Early Eocene vigorous ocean overturning and its contribution to a warm Southern Ocean
The early Eocene ( ∼55 Ma) was the warmest period of the Cenozoic and was most likely characterized by extremely high atmospheric CO 2 concentrations. Here, we analyze simulations of the early Eocene performed with the IPSL-CM5A2 Earth system model, set up with paleogeographic reconstructions of thi...
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ftdoajarticles:oai:doaj.org/article:176ec849f8a44328b68829b2087a6dae 2023-05-15T13:32:28+02:00 Early Eocene vigorous ocean overturning and its contribution to a warm Southern Ocean Y. Zhang T. Huck C. Lique Y. Donnadieu J.-B. Ladant M. Rabineau D. Aslanian 2020-07-01T00:00:00Z https://doi.org/10.5194/cp-16-1263-2020 https://doaj.org/article/176ec849f8a44328b68829b2087a6dae EN eng Copernicus Publications https://cp.copernicus.org/articles/16/1263/2020/cp-16-1263-2020.pdf https://doaj.org/toc/1814-9324 https://doaj.org/toc/1814-9332 doi:10.5194/cp-16-1263-2020 1814-9324 1814-9332 https://doaj.org/article/176ec849f8a44328b68829b2087a6dae Climate of the Past, Vol 16, Pp 1263-1283 (2020) Environmental pollution TD172-193.5 Environmental protection TD169-171.8 Environmental sciences GE1-350 article 2020 ftdoajarticles https://doi.org/10.5194/cp-16-1263-2020 2022-12-31T03:12:44Z The early Eocene ( ∼55 Ma) was the warmest period of the Cenozoic and was most likely characterized by extremely high atmospheric CO 2 concentrations. Here, we analyze simulations of the early Eocene performed with the IPSL-CM5A2 Earth system model, set up with paleogeographic reconstructions of this period from the DeepMIP project and with different levels of atmospheric CO 2 . When compared with proxy-based reconstructions, the simulations reasonably capture both the reconstructed amplitude and pattern of early Eocene sea surface temperature. A comparison with simulations of modern conditions allows us to explore the changes in ocean circulation and the resulting ocean meridional heat transport. At a CO 2 level of 840 ppm, the early Eocene simulation is characterized by a strong abyssal overturning circulation in the Southern Hemisphere (40 Sv at 60 ∘ S), fed by deepwater formation in the three sectors of the Southern Ocean. Deep convection in the Southern Ocean is favored by the closed Drake and Tasmanian passages, which provide western boundaries for the buildup of strong subpolar gyres in the Weddell and Ross seas, in the middle of which convection develops. The strong overturning circulation, associated with subpolar gyres, sustains the poleward advection of saline subtropical water to the convective regions in the Southern Ocean, thereby maintaining deepwater formation. This salt–advection feedback mechanism is akin to that responsible for the present-day North Atlantic overturning circulation. The strong abyssal overturning circulation in the 55 Ma simulations primarily results in an enhanced poleward ocean heat transport by 0.3–0.7 PW in the Southern Hemisphere compared to modern conditions, reaching 1.7 PW southward at 20 ∘ S, and contributes to keeping the Southern Ocean and Antarctica warm in the Eocene. Simulations with different atmospheric CO 2 levels show that ocean circulation and heat transport are relatively insensitive to CO 2 doubling. Article in Journal/Newspaper Antarc* Antarctica North Atlantic Southern Ocean Directory of Open Access Journals: DOAJ Articles Southern Ocean Weddell Climate of the Past 16 4 1263 1283 |
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Directory of Open Access Journals: DOAJ Articles |
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ftdoajarticles |
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English |
topic |
Environmental pollution TD172-193.5 Environmental protection TD169-171.8 Environmental sciences GE1-350 |
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Environmental pollution TD172-193.5 Environmental protection TD169-171.8 Environmental sciences GE1-350 Y. Zhang T. Huck C. Lique Y. Donnadieu J.-B. Ladant M. Rabineau D. Aslanian Early Eocene vigorous ocean overturning and its contribution to a warm Southern Ocean |
