Western Atlantic Ice Sheet Retreat, Sea Level Rise and the evolution of Atlantic Meridional Overturning Circulation across the Last Deglaciation



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Western Atlantic Ice Sheet Retreat, Sea Level Rise and the evolution of Atlantic Meridional Overturning Circulation across the Last Deglaciation

Anders E. Carlson



Department of Geology & Geophysics, University of Wisconsin-Madison
To look at the general phasing of ice sheet retreat, sea level rise, ocean circulation and climate change during the last deglaciation, I review here relatively new and older records of North Atlantic ice sheet behavior, focusing on the Laurentide (LIS) and Greenland (GIS) Ice Sheets. These records indicate that retreat of the LIS was synchronous with the initial rise in boreal summer insolation and that all North Atlantic ice sheets were in retreat by ~19 kyr BP, leading tropical to Southern Hemisphere climate changes. This retreat contributed to the 19 kyr BP Meltwater Pulse, which freshened the surface of the North Atlantic reducing Atlantic meridional overturning circulation (AMOC) and causing the Oldest Dryas cold event. Following still stands and ice margin readvances during the Oldest Dryas, increased AMOC at ~14.7 kyr BP and attendant warming of the North Atlantic region forced a resumption of retreat for all North Atlantic ice sheets. Initial sea level rise contributions were relatively small, however, indicating that North Atlantic ice sheets were not the main source of Meltwater Pulse 1A. Peak retreat rates of the LIS and GIS were reached synchronous with the peak in boreal summer insolation suggesting a complicated response of North Atlantic ice sheets to decreases in AMOC during the Younger Dryas cold event relative to radiative forcing. However, despite variations in ice sheet responses to regional cooling, all North Atlantic ice sheets retreated in kind to North Atlantic climate warming.


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