Climate sensitivity and meridional overturning circulation in the late Eocene using GFDL CM2.1
The Eocene–Oligocene transition (EOT), which took place approximately 34 Ma ago, is an interval of great interest in Earth's climate history, due to the inception of the Antarctic ice sheet and major global cooling. Climate simulations of the transition are needed to help interpret proxy data,...
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ftdoajarticles:oai:doaj.org/article:5d12188667bf4a45a2da8b2ed14f9cb4 2023-05-15T13:50:20+02:00 Climate sensitivity and meridional overturning circulation in the late Eocene using GFDL CM2.1 D. K. Hutchinson A. M. de Boer H. K. Coxall R. Caballero J. Nilsson M. Baatsen 2018-06-01T00:00:00Z https://doi.org/10.5194/cp-14-789-2018 https://doaj.org/article/5d12188667bf4a45a2da8b2ed14f9cb4 EN eng Copernicus Publications https://www.clim-past.net/14/789/2018/cp-14-789-2018.pdf https://doaj.org/toc/1814-9324 https://doaj.org/toc/1814-9332 doi:10.5194/cp-14-789-2018 1814-9324 1814-9332 https://doaj.org/article/5d12188667bf4a45a2da8b2ed14f9cb4 Climate of the Past, Vol 14, Pp 789-810 (2018) Environmental pollution TD172-193.5 Environmental protection TD169-171.8 Environmental sciences GE1-350 article 2018 ftdoajarticles https://doi.org/10.5194/cp-14-789-2018 2022-12-31T01:57:15Z The Eocene–Oligocene transition (EOT), which took place approximately 34 Ma ago, is an interval of great interest in Earth's climate history, due to the inception of the Antarctic ice sheet and major global cooling. Climate simulations of the transition are needed to help interpret proxy data, test mechanistic hypotheses for the transition and determine the climate sensitivity at the time. However, model studies of the EOT thus far typically employ control states designed for a different time period, or ocean resolution on the order of 3°. Here we developed a new higher resolution palaeoclimate model configuration based on the GFDL CM2.1 climate model adapted to a late Eocene (38 Ma) palaeogeography reconstruction. The ocean and atmosphere horizontal resolutions are 1° × 1.5° and 3° × 3.75° respectively. This represents a significant step forward in resolving the ocean geography, gateways and circulation in a coupled climate model of this period. We run the model under three different levels of atmospheric CO 2 : 400, 800 and 1600 ppm. The model exhibits relatively high sensitivity to CO 2 compared with other recent model studies, and thus can capture the expected Eocene high latitude warmth within observed estimates of atmospheric CO 2 . However, the model does not capture the low meridional temperature gradient seen in proxies. Equatorial sea surface temperatures are too high in the model (30–37 °C) compared with observations (max 32 °C), although observations are lacking in the warmest regions of the western Pacific. The model exhibits bipolar sinking in the North Pacific and Southern Ocean, which persists under all levels of CO 2 . North Atlantic surface salinities are too fresh to permit sinking (25–30 psu), due to surface transport from the very fresh Arctic ( ∼ 20 psu), where surface salinities approximately agree with Eocene proxy estimates. North Atlantic salinity increases by 1–2 psu when CO 2 is halved, and similarly freshens when CO 2 is doubled, due to changes in the hydrological cycle. Article in Journal/Newspaper Antarc* Antarctic Arctic Ice Sheet North Atlantic Southern Ocean Directory of Open Access Journals: DOAJ Articles Arctic Antarctic Southern Ocean The Antarctic Pacific Climate of the Past 14 6 789 810 |
institution |
Open Polar |
collection |
Directory of Open Access Journals: DOAJ Articles |
op_collection_id |
ftdoajarticles |
language |
English |
topic |
Environmental pollution TD172-193.5 Environmental protection TD169-171.8 Environmental sciences GE1-350 |
spellingShingle |
Environmental pollution TD172-193.5 Environmental protection TD169-171.8 Environmental sciences GE1-350 D. K. Hutchinson A. M. de Boer H. K. Coxall R. Caballero J. Nilsson M. Baatsen Climate sensitivity and meridional overturning circulation in the late Eocene using GFDL CM2.1 |