topic_facet |
Environmental pollution TD172-193.5 Environmental protection TD169-171.8 Environmental sciences GE1-350 |
description |
The early Eocene ( ∼55 Ma) was the warmest period of the Cenozoic and was most likely characterized by extremely high atmospheric CO 2 concentrations. Here, we analyze simulations of the early Eocene performed with the IPSL-CM5A2 Earth system model, set up with paleogeographic reconstructions of this period from the DeepMIP project and with different levels of atmospheric CO 2 . When compared with proxy-based reconstructions, the simulations reasonably capture both the reconstructed amplitude and pattern of early Eocene sea surface temperature. A comparison with simulations of modern conditions allows us to explore the changes in ocean circulation and the resulting ocean meridional heat transport. At a CO 2 level of 840 ppm, the early Eocene simulation is characterized by a strong abyssal overturning circulation in the Southern Hemisphere (40 Sv at 60 ∘ S), fed by deepwater formation in the three sectors of the Southern Ocean. Deep convection in the Southern Ocean is favored by the closed Drake and Tasmanian passages, which provide western boundaries for the buildup of strong subpolar gyres in the Weddell and Ross seas, in the middle of which convection develops. The strong overturning circulation, associated with subpolar gyres, sustains the poleward advection of saline subtropical water to the convective regions in the Southern Ocean, thereby maintaining deepwater formation. This salt–advection feedback mechanism is akin to that responsible for the present-day North Atlantic overturning circulation. The strong abyssal overturning circulation in the 55 Ma simulations primarily results in an enhanced poleward ocean heat transport by 0.3–0.7 PW in the Southern Hemisphere compared to modern conditions, reaching 1.7 PW southward at 20 ∘ S, and contributes to keeping the Southern Ocean and Antarctica warm in the Eocene. Simulations with different atmospheric CO 2 levels show that ocean circulation and heat transport are relatively insensitive to CO 2 doubling. |
format |
Article in Journal/Newspaper |
author |
Y. Zhang T. Huck C. Lique Y. Donnadieu J.-B. Ladant M. Rabineau D. Aslanian |
author_facet |
Y. Zhang T. Huck C. Lique Y. Donnadieu J.-B. Ladant M. Rabineau D. Aslanian |
author_sort |
Y. Zhang |
title |
Early Eocene vigorous ocean overturning and its contribution to a warm Southern Ocean |
title_short |
Early Eocene vigorous ocean overturning and its contribution to a warm Southern Ocean |
title_full |
Early Eocene vigorous ocean overturning and its contribution to a warm Southern Ocean |
title_fullStr |
Early Eocene vigorous ocean overturning and its contribution to a warm Southern Ocean |
title_full_unstemmed |
Early Eocene vigorous ocean overturning and its contribution to a warm Southern Ocean |
title_sort |
early eocene vigorous ocean overturning and its contribution to a warm southern ocean |
publisher |
Copernicus Publications |
publishDate |
2020 |
url |
https://doi.org/10.5194/cp-16-1263-2020 https://doaj.org/article/176ec849f8a44328b68829b2087a6dae |
geographic |
Southern Ocean Weddell |
geographic_facet |
Southern Ocean Weddell |
genre |
Antarc* Antarctica North Atlantic Southern Ocean |
genre_facet |
Antarc* Antarctica North Atlantic Southern Ocean |
op_source |
Climate of the Past, Vol 16, Pp 1263-1283 (2020) |
op_relation |
https://cp.copernicus.org/articles/16/1263/2020/cp-16-1263-2020.pdf https://doaj.org/toc/1814-9324 https://doaj.org/toc/1814-9332 doi:10.5194/cp-16-1263-2020 1814-9324 1814-9332 https://doaj.org/article/176ec849f8a44328b68829b2087a6dae |
op_doi |
https://doi.org/10.5194/cp-16-1263-2020 |
container_title |
Climate of the Past |
container_volume |
16 |
container_issue |
4 |
container_start_page |
1263 |
op_container_end_page |
1283 |
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1766027255012655104 |