Role of Southern Ocean sea ice on deep ocean circulation and carbon cycle at the Last Glacial Maximum
Compared to the present-day climate, the cold period of the Last Glacial Maximum was characterized by an expanded sea-ice cover in the Southern Ocean, a shoaled Atlantic deep ocean circulation and a lower atmospheric CO2 concentration. These changes are well-documented by indirect observations but d...
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ftinsu:oai:HAL:tel-03623356v2 2024-04-28T08:25:09+00:00 Role of Southern Ocean sea ice on deep ocean circulation and carbon cycle at the Last Glacial Maximum Rôle de la glace de mer australe sur la circulation océanique profonde et le cycle du carbone au Dernier Maximum Glaciaire Lhardy, Fanny Laboratoire des Sciences du Climat et de l'Environnement Gif-sur-Yvette (LSCE) Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)) Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA) Université Paris-Saclay Didier Roche Nathaëlle Bouttes 2021-09-27 https://hal.science/tel-03623356 https://hal.science/tel-03623356v2/document https://hal.science/tel-03623356v2/file/100504_LHARDY_2021_archivage.pdf en eng HAL CCSD NNT: 2021UPASJ013 tel-03623356 https://hal.science/tel-03623356 https://hal.science/tel-03623356v2/document https://hal.science/tel-03623356v2/file/100504_LHARDY_2021_archivage.pdf info:eu-repo/semantics/OpenAccess https://hal.science/tel-03623356 Climatology. Université Paris-Saclay, 2021. English. ⟨NNT : 2021UPASJ013⟩ Deep ocean circulation Sea ice Carbon sequestration Paleoclimate modelling Circulation océanique profonde Glace de mer Contenu en carbone Modélisation des paléoclimats [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology [SDU.OCEAN]Sciences of the Universe [physics]/Ocean Atmosphere info:eu-repo/semantics/doctoralThesis Theses 2021 ftinsu 2024-04-05T00:34:31Z Compared to the present-day climate, the cold period of the Last Glacial Maximum was characterized by an expanded sea-ice cover in the Southern Ocean, a shoaled Atlantic deep ocean circulation and a lower atmospheric CO2 concentration. These changes are well-documented by indirect observations but difficult to represent in simulations of climate models. Indeed, these models tend to simulate a too high atmospheric CO2 concentration, a too deep Atlantic deep ocean circulation, and a sea-ice cover with a too circular distribution in the Southern Ocean and a too small winter extent and seasonal amplitude. The model-data discrepancies observed at the Last Glacial Maximum call into question the model representation of some important climate processes. Several studies have underlined the crucial role of the Southern Ocean sea ice on ocean carbon storage capacity and deep circulation. I have therefore focussed on this region to improve our understanding of the processes associated with this storage. Thanks to simulations performed with the Earth System Model iLOVECLIM, I have demonstrated thatthe uncertainties related to ice sheet reconstructions have a limited impact on the variables examined in this study. In contrast, other choices of boundary conditions (influencing the ocean volume and alkalinity adjustment) can yield large changes of carbon sequestration in the ocean. I also show that a simple parameterization of the sinking of brines consequent to sea-ice formation significantly improves the simulated Southern Ocean sea ice, deep ocean circulation and atmospheric CO2 concentration. A set of simulations including the effects of diverse ocean parameterizations is used to show that the too deep ocean circulation simulated by our model cannot be attributed to an insufficient sea-ice cover, whereas convection processes in the Southern Ocean seem crucial to improve both the Southern Ocean sea ice, the deep ocean circulation and the atmospheric CO2 concentration at the Last Glacial Maximum. La période froide du ... Doctoral or Postdoctoral Thesis Ice Sheet Sea ice Southern Ocean Institut national des sciences de l'Univers: HAL-INSU |
institution |
Open Polar |
collection |
Institut national des sciences de l'Univers: HAL-INSU |
op_collection_id |
ftinsu |
language |
English |
topic |
Deep ocean circulation Sea ice Carbon sequestration Paleoclimate modelling Circulation océanique profonde Glace de mer Contenu en carbone Modélisation des paléoclimats [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology [SDU.OCEAN]Sciences of the Universe [physics]/Ocean Atmosphere |
spellingShingle |
