Antarctic Circumpolar Current: Difference between revisions
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{{short description|Ocean current that flows clockwise from west to east around Antarctica}} | {{short description|Ocean current that flows clockwise from west to east around Antarctica}} | ||
{{Use dmy dates|date=October 2020}} | {{Use dmy dates|date=October 2020}} | ||
[[File:Antarctic Circumpolar Current.png|thumb|320px | [[File:Antarctic Circumpolar Current.png|thumb|320px| Antarctic Circumpolar Current, showing branches connecting to the larger [[thermohaline circulation]]]] | ||
[[File:Thermohaline Circulation using Improved Flow Field.ogv|thumb|320px| Animation of the thermohaline circulation. The later part of this animation shows the Antarctic Circumpolar Current.]] | [[File:Thermohaline Circulation using Improved Flow Field.ogv|thumb|320px| Animation of the thermohaline circulation. The later part of this animation shows the Antarctic Circumpolar Current.]] | ||
'''Antarctic Circumpolar Current''' ('''ACC''') is an [[ocean current]] that flows clockwise (as seen from the South Pole) from west to east around [[Antarctica]]. An alternative name for the ACC is the '''West Wind Drift'''. The ACC is the dominant circulation feature of the [[Southern Ocean]] and has a mean transport estimated at 137 ± 7 [[ | The '''Antarctic Circumpolar Current''' ('''ACC''') is an [[ocean current]] that flows clockwise (as seen from the South Pole) from west to east around [[Antarctica]]. An alternative name for the ACC is the '''West Wind Drift'''. The ACC is the dominant circulation feature of the [[Southern Ocean]] and has a mean transport estimated at 137 ± 7 [[sverdrup]]s (Sv, million m<sup>3</sup>/s),<ref>{{Cite journal |last=Meredith |first=Michael P. |last2=Woodworth |first2=Philip L. |last3=Chereskin |first3=Teresa K. |last4=Marshall |first4=David P. |last5=Allison |first5=Lesley C. |last6=Bigg |first6=Grant R. |last7=Donohue |first7=Kathy |last8=Heywood |first8=Karen J. |last9=Hughes |first9=Chris W. |last10=Hibbert |first10=Angela |last11=Hogg |first11=Andrew McC. |last12=Johnson |first12=Helen L. |last13=Jullion |first13=Loïc |last14=King |first14=Brian A. |last15=Leach |first15=Harry |date=December 2011 |title=SUSTAINED MONITORING OF THE SOUTHERN OCEAN AT DRAKE PASSAGE: PAST ACHIEVEMENTS AND FUTURE PRIORITIES |url=https://hal.archives-ouvertes.fr/hal-00753357/file/2010RG000348.pdf |journal=Reviews of Geophysics |language=en |volume=49 |issue=4 |doi=10.1029/2010RG000348 |issn=8755-1209}}</ref><ref>{{Harvnb|Smith|Desflots|White|Mariano|2013}}</ref> or possibly even higher,<ref>{{cite journal|last1=Donohue|first1=K.A.|display-authors=et al|title=Mean Antarctic Circumpolar Current transport measured in Drake Passage |journal=Geophysical Research Letters|date=21 November 2016|volume=43|issue=11|page=760 |doi=10.1002/2016GL070319|bibcode=2016GeoRL..4311760D|doi-access=free|hdl=11336/47067|hdl-access=free|url=https://digitalcommons.uri.edu/gsofacpubs/1235}}</ref> making it the largest ocean current. The current is circumpolar due to the lack of any landmass connecting with Antarctica and this keeps warm ocean waters away from Antarctica, enabling that continent to maintain its huge [[ice sheet]]. | ||
Associated with the Circumpolar Current is the [[Antarctic Convergence]], where the cold Antarctic waters meet the warmer waters of the [[subantarctic]], creating a zone of upwelling nutrients. These nurture high levels of [[phytoplankton]] with associated [[copepod]]s and [[krill]], and resultant [[food chain]]s supporting fish, whales, [[Pinniped|seals]], penguins, [[albatross]]es, and a wealth of [[Wildlife of Antarctica|other species]]. | Associated with the Circumpolar Current is the [[Antarctic Convergence]], where the cold Antarctic waters meet the warmer waters of the [[subantarctic]], creating a zone of upwelling nutrients. These nurture high levels of [[phytoplankton]] with associated [[copepod]]s and [[krill]], and resultant [[food chain]]s supporting fish, whales, [[Pinniped|seals]], penguins, [[albatross]]es, and a wealth of [[Wildlife of Antarctica|other species]]. | ||
