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Published Online April 17, 2008
Science DOI: 10.1126/science.1153288

Reports

Submitted on November 26, 2007
Accepted on March 31, 2008

Seasonal Speedup Along the Western Flank of the Greenland Ice Sheet

Ian Joughin 1*, Sarah B. Das 2, Matt A. King 3, Ben E. Smith 1, Ian M. Howat 1, Twila Moon 1

1 Polar Science Center, Applied Physics Lab, University of Washington, 1013 NE 40th Street, Seattle, WA 98105–6698, USA.
2 Department of Geology and Geophysics, Woods Hole Oceanographic Institute, Woods Hole, MA 02543, USA.
3 School of Civil Engineering and Geosciences, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK.

* To whom correspondence should be addressed.
Ian Joughin , E-mail: ian{at}apl.washington.edu

It has been widely hypothesized that a warmer climate in Greenland would increase the volume of lubricating surface-melt reaching the ice-bedrock interface, accelerating ice flow and increasing mass loss. We have assembled a dataset that provides a synoptic-scale view, spanning ice-sheet to outlet-glacier flow, with which to evaluate this hypothesis. On the ice sheet, these data reveal summer speedups (50-100%) consistent with, but somewhat larger than, earlier observations. The relative speedup of outlet glaciers, however, is far smaller (<15%). Furthermore, the dominant seasonal influence on Jakobshavn Isbrae’s flow is the calving front’s annual advance and retreat. With other effects producing outlet-glacier speedups an order of magnitude larger, seasonal melt’s influence on ice flow is likely confined to those regions dominated by ice-sheet flow.


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