On the mechanism of centennial thermohaline oscillations
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...
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2006
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Online Access: | https://eprints.soton.ac.uk/339728/ |
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ftsouthampton:oai:eprints.soton.ac.uk:339728 2023-07-30T03:58:30+02:00 On the mechanism of centennial thermohaline oscillations Sévellec, Florian Huck, Thierry Ben Jelloul, Mahdi 2006-05 https://eprints.soton.ac.uk/339728/ unknown Sévellec, Florian, Huck, Thierry and Ben Jelloul, Mahdi (2006) On the mechanism of centennial thermohaline oscillations. Journal of Marine Research, 64 (3), 355-392. (doi:10.1357/002224006778189608 <http://dx.doi.org/10.1357/002224006778189608>). Article PeerReviewed 2006 ftsouthampton https://doi.org/10.1357/002224006778189608 2023-07-09T21:39:26Z 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 University of Southampton: e-Prints Soton Antarctic Journal of Marine Research 64 3 355 392 |
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Open Polar |
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University of Southampton: e-Prints Soton |
op_collection_id |
ftsouthampton |
language |
unknown |
description |
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. |
format |
Article in Journal/Newspaper |
author |
Sévellec, Florian Huck, Thierry Ben Jelloul, Mahdi |
spellingShingle |
Sévellec, Florian Huck, Thierry Ben Jelloul, Mahdi On the mechanism of centennial thermohaline oscillations |
author_facet |
Sévellec, Florian Huck, Thierry Ben Jelloul, Mahdi |
author_sort |
Sévellec, Florian |
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 |
publishDate |
2006 |
url |
https://eprints.soton.ac.uk/339728/ |
geographic |
Antarctic |
geographic_facet |
Antarctic |
genre |
Antarc* Antarctic |
genre_facet |
Antarc* Antarctic |
op_relation |
Sévellec, Florian, Huck, Thierry and Ben Jelloul, Mahdi (2006) On the mechanism of centennial thermohaline oscillations. Journal of Marine Research, 64 (3), 355-392. (doi:10.1357/002224006778189608 <http://dx.doi.org/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_ |
1772821284906860544 |