Seasonal evolution of subglacial drainage and acceleration in a Greenland outlet glacier, Nature Geosci., I. Bartholomew, P. Nienow, D. Mair, A. Hubbard, M. A. King & A. Sole

Nature Geoscience, 3 (2010) 408-411, published online 9 May 2010; doi: 10.1038/ngeo863

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

Ian Bartholomew* and Peter Nienow (University of Edinburgh, School of Geosciences, Edinburgh EH8 9XP, U.K.), Douglas Mair (University of Aberdeen, School of Geosciences, Aberdeen AB24 3UF, U.K.), Alun Hubbard (University of Aberystwyth, Institute of Geography & Earth Sciences, Aberystwyth SY23 3DB, U.K.), Matt A. King (Newcastle University, School of Civil Engineering and Geosciences, Newcastle upon Tyne NE1 7RU, U.K.) and Andrew Sole (University of Aberdeen, School of Geosciences, Aberdeen AB24 3UF, U.K.)

Abstract

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 motion^{2, 3, 4}. Surface melt waters can reach the base of the ice sheet and enhance basal ice motion^{5, 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.

 

*Correspondence e-mail: ian.bartholomew@ed.ac.uk

Link:  http://www.nature.com/ngeo/journal/v3/n6/abs/ngeo863.html

See also:  http://climatechangepsychology.blogspot.com/2009/07/fluorescent-dye-may-reveal-ultimate.html