Surface Constraints on the Depth of the Atlantic Meridional Overturning Circulation: Southern Ocean versus North Atlantic Surface Constraints on the Depth of the Atlantic Meridional Overturning Circulation: Southern Ocean versus North Atlantic
Paleoclimate proxy evidence suggests that the Atlantic meridional overturning circulation (AMOC) was about 1000 m shallower at the Last Glacial Maximum (LGM) compared to the present. Yet it remains unresolved what caused this glacial shoaling of the AMOC, and many climate models instead simulate a d...
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ftcdlib:oai:escholarship.org:ark:/13030/qt8fx8t0nj 2023-06-18T03:41:54+02:00 Surface Constraints on the Depth of the Atlantic Meridional Overturning Circulation: Southern Ocean versus North Atlantic Surface Constraints on the Depth of the Atlantic Meridional Overturning Circulation: Southern Ocean versus North Atlantic Sun, Shantong Eisenman, Ian Zanna, Laure Stewart, Andrew L 3125 - 3149 2020-04-01 application/pdf https://escholarship.org/uc/item/8fx8t0nj unknown eScholarship, University of California qt8fx8t0nj https://escholarship.org/uc/item/8fx8t0nj public Journal of Climate, vol 33, iss 8 Climate Action Life Below Water Abyssal circulation Thermohaline circulation General circulation models Atmospheric Sciences Oceanography Geomatic Engineering Meteorology & Atmospheric Sciences article 2020 ftcdlib 2023-06-05T17:58:54Z Paleoclimate proxy evidence suggests that the Atlantic meridional overturning circulation (AMOC) was about 1000 m shallower at the Last Glacial Maximum (LGM) compared to the present. Yet it remains unresolved what caused this glacial shoaling of the AMOC, and many climate models instead simulate a deeper AMOC under LGM forcing. While some studies suggest that Southern Ocean surface buoyancy forcing controls the AMOC depth, others have suggested alternatively that North Atlantic surface forcing or interior diabatic mixing plays the dominant role. To investigate the key processes that set the AMOC depth, here we carry out a number of MITgcm ocean-only simulations with surface forcing fields specified from the simulation results of three coupled climate models that span much of the range of glacial AMOC depth changes in phase 3 of the Paleoclimate Model Intercomparison Project (PMIP3). We find that the MITgcm simulations successfully reproduce the changes in AMOC depth between glacial and modern conditions simulated in these three PMIP3 models. By varying the restoring time scale in the surface forcing, we show that the AMOC depth is more strongly constrained by the surface density field than the surface buoyancy flux field. Based on these results, we propose a mechanism by which the surface density fields in the high latitudes of both hemispheres are connected to the AMOC depth. We illustrate the mechanism using MITgcm simulations with idealized surface forcing perturbations as well as an idealized conceptual geometric model. These results suggest that the AMOC depth is largely determined by the surface density fields in both the North Atlantic and the Southern Ocean. Article in Journal/Newspaper North Atlantic Southern Ocean University of California: eScholarship Southern Ocean |
institution |
Open Polar |
collection |
University of California: eScholarship |
op_collection_id |
ftcdlib |
language |
unknown |
topic |
Climate Action Life Below Water Abyssal circulation Thermohaline circulation General circulation models Atmospheric Sciences Oceanography Geomatic Engineering Meteorology & Atmospheric Sciences |
spellingShingle |
Climate Action Life Below Water Abyssal circulation Thermohaline circulation General circulation models Atmospheric Sciences Oceanography Geomatic Engineering Meteorology & Atmospheric Sciences Sun, Shantong Eisenman, Ian Zanna, Laure Stewart, Andrew L Surface Constraints on the Depth of the Atlantic Meridional Overturning Circulation: Southern Ocean versus North Atlantic Surface Constraints on the Depth of the Atlantic Meridional Overturning Circulation: Southern Ocean versus North Atlantic |
topic_facet |
