Geostrophic dynamics of meridional transport variability in the subpolar North Atlantic
The North Atlantic meridional overturning circulation (MOC) is believed to play an important role in regulating the Earth's climate. Yet, there is still much uncertainty regarding the dynamics of the MOC and its variability. It is well established, however, that through geostrophy the zonally i...
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2009
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ftunivnewcastle:oai:eprint.ncl.ac.uk:153777 2023-05-15T17:31:17+02:00 Geostrophic dynamics of meridional transport variability in the subpolar North Atlantic Bingham RJ Hughes CW 31-12-2009 application/pdf https://eprint.ncl.ac.uk/fulltext.aspx?url=152756/5BFDE0DC-FF76-4F5F-A910-2A22CD888319.pdf&pub_id=153777 unknown American Geophysical Union Journal of Geophysical Research: Oceans, 31-12-2009 Article 2009 ftunivnewcastle 2020-06-11T23:03:03Z The North Atlantic meridional overturning circulation (MOC) is believed to play an important role in regulating the Earth's climate. Yet, there is still much uncertainty regarding the dynamics of the MOC and its variability. It is well established, however, that through geostrophy the zonally integrated meridional transport at a particular latitude and depth can be determined from the east-west bottom pressure difference across the basin. Therefore, rather than consider the MOC as a large-scale system, this paper focuses on the dynamics of this geostrophic relationship in two numerical ocean models at a single latitude (50 degrees N) in the subpolar Atlantic. First, it is shown that the bottom pressure on the western boundary is sufficient to recover, with high fidelity, the interannual meridional transport variability at 50 degrees N over a 100 year period in the climate model HadCM3. It is found that the variability of western boundary pressure is closely associated with density changes over the continental slope. These changes lead to a large zonal gradient in potential energy and imply an unfeasible depth-mean velocity over the slope. The western boundary pressure, from which the meridional transport can be recovered, is generated as a compensation to this and limits the depth-mean flow. This demonstrates that in numerical ocean models, at least, meridional transport variability is generated as a local response to density changes on the western slope. Whether this is a true representation of actual ocean variability is uncertain, but if it were, then meridional transport variability could largely be determined using only the density field on the western slope. Article in Journal/Newspaper North Atlantic Newcastle University Library ePrints Service |
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The North Atlantic meridional overturning circulation (MOC) is believed to play an important role in regulating the Earth's climate. Yet, there is still much uncertainty regarding the dynamics of the MOC and its variability. It is well established, however, that through geostrophy the zonally integrated meridional transport at a particular latitude and depth can be determined from the east-west bottom pressure difference across the basin. Therefore, rather than consider the MOC as a large-scale system, this paper focuses on the dynamics of this geostrophic relationship in two numerical ocean models at a single latitude (50 degrees N) in the subpolar Atlantic. First, it is shown that the bottom pressure on the western boundary is sufficient to recover, with high fidelity, the interannual meridional transport variability at 50 degrees N over a 100 year period in the climate model HadCM3. It is found that the variability of western boundary pressure is closely associated with density changes over the continental slope. These changes lead to a large zonal gradient in potential energy and imply an unfeasible depth-mean velocity over the slope. The western boundary pressure, from which the meridional transport can be recovered, is generated as a compensation to this and limits the depth-mean flow. This demonstrates that in numerical ocean models, at least, meridional transport variability is generated as a local response to density changes on the western slope. Whether this is a true representation of actual ocean variability is uncertain, but if it were, then meridional transport variability could largely be determined using only the density field on the western slope. |
format |
Article in Journal/Newspaper |
author |
Bingham RJ Hughes CW |
spellingShingle |
Bingham RJ Hughes CW Geostrophic dynamics of meridional transport variability in the subpolar North Atlantic |
author_facet |
Bingham RJ Hughes CW |
author_sort |
Bingham RJ |
title |
Geostrophic dynamics of meridional transport variability in the subpolar North Atlantic |
title_short |
Geostrophic dynamics of meridional transport variability in the subpolar North Atlantic |
title_full |
Geostrophic dynamics of meridional transport variability in the subpolar North Atlantic |
title_fullStr |
Geostrophic dynamics of meridional transport variability in the subpolar North Atlantic |
title_full_unstemmed |
Geostrophic dynamics of meridional transport variability in the subpolar North Atlantic |
title_sort |
geostrophic dynamics of meridional transport variability in the subpolar north atlantic |
publisher |
American Geophysical Union |
publishDate |
2009 |
url |
https://eprint.ncl.ac.uk/fulltext.aspx?url=152756/5BFDE0DC-FF76-4F5F-A910-2A22CD888319.pdf&pub_id=153777 |
genre |
North Atlantic |
genre_facet |
North Atlantic |
op_source |
Journal of Geophysical Research: Oceans, 31-12-2009 |
_version_ |
1766128771904045056 |