] and, with less certainty, [[Callisto (moon)|Callisto]], [[Ganymede (moon)|Ganymede]]<ref name="clubsandwich 2014">{{cite news |last=Clavin |first=Whitney |url=http://www.jpl.nasa.gov/news/news.php?release=2014-138 |title=Ganymede May Harbor 'Club Sandwich' of Oceans and Ice |work=NASA |publisher=Jet Propulsion Laboratory |date=May 1, 2014 |accessdate=2014-05-01 }}</ref><ref name="Vance">{{cite journal |title=Ganymede's internal structure including thermodynamics of magnesium sulfate oceans in contact with ice |journal=Planetary and Space Science |date=12 April 2014 |last=Vance |first=Steve |last2=Bouffard |first2=Mathieu |last3=Choukroun |first3=Mathieu |last4=Sotina |first4=Christophe |url=http://www.sciencedirect.com/science/article/pii/S0032063314000695 |accessdate=2014-05-02 |doi=10.1016/j.pss.2014.03.011 |bibcode=2014P&SS...96...62V}}</ref> and [[Triton (moon)|Triton]].<ref name="EncycSolSys-Triton">{{cite encyclopedia |title=Encyclopedia of the Solar System |chapter=Triton |last1=McKinnon |first1=William B. |last2=Kirk |first2=Randolph L. |publisher=Academic Press |year=2007 |editor=Lucy Ann Adams McFadden, Lucy-Ann Adams, Paul Robert Weissman, Torrence V. Johnson |edition=2nd |location=Amsterdam; Boston |isbn=978-0-12-088589-3 |pages=483–502 }}</ref><ref name="ocean_triton">{{cite journal |first=Javier |last=Ruiz |title=Heat flow and depth to a possible internal ocean on Triton |journal=Icarus |volume=166 |issue=2 |pages=436–439 |date=December 2003 |doi=10.1016/j.icarus.2003.09.009 |bibcode=2003Icar..166..436R }}</ref> A [[magma]] ocean is thought to be present on [[Io (moon)|Io]]. [[Geyser]]s have been found on Saturn's moon [[Enceladus (moon)|Enceladus]], possibly originating from about {{convert|10|km|sp=us}} deep ocean beneath an ice shell.<ref name="NASA-20140403">{{cite web |last=Platt |first=Jane |last2=Bell |first2=Brian |title=NASA Space Assets Detect Ocean inside Saturn Moon |url=http://www.jpl.nasa.gov/news/news.php?release=2014-103 |work=[[NASA]] |date=2014-04-03 |accessdate=2014-04-03 }}</ref> Other icy moons may also have internal oceans, or may once have had internal oceans that have now frozen.<ref name="Hussmann Sohl et al. 2006">{{cite doi | 10.1016/j.icarus.2006.06.005 }}</ref>

Large bodies of liquid hydrocarbons are thought to be present on the surface of [[Titan (moon)|Titan]], although they are not large enough to be considered oceans and are sometimes referred to as ''lakes'' or seas. The [[Cassini–Huygens]] space mission initially discovered only what appeared to be dry lakebeds and empty river channels, suggesting that Titan had lost what surface liquids it might have had. Cassini's more recent fly-by of Titan offers radar images that strongly suggest hydrocarbon lakes exist near the colder polar regions. Titan is thought to have a subsurface liquid-water ocean under the ice and hydrocarbon mix that forms its outer crust.

=== Dwarf planets and trans-Neptunian objects ===
[[File:Ceres Cutaway.jpg|left|thumb|Diagram showing a possible internal structure of [[Ceres (dwarf planet)|Ceres]]]]

