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

Abstract:

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.