Southern Caribbean upwelling system: Difference between revisions
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The '''Southern Caribbean Upwelling system''' (SCUS) is a low latitude tropical upwelling system at about 10°N on the southern coast of the Caribbean sea basin off Colombia, Venezuela, and Trinidad. The intensity of the Caribbean low-level jet (effect of the trade winds) and the coastal orientation are determining the timing and spatial variability of |
The '''Southern Caribbean Upwelling system''' (SCUS) is a low latitude tropical [[upwelling]] system at about 10°N on the southern coast of the [[Caribbean Sea|Caribbean sea]] basin off [[Colombia]], [[Venezuela]], and [[Trinidad]]. The intensity of the Caribbean low-level jet (effect of the trade winds) and the coastal orientation are determining the timing and spatial variability of this upwelling system. The system is likely to be responsible for a major part in the primary production due to the addition of nutrients that are added to the system through the upwelling.<ref name=":0">{{Cite web|last=Correa-Ramirez|first=Marco|last2=Rodriguez-Santana|first2=Ángel|last3=Ricaurte-Villota|first3=Constanza|last4=Paramo|first4=Jorge|date=2019-03-27|title=Water masses and mixing processes in the Southern Caribbean upwelling system off Colombia|url=http://dx.doi.org/10.5194/os-2019-17|access-date=2021-05-12|website=dx.doi.org}}</ref> |
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[[File:WUZ EUZ.jpg|thumb|427x427px|A comparison between the WUZ and EUZ showing the minimum and maximum values for: wind speed (W), Turbulence (Turb), alongshore wind speed (alongW), Offshore Ekman transport due too wind (offshET). Vertical transport due too Ekman pumping intergrated too 100k offshore (EP100), Sea Surface Temperature (SST), chlorophyll-a(Chl).]] |
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There are two main upwelling zones in the system that vary in intensity throughout the year; The Western Upwelling Zone (WUZ); and the Eastern Upwelling Zone; (EUZ). |
There are two main upwelling zones in the system that vary in intensity throughout the year; The Western Upwelling Zone (WUZ); and the Eastern Upwelling Zone; (EUZ). |
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The western the WUZ is situated between 74-71°W and generates mainly seasonal upwelling and |
The western the WUZ is situated between 74-71°W and generates mainly seasonal upwelling and high offshore transport due to intense winds. The EUZ, situated between 71-60°W is less intense but is more favourable for the upwelling throughout the year. |
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The last thirty years the upwelling |
The last thirty years the upwelling has intensified which is producing cooling of the [[sea surface temperature]] (SST) in the WUZ, this is in contrast to the general temperature in the Caribbean sea which has shown to increase.<ref name=":0" /> The "typical" Caribbean surface water is a mixture of North Atlantic Surface Water (NASW) and riverine waters from the Orinoco and Amazon rivers. |
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Under the Caribbean surface waters |
Under the Caribbean surface waters more saline water is found with values close to those typical for the [[Subtropical underwate]]<nowiki/>r (SUW) SA ~37, Θ ~22 °C. This forms a subsurface maximum(SSM).<ref name=":0" /> After the rainy season the SSM is lower due to dilution of the surface waters. |
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== Characterization of the SCUS == |
== Characterization of the SCUS == |
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Sinds 1994 variations in upwelling are studied using cycles of satellite SST. The SST this is used as a proxy for upwelling in this tropical region Aswell as the dominat winds and chloropyll-a. These are all proxies that are relatively easy to measure and quite easily accessibe. |
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[[File:Upwelling zones.jpg|thumb|514x514px|Upwelling zones in the Southern Caribbean]] |
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| ⚫ | The [[Rossby radius of deformation|Rossby radius]] <math>R = \sqrt{{g}\frac{\Delta\rho}{\rho}\frac{h}{f}}</math> changes the relative position of the upwelling zone due to the effect of the rossby waves. The Rossby radius for this region is ~19 km; estimated using a mean depth h= 35m, gravity g = 9,81 m s -1<ref name=":0" />. The upwelling zones are found close to the coast roughly withing the 19 km found within the Rossby radius. However, in rare cases upwelled water move offshore up to over 250 km from the coast.<ref name=":1">{{Cite journal|last=Rueda-Roa|first=Digna T.|last2=Muller-Karger|first2=Frank E.|date=August 2013|title=The southern Caribbean upwelling system: Sea surface temperature, wind forcing and chlorophyll concentration patterns|url=http://dx.doi.org/10.1016/j.dsr.2013.04.008|journal=Deep Sea Research Part I: Oceanographic Research Papers|volume=78|pages=102–114|doi=10.1016/j.dsr.2013.04.008|issn=0967-0637}}</ref> |
