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Originally published in Science Express on 17 April 2008
Science 9 May 2008:
Vol. 320. no. 5877, pp. 781 - 783
DOI: 10.1126/science.1153288
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Reports

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{dagger} Twila Moon1

It has been widely hypothesized that a warmer climate in Greenland would increase the volume of lubricating surface meltwater reaching the ice-bedrock interface, accelerating ice flow and increasing mass loss. We have assembled a data set 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 to 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.

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, MA02543, USA.
3 School of Civil Engineering and Geosciences, Newcastle University, Newcastle upon Tyne NE1 7RU, UK.

{dagger} Present address: The Ohio State University, 1090 Carmack Road, Columbus, OH 43210–1002, USA.

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

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Science. ISSN 0036-8075 (print), 1095-9203 (online)