[[Ceres (dwarf planet)|Ceres]] appears to be [[Planetary differentiation|differentiated]] into a [[Rock (geology)|rocky]] [[core (geology)|core]] and icy [[mantle (geology)|mantle]] and may harbour a liquid-water ocean under its surface.<ref name="mccord.2005">{{cite journal |last=McCord |first=Thomas B. |title=Ceres: Evolution and current state |journal=Journal of Geophysical Research |volume=110 |issue=E5 |page=E05009 |year=2005 |doi=10.1029/2004JE002244 |bibcode=2005JGRE..11005009M }}</ref><ref name="cr.ceres">{{cite journal |last=Castillo-Rogez |first=J. C. |last2=McCord |first2=T. B. |last3=Davis |first3=A. G. |title=Ceres: evolution and present state |journal=Lunar and Planetary Science |volume=XXXVIII |pages=2006–2007 |year=2007 |url=http://www.lpi.usra.edu/meetings/lpsc2007/pdf/2006.pdf |format=PDF |accessdate=2009-06-25 }}</ref>

Not enough is known of the larger [[Trans-Neptunian object]]s to determine whether they are differentiated bodies capable of possessing oceans, although models of radioactive decay suggest that [[Pluto (dwarf planet)|Pluto]],<ref name="pluto">{{cite web |title=The Inside Story |publisher=Johns Hopkins University Applied Physics Laboratory |work=pluto.jhuapl.edu&nbsp;— NASA New Horizons mission site |url=http://pluto.jhuapl.edu/science/everything_pluto/9_insideStory.php |year=2013 |accessdate=2 August 2013 }}</ref> [[Eris (dwarf planet)|Eris]], [[90377 Sedna|Sedna]], and [[90482 Orcus|Orcus]] have oceans beneath solid icy crusts at the core-boundary approximately {{nowrap|100 to 180 km}} thick.<ref name="Hussmann Sohl et al. 2006" />

=== Extrasolar ===
[[File:UpsilonAndromedae D moons.jpg|thumb|right|Rendering of a hypothetical large [[extrasolar moon]] with surface liquid-water oceans]]

Some planets and natural satellites beyond the Solar System are likely to possess oceans, including possible water ocean planets similar to Earth in the [[habitable zone]] or "liquid-water belt". The detection of oceans, even through the [[spectroscopy]] method, however is likely to prove extremely difficult and inconclusive.

Theoretical models have been used to predict with high probability that [[GJ 1214 b]], detected by transit, is composed of exotic form of [[ice VII]], making up 75% of its mass,<ref name="cfa.pr200924">{{cite web |url=http://www.cfa.harvard.edu/news/2009/pr200924.html |title=Astronomers Find Super-Earth Using Amateur, Off-the-Shelf Technology |first=David A. |last=Aguilar |date=2009-12-16 |work= |publisher=Harvard-Smithsonian Center for Astrophysics |accessdate=January 23, 2010 }}</ref>
making it an [[ocean planet]].

Other possible candidates are merely speculated based on their mass and position in the habitable zone include planet though little is actually known of their composition. Some scientists speculate [[Kepler-22b]] may be an "ocean-like" planet.<ref name="upr.exo">{{cite web |url=http://phl.upr.edu/library/notes/updatesonexoplanetsduringthefirstkeplerscienceconference |title=Updates on Exoplanets during the First Kepler Science Conference |date=2011-12-08 |first=Abel |last=Mendez Torres |publisher=Planetary Habitability Laboratory at [[University of Puerto Rico at Arecibo|UPR Arecibo]] }}</ref> Models have been proposed for [[Gliese 581 d]] that could include surface oceans. [[Gliese 436 b]] is speculated to have an ocean of "hot ice".<ref name="r.20070516">{{cite news |url=http://www.reuters.com/article/2007/05/16/us-space-planet-idUSN1621607620070516 |title=Hot "ice" may cover recently discovered planet |first=Maggie |last=Fox |work=[[Reuters]] |date=May 16, 2007 |accessdate=May 18, 2012 }}</ref> [[Extrasolar moon]]s orbiting planets, particularly gas giants within their parent star's habitable zone may theoretically possess surface oceans.

