ICE-FREE GREENLAND DURING THE MID-PLEISTOCENE?

Abstract:

In the face of accelerated ice sheet contribution to sea level rise, in part fueled by rapid thinning and retreat of marine terminating outlet glaciers, it remains uncertain how the Greenland Ice Sheet (GrIS) will adjust to a warming Arctic, declining sea ice and related changing precipitation patterns. This is concerning, given that future sea level rise is strongly dependent on the GrIS’s response to Arctic change. The scientific community is currently torn between a model of a dynamic GrIS that becomes greatly reduced during interglacials and a model where the GrIS is relatively stable, even through interglacials that were warmer than today.

We review the paleo-stability of the GrIS and discuss the implications for GrIS predictions. Based on new cosmogenic data from the bedrock core drilled underneath the GISP2 ice core, we present the case that Greenland might have been free of ice at least once during the Pleistocene, highlighting its vulnerability. An immediate climate driver for the GrIS collapse is not evident from the existing paleo-climate database, motivating re-intensified research of physical mechanisms to melt the GrIS. We discuss a few preliminary climate scenarios that might have contributed to this dramatic ice-sheet collapse.

On the shorter time-scale, we present tentative strategies how to investigate the stability of the GrIS during the Holocene Climate Optimum, a period of arguable-warmer-than today temperatures. Finally, we summarize the value of the paleo-data for predictions of the GrIS stability.