Rapid changes at the margins of the Greenland Ice Sheet

Mark A. Fahnestock

University of New Hampshire

Absract

Systematic satellite and aircraft observation of outlet glaciers from the Greenland ice sheet over the last decade have documented large increases in ice flow speed and ice discharge, and significant surface lowering, in all quadrants. At the same time, satellite radar altimeters have shown strong increases in surface elevation in the interior of the ice sheet. The resulting estimates of mass balance vary greatly in amount, and even in sign. A brief attempt at reconciling these measurements is just the first step in understanding the role the ice sheet may play in the near-term. Capturing the role of outlet glacier dynamics, and looking for the factors behind rapid change in outlet systems, can inform predictions of future ice sheet change, but the problem is complex and poorly constrained at present. A look at the rapid changes taking place in one of the largest outlet glacier systems in Greenland, and our attempts at directly measuring the changes in progress, will be used to illustrate the problem as I understand it.