Southwest Greenland Ice-Sheet Sensitivity to Climate Warming: A Holocene Perspective

A Department of Earth and Space Sciences Colloquium presented by Anders Carlson, University of Wisconsin

Thursday, October 18, 2012
4:00 PM - 5:00 PM
Geology 3656

One the largest uncertainties in predicting future sea-level rise from global warming is the contribution from the Greenland Ice Sheet (GIS). A key question is whether recent changes in the GIS are a response to global warming or just part of natural ice-sheet "weather". Here, I will directly date the last time the southwest GIS was smaller than it is today during the early Holocene when the Earth was closer to the Sun during boreal summer, which provides a geological reference for present and future GIS behavior. I will then compare the climate forcing from the early Holocene that drove the GIS to its smaller-than-present extent against present and future climate forcing on the GIS from anthropogenic greenhouse gas emissions using couple climate model simulations. These results show that the present climate forcing on the southwest GIS is equivalent to ~5,000 years ago when the GIS was smaller than it is today and actively retreating. Thus the current mass loss from the GIS is at least in part due to human greenhouse gas emissions and the beginning of a long-term trend rather than a natural climate fluctuation.