On the mechanism of centennial thermohaline oscillations.
International audience Centennial oscillations of the ocean thermohaline circulation are studied in a 2-D latitude-depth model under mixed boundary conditions (i.e. restoring surface temperature and prescribed freshwater flux). The oscillations are revealed through linear stability analysis of a ste...
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ftunivnantes:oai:HAL:hal-00308767v1 2023-05-15T13:37:55+02:00 On the mechanism of centennial thermohaline oscillations. Florian, Sévellec Thierry, Huck Mahdi Ben, Jelloul 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) 2006-05-03 https://hal.science/hal-00308767 https://doi.org/10.1357/002224006778189608 en eng HAL CCSD Yale University info:eu-repo/semantics/altIdentifier/doi/10.1357/002224006778189608 hal-00308767 https://hal.science/hal-00308767 doi:10.1357/002224006778189608 ISSN: 0022-2402 EISSN: 1543-9542 Journal of marine research https://hal.science/hal-00308767 Journal of marine research, 2006, 64 (3), pp.355-392. ⟨10.1357/002224006778189608⟩ [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography info:eu-repo/semantics/article Journal articles 2006 ftunivnantes https://doi.org/10.1357/002224006778189608 2023-02-08T05:01:36Z International audience Centennial oscillations of the ocean thermohaline circulation are studied in a 2-D latitude-depth model under mixed boundary conditions (i.e. restoring surface temperature and prescribed freshwater flux). The oscillations are revealed through linear stability analysis of a steady state obtained in a single hemisphere configuration. A density variance budget is performed and helps determine the physical processes sustaining these oscillations: the restoring surface temperature appears as a source of density variance - this is a consequence of positively-correlated temperature and salinity anomalies. A minimal model, the Howard-Malkus loop oscillator, enables us to understand physically the oscillatory and growth mechanisms. The centennial oscillation is connected to the advection of salinity anomaly around the loop; it is also related to the salinity feedback on the overturning which reinforces anomalies through a change of residence time in the freshwater flux regions. Analytical solutions of this loop model show that these centennial oscillations exist in a specific parameter regime in terms of the freshwater flux amplitude F0: oscillations are damped if F0 is too weak, but if F0 is too large, the instability grows exponentially without oscillating-the latter regime is known as the positive salinity feedback. The robustness of these oscillations is then analyzed in more realistic bihemispheric configurations, some including a highly idealized Antarctic Circumpolar Current: oscillations are then always damped. These results are rationalized with the loop model, and compared to the oscillations found in general circulation models. Article in Journal/Newspaper Antarc* Antarctic Université de Nantes: HAL-UNIV-NANTES Antarctic Journal of Marine Research 64 3 355 392 |
institution |
Open Polar |
collection |
Université de Nantes: HAL-UNIV-NANTES |
op_collection_id |
ftunivnantes |
language |
English |
topic |
[SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography |
spellingShingle |
[SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography Florian, Sévellec Thierry, Huck Mahdi Ben, Jelloul On the mechanism of centennial thermohaline oscillations. |
topic_facet |
[SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography |
description |
International audience Centennial oscillations of the ocean thermohaline circulation are studied in a 2-D latitude-depth model under mixed boundary conditions (i.e. restoring surface temperature and prescribed freshwater flux). The oscillations are revealed through linear stability analysis of a steady state obtained in a single hemisphere configuration. A density variance budget is performed and helps determine the physical processes sustaining these oscillations: the restoring surface temperature appears as a source of density variance - this is a consequence of positively-correlated temperature and salinity anomalies. A minimal model, the Howard-Malkus loop oscillator, enables us to understand physically the oscillatory and growth mechanisms. The centennial oscillation is connected to the advection of salinity anomaly around the loop; it is also related to the salinity feedback on the overturning which reinforces anomalies through a change of residence time in the freshwater flux regions. Analytical solutions of this loop model show that these centennial oscillations exist in a specific parameter regime in terms of the freshwater flux amplitude F0: oscillations are damped if F0 is too weak, but if F0 is too large, the instability grows exponentially without oscillating-the latter regime is known as the positive salinity feedback. The robustness of these oscillations is then analyzed in more realistic bihemispheric configurations, some including a highly idealized Antarctic Circumpolar Current: oscillations are then always damped. These results are rationalized with the loop model, and compared to the oscillations found in general circulation models. |
author2 |
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 |
Florian, Sévellec Thierry, Huck Mahdi Ben, Jelloul |
author_facet |
Florian, Sévellec Thierry, Huck Mahdi Ben, Jelloul |
author_sort |
Florian, Sévellec |
title |
On the mechanism of centennial thermohaline oscillations. |
title_short |
On the mechanism of centennial thermohaline oscillations. |
title_full |
On the mechanism of centennial thermohaline oscillations. |
title_fullStr |
On the mechanism of centennial thermohaline oscillations. |
title_full_unstemmed |
On the mechanism of centennial thermohaline oscillations. |
title_sort |
on the mechanism of centennial thermohaline oscillations. |
publisher |
HAL CCSD |
publishDate |
2006 |
url |
https://hal.science/hal-00308767 https://doi.org/10.1357/002224006778189608 |
geographic |
Antarctic |
geographic_facet |
Antarctic |
genre |
Antarc* Antarctic |
genre_facet |
Antarc* Antarctic |
op_source |
ISSN: 0022-2402 EISSN: 1543-9542 Journal of marine research https://hal.science/hal-00308767 Journal of marine research, 2006, 64 (3), pp.355-392. ⟨10.1357/002224006778189608⟩ |
op_relation |
info:eu-repo/semantics/altIdentifier/doi/10.1357/002224006778189608 hal-00308767 https://hal.science/hal-00308767 doi:10.1357/002224006778189608 |
op_doi |
https://doi.org/10.1357/002224006778189608 |
container_title |
Journal of Marine Research |
container_volume |
64 |
container_issue |
3 |
container_start_page |
355 |
op_container_end_page |
392 |
_version_ |
1766099548383477760 |