The dynamics of equatorially asymmetric thermohaline circulations
The three-dimensional dynamics of equatorially asymmetric thermohaline how are investigated using an ocean general circulation model in a highly idealized configuration with no wind forcing and nearly fixed surface density. Small asymmetries in surface density lead to strongly asymmetric meridional...
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ftpubman:oai:pure.mpg.de:item_1593186 2023-08-27T04:10:41+02:00 The dynamics of equatorially asymmetric thermohaline circulations Marotzke, J. Klinger, B. 2000 application/pdf http://hdl.handle.net/11858/00-001M-0000-0014-3ACC-1 http://hdl.handle.net/11858/00-001M-0000-0014-3ACE-E eng eng info:eu-repo/semantics/altIdentifier/doi/10.1175/1520-0485(2000)030<0955:TDOEAT>2.0.CO;2 http://hdl.handle.net/11858/00-001M-0000-0014-3ACC-1 http://hdl.handle.net/11858/00-001M-0000-0014-3ACE-E info:eu-repo/semantics/openAccess Journal of Physical Oceanography info:eu-repo/semantics/article 2000 ftpubman https://doi.org/10.1175/1520-0485(2000)030<0955:TDOEAT>2.0.CO;2 2023-08-02T01:15:04Z The three-dimensional dynamics of equatorially asymmetric thermohaline how are investigated using an ocean general circulation model in a highly idealized configuration with no wind forcing and nearly fixed surface density. Small asymmetries in surface density lead to strongly asymmetric meridional overturning patterns, with deep water formed in the denser (northern) hemisphere filling the abyss. The poleward deep transport in the lighter hemisphere implies that the deep zonal-mean zonal pressure gradient reverses across the equator. Density along the eastern boundary and the zonally averaged density are nearly symmetric about the equator except at very high latitudes; the Southern Hemisphere western boundary thermocline, in contrast, is balanced by weaker upwelling and is hence broader than its northern counterpart. This pattern is explained through the spinup of the asymmetric circulation from a symmetric one, the timescale of which is set through advection by the mean deep western boundary current. For the strength of the interhemispheric transport, a lower bound of one-half the one-hemisphere overturning strength is derived theoretically for small finite forcing asymmetries, implying that the symmetric circulation is unlikely to be realized. Under asymmetric surface forcing, enhanced mixing in the denser hemisphere suppresses interhemispheric transport. Conversely, very strong cross-equatorial transport is caused by enhanced mixing in the lighter hemisphere. These results indicate that, once the surface densities determine that North Atlantic Deep Water is the dominant ventilating source, its export rate from the North Atlantic is controlled by mixing and upwelling in the rest of the World Ocean. Article in Journal/Newspaper North Atlantic Deep Water North Atlantic Max Planck Society: MPG.PuRe |
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Open Polar |
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Max Planck Society: MPG.PuRe |
op_collection_id |
ftpubman |
language |
English |
description |
The three-dimensional dynamics of equatorially asymmetric thermohaline how are investigated using an ocean general circulation model in a highly idealized configuration with no wind forcing and nearly fixed surface density. Small asymmetries in surface density lead to strongly asymmetric meridional overturning patterns, with deep water formed in the denser (northern) hemisphere filling the abyss. The poleward deep transport in the lighter hemisphere implies that the deep zonal-mean zonal pressure gradient reverses across the equator. Density along the eastern boundary and the zonally averaged density are nearly symmetric about the equator except at very high latitudes; the Southern Hemisphere western boundary thermocline, in contrast, is balanced by weaker upwelling and is hence broader than its northern counterpart. This pattern is explained through the spinup of the asymmetric circulation from a symmetric one, the timescale of which is set through advection by the mean deep western boundary current. For the strength of the interhemispheric transport, a lower bound of one-half the one-hemisphere overturning strength is derived theoretically for small finite forcing asymmetries, implying that the symmetric circulation is unlikely to be realized. Under asymmetric surface forcing, enhanced mixing in the denser hemisphere suppresses interhemispheric transport. Conversely, very strong cross-equatorial transport is caused by enhanced mixing in the lighter hemisphere. These results indicate that, once the surface densities determine that North Atlantic Deep Water is the dominant ventilating source, its export rate from the North Atlantic is controlled by mixing and upwelling in the rest of the World Ocean. |
format |
Article in Journal/Newspaper |
author |
Marotzke, J. Klinger, B. |
spellingShingle |
Marotzke, J. Klinger, B. The dynamics of equatorially asymmetric thermohaline circulations |
author_facet |
Marotzke, J. Klinger, B. |
author_sort |
Marotzke, J. |
title |
The dynamics of equatorially asymmetric thermohaline circulations |
title_short |
The dynamics of equatorially asymmetric thermohaline circulations |
title_full |
The dynamics of equatorially asymmetric thermohaline circulations |
title_fullStr |
The dynamics of equatorially asymmetric thermohaline circulations |
title_full_unstemmed |
The dynamics of equatorially asymmetric thermohaline circulations |
title_sort |
dynamics of equatorially asymmetric thermohaline circulations |
publishDate |
2000 |
url |
http://hdl.handle.net/11858/00-001M-0000-0014-3ACC-1 http://hdl.handle.net/11858/00-001M-0000-0014-3ACE-E |
genre |
North Atlantic Deep Water North Atlantic |
genre_facet |
North Atlantic Deep Water North Atlantic |
op_source |
Journal of Physical Oceanography |
op_relation |
info:eu-repo/semantics/altIdentifier/doi/10.1175/1520-0485(2000)030<0955:TDOEAT>2.0.CO;2 http://hdl.handle.net/11858/00-001M-0000-0014-3ACC-1 http://hdl.handle.net/11858/00-001M-0000-0014-3ACE-E |
op_rights |
info:eu-repo/semantics/openAccess |
op_doi |
https://doi.org/10.1175/1520-0485(2000)030<0955:TDOEAT>2.0.CO;2 |
_version_ |
1775352927429328896 |