Ekman transport as the driver of extreme interannual formation rates of Eighteen Degree Water
In the North Atlantic subtropical gyre, the Eighteen Degree Water (EDW) is a voluminous heat reservoir, submerged under a seasonal pycnocline that can be progressively removed through the winter, allowing EDW ventilation in the early spring. We target the EDW formation extremes, namely 2004-2005, 20...
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ftarchimer:oai:archimer.ifremer.fr:85551 2023-05-15T17:29:15+02:00 Ekman transport as the driver of extreme interannual formation rates of Eighteen Degree Water Li, Ke Maze, Guillaume Mercier, Herle 2022-01 application/pdf https://archimer.ifremer.fr/doc/00743/85551/90674.pdf https://doi.org/10.1029/2021JC017696 https://archimer.ifremer.fr/doc/00743/85551/ eng eng American Geophysical Union (AGU) https://archimer.ifremer.fr/doc/00743/85551/90674.pdf doi:10.1029/2021JC017696 https://archimer.ifremer.fr/doc/00743/85551/ info:eu-repo/semantics/openAccess restricted use Journal Of Geophysical Research-oceans (2169-9275) (American Geophysical Union (AGU)), 2022-01 , Vol. 127 , N. 1 , P. e2021JC017696 (15p.) North Atlantic Subtropical mode water Ekman current Argo floats subtropical gyre ocean stratification text Publication info:eu-repo/semantics/article 2022 ftarchimer https://doi.org/10.1029/2021JC017696 2022-07-12T22:50:15Z In the North Atlantic subtropical gyre, the Eighteen Degree Water (EDW) is a voluminous heat reservoir, submerged under a seasonal pycnocline that can be progressively removed through the winter, allowing EDW ventilation in the early spring. We target the EDW formation extremes, namely 2004-2005, 2009-2010, and 2012-2013 for the strong years, and 2007-2008, 2008-2009, 2011-2012, and 2013-2014 for the weak years. We employ gridded hydrographic datasets mainly measured by Argo floats over the last 20 years, and provide a synthetic study on the extreme events of strong and weak EDW formation of this time period. We found that the Ekman transport is the indicator and driving mechanism explaining these extremes. Strong (Weak) EDW formation years correspond with atmospheric patterns resembling NAO- (NAO+), attributed to a strong (weak) winter air-sea surface heat loss, and a strong (weak) winter heat loss due to Ekman transport. Further, we show that such extreme Ekman advection patterns can be linked to mid-latitude storms, of which both intensity and duration have an impact on the extreme of EDW ventilation in the western subtropical North Atlantic. To yield a strong EDW formation, it requires a large winter heat deficit due to Ekman divergence, which can be sufficiently represented by numbers of strong winter storms, most notably, remnants of hurricanes and US east coast snowstorms. Meanwhile, to yield a weak EDW formation, apart from weak atmospheric forcings, a remnant positive heat content anomaly carried through from previous years would serve as an unfavorable preconditioning, hindering the EDW formation. Plain Language Summary The EDW is the most voluminous water body in the North Atlantic subtropical region. It is critical in the biology cycle and the ocean dynamics. For most of the year, EDW is buried underneath the sea surface. In winter, when sea surface loses enough heat, sinking cold water reaches the EDW bulk, forming fresh EDW. In this research, we target the EDW formation extremes, namely 2004-2005, ... Article in Journal/Newspaper North Atlantic Archimer (Archive Institutionnelle de l'Ifremer - Institut français de recherche pour l'exploitation de la mer) Journal of Geophysical Research: Oceans 127 1 |
institution |
Open Polar |
collection |
Archimer (Archive Institutionnelle de l'Ifremer - Institut français de recherche pour l'exploitation de la mer) |
op_collection_id |
ftarchimer |
language |
English |
topic |
North Atlantic Subtropical mode water Ekman current Argo floats subtropical gyre ocean stratification |
spellingShingle |
