Impact of Southern Ocean surface conditions on deep ocean circulation during the LGM: a model analysis
Changes in water mass distribution are considered to be a significant contributor to the atmospheric CO2 concentration drop to around 186 ppm recorded during the Last Glacial Maximum (LGM). Yet simulating a glacial Atlantic Meridional Overturning Circulation (AMOC) in agreement with paleotracer data...
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2021
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Online Access: | https://oskar-bordeaux.fr/handle/20.500.12278/188611 https://hdl.handle.net/20.500.12278/188611 https://doi.org/10.5194/cp-17-1139-2021 |
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ftoskarbordeaux:oai:oskar-bordeaux.fr:20.500.12278/188611 2024-04-07T07:47:04+00:00 Impact of Southern Ocean surface conditions on deep ocean circulation during the LGM: a model analysis LHARDY, Fanny BOUTTES, Nathaëlle ROCHE, Didier M. CROSTA, Xavier WAELBROECK, Claire PAILLARD, Didier 2021 https://oskar-bordeaux.fr/handle/20.500.12278/188611 https://hdl.handle.net/20.500.12278/188611 https://doi.org/10.5194/cp-17-1139-2021 EN eng 1814-9324 https://oskar-bordeaux.fr/handle/20.500.12278/188611 doi:10.5194/cp-17-1139-2021 Attribution 3.0 United States open http://creativecommons.org/licenses/by/3.0/us/ CC BY Last Glacial Maximum Southern Ocean iLOVECLIM model Planète et Univers [physics]/Sciences de la Terre/Océanographie Planète et Univers [physics]/Sciences de la Terre/Climatologie Article de revue 2021 ftoskarbordeaux https://doi.org/20.500.12278/18861110.5194/cp-17-1139-2021 2024-03-14T20:15:21Z Changes in water mass distribution are considered to be a significant contributor to the atmospheric CO2 concentration drop to around 186 ppm recorded during the Last Glacial Maximum (LGM). Yet simulating a glacial Atlantic Meridional Overturning Circulation (AMOC) in agreement with paleotracer data remains a challenge, with most models from previous Paleoclimate Modelling Intercomparison Project (PMIP) phases showing a tendency to simulate a strong and deep North Atlantic Deep Water (NADW) instead of the shoaling inferred from proxy records of water mass distribution. Conversely, the simulated Antarctic Bottom Water (AABW) is often reduced compared to its pre-industrial volume, and the Atlantic Ocean stratification is underestimated with respect to paleoproxy data. Inadequate representation of surface conditions, driving deep convection around Antarctica, may explain inaccurately simulated bottom water properties in the Southern Ocean. We investigate here the impact of a range of surface conditions in the Southern Ocean in the iLOVECLIM model using nine simulations obtained with different LGM boundary conditions associated with the ice sheet reconstruction (e.g., changes of elevation, bathymetry, and land–sea mask) and/or modeling choices related to sea-ice export, formation of salty brines, and freshwater input. Based on model–data comparison of sea-surface temperatures and sea ice, we find that only simulations with a cold Southern Ocean and a quite extensive sea-ice cover show an improved agreement with proxy records of sea ice, despite systematic model biases in the seasonal and regional patterns. We then show that the only simulation which does not display a much deeper NADW is obtained by parameterizing the sinking of brines along Antarctica, a modeling choice reducing the open-ocean convection in the Southern Ocean. These results highlight the importance of the representation of convection processes, which have a large impact on the water mass properties, while the choice of boundary conditions appears ... Article in Journal/Newspaper Antarc* Antarctic Antarctica Ice Sheet NADW North Atlantic Deep Water North Atlantic Sea ice Southern Ocean OSKAR Bordeaux (Open Science Knowledge ARchive) Antarctic Southern Ocean Climate of the Past 17 3 1139 1159 |
institution |
Open Polar |
collection |
OSKAR Bordeaux (Open Science Knowledge ARchive) |
op_collection_id |
ftoskarbordeaux |
language |
English |
topic |
Last Glacial Maximum Southern Ocean iLOVECLIM model Planète et Univers [physics]/Sciences de la Terre/Océanographie Planète et Univers [physics]/Sciences de la Terre/Climatologie |
spellingShingle |