Deep ocean circulation Sea ice Carbon sequestration Paleoclimate modelling Circulation océanique profonde Glace de mer Contenu en carbone Modélisation des paléoclimats [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology [SDU.OCEAN]Sciences of the Universe [physics]/Ocean Atmosphere Lhardy, Fanny Role of Southern Ocean sea ice on deep ocean circulation and carbon cycle at the Last Glacial Maximum |
topic_facet |
Deep ocean circulation Sea ice Carbon sequestration Paleoclimate modelling Circulation océanique profonde Glace de mer Contenu en carbone Modélisation des paléoclimats [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology [SDU.OCEAN]Sciences of the Universe [physics]/Ocean Atmosphere |
description |
Compared to the present-day climate, the cold period of the Last Glacial Maximum was characterized by an expanded sea-ice cover in the Southern Ocean, a shoaled Atlantic deep ocean circulation and a lower atmospheric CO2 concentration. These changes are well-documented by indirect observations but difficult to represent in simulations of climate models. Indeed, these models tend to simulate a too high atmospheric CO2 concentration, a too deep Atlantic deep ocean circulation, and a sea-ice cover with a too circular distribution in the Southern Ocean and a too small winter extent and seasonal amplitude. The model-data discrepancies observed at the Last Glacial Maximum call into question the model representation of some important climate processes. Several studies have underlined the crucial role of the Southern Ocean sea ice on ocean carbon storage capacity and deep circulation. I have therefore focussed on this region to improve our understanding of the processes associated with this storage. Thanks to simulations performed with the Earth System Model iLOVECLIM, I have demonstrated thatthe uncertainties related to ice sheet reconstructions have a limited impact on the variables examined in this study. In contrast, other choices of boundary conditions (influencing the ocean volume and alkalinity adjustment) can yield large changes of carbon sequestration in the ocean. I also show that a simple parameterization of the sinking of brines consequent to sea-ice formation significantly improves the simulated Southern Ocean sea ice, deep ocean circulation and atmospheric CO2 concentration. A set of simulations including the effects of diverse ocean parameterizations is used to show that the too deep ocean circulation simulated by our model cannot be attributed to an insufficient sea-ice cover, whereas convection processes in the Southern Ocean seem crucial to improve both the Southern Ocean sea ice, the deep ocean circulation and the atmospheric CO2 concentration at the Last Glacial Maximum. La période froide du ... |
author2 |
Laboratoire des Sciences du Climat et de l'Environnement Gif-sur-Yvette (LSCE) Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)) Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA) Université Paris-Saclay Didier Roche Nathaëlle Bouttes |
format |
Doctoral or Postdoctoral Thesis |
author |
Lhardy, Fanny |
author_facet |
Lhardy, Fanny |
author_sort |
Lhardy, Fanny |
title |
Role of Southern Ocean sea ice on deep ocean circulation and carbon cycle at the Last Glacial Maximum |
title_short |
Role of Southern Ocean sea ice on deep ocean circulation and carbon cycle at the Last Glacial Maximum |
title_full |
Role of Southern Ocean sea ice on deep ocean circulation and carbon cycle at the Last Glacial Maximum |
title_fullStr |
Role of Southern Ocean sea ice on deep ocean circulation and carbon cycle at the Last Glacial Maximum |
title_full_unstemmed |
Role of Southern Ocean sea ice on deep ocean circulation and carbon cycle at the Last Glacial Maximum |
title_sort |
role of southern ocean sea ice on deep ocean circulation and carbon cycle at the last glacial maximum |
publisher |
HAL CCSD |
publishDate |
2021 |
url |
https://hal.science/tel-03623356 https://hal.science/tel-03623356v2/document https://hal.science/tel-03623356v2/file/100504_LHARDY_2021_archivage.pdf |
genre |
Ice Sheet Sea ice Southern Ocean |
genre_facet |
Ice Sheet Sea ice Southern Ocean |
op_source |
https://hal.science/tel-03623356 Climatology. Université Paris-Saclay, 2021. English. ⟨NNT : 2021UPASJ013⟩ |
op_relation |
NNT: 2021UPASJ013 tel-03623356 https://hal.science/tel-03623356 https://hal.science/tel-03623356v2/document https://hal.science/tel-03623356v2/file/100504_LHARDY_2021_archivage.pdf |
op_rights |
info:eu-repo/semantics/OpenAccess |
_version_ |
1797585060365336576 |