Dynamics of Glacial Terminations Simulated By a Coupled Ice-Sheet-Earth System Model

Thursday, 18 December 2014: 4:45 PM
Axel Timmermann, IPRC-SOEST, Honolulu, HI, United States, Malte Heinemann, University of Hawaii at Manoa, Honolulu, HI, United States, David Pollard, Pennsylvania State University, University Park, PA, United States, Ayako Abe-Ouchi, University of Tokyo, Bunkyo-ku, Japan and Fuyuki Saito, JAMSTEC Japan Agency for Marine-Earth Science and Technology, Kanagawa, Japan
It still remains uncertain how much of the deglacial retreat of the massive Northern Hemisphere ice-sheets (19-10 ka) was caused by direct shortwave orbital forcing vis-à-vis greenhouse gas changes. To quantify the relative effects of these forcings on ice-sheet dynamics, a series of a transient simulations was conducted with a coupled ice-sheet-earth system modeling framework. The numerical experiments are based on the earth system model LOVECLIM which can be coupled to two different ice-sheet models:
A.) The ice-sheet model for Integrated Earth system Studies (IcIES) is used to evaluate the large-scale ice-sheet response to the time-varying climate fields and potential ice-sheet/climate feedbacks
B.) The Penn State University ice-sheet model in addition, captures ice shelf dynamics and grounding line movements.

Results from our transient simulations for the past 30 ka reveal that the observed CO2 changes are an essential element in destabilizing the glacial ice-sheets. Without the deglacial CO2 increase, our planet would still be in a glacial state. We further demonstrate that neither orbital nor CO2 forcing alone were sufficient to complete the deglaciation.