A new mechanism for the two-step δ18O signal at the Eocene-Oligocene boundary
The most marked step in the global climate transition from "Greenhouse" to "Icehouse" Earth occurred at the Eocene-Oligocene (E-O) boundary, 33.7 Ma. Evidence for climatic changes comes from many sources, including the marine benthic δ18O record, showing an increase by 1.2–1.5‰ a...
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fttriple:oai:gotriple.eu:oai:doaj.org/article:65f0c0b848ac4b66bf19a0f8145138c5 2023-05-15T13:47:18+02:00 A new mechanism for the two-step δ18O signal at the Eocene-Oligocene boundary A. S. von der Heydt H. A. Dijkstra M. Tigchelaar 2011-03-01 https://doi.org/10.5194/cp-7-235-2011 http://www.clim-past.net/7/235/2011/cp-7-235-2011.pdf https://doaj.org/article/65f0c0b848ac4b66bf19a0f8145138c5 en eng Copernicus Publications doi:10.5194/cp-7-235-2011 1814-9324 1814-9332 http://www.clim-past.net/7/235/2011/cp-7-235-2011.pdf https://doaj.org/article/65f0c0b848ac4b66bf19a0f8145138c5 undefined Climate of the Past, Vol 7, Iss 1, Pp 235-247 (2011) geo envir Journal Article https://vocabularies.coar-repositories.org/resource_types/c_6501/ 2011 fttriple https://doi.org/10.5194/cp-7-235-2011 2023-01-22T19:27:31Z The most marked step in the global climate transition from "Greenhouse" to "Icehouse" Earth occurred at the Eocene-Oligocene (E-O) boundary, 33.7 Ma. Evidence for climatic changes comes from many sources, including the marine benthic δ18O record, showing an increase by 1.2–1.5‰ at this time. This positive excursion is characterised by two steps, separated by a plateau. The increase in δ18O values has been attributed to rapid glaciation of the Antarctic continent, previously ice-free. Simultaneous changes in the δ13C record are suggestive of a greenhouse gas control on climate. Previous modelling studies show that a decline in pCO2 beyond a certain threshold value may have initiated the growth of a Southern Hemispheric ice sheet. These studies were not able to conclusively explain the remarkable two-step profile in δ18O. Furthermore, they considered changes in the ocean circulation only regionally, or indirectly through the oceanic heat transport. The potential role of global changes in ocean circulation in the E-O transition has not been addressed yet. Here a new interpretation of the δ18O signal is presented, based on model simulations using a simple coupled 8-box-ocean, 4-box-atmosphere model with an added land ice component. The model was forced with a slowly decreasing atmospheric carbon dioxide concentration. It is argued that the first step in the δ18O record reflects a shift in meridional overturning circulation from a Southern Ocean to a bipolar source of deep-water formation, which is associated with a cooling of the deep sea. The second step in the δ18O profile occurs due to a rapid glaciation of the Antarctic continent. This new mechanism is a robust outcome of our model and is qualitatively in close agreement with proxy data. Article in Journal/Newspaper Antarc* Antarctic Ice Sheet Southern Ocean Unknown Antarctic Southern Ocean The Antarctic Climate of the Past 7 1 235 247 |
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geo envir A. S. von der Heydt H. A. Dijkstra M. Tigchelaar A new mechanism for the two-step δ18O signal at the Eocene-Oligocene boundary |
topic_facet |
geo envir |
description |
The most marked step in the global climate transition from "Greenhouse" to "Icehouse" Earth occurred at the Eocene-Oligocene (E-O) boundary, 33.7 Ma. Evidence for climatic changes comes from many sources, including the marine benthic δ18O record, showing an increase by 1.2–1.5‰ at this time. This positive excursion is characterised by two steps, separated by a plateau. The increase in δ18O values has been attributed to rapid glaciation of the Antarctic continent, previously ice-free. Simultaneous changes in the δ13C record are suggestive of a greenhouse gas control on climate. Previous modelling studies show that a decline in pCO2 beyond a certain threshold value may have initiated the growth of a Southern Hemispheric ice sheet. These studies were not able to conclusively explain the remarkable two-step profile in δ18O. Furthermore, they considered changes in the ocean circulation only regionally, or indirectly through the oceanic heat transport. The potential role of global changes in ocean circulation in the E-O transition has not been addressed yet. Here a new interpretation of the δ18O signal is presented, based on model simulations using a simple coupled 8-box-ocean, 4-box-atmosphere model with an added land ice component. The model was forced with a slowly decreasing atmospheric carbon dioxide concentration. It is argued that the first step in the δ18O record reflects a shift in meridional overturning circulation from a Southern Ocean to a bipolar source of deep-water formation, which is associated with a cooling of the deep sea. The second step in the δ18O profile occurs due to a rapid glaciation of the Antarctic continent. This new mechanism is a robust outcome of our model and is qualitatively in close agreement with proxy data. |
format |
Article in Journal/Newspaper |
author |
A. S. von der Heydt H. A. Dijkstra M. Tigchelaar |
author_facet |
A. S. von der Heydt H. A. Dijkstra M. Tigchelaar |
author_sort |
A. S. von der Heydt |
title |
A new mechanism for the two-step δ18O signal at the Eocene-Oligocene boundary |
title_short |
A new mechanism for the two-step δ18O signal at the Eocene-Oligocene boundary |
title_full |
A new mechanism for the two-step δ18O signal at the Eocene-Oligocene boundary |
title_fullStr |
A new mechanism for the two-step δ18O signal at the Eocene-Oligocene boundary |
title_full_unstemmed |
A new mechanism for the two-step δ18O signal at the Eocene-Oligocene boundary |
title_sort |
new mechanism for the two-step δ18o signal at the eocene-oligocene boundary |
publisher |
Copernicus Publications |
publishDate |
2011 |
url |
https://doi.org/10.5194/cp-7-235-2011 http://www.clim-past.net/7/235/2011/cp-7-235-2011.pdf https://doaj.org/article/65f0c0b848ac4b66bf19a0f8145138c5 |
geographic |
Antarctic Southern Ocean The Antarctic |
geographic_facet |
Antarctic Southern Ocean The Antarctic |
genre |
Antarc* Antarctic Ice Sheet Southern Ocean |
genre_facet |
Antarc* Antarctic Ice Sheet Southern Ocean |
op_source |
Climate of the Past, Vol 7, Iss 1, Pp 235-247 (2011) |
op_relation |
doi:10.5194/cp-7-235-2011 1814-9324 1814-9332 http://www.clim-past.net/7/235/2011/cp-7-235-2011.pdf https://doaj.org/article/65f0c0b848ac4b66bf19a0f8145138c5 |
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undefined |
op_doi |
https://doi.org/10.5194/cp-7-235-2011 |
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Climate of the Past |
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7 |
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1 |
container_start_page |
235 |
op_container_end_page |
247 |
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