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| ⚫ | Upwelled waters in the SCUS are consistent in geochemical compositions of the "Subtropical underwater", which is a water mass that comes from the [[Atlantic Ocean|central Atlantic]] and due to its relative dense water properties (SA ~37, Θ ~22 °C) lays under the Caribbean surface waters, and is likely coming from this water mass. |
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| ⚫ | The [[Rossby radius of deformation|Rossby radius]] <math>R = \sqrt{{g}\frac{\Delta\rho}{\rho}\frac{h}{f}}</math> changes the relative position of the upwelling zone due to the effect of the rossby waves. The Rossby radius for this region is ~19 km; estimated using a mean depth h= 35m, gravity g = 9,81 m s -1. The upwelling zones are found close to the coast roughly withing the 19 km found within the Rossby radius. However, in rare cases upwelled water move offshore up to over 250 km from the coast.<ref name=":1">{{Cite journal|last=Rueda-Roa|first=Digna T.|last2=Muller-Karger|first2=Frank E.|date=August 2013|title=The southern Caribbean upwelling system: Sea surface temperature, wind forcing and chlorophyll concentration patterns|url=http://dx.doi.org/10.1016/j.dsr.2013.04.008|journal=Deep Sea Research Part I: Oceanographic Research Papers|volume=78|pages=102–114|doi=10.1016/j.dsr.2013.04.008|issn=0967-0637}}</ref> |
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| ⚫ | Upwelled waters in the SCUS are consistent in geochemical compositions of the "Subtropical underwater", which is a |
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=== Sea surface temperature (SST) === |
=== Sea surface temperature (SST) === |
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The SCUS is studied through the SST at a high resolution (1 km grid) radiometer ([[National Oceanic and Atmospheric Administration]] / NOAA) |
The SCUS is studied through the SST at a high resolution (1 km grid) radiometer ([[National Oceanic and Atmospheric Administration]] / NOAA). This data is used to identify differences in the SST and with that locate upwelling regions. There is a semi-annual cycle of SST within the upwelling areas. With cooling periodically occurring between December and April, showing 2-4 upwelling pulses peaking during February–March. Around May there is a typical increase in SST followed by cooling during June–August due to a midyear upwelling.<ref name=":1" /> |
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=== Wind === |
=== Wind === |
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[[File:Seasonal differences.jpg|thumb|357x357px|Seasonal differences in wind and connected SST]] |
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The [[Trade winds]] that blow over the southern Caribbean Sea (also called the low-level jet) generate northward [[Ekman transport]]. The intensity of the trade winds vary per season and explain the variation in upwelling and the measured differences in SST that are mentioned above. The driving forces of the Ekman transport is wind-stress or "τ" The driving winds are divided in multiple areas. East of 68°W have relative stable wind speed (>6 m <math>s^-1</math>), and slightly lower during August–November (4 – 6 m <math>s^-1</math>). |
The [[Trade winds]] that blow over the southern Caribbean Sea (also called the low-level jet) generate northward [[Ekman transport]]. The intensity of the [[trade winds]] vary per season (image 2 shows the WUZ b) and c) in December and d) and e) in February) and explain the variation in upwelling and the measured differences in SST that are mentioned above. The driving forces of the Ekman transport is wind-stress or "τ" The driving winds are divided in multiple areas. East of 68°W have relative stable wind speed (>6 m <math>s^-1</math>), and slightly lower during August–November (4 – 6 m <math>s^-1</math>). |
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The direction of the wind is generally parallel to the southern Caribbean Sea margin, however, between May and October the EUZ has more along shore winds that are ~1.7° varying from the along shore direction and |
The direction of the wind is generally parallel to the southern Caribbean Sea margin, however, between May and October the EUZ has more along shore winds that are ~1.7° varying from the along shore direction and during November until April the direction is more onshore with ~12°. In the WUZ the wind is more offshore in the majority of the year ~-14°. This changes during October–November when winds are aligned with the shoreline ~0.2°. |
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These wind directions respectively to the coast produce the northward and thus offshore Ekman transport that are favourable year round for the SCUS. |
These wind directions respectively to the coast produce the northward wind curl and thus offshore Ekman transport that are favourable year round for the SCUS. |
