The Cryosphere Discuss., 7, 1101-1118, 2013
© Author(s) 2013. This work is distributed
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This discussion paper has been under review for the journal The Cryosphere (TC). Please refer to the corresponding final paper in TC.
Influence of supraglacial lakes and ice-sheet geometry on seasonal ice-flow variability
I. Joughin1, S. B. Das2, G. E. Flowers3, M. D. Behn2, R. B. Alley4, M. A. King5,6, B. E. Smith1, J. Bamber7, M. R. van den Broeke8, and J. H. van Angelen8
1Polar Science Center, Applied Physics Lab, University of Washington, 1013 NE 40th St., Seattle, WA 98105–6698, USA
2Department of Geology and Geophysics, Woods Hole Oceanographic Institute, Woods Hole, MA 02543, USA
3Department of Earth Sciences, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia, V5A 1S6, Canada
4Department of Geosciences, and Earth and Environmental Systems Institute, Pennsylvania State University, University Park, PA 16802, USA
5School of Geography and Environmental Studies, University of Tasmania, Private Bag 76, Hobart, Tasmania, 7001, Australia
6School of Civil Engineering and Geoscience, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK
7Centre for Polar Observations and Modelling, School of Geographical Sciences, University of Bristol, University Road, Bristol, BS8 1SS, UK
8Institute for Marine and Atmospheric Research, Utrecht University, 3584 CC Utrecht, the Netherlands

Abstract. Supraglacial lakes play an important role in establishing hydrological connections that allow lubricating seasonal melt water to reach the base of the Greenland Ice Sheet. Here we use new surface velocity observations to examine the influence of supraglacial lake drainages and surface melt rate on ice flow. We find large, spatially extensive speedups concurrent with times of lake drainage, showing that lakes play a key role in modulating regional ice flow. While surface meltwater is supplied to the bed via a geographically sparse network of moulins, the observed ice-flow enhancement suggests that this meltwater spreads widely over the ice-sheet bed. We also find that the complex spatial pattern of speedup is strongly determined by the combined influence of bed and surface topography on subglacial water flow. Thus, modeling of ice-sheet basal hydrology likely will require knowledge of bed topography resolved at scales (sub-kilometer) far finer than existing data (several km).

Citation: Joughin, I., Das, S. B., Flowers, G. E., Behn, M. D., Alley, R. B., King, M. A., Smith, B. E., Bamber, J., van den Broeke, M. R., and van Angelen, J. H.: Influence of supraglacial lakes and ice-sheet geometry on seasonal ice-flow variability, The Cryosphere Discuss., 7, 1101-1118, doi:10.5194/tcd-7-1101-2013, 2013.
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