Terrestrial planets will acquire water during their accretion, some of which will be buried in the magma ocean but most of it will go into a steam atmosphere, and when the atmosphere cools it will collapse on to the surface forming an ocean. There will also be outgassing of water from the mantle as the magma solidifies—this will happen even for planets with a low percentage of their mass composed of water, so "super-Earth exoplanets may be expected to commonly produce water oceans within tens to hundreds of millions of years of their last major accretionary impact."<ref name="ass.332">{{cite journal |last=Elkins-Tanton |doi=10.1007/s10509-010-0535-3 |title=Formation of Early Water Oceans on Rocky Planets |year=2010 |journal=Astrophysics and Space Science |volume=332 |issue=2 |pages=359–364 |arxiv=1011.2710 |bibcode=2011Ap&SS.332..359E }}</ref>

=== Non-water surface liquids ===

Oceans, seas, lakes, etc., can be composed of liquids other than water: e.g. the [[hydrocarbon]] [[lake]]s on [[Titan (moon)|Titan]]. The possibility of seas of [[nitrogen]] on [[Triton (moon)|Triton]] was also considered but ruled out.<ref name="encyc">{{cite encyclopedia |title=Encyclopedia of the Solar System |chapter=Triton |last1=McKinnon |first1=William B. |last2=Kirk |first2=Randolph L. |publisher=Academic Press |year=2007 |editor=Lucy Ann Adams McFadden, Lucy-Ann Adams, Paul Robert Weissman, Torrence V. Johnson |edition=2nd |location=Amsterdam; Boston |isbn=978-0-12-088589-3 |page=485 }}</ref> Underneath the thick atmospheres of [[Uranus]] and [[Neptune]] it is expected that these planets are composed of oceans of hot high-density fluid mixtures of water, ammonia and other volatiles.<ref name="cosis.05179">{{cite journal |url=http://www.cosis.net/abstracts/EGU06/05179/EGU06-J-05179-1.pdf |format=PDF |title=Water-ammonia ionic ocean on Uranus and Neptune? |first1=S. |last1=Atreya |first2=P. |last2=Egeler |first3=K. |last3=Baines |journal=Geophysical Research Abstracts |volume=8 |page=05179 |year=2006 |bibcode=2005AGUFM.P11A0088A }}</ref> The gaseous outer layers of [[Jupiter]] and [[Saturn]] transition smoothly into oceans of [[supercritical fluid|supercritical]] [[hydrogen]].<ref name="pss.1999">{{cite journal |last=Guillot |first=T. |title=A comparison of the interiors of Jupiter and Saturn |journal=Planetary and Space Science |year=1999 |volume=47 |issue=10–11 |pages=1183–200 |bibcode=1999P&SS...47.1183G |arxiv=astro-ph/9907402 |doi=10.1016/S0032-0633(99)00043-4 }}</ref><ref name="lang03">{{cite web |last=Lang |first=Kenneth R. |year=2003 |url=http://ase.tufts.edu/cosmos/view_chapter.asp?id=9&page=3 |title=Jupiter: a giant primitive planet |publisher=NASA |accessdate=2007-01-10 }}</ref> There is evidence that the icy surfaces of the moons [[Ganymede (moon)|Ganymede]], [[Callisto (moon)|Callisto]], [[Europa (moon)|Europa]], Titan and [[Enceladus (moon)|Enceladus]] are shells floating on oceans of very dense liquid water or water–ammonia.<ref name="agu.p21a">{{cite journal |bibcode=2008AGUFM.P21A1346C |year=2008 |page=1346 |volume=21 |journal=American Geophysical Union |contribution=The Titan Saturn System Mission |title=American Geophysical Union, Fall Meeting 2008, abstract #P21A-1346 |last1=Coustenis |first1=A. |last2=Lunine |first2=J. |last3=Lebreton |first3=J. |last4=Matson |first4=D. |last5=Erd |first5=C. |last6=Reh |first6=K. |last7=Beauchamp |first7=P. |last8=Lorenz |first8=R. |last9=Waite |first9=H. |last10=Sotin |first10=C. |last11=Tssm Jsdt |first11=T. |quote=the Titan system, rich in organics, containing a vast subsurface ocean of liquid water }}</ref><ref name="ic.208">{{cite journal |doi=10.1016/j.icarus.2010.02.020 |journal=Icarus |volume=208 |issue=2 |year=2010 |pages=896–904 |title=Shell thickness variations and the long-wavelength topography of Titan |first1=F. |last1=Nimmo |first2=B. G. |last2=Bills |quote=observations can be explained if Titan has a floating, isostatically-compensated ice shell |bibcode=2010Icar..208..896N }}</ref><ref