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Unraveling the Influence of the Atlantic Subpolar Gyre on the Thermohaline Circulation for the Past 20,000 Years.
* 1 , 2
1  Irreversible Climate Change Research Center, Yonsei University, South Korea
2  Department of Earth Sciences, National Central University, Taoyuan, Taiwan
Academic Editor: Tomeu Rigo (registering DOI)

Recent studies have widely implicated that the strength of the North Atlantic subpolar gyre (SPG) is dynamically linked with the North Atlantic thermohaline circulation, affecting the subpolar marine environment. Therefore, it is crucial to understand the past changes in the SPG strength with changes in arctic sea ice and Atlantic meridional overturning circulation (AMOC). This climate modeling study employs a fully coupled atmosphere-ocean-sea ice Earth system model to explore the dynamics in the North Atlantic subpolar for the past 20ka (ka is thousand years before the present). This study highlights a close relationship between the strength of the SPG, Atlantic sea ice coverage, and AMOC circulation in the centennial timescale resolution for the past 20ka. The simulation shows that the changes in SPG and AMOC are in phase. However, the Atlantic sea ice coverage varied inversely to SPG and AMOC strength. Particularly during the Heinrich 1 (19ka14.6ka) and Younger Dryas (12.9ka11.7ka) events, the SPG strength decreased in unison with AMOC strength which reduced the northward meridional heat transport and resulted in the increase in the Atlantic sea ice coverage. However, the dynamic linkage between Atlantic sea ice coverage and ocean circulation does not follow during the prescribed unnatural freshwater supply during the meltwater pulse 1A (mwp-1A) event at about 14.1ka, which caused the Allerød warm period (14ka12.9ka). This finding demonstrates that an abrupt change in freshwater discharge into the North Atlantic subpolar may destabilize the polar ocean-sea ice dynamics.

Keywords: Subpolar Gyre; AMOC; Atlantic Sea Ice; Heinrich 1; Younger Dryas; meltwater pulse 1A