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Science 4 July 2008:
Vol. 321. no. 5885, pp. 111 - 113
DOI: 10.1126/science.1158540
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Reports

Large and Rapid Melt-Induced Velocity Changes in the Ablation Zone of the Greenland Ice Sheet

R. S. W. van de Wal,* W. Boot, M. R. van den Broeke, C. J. P. P. Smeets, C. H. Reijmer, J. J. A. Donker, J. Oerlemans

Continuous Global Positioning System observations reveal rapid and large ice velocity fluctuations in the western ablation zone of the Greenland Ice Sheet. Within days, ice velocity reacts to increased meltwater production and increases by a factor of 4. Such a response is much stronger and much faster than previously reported. Over a longer period of 17 years, annual ice velocities have decreased slightly, which suggests that the englacial hydraulic system adjusts constantly to the variable meltwater input, which results in a more or less constant ice flux over the years. The positive-feedback mechanism between melt rate and ice velocity appears to be a seasonal process that may have only a limited effect on the response of the ice sheet to climate warming over the next decades.

Institute for Marine and Atmospheric research Utrecht, Utrecht University, Netherlands.

* To whom correspondence should be addressed. E-mail: r.s.w.vandewal{at}uu.nl

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THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Sea levels: science and society.
R. Edwards (2008)
Progress in Physical Geography 32, 557-574
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Science. ISSN 0036-8075 (print), 1095-9203 (online)