Global-scale analysis of satellite-derived debris distribution on glacier

Abstract:

In high relief mountain regions, many glaciers have supraglacial debris in their ablation area, which affects the response of these glaciers to climate change through altering ice melting rates. The thin debris accelerates ice melting and the thick one suppresses it. In order to understand the changes of glacier mass balance and runoff patterns under climate change, it is important to assess the effect of debris-cover on these glaciers. However, the assessment of the debris effect is difficult because it is difficult to measure debris thickness at large scale only from field measurements. Here, we attempted to estimate a global distribution of debris thickness on glaciers by using a thermal resistance of supraglacial debris derived from Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) satellite stereo imageries and radiometer products of Clouds and the Earth’s Radiant Energy System (CERES). The obtained distribution map covers approximately 88% of total glacier area recorded in a global glacier outline of the Randorf Glacier Inventory (RGI). Investigations on several glaciers showed that the ASTER-derived thermal resistances correlated reasonably well with ground-surveyed debris thickness. The results indicate that 11% of total global glaciers are covered by supraglacial debris cover and the regional differences in debris distribution are apparent from region to region. Debris cover is relatively thin and accelerates ice melting in western Himalaya, North America, Canada, and Scandinavia, whereas debris cover is relatively thick and inhibits ice melting in eastern Himalaya, Alps, Caucasus and Andes region.