Recession, thinning, and slowdown of Greenland's Mittivakkat Gletscher

Abstract. Glaciers in Southeast Greenland have thinned and receded during the past several decades. Here, we document changes for the Mittivakkat Gletscher, the only glacier in Greenland with long-term mass balance observations and surface velocity measurements (since 1995). Between 1986 and 2011, this glacier shrank by 18 % in surface area, 20 % in mean ice thickness, and 33 % in volume. We attribute these changes to summertime warming and to drier winter conditions. Meanwhile, the annual mean ice surface velocity decreased by 30 %, likely as a dynamic result of thinning. This dynamic thinning is predicted by ice deformation theory but has rarely been observed on decadal time scales. Mittivakkat Gletscher summer surface velocities were on average 50–60 % above winter background values, and up to 160 % higher during peak velocity events. The transition from winter to summer values followed the onset of positive temperatures. Satellite observations show area losses for most other glaciers in the region; these glaciers are likely also to have lost volume (in average around one-third) and slowed down in recent decades.