Last Glacial Maximum Southern Ocean iLOVECLIM model Planète et Univers [physics]/Sciences de la Terre/Océanographie Planète et Univers [physics]/Sciences de la Terre/Climatologie LHARDY, Fanny BOUTTES, Nathaëlle ROCHE, Didier M. CROSTA, Xavier WAELBROECK, Claire PAILLARD, Didier Impact of Southern Ocean surface conditions on deep ocean circulation during the LGM: a model analysis |
topic_facet |
Last Glacial Maximum Southern Ocean iLOVECLIM model Planète et Univers [physics]/Sciences de la Terre/Océanographie Planète et Univers [physics]/Sciences de la Terre/Climatologie |
description |
Changes in water mass distribution are considered to be a significant contributor to the atmospheric CO2 concentration drop to around 186 ppm recorded during the Last Glacial Maximum (LGM). Yet simulating a glacial Atlantic Meridional Overturning Circulation (AMOC) in agreement with paleotracer data remains a challenge, with most models from previous Paleoclimate Modelling Intercomparison Project (PMIP) phases showing a tendency to simulate a strong and deep North Atlantic Deep Water (NADW) instead of the shoaling inferred from proxy records of water mass distribution. Conversely, the simulated Antarctic Bottom Water (AABW) is often reduced compared to its pre-industrial volume, and the Atlantic Ocean stratification is underestimated with respect to paleoproxy data. Inadequate representation of surface conditions, driving deep convection around Antarctica, may explain inaccurately simulated bottom water properties in the Southern Ocean. We investigate here the impact of a range of surface conditions in the Southern Ocean in the iLOVECLIM model using nine simulations obtained with different LGM boundary conditions associated with the ice sheet reconstruction (e.g., changes of elevation, bathymetry, and land–sea mask) and/or modeling choices related to sea-ice export, formation of salty brines, and freshwater input. Based on model–data comparison of sea-surface temperatures and sea ice, we find that only simulations with a cold Southern Ocean and a quite extensive sea-ice cover show an improved agreement with proxy records of sea ice, despite systematic model biases in the seasonal and regional patterns. We then show that the only simulation which does not display a much deeper NADW is obtained by parameterizing the sinking of brines along Antarctica, a modeling choice reducing the open-ocean convection in the Southern Ocean. These results highlight the importance of the representation of convection processes, which have a large impact on the water mass properties, while the choice of boundary conditions appears ... |
format |
Article in Journal/Newspaper |
author |
LHARDY, Fanny BOUTTES, Nathaëlle ROCHE, Didier M. CROSTA, Xavier WAELBROECK, Claire PAILLARD, Didier |
author_facet |
LHARDY, Fanny BOUTTES, Nathaëlle ROCHE, Didier M. CROSTA, Xavier WAELBROECK, Claire PAILLARD, Didier |
author_sort |
LHARDY, Fanny |
title |
Impact of Southern Ocean surface conditions on deep ocean circulation during the LGM: a model analysis |
title_short |
Impact of Southern Ocean surface conditions on deep ocean circulation during the LGM: a model analysis |
title_full |
Impact of Southern Ocean surface conditions on deep ocean circulation during the LGM: a model analysis |
title_fullStr |
Impact of Southern Ocean surface conditions on deep ocean circulation during the LGM: a model analysis |
title_full_unstemmed |
Impact of Southern Ocean surface conditions on deep ocean circulation during the LGM: a model analysis |
title_sort |
impact of southern ocean surface conditions on deep ocean circulation during the lgm: a model analysis |
publishDate |
2021 |
url |
https://oskar-bordeaux.fr/handle/20.500.12278/188611 https://hdl.handle.net/20.500.12278/188611 https://doi.org/10.5194/cp-17-1139-2021 |
geographic |
Antarctic Southern Ocean |
geographic_facet |
Antarctic Southern Ocean |
genre |
Antarc* Antarctic Antarctica Ice Sheet NADW North Atlantic Deep Water North Atlantic Sea ice Southern Ocean |
genre_facet |
Antarc* Antarctic Antarctica Ice Sheet NADW North Atlantic Deep Water North Atlantic Sea ice Southern Ocean |
op_relation |
1814-9324 https://oskar-bordeaux.fr/handle/20.500.12278/188611 doi:10.5194/cp-17-1139-2021 |
op_rights |
Attribution 3.0 United States open http://creativecommons.org/licenses/by/3.0/us/ CC BY |
op_doi |
https://doi.org/20.500.12278/18861110.5194/cp-17-1139-2021 |
container_title |
Climate of the Past |
container_volume |
17 |
container_issue |
3 |
container_start_page |
1139 |
op_container_end_page |
1159 |
_version_ |
1795671458421145600 |