Effect of the Ordovician paleogeography on the (in)stability of the climate
The Ordovician Period (485–443 Ma) is characterized by abundant evidence for continental-sized ice sheets. Modeling studies published so far require a sharp CO2 drawdown to initiate this glaciation. They mostly used non-dynamic slab mixed-layer ocean models. Here, we use a general circulation model...
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Online Access: | https://doi.org/10.5194/cp-10-2053-2014 https://cp.copernicus.org/articles/10/2053/2014/ |
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fttriple:oai:gotriple.eu:6n7cT_BhyZW7KkCi-1iSV 2023-05-15T18:17:31+02:00 Effect of the Ordovician paleogeography on the (in)stability of the climate Pohl, A. Donnadieu, Y. Le Hir, G. Buoncristiani, J.-F. Vennin, E. 2018-09-27 https://doi.org/10.5194/cp-10-2053-2014 https://cp.copernicus.org/articles/10/2053/2014/ en eng Copernicus Publications doi:10.5194/cp-10-2053-2014 10670/1.vh4y7w 1814-9324 1814-9332 https://cp.copernicus.org/articles/10/2053/2014/ undefined Geographica Helvetica - geography eISSN: 1814-9332 geo envir Text https://vocabularies.coar-repositories.org/resource_types/c_18cf/ Journal Article https://vocabularies.coar-repositories.org/resource_types/c_6501/ 2018 fttriple https://doi.org/10.5194/cp-10-2053-2014 2023-01-22T17:54:49Z The Ordovician Period (485–443 Ma) is characterized by abundant evidence for continental-sized ice sheets. Modeling studies published so far require a sharp CO2 drawdown to initiate this glaciation. They mostly used non-dynamic slab mixed-layer ocean models. Here, we use a general circulation model with coupled components for ocean, atmosphere, and sea ice to examine the response of Ordovician climate to changes in CO2 and paleogeography. We conduct experiments for a wide range of CO2 (from 16 to 2 times the preindustrial atmospheric CO2 level (PAL)) and for two continental configurations (at 470 and at 450 Ma) mimicking the Middle and the Late Ordovician conditions. We find that the temperature-CO2 relationship is highly non-linear when ocean dynamics are taken into account. Two climatic modes are simulated as radiative forcing decreases. For high CO2 concentrations (≥ 12 PAL at 470 Ma and ≥ 8 PAL at 450 Ma), a relative hot climate with no sea ice characterizes the warm mode. When CO2 is decreased to 8 PAL and 6 PAL at 470 and 450 Ma, a tipping point is crossed and climate abruptly enters a runaway icehouse leading to a cold mode marked by the extension of the sea ice cover down to the mid-latitudes. At 450 Ma, the transition from the warm to the cold mode is reached for a decrease in atmospheric CO2 from 8 to 6 PAL and induces a ~9 °C global cooling. We show that the tipping point is due to the existence of a 95% oceanic Northern Hemisphere, which in turn induces a minimum in oceanic heat transport located around 40° N. The latter allows sea ice to stabilize at these latitudes, explaining the potential existence of the warm and of the cold climatic modes. This major climatic instability potentially brings a new explanation to the sudden Late Ordovician Hirnantian glacial pulse that does not require any large CO2 drawdown. Article in Journal/Newspaper Sea ice Unknown Climate of the Past 10 6 2053 2066 |
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geo envir Pohl, A. Donnadieu, Y. Le Hir, G. Buoncristiani, J.-F. Vennin, E. Effect of the Ordovician paleogeography on the (in)stability of the climate |
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The Ordovician Period (485–443 Ma) is characterized by abundant evidence for continental-sized ice sheets. Modeling studies published so far require a sharp CO2 drawdown to initiate this glaciation. They mostly used non-dynamic slab mixed-layer ocean models. Here, we use a general circulation model with coupled components for ocean, atmosphere, and sea ice to examine the response of Ordovician climate to changes in CO2 and paleogeography. We conduct experiments for a wide range of CO2 (from 16 to 2 times the preindustrial atmospheric CO2 level (PAL)) and for two continental configurations (at 470 and at 450 Ma) mimicking the Middle and the Late Ordovician conditions. We find that the temperature-CO2 relationship is highly non-linear when ocean dynamics are taken into account. Two climatic modes are simulated as radiative forcing decreases. For high CO2 concentrations (≥ 12 PAL at 470 Ma and ≥ 8 PAL at 450 Ma), a relative hot climate with no sea ice characterizes the warm mode. When CO2 is decreased to 8 PAL and 6 PAL at 470 and 450 Ma, a tipping point is crossed and climate abruptly enters a runaway icehouse leading to a cold mode marked by the extension of the sea ice cover down to the mid-latitudes. At 450 Ma, the transition from the warm to the cold mode is reached for a decrease in atmospheric CO2 from 8 to 6 PAL and induces a ~9 °C global cooling. We show that the tipping point is due to the existence of a 95% oceanic Northern Hemisphere, which in turn induces a minimum in oceanic heat transport located around 40° N. The latter allows sea ice to stabilize at these latitudes, explaining the potential existence of the warm and of the cold climatic modes. This major climatic instability potentially brings a new explanation to the sudden Late Ordovician Hirnantian glacial pulse that does not require any large CO2 drawdown. |
format |
Article in Journal/Newspaper |
author |
Pohl, A. Donnadieu, Y. Le Hir, G. Buoncristiani, J.-F. Vennin, E. |
author_facet |
Pohl, A. Donnadieu, Y. Le Hir, G. Buoncristiani, J.-F. Vennin, E. |
author_sort |
Pohl, A. |
title |
Effect of the Ordovician paleogeography on the (in)stability of the climate |
title_short |
Effect of the Ordovician paleogeography on the (in)stability of the climate |
title_full |
Effect of the Ordovician paleogeography on the (in)stability of the climate |
title_fullStr |
Effect of the Ordovician paleogeography on the (in)stability of the climate |
title_full_unstemmed |
Effect of the Ordovician paleogeography on the (in)stability of the climate |
title_sort |
effect of the ordovician paleogeography on the (in)stability of the climate |
publisher |
Copernicus Publications |
publishDate |
2018 |
url |
https://doi.org/10.5194/cp-10-2053-2014 https://cp.copernicus.org/articles/10/2053/2014/ |
genre |
Sea ice |
genre_facet |
Sea ice |
op_source |
Geographica Helvetica - geography eISSN: 1814-9332 |
op_relation |
doi:10.5194/cp-10-2053-2014 10670/1.vh4y7w 1814-9324 1814-9332 https://cp.copernicus.org/articles/10/2053/2014/ |
op_rights |
undefined |
op_doi |
https://doi.org/10.5194/cp-10-2053-2014 |
container_title |
Climate of the Past |
container_volume |
10 |
container_issue |
6 |
container_start_page |
2053 |
op_container_end_page |
2066 |
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1766191776830324736 |