Pan-Arctic Controls on the Rapid Retreat of Marine-Terminating Arctic Outlet Glaciers

Abstract:

Arctic ice masses have lost mass rapidly during the past two decades and accelerated discharge through marine-terminating outlet glaciers has been a primary component of deficits from the Greenland Ice Sheet. However, previous studies have focused on individual glaciers or regions, meaning that little is known about broad-scale trends in outlet glacier retreat rates, their spatial variation across the Arctic and/or their differing response to forcing. Here we present the first pan-Atlantic-Arctic assessment of outlet glacier retreat rates and their relationship to forcing factors. During the past two decades (1992-2010) we demonstrate an almost ubiquitous trend of rapid and accelerating outlet glacier retreat trend across the Atlantic Arctic. Between 1992 and 2000, 77 % of our 321 study glaciers retreated, compared to 95 % between 2000 and 2010. Mean retreat rates increased five-fold between these two intervals, from 23.6 m a^-1 in 1992-2000 to 107.2 m a^-1 for 2000-2010. The highest retreat rates occurred in northern Greenland between 2000 and 2010 (mean ~ 400 m a^-1), followed by central-west (168.0 m a^-1), south-east (125.7 m a^-1) and north-west (111.2 m a^-1) Greenland. Retreat also increased dramatically on Novaya Zemlya and Spitzbergen, were rates were comparable to east Greenland for the period 2000-2010. Oceanic warming appears to be a widespread control on glacier retreat and the influence of sea ice is significant in several regions. Despite regional trends, we document large variations in retreat rates between individual glaciers, with the areas exhibiting the highest retreat rates also showing the greatest variability. We show a widespread statistical relationship between fjord width variability and outlet glacier retreat rate, particularly in areas where glaciers are constrained by mountainous topography.