Higher Laurentide and Greenland ice sheets strengthen the North Atlantic ocean circulation
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During the last glacial–interglacial cycle, changes in the large-scale North Atlantic ocean circulation occurred, and at the same time topography of the Laurentide and Greenland ice sheets also varied. In this study, we focus on detecting the changes of the North Atlantic gyres, western boundary current, and the Atlantic meridional overturning circulation (AMOC) corresponding to different Laurentide and Greenland ice sheet topographies. Using an Earth System Model, we conducted simulations for five climate states with different ice sheet topographies: Pre-industrial, Mid Holocene, Last Glacial Maximum, 32 kilo years before present and Eemian interglacial. Our simulation results indicate that higher topographies of the Laurentide and Greenland ice sheets strengthen surface wind stress curl over the North Atlantic ocean, intensifying the subtropical and subpolar gyres and the western boundary currents. The corresponding decrease in sea surface height from subtropical to subpolar favors a stronger AMOC. An offshore shift of the Gulf Stream is also identified during the glacial periods relative to that during the Pre-industrial due to lower sea levels, explaining a weaker glacial Gulf Stream detected in proxy data. Meanwhile, the North Atlantic gyres and AMOC demonstrate a positively correlated relation under each of the climate conditions with higher ice sheets.
KeywordsNorth Atlantic gyres Western boundary current Atlantic meridional overturning circulation Ice sheet Glacial climate states
The authors thank their colleagues from the Paleo-climate Dynamics Group of Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research for continuing support and discussion. Especially, we thank the colleagues Dr. Paola Moffa Sanchez and Dr. Lukas Jonkers in the School of Earth and Ocean Sciences, Cardiff University, for several effective discussions. The study presented by this paper was initiated when X.G. visited the International Arctic Research Center (IARC), University of Alaska Fairbanks, in 2011 under the support of German Helmholtz POLMAR Project and Japan Agency for Marine-Earth Science and Technology through IARC.
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