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=== Chlorophyll-a === |
=== Chlorophyll-a === |
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[[Chlorophyll a]] is used to see the productivity of zooplankton, amounts of |
[[Chlorophyll a]] is used to see the productivity of zooplankton, amounts of chlorophyll-a increase with higher nutrient concentrations that are found in upwelled water and can therefore be used as a proxy for upwelling systems.<ref>{{Cite journal|last=Walsh|first=Sheila M.|date=2011|title=Ecosystem-Scale Effects of Nutrients and Fishing on Coral Reefs|url=http://dx.doi.org/10.1155/2011/187248|journal=Journal of Marine Biology|volume=2011|pages=1–13|doi=10.1155/2011/187248|issn=1687-9481|doi-access=free}}</ref> Withing the SCUS there are strong correlations between the SST and Chlorophyll-a. These show a Chlorophyll-a maximum in December and April and a shorter maximum between June and July. |
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Nutrient concentrations that come with the water from the SUW have a strong positive impact on the phytoplankton productivity, it is estimated that up to 95% of the small pelagic biomass is the southern Caribbean sea is sustained by the primary production that comes with these upwelled waters. |
Nutrient concentrations that come with the water from the SUW have a strong positive impact on the phytoplankton productivity, it is estimated that up to 95% of the small pelagic biomass is the southern Caribbean sea is sustained by the primary production that comes with these upwelled waters. |
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In the EUZ there a four time higher amount of small pelagic biomass compared to the WUZ. This difference is contributed to the prolonged duration of the upwelling. The water in the EUZ has a SST < 26C° for 8.5 months and the WUZ for 6.9. In addition to that, the EUZ has a wider continental shelf. Upwelling over wide and shallow continental shelves can generate resuspension and transport of essential microelements from the benthic boundary layer to the surface.<ref>{{Cite journal|last=Huhn|first=K.|last2=Paul|first2=A.|last3=Seyferth|first3=M.|date=2007-10-04|title=Modeling sediment transport patterns during an upwelling event|url=http://dx.doi.org/10.1029/2005jc003107|journal=Journal of Geophysical Research|volume=112|issue=C10|doi=10.1029/2005jc003107|issn=0148-0227|doi-access=free}}</ref> |
In the EUZ there is a four time higher amount of small pelagic biomass compared to the WUZ. This difference is contributed to the prolonged duration of the upwelling. The water in the EUZ has a SST < 26C° for 8.5 months and the WUZ for 6.9. In addition to that, the EUZ has a wider continental shelf. Upwelling over wide and shallow continental shelves can generate resuspension and transport of essential microelements from the benthic boundary layer to the surface.<ref>{{Cite journal|last=Huhn|first=K.|last2=Paul|first2=A.|last3=Seyferth|first3=M.|date=2007-10-04|title=Modeling sediment transport patterns during an upwelling event|url=http://dx.doi.org/10.1029/2005jc003107|journal=Journal of Geophysical Research|volume=112|issue=C10|doi=10.1029/2005jc003107|issn=0148-0227|doi-access=free}}</ref> |
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== References == |
== References == |
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Revision as of 20:08, 17 May 2021
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The Southern Caribbean Upwelling system (SCUS) is a low latitude tropical upwelling system at about 10°N on the southern coast of the Caribbean sea basin off Colombia, Venezuela, and Trinidad. The intensity of the Caribbean low-level jet (effect of the trade winds) and the coastal orientation are determining the timing and spatial variability of this upwelling system. The system is likely to be responsible for a major part in the primary production due to the addition of nutrients that are added to the system through the upwelling.[1]
There are two main upwelling zones in the system that vary in intensity throughout the year; The Western Upwelling Zone (WUZ); and the Eastern Upwelling Zone; (EUZ).
The western the WUZ is situated between 74-71°W and generates mainly seasonal upwelling and high offshore transport due to intense winds. The EUZ, situated between 71-60°W is less intense but is more favourable for the upwelling throughout the year.
The last thirty years the upwelling has intensified which is producing cooling of the sea surface temperature (SST) in the WUZ, this is in contrast to the general temperature in the Caribbean sea which has shown to increase.[1] The "typical" Caribbean surface water is a mixture of North Atlantic Surface Water (NASW) and riverine waters from the Orinoco and Amazon rivers.
Under the Caribbean surface waters more saline water is found with values close to those typical for the Subtropical underwater (SUW) SA ~37, Θ ~22 °C. This forms a subsurface maximum(SSM).[1] After the rainy season the SSM is lower due to dilution of the surface waters.