name="ar.0032">{{cite journal |arxiv=0910.0032 |title=Elastic ice shells of synchronous moons: Implications for cracks on Europa and non-synchronous rotation of Titan |first1=Peter M. |last1=Goldreich |first2=Jonathan L. |last2=Mitchell |doi=10.1016/j.icarus.2010.04.013 |journal=Icarus |volume=209 |issue=2 |year=2010 |pages=631–638 |quote=A number of synchronous moons are thought to harbor water oceans beneath their outer ice shells. A subsurface ocean frictionally decouples the shell from the interior |bibcode=2010Icar..209..631G }}</ref><ref name="cop.213">{{cite web |url=http://meetingorganizer.copernicus.org/EPSC2009/EPSC2009-213.pdf |title=Study of the ice shells and possible subsurface oceans of the Galilean satellites using laser altimeters on board the Europa and Ganymede orbiters JEO and JGO |format=PDF |accessdate=2011-10-14 }}</ref><ref name="ucsc.2008">{{cite web |url=http://www.pmc.ucsc.edu/~jhr/research/Roberts_Nimmo_2008_Icarus.pdf |format=PDF |title=Tidal heating and the long-term stability of a subsurface ocean on Enceladus |accessdate=2011-10-14 }}</ref> Earth is often called ''the'' ocean planet because it is 70% covered in water.<ref name="nih.12349465">{{cite web |url=http://www.ncbi.nlm.nih.gov/pubmed/12349465 |title=The ocean planet |publisher=Ncbi.nlm.nih.gov |date=2011-10-03 |accessdate=2011-10-14 }}</ref><ref name="sci.1998">{{cite web |url=http://www.sciamdigital.com/index.cfm?fa=Products.ViewIssuePreview&ISSUEID_CHAR=639198AF-0E70-4121-9F4C-465C7C35B05&ARTICLEID_CHAR=86FB36E4-843C-4DC5-AA23-DFCA681FBB2 |title=Irrigating Crops with Seawater |last= |first= |date=August 1998 |work=Scientific American |publisher= }}</ref> The [[atmosphere of Venus]] is 96.5% [[carbon dioxide]] and at the surface the pressure makes the CO<sub>2</sub> a [[supercritical fluid]]. Extrasolar [[terrestrial planet]]s that are extremely close to their parent star will be tidally locked and so one half of the planet will be a magma ocean.<ref name="ar.1204">{{cite journal |arxiv=0906.1204 |title=Chemistry of Silicate Atmospheres of Evaporating Super-Earths |first1=Laura |last1=Schaefer |first2=Bruce, Jr. |last2=Fegley |journal=The Astrophysical Journal Letters |year=2009 |volume=703 |issue=2 |pages=L113–L117 |doi=10.1088/0004-637X/703/2/L113 |bibcode=2009ApJ...703L.113S }}</ref> It is also possible that terrestrial planets had magma oceans at some point during their formation as a result of giant impacts.<ref name="nmsu.oem">{{cite web |url=http://geophysics.nmsu.edu/slava/publications/OEM.pdf |format=PDF |title=Fluid Dynamics of a Terrestrial Magma Ocean |first=V. S. |last=Solomatov |year=2000 |work= |publisher= }}</ref> Where there are suitable temperatures and pressures, volatile chemicals that might exist as liquids in abundant quantities on planets include [[ammonia]], [[argon]], [[carbon disulfide]], [[ethane]], [[hydrazine]], [[hydrogen]], [[hydrogen cyanide]], [[hydrogen sulfide]], [[methane]], [[neon]], [[nitrogen]], [[nitric oxide]], [[phosphine]], [[silane]], [[sulfuric acid]], and [[water]].<ref name="ifa.a281">Tables 3 and 4 in {{cite web |url=http://www.ifa.hawaii.edu/~meech/a281/handouts/Baines_astrobio04.pdf |format=PDF |title=Many Chemistries Could Be Used to Build Living Systems |first=William |last=Bains |work=Astrobiology |volume=4 |number=2 |year=2004 }}</ref> [[Hot Neptune]]s close to their star could lose their atmospheres via [[hydrodynamic escape]], leaving behind their cores with various liquids on the surface.<ref name="epsc.542">{{cite journal |url=http://meetingorganizer.copernicus.org/EPSC2009/EPSC2009-542.pdf |format=PDF |title=Atmospheric Loss of Sub-Neptune's and Implications for Liquid Phases of Different Solvents on Their Surfaces |first=J.J. |last=Leitner |first2=H. |last2=Lammer |first3=P. |last3=Odert |first4=M. |last4=Leitzinger |first5=M.G. |last5=Firneis |first6=A. |last6=Hanslmeier |work=EPSC Abstracts |volume=4 |id=EPSC2009-542 |year=2009 |conference=European Planetary Science Congress }}</ref>

