TC The Cryosphere TC 1994-0424 Copernicus GmbH Göttingen, Germany 10.5194/tc-4-261-2010 An explanation for the dark region in the western melt zone of the Greenland ice sheet Wientjes I. G. M. 1 Oerlemans J. 1 Institute for Marine and Atmospheric Research (IMAU), Utrecht University, Utrecht, The Netherlands 23 07 2010 4 3 261 268 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.the-cryosphere.net/4/261/2010/tc-4-261-2010.html The full text article is available as a PDF file from http://www.the-cryosphere.net/4/261/2010/tc-4-261-2010.pdf

The western part of the Greenland ice sheet contains a region that is darker than the surrounding ice. This feature has been analysed with the help of MODIS images. The dark region appears every year during the summer season and can always be found at the same location, which makes meltwater unlikely as the only source for the low albedos. Spectral information indicates that the ice in this region contains more debris than the ice closer to the margin. ASTER images reveal a wavy pattern in the darker ice. Based on these findings we conclude that ice, containing dust from older periods, is presently outcropping near the margin, leading to albedos lower than observed for the remaining ablation area. Therefore it can be concluded that the accumulation of meltwater is a result rather than a cause of the darkening.

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