topic_facet |
Environmental pollution TD172-193.5 Environmental protection TD169-171.8 Environmental sciences GE1-350 |
description |
The Eocene–Oligocene transition (EOT), which took place approximately 34 Ma ago, is an interval of great interest in Earth's climate history, due to the inception of the Antarctic ice sheet and major global cooling. Climate simulations of the transition are needed to help interpret proxy data, test mechanistic hypotheses for the transition and determine the climate sensitivity at the time. However, model studies of the EOT thus far typically employ control states designed for a different time period, or ocean resolution on the order of 3°. Here we developed a new higher resolution palaeoclimate model configuration based on the GFDL CM2.1 climate model adapted to a late Eocene (38 Ma) palaeogeography reconstruction. The ocean and atmosphere horizontal resolutions are 1° × 1.5° and 3° × 3.75° respectively. This represents a significant step forward in resolving the ocean geography, gateways and circulation in a coupled climate model of this period. We run the model under three different levels of atmospheric CO 2 : 400, 800 and 1600 ppm. The model exhibits relatively high sensitivity to CO 2 compared with other recent model studies, and thus can capture the expected Eocene high latitude warmth within observed estimates of atmospheric CO 2 . However, the model does not capture the low meridional temperature gradient seen in proxies. Equatorial sea surface temperatures are too high in the model (30–37 °C) compared with observations (max 32 °C), although observations are lacking in the warmest regions of the western Pacific. The model exhibits bipolar sinking in the North Pacific and Southern Ocean, which persists under all levels of CO 2 . North Atlantic surface salinities are too fresh to permit sinking (25–30 psu), due to surface transport from the very fresh Arctic ( ∼ 20 psu), where surface salinities approximately agree with Eocene proxy estimates. North Atlantic salinity increases by 1–2 psu when CO 2 is halved, and similarly freshens when CO 2 is doubled, due to changes in the hydrological cycle. |
format |
Article in Journal/Newspaper |
author |
D. K. Hutchinson A. M. de Boer H. K. Coxall R. Caballero J. Nilsson M. Baatsen |
author_facet |
D. K. Hutchinson A. M. de Boer H. K. Coxall R. Caballero J. Nilsson M. Baatsen |
author_sort |
D. K. Hutchinson |
title |
Climate sensitivity and meridional overturning circulation in the late Eocene using GFDL CM2.1 |
title_short |
Climate sensitivity and meridional overturning circulation in the late Eocene using GFDL CM2.1 |
title_full |
Climate sensitivity and meridional overturning circulation in the late Eocene using GFDL CM2.1 |
title_fullStr |
Climate sensitivity and meridional overturning circulation in the late Eocene using GFDL CM2.1 |
title_full_unstemmed |
Climate sensitivity and meridional overturning circulation in the late Eocene using GFDL CM2.1 |
title_sort |
climate sensitivity and meridional overturning circulation in the late eocene using gfdl cm2.1 |
publisher |
Copernicus Publications |
publishDate |
2018 |
url |
https://doi.org/10.5194/cp-14-789-2018 https://doaj.org/article/5d12188667bf4a45a2da8b2ed14f9cb4 |
geographic |
Arctic Antarctic Southern Ocean The Antarctic Pacific |
geographic_facet |
Arctic Antarctic Southern Ocean The Antarctic Pacific |
genre |
Antarc* Antarctic Arctic Ice Sheet North Atlantic Southern Ocean |
genre_facet |
Antarc* Antarctic Arctic Ice Sheet North Atlantic Southern Ocean |
op_source |
Climate of the Past, Vol 14, Pp 789-810 (2018) |
op_relation |
https://www.clim-past.net/14/789/2018/cp-14-789-2018.pdf https://doaj.org/toc/1814-9324 https://doaj.org/toc/1814-9332 doi:10.5194/cp-14-789-2018 1814-9324 1814-9332 https://doaj.org/article/5d12188667bf4a45a2da8b2ed14f9cb4 |
op_doi |
https://doi.org/10.5194/cp-14-789-2018 |
container_title |
Climate of the Past |
container_volume |
14 |
container_issue |
6 |
container_start_page |
789 |
op_container_end_page |
810 |
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1766253362026643456 |