== See also ==
{{Portal|Ecology|Environment|Geography|Weather}}
<!-- {{Wikipedia-Books}}
{{main|Outline of the oceans|Index of ocean-related articles}} -->
{{colbegin|4}}
* [[Blue carbon]]
* [[Biosalinity]]
* [[Brackish water]]
* [[Effects of global warming on oceans]]
* [[European Atlas of the Seas]]
* [[Four Seas]]
* [[International Maritime Organization]]
* [[List of bodies of water by salinity]]
* [[List of largest lakes and seas in the Solar System]]
* [[List of Oceans with alternative names]]
* [[List of seas]]
* [[Marine debris]]
* [[Marine pollution]]
* [[Ocean acidification]]
* [[Ocean current]]
* [[Ocean governance]]
* [[Oceanography]]
* [[Oceans (2009 film)|''Oceans'' (2009 film)]]
* [[Ogyges]]
* [[Pelagic zone]]
* [[Physical oceanography]]
* [[Polar seas]]
* [[Saline water]]
* [[Salinity]]
* [[Sea]]
* [[Sea ice]]
* [[Sea in culture]]
* [[Sea level]] and [[sea level rise]]
* [[Sea salt]]
* [[Sea state]]
* [[Seawater]]
* [[Sea water gel]]
* [[Seven Seas]]
* [[United Nations Convention on the Law of the Sea]]
* [[Water]]
* [[Water distribution on Earth]]
* [[Wind waves]]
* [[World Ocean Atlas]]
* [[World Ocean Day]]

On other bodies:

* [[Extraterrestrial liquid water]]
* [[Ocean planet]]
* [[Ice planet]]
{{colend}}

== References ==
{{reflist|35em}}

== Further reading ==
* Matthias Tomczak and J. Stuart Godfrey. 2003. ''Regional Oceanography: an Introduction''. (see [http://www.es.flinders.edu.au/~mattom/regoc/ the site])
* Pope, F. 2009. From eternal darkness springs cast of angels and jellied jewels. ''in'' '''The Times'''. November 23. 2009 p.&nbsp;16–17.

== External links ==
{{commons}}
{{wikiquote|Oceans}}
{{Wiktionary}}
* {{dmoz|Science/Environment/Water_Resources/Oceans|Oceans}}
* [http://ocean.si.edu Smithsonian Ocean Portal]
* [http://www.noaa.gov/ocean.html NOAA – National Oceanic and Atmospheric Administration – Ocean]
* [http://www.sciencedaily.com/articles/o/ocean.htm Ocean :: Science Daily]
* [http://www.sciencedaily.com/releases/2008/12/081215091011.htm Ocean-bearing Planets: Looking For Extraterrestrial Life In All The Right Places]
* [http://mindblowingscience.com/latest-news/titan-likely-to-have-huge-underground-ocean/ Titan Likely To Have Huge Underground Ocean | Mind Blowing Science]
* [http://www.oceansatlas.com/unatlas/about/howoceanswereformed2/originsofoceans/originofocean2jte.html Origins of the oceans and continents]". ''[http://www.oceansatlas.com/ UN Atlas of the Oceans].''

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[[Category:Oceans| ]]
[[Category:Oceanography|Oceans]]
[[Category:Coastal and oceanic landforms]]
[[Category:Bodies of water]]

[[ur:بحر (سمندر)]]