Did changes in the Subpolar North Atlantic trigger the recent mass loss from the Greenland Ice Sheet?

The Greenland Ice Sheet's (GIS) contribution to sea level rise more than doubled in the last seven years due to a surprisingly rapid (and unpredicted) mass loss. The loss was not so much a result of increased surface melt but, rather, of ice loss due to the widespread and nearly-simultaneous acceleration of several outlet glaciers in Greenland’s western and southeastern sectors [Rignot and Kanagaratnam, 2006]. Since Greenland's accelerating outlet glaciers terminate at tidewater in deep fjords and their floating ice shelves extend several hundreds of meters below sea-level it has been suggested that the acceleration may have been driven by oceanic changes [Bindschadler, 2006; Holland et al. 2008]. Specifically, increased melting due, for example, to warming ocean waters can speed up ice flow through a reduction of both the basal friction and the frontal buttressing to glacier flow. Indeed Greenland's accelerating glaciers lost their buttressing ice shelves either prior or during the acceleration. The ocean trigger hypothesis is empirically supported by the fact that the accelerating glaciers are located along the margins of the North Atlantic’s subpolar gyre whose waters started to warm roughly at the same time as the glaciers began to accelerate [Bersch et al. 2007; Yashayaev et al. 2007]. Yet, the connection between Greenland’s outlet glaciers and the large-scale subpolar ocean is new and far from obvious.