Estimating the extent of drained supraglacial lakes on the Greenland Ice Sheet

Supraglacial lakes are a common feature of the ablation zone of the Greenland Ice Sheet and have significant implications for the water budget of the area, because when they drain they can increase the speed at which ice moves to lower elevations. One valuable tool in assessing the water balance of ice sheets is to track the volume of lakes as they form, through in situ measurements or by determining lake area and depth from aircraft or spacecraft imagery. However, since supraglacial lakes drain unpredictably and rapidly, it is possible that they can form and drain without being observed. Therefore, it is valuable to create tools that can detect the previous presence of supraglacial lakes after they have drained. Three methods of distinguishing drained supraglacial lakes in Landsat Enhanced Thematic Mapper Plus (ETM+) satellite imagery and hyperspectral airborne imagery were analysed: spectral signature analysis on raw data, band ratio analysis, and textural analysis. All three methods show promise that they could be used to detect former (i.e. drained) supraglacial lakes, thereby refining estimates of the water balance of the Greenland Ice Sheet and providing valuable data to climate models.