Seasonal speedup of the Greenland Ice Sheet linked to routing of surface water

We use interferometric synthetic aperture radar observations recorded in a land-terminating sector of western Greenland to characterise the ice sheet surface hydrology and to quantify spatial variations in the seasonality of ice sheet flow. Our data reveal a non-uniform pattern of late-summer ice speedup that, in places, extends over 100 km inland. We show that the degree of late-summer speedup is positively correlated with modelled runoff within the 10 glacier catchments of our survey, and that the pattern of late-summer speedup follows that of water routed at the ice sheet surface. In late-summer, ice within the largest catchment flows on average 48% faster than during winter, whereas changes in smaller catchments are less pronounced. Our observations show that the routing of seasonal runoff at the ice sheet surface plays an important role in shaping the magnitude and extent of seasonal ice sheet speedup.

Research Highlights
► Acceleration of the GrIS is intimately linked to the routing of water at its surface.
► Coupling is highly non-uniform and extends in places up to 100 km from the margin.
► Our data extends farther inland and to higher elevations than previously observed.
► Temporal evolution in speedup with elevation is observed over the meting season.
► Provides a basis for simulating the ice sheet response to expected climate warming.