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The current is accompanied by three [[Front (Oceanography)|fronts]]: the Subantarctic front (SAF), the [[Polar front]] (PF), and the Southern ACC front (SACC).<ref>{{Harvnb|Stewart|2007}}</ref> Furthermore, the waters of the Southern Ocean are separated from the warmer and saltier subtropical waters by the [[subtropical front]] (STF).<ref>{{Harvnb|Orsi|Whitworth|Nowlin|1995|loc=Introduction, p. 641}}</ref> | The current is accompanied by three [[Front (Oceanography)|fronts]]: the Subantarctic front (SAF), the [[Polar front]] (PF), and the Southern ACC front (SACC).<ref>{{Harvnb|Stewart|2007}}</ref> Furthermore, the waters of the Southern Ocean are separated from the warmer and saltier subtropical waters by the [[subtropical front]] (STF).<ref>{{Harvnb|Orsi|Whitworth|Nowlin|1995|loc=Introduction, p. 641}}</ref> | ||
The northern boundary of the ACC is defined by the northern edge of the SAF, this being the most northerly water to pass through Drake Passage and therefore be circumpolar. Much of the ACC transport is carried in this front, which is defined as the latitude at which a subsurface salinity minimum or a thick layer of unstratified Subantarctic [[mode water]] first appears, allowed by temperature dominating density stratification. Still further south lies the PF, which is marked by a transition to very cold, relatively fresh, Antarctic Surface Water at the surface. Here a temperature minimum is allowed by salinity dominating density stratification, due to the lower temperatures. Farther south still is the SACC, which is determined as the southernmost extent of [[Circumpolar deep water]] (temperature of about 2 °C at 400 m). This water mass flows along the shelfbreak of the western Antarctic Peninsula and thus marks the most southerly water flowing through Drake Passage and therefore circumpolar. The bulk of the transport is carried in the middle two fronts. | The northern boundary of the ACC is defined by the northern edge of the SAF, this being the most northerly water to pass through the Drake Passage and therefore be circumpolar. Much of the ACC transport is carried in this front, which is defined as the latitude at which a subsurface salinity minimum or a thick layer of unstratified Subantarctic [[mode water]] first appears, allowed by temperature dominating density stratification. Still further south lies the PF, which is marked by a transition to very cold, relatively fresh, Antarctic Surface Water at the surface. Here a temperature minimum is allowed by salinity dominating density stratification, due to the lower temperatures. Farther south still is the SACC, which is determined as the southernmost extent of [[Circumpolar deep water]] (temperature of about 2 °C at 400 m). This water mass flows along the shelfbreak of the western Antarctic Peninsula and thus marks the most southerly water flowing through Drake Passage and therefore circumpolar. The bulk of the transport is carried in the middle two fronts. | ||
The total transport of the ACC at Drake Passage is estimated to be around 135 Sv, or about 135 times the transport of all the world's rivers combined. There is a relatively small addition of flow in the Indian Ocean, with the transport south of [[Tasmania]] reaching around 147 Sv, at which point the current is probably the largest on the planet. | The total transport of the ACC at Drake Passage is estimated to be around 135 Sv, or about 135 times the transport of all the world's rivers combined. There is a relatively small addition of flow in the Indian Ocean, with the transport south of [[Tasmania]] reaching around 147 Sv, at which point the current is probably the largest on the planet. | ||
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The "State of the Cryosphere" report found, that the Antarctic Circumpolar Current became weaker. By 2050 it expected to lose 20% of its strength with "widespread impacts on ocean circulation and climate." The [[Weddell Sea Bottom Water]] has lost 30% of its volume in the latest 32 years, and the [[Antarctic bottom water|Antarctic Bottom Water]] is expected to shrink. This will impact ocean circulation, nutrients, heat content and carbon sequestration.