North Atlantic Subtropical mode water Ekman current Argo floats subtropical gyre ocean stratification Li, Ke Maze, Guillaume Mercier, Herle Ekman transport as the driver of extreme interannual formation rates of Eighteen Degree Water |
topic_facet |
North Atlantic Subtropical mode water Ekman current Argo floats subtropical gyre ocean stratification |
description |
In the North Atlantic subtropical gyre, the Eighteen Degree Water (EDW) is a voluminous heat reservoir, submerged under a seasonal pycnocline that can be progressively removed through the winter, allowing EDW ventilation in the early spring. We target the EDW formation extremes, namely 2004-2005, 2009-2010, and 2012-2013 for the strong years, and 2007-2008, 2008-2009, 2011-2012, and 2013-2014 for the weak years. We employ gridded hydrographic datasets mainly measured by Argo floats over the last 20 years, and provide a synthetic study on the extreme events of strong and weak EDW formation of this time period. We found that the Ekman transport is the indicator and driving mechanism explaining these extremes. Strong (Weak) EDW formation years correspond with atmospheric patterns resembling NAO- (NAO+), attributed to a strong (weak) winter air-sea surface heat loss, and a strong (weak) winter heat loss due to Ekman transport. Further, we show that such extreme Ekman advection patterns can be linked to mid-latitude storms, of which both intensity and duration have an impact on the extreme of EDW ventilation in the western subtropical North Atlantic. To yield a strong EDW formation, it requires a large winter heat deficit due to Ekman divergence, which can be sufficiently represented by numbers of strong winter storms, most notably, remnants of hurricanes and US east coast snowstorms. Meanwhile, to yield a weak EDW formation, apart from weak atmospheric forcings, a remnant positive heat content anomaly carried through from previous years would serve as an unfavorable preconditioning, hindering the EDW formation. Plain Language Summary The EDW is the most voluminous water body in the North Atlantic subtropical region. It is critical in the biology cycle and the ocean dynamics. For most of the year, EDW is buried underneath the sea surface. In winter, when sea surface loses enough heat, sinking cold water reaches the EDW bulk, forming fresh EDW. In this research, we target the EDW formation extremes, namely 2004-2005, ... |
format |
Article in Journal/Newspaper |
author |
Li, Ke Maze, Guillaume Mercier, Herle |
author_facet |
Li, Ke Maze, Guillaume Mercier, Herle |
author_sort |
Li, Ke |
title |
Ekman transport as the driver of extreme interannual formation rates of Eighteen Degree Water |
title_short |
Ekman transport as the driver of extreme interannual formation rates of Eighteen Degree Water |
title_full |
Ekman transport as the driver of extreme interannual formation rates of Eighteen Degree Water |
title_fullStr |
Ekman transport as the driver of extreme interannual formation rates of Eighteen Degree Water |
title_full_unstemmed |
Ekman transport as the driver of extreme interannual formation rates of Eighteen Degree Water |
title_sort |
ekman transport as the driver of extreme interannual formation rates of eighteen degree water |
publisher |
American Geophysical Union (AGU) |
publishDate |
2022 |
url |
https://archimer.ifremer.fr/doc/00743/85551/90674.pdf https://doi.org/10.1029/2021JC017696 https://archimer.ifremer.fr/doc/00743/85551/ |
genre |
North Atlantic |
genre_facet |
North Atlantic |
op_source |
Journal Of Geophysical Research-oceans (2169-9275) (American Geophysical Union (AGU)), 2022-01 , Vol. 127 , N. 1 , P. e2021JC017696 (15p.) |
op_relation |
https://archimer.ifremer.fr/doc/00743/85551/90674.pdf doi:10.1029/2021JC017696 https://archimer.ifremer.fr/doc/00743/85551/ |
op_rights |
info:eu-repo/semantics/openAccess restricted use |
op_doi |
https://doi.org/10.1029/2021JC017696 |
container_title |
Journal of Geophysical Research: Oceans |
container_volume |
127 |
container_issue |
1 |
_version_ |
1766122905694896128 |