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Originally published in Science Express on 17 April 2008
Science 9 May 2008:
Vol. 320. no. 5877, pp. 778 - 781
DOI: 10.1126/science.1153360
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Reports

Fracture Propagation to the Base of the Greenland Ice Sheet During Supraglacial Lake Drainage

Sarah B. Das,1* Ian Joughin,2 Mark D. Behn,1 Ian M. Howat,2,3 Matt A. King,4 Dan Lizarralde,1 Maya P. Bhatia5

Surface meltwater that reaches the base of an ice sheet creates a mechanism for the rapid response of ice flow to climate change. The process whereby such a pathway is created through thick, cold ice has not, however, been previously observed. We describe the rapid (<2 hours) drainage of a large supraglacial lake down 980 meters through to the bed of the Greenland Ice Sheet initiated by water-driven fracture propagation evolving into moulin flow. Drainage coincided with increased seismicity, transient acceleration, ice-sheet uplift, and horizontal displacement. Subsidence and deceleration occurred over the subsequent 24 hours. The short-lived dynamic response suggests that an efficient drainage system dispersed the meltwater subglacially. The integrated effect of multiple lake drainages could explain the observed net regional summer ice speedup.

1 Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA.
2 Polar Science Center, Applied Physics Lab, University of Washington, 1013 NE 40th Street, Seattle, WA 98105–6698, USA.
3 School of Earth Sciences and Byrd Polar Research Center, The Ohio State University, 1090 Carmack Road, Columbus, OH 43210–1002, USA.
4 School of Civil Engineering and Geosciences, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK.
5 Department of Geology and Geophysics, Massachusetts Institute of Technology/Woods Hole Oceanographic Institution Joint Program, Woods Hole, MA 02543, USA.

* To whom correspondence should be addressed. E-mail: sdas{at}whoi.edu

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