Characterization of the SCUS
Sinds 1994 variations in upwelling are studied using cycles of satellite SST. The SST this is used as a proxy for upwelling in this tropical region Aswell as the dominat winds and chloropyll-a. These are all proxies that are relatively easy to measure and quite easily accessibe.
The Rossby radius changes the relative position of the upwelling zone due to the effect of the rossby waves. The Rossby radius for this region is ~19 km; estimated using a mean depth h= 35m, gravity g = 9,81 m s -1[1]. The upwelling zones are found close to the coast roughly withing the 19 km found within the Rossby radius. However, in rare cases upwelled water move offshore up to over 250 km from the coast.[2]
Upwelled waters in the SCUS are consistent in geochemical compositions of the "Subtropical underwater", which is a water mass that comes from the central Atlantic and due to its relative dense water properties (SA ~37, Θ ~22 °C) lays under the Caribbean surface waters, and is likely coming from this water mass.
Sea surface temperature (SST)
The SCUS is studied through the SST at a high resolution (1 km grid) radiometer (National Oceanic and Atmospheric Administration / NOAA). This data is used to identify differences in the SST and with that locate upwelling regions. There is a semi-annual cycle of SST within the upwelling areas. With cooling periodically occurring between December and April, showing 2-4 upwelling pulses peaking during February–March. Around May there is a typical increase in SST followed by cooling during June–August due to a midyear upwelling.[2]
Wind
The Trade winds that blow over the southern Caribbean Sea (also called the low-level jet) generate northward Ekman transport. The intensity of the trade winds vary per season (image 2 shows the WUZ b) and c) in December and d) and e) in February) and explain the variation in upwelling and the measured differences in SST that are mentioned above. The driving forces of the Ekman transport is wind-stress or "τ" The driving winds are divided in multiple areas. East of 68°W have relative stable wind speed (>6 m ), and slightly lower during August–November (4 – 6 m ).
The direction of the wind is generally parallel to the southern Caribbean Sea margin, however, between May and October the EUZ has more along shore winds that are ~1.7° varying from the along shore direction and during November until April the direction is more onshore with ~12°. In the WUZ the wind is more offshore in the majority of the year ~-14°. This changes during October–November when winds are aligned with the shoreline ~0.2°.
These wind directions respectively to the coast produce the northward wind curl and thus offshore Ekman transport that are favourable year round for the SCUS.
Chlorophyll-a
Chlorophyll a is used to see the productivity of zooplankton, amounts of chlorophyll-a increase with higher nutrient concentrations that are found in upwelled water and can therefore be used as a proxy for upwelling systems.[3] Withing the SCUS there are strong correlations between the SST and Chlorophyll-a. These show a Chlorophyll-a maximum in December and April and a shorter maximum between June and July.
Biological impact
Nutrient concentrations that come with the water from the SUW have a strong positive impact on the phytoplankton productivity, it is estimated that up to 95% of the small pelagic biomass is the southern Caribbean sea is sustained by the primary production that comes with these upwelled waters.
In the EUZ there is a four time higher amount of small pelagic biomass compared to the WUZ. This difference is contributed to the prolonged duration of the upwelling. The water in the EUZ has a SST < 26C° for 8.5 months and the WUZ for 6.9. In addition to that, the EUZ has a wider continental shelf. Upwelling over wide and shallow continental shelves can generate resuspension and transport of essential microelements from the benthic boundary layer to the surface.[4]
References
- ^ a b c d Correa-Ramirez, Marco; Rodriguez-Santana, Ángel; Ricaurte-Villota, Constanza; Paramo, Jorge (2019-03-27). "Water masses and mixing processes in the Southern Caribbean upwelling system off Colombia". dx.doi.org. Retrieved 2021-05-12.
- ^ a b Rueda-Roa, Digna T.; Muller-Karger, Frank E. (August 2013). "The southern Caribbean upwelling system: Sea surface temperature, wind forcing and chlorophyll concentration patterns". Deep Sea Research Part I: Oceanographic Research Papers. 78: 102–114. doi:10.1016/j.dsr.2013.04.008. ISSN 0967-0637.
- ^ Walsh, Sheila M. (2011). "Ecosystem-Scale Effects of Nutrients and Fishing on Coral Reefs". Journal of Marine Biology. 2011: 1–13. doi:10.1155/2011/187248. ISSN 1687-9481.
- ^ Huhn, K.; Paul, A.; Seyferth, M. (2007-10-04). "Modeling sediment transport patterns during an upwelling event". Journal of Geophysical Research. 112 (C10). doi:10.1029/2005jc003107. ISSN 0148-0227.