The Greenland ice sheet contains enough water to raise sea levels by 7 m. However, its present mass balance and future contribution to sea level rise is poorly understood. Accelerated mass loss has been observed near the ice sheet margin, partly as a result of faster ice motion. Surface melt waters can reach the base of the ice sheet and enhance basal ice motion. However, the response of ice motion to seasonal variations in meltwater supply is poorly constrained both in space and time. Here we present ice motion data obtained with global positioning system receivers located along a 35 km transect at the western margin of the Greenland ice sheet throughout a summer melt season. Our measurements reveal substantial increases in ice velocity during summer, up to 220% above winter background values. These speed-up events migrate up the glacier over the course of the summer. The relationship between melt and ice motion varies both at each site throughout the melt season and between sites. We suggest that these patterns can be explained by the seasonal evolution of the subglacial drainage system similar to hydraulic forcing mechanisms for ice dynamics that have been observedat smaller glaciers. © 2010 Macmillan Publishers Limited. All rights reserved.

Item Type:	Refereed Article
Keywords:	acceleration; basal ice; GPS; ice sheet; mass balance; meltwater; sea level change; seasonal variation; subglacial environment; velocity; Arctic; Greenland
Research Division:	Earth Sciences
Research Group:	Physical geography and environmental geoscience
Research Field:	Physical geography and environmental geoscience not elsewhere classified
Objective Division:	Expanding Knowledge
Objective Group:	Expanding knowledge
Objective Field:	Expanding knowledge in the earth sciences
UTAS Author:	King, MA (Professor Matt King)
ID Code:	82111
Year Published:	2010
Web of Science® Times Cited:	277
Deposited By:	Geography and Environmental Studies
Deposited On:	2013-01-16
Last Modified:	2013-01-16
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