<ref>{{cite book |title=State of the Cryosphere 2024 Lost Ice, Global Damage |date=November 2024 |publisher=International Cryosphere Climate Initiative |pages=x (in the beginning), 8, 48, 52 |url=https://articles.unesco.org/sites/default/files/medias/fichiers/2024/11/State%20of%20the%20Cryosphere%20Report%202024.pdf |access-date=20 November 2024}}</ref> [[UNESCO]] mentions that the report in the first time "notes a growing scientific consensus that melting Greenland and Antarctic ice sheets, among other factors, may be slowing important ocean currents at both poles, with potentially dire consequences for a much colder northern Europe and greater sea-level rise along the U.S. East Coast."<ref>{{cite web |title=State of the Cryosphere Report 2024 Lost Ice, Global Damage |url=https://www.unesco.org/en/articles/state-cryosphere-report-2024 |website=UNESCO |access-date=20 November 2024}}</ref> The findings were bolstered by a 2025 study published in [[Environmental Research Letters]].<ref>{{cite journal |last1=Sohail |first1=Taimoor |last2=Gayen |first2=Bishakhdatta |last3=Klocker |first3=Andreas |title=Decline of Antarctic Circumpolar Current due to polar ocean freshening |journal=Environmental Research Letters |date=3 March 2025 |volume=20 |issue=3 |page=034046 |doi=10.1088/1748-9326/adb31c |doi-access=free |bibcode=2025ERL....20c4046S }}</ref> | The "State of the Cryosphere" report found, that the Antarctic Circumpolar Current became weaker. By 2050 it expected to lose 20% of its strength with "widespread impacts on ocean circulation and climate." The [[Weddell Sea Bottom Water]] has lost 30% of its volume in the latest 32 years, and the [[Antarctic bottom water|Antarctic Bottom Water]] is expected to shrink. This will impact ocean circulation, nutrients, heat content and carbon sequestration.<ref>{{cite book |title=State of the Cryosphere 2024 Lost Ice, Global Damage |date=November 2024 |publisher=International Cryosphere Climate Initiative |pages=x (in the beginning), 8, 48, 52 |url=https://articles.unesco.org/sites/default/files/medias/fichiers/2024/11/State%20of%20the%20Cryosphere%20Report%202024.pdf |access-date=20 November 2024}}</ref> [[UNESCO]] mentions that the report in the first time "notes a growing scientific consensus that melting Greenland and Antarctic ice sheets, among other factors, may be slowing important ocean currents at both poles, with potentially dire consequences for a much colder northern Europe and greater sea-level rise along the U.S. East Coast."<ref>{{cite web |title=State of the Cryosphere Report 2024 Lost Ice, Global Damage |url=https://www.unesco.org/en/articles/state-cryosphere-report-2024 |website=UNESCO |access-date=20 November 2024}}</ref> The findings were bolstered by a 2025 study published in [[Environmental Research Letters]].<ref>{{cite journal |last1=Sohail |first1=Taimoor |last2=Gayen |first2=Bishakhdatta |last3=Klocker |first3=Andreas |title=Decline of Antarctic Circumpolar Current due to polar ocean freshening |journal=Environmental Research Letters |date=3 March 2025 |volume=20 |issue=3 |page=034046 |doi=10.1088/1748-9326/adb31c |doi-access=free |bibcode=2025ERL....20c4046S }}</ref> | ||
== See also == | |||
* [[Diego Ramirez Islands & Drake Passage National Park]] | |||
== References == | == References == | ||
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| title = Bone-eating worms from the Antarctic: the contrasting fate of whale and wood remains on the Southern Ocean seafloor | | title = Bone-eating worms from the Antarctic: the contrasting fate of whale and wood remains on the Southern Ocean seafloor | ||
| year = 2013 | journal = Proceedings of the Royal Society B | volume = 280 | issue = 1768 | | year = 2013 | journal = Proceedings of the Royal Society B | volume = 280 | issue = 1768 | ||
| doi = 10.1098/rspb.2013.1390 | | | doi = 10.1098/rspb.2013.1390 | article-number=20131390 | pmid=23945684 | pmc=3757972}}<!-- {{Harvnb|Glover|Wiklund|Taboada|Avila|2013}} --> | ||
**{{cite news |first=Jonathan |last=Amos |date=14 August 2013 |title=Antarctic: Where 'zombies' thrive and shipwrecks are preserved |work=BBC News |url=https://www.bbc.co.uk/news/science-environment-23682521}} | **{{cite news |first=Jonathan |last=Amos |date=14 August 2013 |title=Antarctic: Where 'zombies' thrive and shipwrecks are preserved |work=BBC News |url=https://www.bbc.co.uk/news/science-environment-23682521}} | ||
* {{Cite journal | * {{Cite journal | ||