Supraglacial melt channel networks in the Jakobshavn Isbrae region during the 2007 melt season

Supraglacial channels are an important mechanism for surface water transport over the ablation zone of western Greenland. The first assessment of the spatio-temporal distribution of surface melt channels and their relationship to supraglacial lakes over the Jakobshavn Isbrae region of Western Greenland was analysed using Landsat Enhanced Thematic Mapper Plus panchromatic images during the 2007 melt season. A total of 1188 melt channels were delineated and show an increase in the number of melt channels throughout the season, reaching a peak on 9 August. Water-filled melt channels advanced to amaximum elevation of 1647m on 9 August and attained a minimumaverage slope of 0.009 on 8 July. The ablation zone demonstrates two hydrologic modes, where crevasse and moulin terminating channels dominate at elevations <800m and higher-order channel networks >800m. Development of higher-order networks is interrupted by flow divergence due to partitioning of melt water into vertical infiltration through moulins and crevasse fields prevalent at lower elevations. Tributary and connector networks between 800 and 1200m in elevation are correlated with fewer lake occurrences, lower surface velocities (similar to 50ma(-1)), and ice flow dominated by internal deformation over basal sliding. High-order channels are associated with lake basins that exceed melt water storage capacity. Evolution of channel networks is coupled to changes in melt water production, runoff, and ice dynamics with implication for the englacial and subglacial environments. (C) 2013 The Authors. Hydrological Processes Published by John Wiley & Sons, Ltd.