Climate Action Life Below Water Abyssal circulation Thermohaline circulation General circulation models Atmospheric Sciences Oceanography Geomatic Engineering Meteorology & Atmospheric Sciences |
description |
Paleoclimate proxy evidence suggests that the Atlantic meridional overturning circulation (AMOC) was about 1000 m shallower at the Last Glacial Maximum (LGM) compared to the present. Yet it remains unresolved what caused this glacial shoaling of the AMOC, and many climate models instead simulate a deeper AMOC under LGM forcing. While some studies suggest that Southern Ocean surface buoyancy forcing controls the AMOC depth, others have suggested alternatively that North Atlantic surface forcing or interior diabatic mixing plays the dominant role. To investigate the key processes that set the AMOC depth, here we carry out a number of MITgcm ocean-only simulations with surface forcing fields specified from the simulation results of three coupled climate models that span much of the range of glacial AMOC depth changes in phase 3 of the Paleoclimate Model Intercomparison Project (PMIP3). We find that the MITgcm simulations successfully reproduce the changes in AMOC depth between glacial and modern conditions simulated in these three PMIP3 models. By varying the restoring time scale in the surface forcing, we show that the AMOC depth is more strongly constrained by the surface density field than the surface buoyancy flux field. Based on these results, we propose a mechanism by which the surface density fields in the high latitudes of both hemispheres are connected to the AMOC depth. We illustrate the mechanism using MITgcm simulations with idealized surface forcing perturbations as well as an idealized conceptual geometric model. These results suggest that the AMOC depth is largely determined by the surface density fields in both the North Atlantic and the Southern Ocean. |
format |
Article in Journal/Newspaper |
author |
Sun, Shantong Eisenman, Ian Zanna, Laure Stewart, Andrew L |
author_facet |
Sun, Shantong Eisenman, Ian Zanna, Laure Stewart, Andrew L |
author_sort |
Sun, Shantong |
title |
Surface Constraints on the Depth of the Atlantic Meridional Overturning Circulation: Southern Ocean versus North Atlantic Surface Constraints on the Depth of the Atlantic Meridional Overturning Circulation: Southern Ocean versus North Atlantic |
title_short |
Surface Constraints on the Depth of the Atlantic Meridional Overturning Circulation: Southern Ocean versus North Atlantic Surface Constraints on the Depth of the Atlantic Meridional Overturning Circulation: Southern Ocean versus North Atlantic |
title_full |
Surface Constraints on the Depth of the Atlantic Meridional Overturning Circulation: Southern Ocean versus North Atlantic Surface Constraints on the Depth of the Atlantic Meridional Overturning Circulation: Southern Ocean versus North Atlantic |
title_fullStr |
Surface Constraints on the Depth of the Atlantic Meridional Overturning Circulation: Southern Ocean versus North Atlantic Surface Constraints on the Depth of the Atlantic Meridional Overturning Circulation: Southern Ocean versus North Atlantic |
title_full_unstemmed |
Surface Constraints on the Depth of the Atlantic Meridional Overturning Circulation: Southern Ocean versus North Atlantic Surface Constraints on the Depth of the Atlantic Meridional Overturning Circulation: Southern Ocean versus North Atlantic |
title_sort |
surface constraints on the depth of the atlantic meridional overturning circulation: southern ocean versus north atlantic surface constraints on the depth of the atlantic meridional overturning circulation: southern ocean versus north atlantic |
publisher |
eScholarship, University of California |
publishDate |
2020 |
url |
https://escholarship.org/uc/item/8fx8t0nj |
op_coverage |
3125 - 3149 |
geographic |
Southern Ocean |
geographic_facet |
Southern Ocean |
genre |
North Atlantic Southern Ocean |
genre_facet |
North Atlantic Southern Ocean |
op_source |
Journal of Climate, vol 33, iss 8 |
op_relation |
qt8fx8t0nj https://escholarship.org/uc/item/8fx8t0nj |
op_rights |
public |
_version_ |
1769007610787266560 |