Glacial mode shift of the Atlantic meridional overturning circulation by warming over the Southern Ocean

Abstract Abrupt climate warming events, known as Dansgaard-Oeschger events, occurred frequently during glacial periods, and are thought to be linked to changes in the Atlantic meridional overturning circulation. However, the mechanism responsible is not fully understood. Here, we present numerical s...

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Bibliographic Details
Published in:Communications Earth & Environment
Main Authors: Oka, Akira, Abe-Ouchi, Ayako, Sherriff-Tadano, Sam, Yokoyama, Yusuke, Kawamura, Kenji, Hasumi, Hiroyasu
Other Authors: MEXT | Japan Science and Technology Agency
Format: Article in Journal/Newspaper
Language:English
Published: Springer Science and Business Media LLC 2021
Subjects:
General Earth and Planetary Sciences
General Environmental Science
Southern Ocean
Dansgaard-Oeschger events
Sea ice
Online Access:http://dx.doi.org/10.1038/s43247-021-00226-3
https://www.nature.com/articles/s43247-021-00226-3.pdf
https://www.nature.com/articles/s43247-021-00226-3
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Summary:Abstract Abrupt climate warming events, known as Dansgaard-Oeschger events, occurred frequently during glacial periods, and are thought to be linked to changes in the Atlantic meridional overturning circulation. However, the mechanism responsible is not fully understood. Here, we present numerical simulations with a sea-ice coupled ocean general circulation model that systematically investigate the thermal threshold where deep water formation, and hence the overturning circulation, shift abruptly when the sea surface cools or warms sufficiently. Specifically, in our simulations where the magnitude of the sea surface cooling is changed separately or simultaneously in the Northern and Southern Hemispheres, a prominent threshold is identified when the Southern Hemisphere is slightly warmer than during glacial maxima. Abrupt mode changes of the Atlantic Meridional Overturning Circulation, like those during Dansgaard-Oeschger events, occur past a threshold in a transient simulation where the Southern Hemisphere is gradually warmed. We propose that the Southern Ocean plays a role in controlling the thermal threshold of the Atlantic Meridional Overturning Circulation in a glacial climate and that Southern Ocean warming may have triggered Dansgaard-Oeschger events which occurred with long interval.

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