HR: 10:20h
AN: PP12A-01 INVITED    [Abstracts]
TI: Rain driven by receding ice sheets as a cause of past climate change
AU: * Eisenman, I
EM: eisenman@fas.harvard.edu
AF: Harvard University, 24 Oxford St, Cambridge, MA 02138, United States
AU: Bitz, C
EM: bitz@atmos.washington.edu
AF: University of Washington, MB 351640, Seattle, WA 98195, United States
AU: Tziperman, E
EM: eli@eps.harvard.edu
AF: Harvard University, 24 Oxford St, Cambridge, MA 02138, United States
AB: The Yonger Dryas cold period is one of the most dramatic incidents of abrupt climate change reconstructed from paleoclimate proxy records. Changes in the Atlantic Ocean overturning circulation in response to freshwater fluxes from melting ice are frequently invoked to explain this and other past climate changes. Here we propose an alternative mechanism which is supported by the results of a state-of-the-art global climate model. We show that reducing the size of the Laurentide Ice Sheet can cause the model atmospheric circulation to enter a regime characterized by greater net precipitation in the North Atlantic region. This leads to a significant reduction in ocean overturning circulation, causing an increase in sea ice extent and hence colder temperatures. Positive feedbacks associated with the sea ice amplify the cooling. This suggests that the atmospheric precipitation response to receding glacial ice sheets could have contributed to the Younger Dryas cooling, as well as other past climate changes involving ocean overturning circulation.
DE: 1807 Climate impacts
DE: 3344 Paleoclimatology (0473, 4900)
DE: 4901 Abrupt/rapid climate change (1605)
DE: 4928 Global climate models (1626, 3337)
DE: 4962 Thermohaline
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting