Quantifying summer ice flow off the Greenland Ice Sheet

Steven Palmer, Andrew Shepherd, Peter Nienow, and Ian Joughin, Seasonal speedup of the Greenland Ice Sheet linked to routing of surface water, Earth and Planetary Science Letters, doi: 10.1016/j.epsl.2010.12.037

Ice motion on the western part of the Greenland Ice Sheet (GrIS) can vary seasonally by up to 200%. Observations suggest that large amounts of surface water can reach the base of thick, cold ice, but it has proven difficult to quantify the present and future role of meltwater in accelerating GrIS motion. Based on data gathered by interferometric synthetic aperture radar, the authors find a spatially complex pattern of ice flow, with late-summer speed-up observed as far as 100 kilometers (60 miles) inland and at elevations up to 1,600 meters (5,200 feet). Some points on the western GrIS were observed to flow more than twice as quickly in late summer than in winter, while 15% of the survey area showed no significant seasonal change in flow velocity. Areas of summer speed-up were strongly correlated with lakes atop the ice, implying that water is routed directly from these surface features to the bottom of the ice.