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Seasonal evolution of subglacial drainage and acceleration in a Greenland outlet glacier

Nature Geoscience volume 3, pages 408411 (2010) | Download Citation


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 understood1. Accelerated mass loss has been observed near the ice sheet margin, partly as a result of faster ice motion2,3,4. Surface melt waters can reach the base of the ice sheet and enhance basal ice motion5,6. 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 observed at smaller glaciers.

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We thank for financial support: UK Natural Environment Research Council (NERC, through a studentship to I.B. and grants to P.N./D.M.), Edinburgh University Moss Centenary Scholarship (I.B.), Edinburgh University Small Project Grants (P.N.), Carnegie Foundation (D.M.), SKB Sweden (A.H.), Royal Geographical Society Dudley Stamp Memorial Award (I.B.), Research Councils UK Academic Fellowship (M.A.K.), Aberystwyth University Research Award (A.H.), Royal Society Research Grant and Royal Geographical Society Gilchrist Fieldwork Grant (A.H.). GPS equipment and training were provided by the NERC Geophysical Equipment Facility. We also thank B. Anderson for thoughtful comments that helped improve the manuscript.

Author information


  1. University of Edinburgh, School of Geosciences, Edinburgh, EH8 9XP, UK

    • Ian Bartholomew
    •  & Peter Nienow
  2. University of Aberdeen, School of Geosciences, Aberdeen, AB24 3UF, UK

    • Douglas Mair
    •  & Andrew Sole
  3. University of Aberystwyth, Institute of Geography & Earth Sciences, Aberystwyth, SY23 3DB, UK

    • Alun Hubbard
  4. Newcastle University, School of Civil Engineering and Geosciences, Newcastle upon Tyne, NE1 7RU, UK

    • Matt A. King


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All authors contributed extensively to the work presented in this letter. P.N. and D.M. conceived the project. M.A.K. processed the GPS data. I.B., P.N., D.M., A.H. and A.S. collected the field data. I.B. wrote the manuscript. All authors discussed the results and implications and commented on the manuscript.

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The authors declare no competing financial interests.

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Correspondence to Ian Bartholomew.

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