Geostrophic Closure of the Zonally Averaged Atlantic Meridional Overturning Circulation
International audience It is typically assumed that the meridional density gradient in the North Atlantic is well and positively correlated with the Atlantic meridional overturning circulation (AMOC). In numerical “water-hosing” experiments, for example, imposing an anomalous freshwater flux in the...
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ftccsdartic:oai:HAL:hal-01575298v1 2023-05-15T17:34:11+02:00 Geostrophic Closure of the Zonally Averaged Atlantic Meridional Overturning Circulation Sevellec, F. Huck, Thierry Ocean and Earth Science Southampton University of Southampton-National Oceanography Centre (NOC) Laboratoire de physique des océans (LPO) Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS) 2016-03 https://hal.archives-ouvertes.fr/hal-01575298 https://doi.org/10.1175/JPO-D-14-0148.1 en eng HAL CCSD American Meteorological Society info:eu-repo/semantics/altIdentifier/doi/10.1175/JPO-D-14-0148.1 hal-01575298 https://hal.archives-ouvertes.fr/hal-01575298 doi:10.1175/JPO-D-14-0148.1 ISSN: 0022-3670 EISSN: 1520-0485 Journal of Physical Oceanography https://hal.archives-ouvertes.fr/hal-01575298 Journal of Physical Oceanography, American Meteorological Society, 2016, 46 (3), pp.895-917. ⟨10.1175/JPO-D-14-0148.1⟩ Atm/Ocean Structure/ Phenomena Ocean circulation Meridional overturning circulation Baroclinic flows Circulation/ Dynamics Atlantic Ocean Geographic location/entity Ekman pumping Thermohaline circulation [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography [SDU.OCEAN]Sciences of the Universe [physics]/Ocean Atmosphere info:eu-repo/semantics/article Journal articles 2016 ftccsdartic https://doi.org/10.1175/JPO-D-14-0148.1 2021-11-21T02:23:11Z International audience It is typically assumed that the meridional density gradient in the North Atlantic is well and positively correlated with the Atlantic meridional overturning circulation (AMOC). In numerical “water-hosing” experiments, for example, imposing an anomalous freshwater flux in the Northern Hemisphere leads to a slowdown of the AMOC. However, on planetary scale, the first-order dynamics are linked to the geostrophic balance, relating the north–south pressure gradient to the zonal circulation. In this study, these two approaches are reconciled. At steady state and under geostrophic dynamics, an analytical expression is derived to relate the zonal and meridional pressure gradient. This solution is only valid where the meridional density gradient length scale is shorter than Earth’s curvature length scale, that is, north of 35°N. This theoretical expression links the north–south density gradient to the AMOC and can be used as a closure for zonally averaged ocean models. Assumptions and shortcomings of the approach are presented. Implications of these results for paleoclimate problems such as AMOC collapse and asymmetry in the meridional overturning circulation of the Atlantic and of the Pacific are discussed. Article in Journal/Newspaper North Atlantic Archive ouverte HAL (Hyper Article en Ligne, CCSD - Centre pour la Communication Scientifique Directe) Pacific Journal of Physical Oceanography 46 3 895 917 |
institution |
Open Polar |
collection |
Archive ouverte HAL (Hyper Article en Ligne, CCSD - Centre pour la Communication Scientifique Directe) |
op_collection_id |
ftccsdartic |
language |
English |
topic |
Atm/Ocean Structure/ Phenomena Ocean circulation Meridional overturning circulation Baroclinic flows Circulation/ Dynamics Atlantic Ocean Geographic location/entity Ekman pumping Thermohaline circulation [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography [SDU.OCEAN]Sciences of the Universe [physics]/Ocean Atmosphere |
spellingShingle |
Atm/Ocean Structure/ Phenomena Ocean circulation Meridional overturning circulation Baroclinic flows Circulation/ Dynamics Atlantic Ocean Geographic location/entity Ekman pumping Thermohaline circulation [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography [SDU.OCEAN]Sciences of the Universe [physics]/Ocean Atmosphere Sevellec, F. Huck, Thierry Geostrophic Closure of the Zonally Averaged Atlantic Meridional Overturning Circulation |
topic_facet |
Atm/Ocean Structure/ Phenomena Ocean circulation Meridional overturning circulation Baroclinic flows Circulation/ Dynamics Atlantic Ocean Geographic location/entity Ekman pumping Thermohaline circulation [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography [SDU.OCEAN]Sciences of the Universe [physics]/Ocean Atmosphere |
description |
International audience It is typically assumed that the meridional density gradient in the North Atlantic is well and positively correlated with the Atlantic meridional overturning circulation (AMOC). In numerical “water-hosing” experiments, for example, imposing an anomalous freshwater flux in the Northern Hemisphere leads to a slowdown of the AMOC. However, on planetary scale, the first-order dynamics are linked to the geostrophic balance, relating the north–south pressure gradient to the zonal circulation. In this study, these two approaches are reconciled. At steady state and under geostrophic dynamics, an analytical expression is derived to relate the zonal and meridional pressure gradient. This solution is only valid where the meridional density gradient length scale is shorter than Earth’s curvature length scale, that is, north of 35°N. This theoretical expression links the north–south density gradient to the AMOC and can be used as a closure for zonally averaged ocean models. Assumptions and shortcomings of the approach are presented. Implications of these results for paleoclimate problems such as AMOC collapse and asymmetry in the meridional overturning circulation of the Atlantic and of the Pacific are discussed. |
author2 |
Ocean and Earth Science Southampton University of Southampton-National Oceanography Centre (NOC) Laboratoire de physique des océans (LPO) Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS) |
format |
Article in Journal/Newspaper |
author |
Sevellec, F. Huck, Thierry |
author_facet |
Sevellec, F. Huck, Thierry |
author_sort |
Sevellec, F. |
title |
Geostrophic Closure of the Zonally Averaged Atlantic Meridional Overturning Circulation |
title_short |
Geostrophic Closure of the Zonally Averaged Atlantic Meridional Overturning Circulation |
title_full |
Geostrophic Closure of the Zonally Averaged Atlantic Meridional Overturning Circulation |
title_fullStr |
Geostrophic Closure of the Zonally Averaged Atlantic Meridional Overturning Circulation |
title_full_unstemmed |
Geostrophic Closure of the Zonally Averaged Atlantic Meridional Overturning Circulation |
title_sort |
geostrophic closure of the zonally averaged atlantic meridional overturning circulation |
publisher |
HAL CCSD |
publishDate |
2016 |
url |
https://hal.archives-ouvertes.fr/hal-01575298 https://doi.org/10.1175/JPO-D-14-0148.1 |
geographic |
Pacific |
geographic_facet |
Pacific |
genre |
North Atlantic |
genre_facet |
North Atlantic |
op_source |
ISSN: 0022-3670 EISSN: 1520-0485 Journal of Physical Oceanography https://hal.archives-ouvertes.fr/hal-01575298 Journal of Physical Oceanography, American Meteorological Society, 2016, 46 (3), pp.895-917. ⟨10.1175/JPO-D-14-0148.1⟩ |
op_relation |
info:eu-repo/semantics/altIdentifier/doi/10.1175/JPO-D-14-0148.1 hal-01575298 https://hal.archives-ouvertes.fr/hal-01575298 doi:10.1175/JPO-D-14-0148.1 |
op_doi |
https://doi.org/10.1175/JPO-D-14-0148.1 |
container_title |
Journal of Physical Oceanography |
container_volume |
46 |
container_issue |
3 |
container_start_page |
895 |
op_container_end_page |
917 |
_version_ |
1766132945892933632 |