A physically-based method for mapping glacial debris-cover thickness from ASTER satellite imagery: development and testing at Miage Glacier, Italian Alps

Debris-covered glaciers (>50% of the ablation zone covered by debris) are common in many of the world's major mountain ranges and represent an important freshwater resource. Previous studies have established that surface melt rates decrease strongly for an increase in supraglacial debris thickness from a few cm up to 20-30 cm, whereas, thin and patchy debris cover enhances melt due to albedo reduction. It is therefore important to develop methods to map and monitor changes in debris cover to enable predictions of glacier responses to climate change through numerical modelling. It is not possible to achieve this from ground-based measurements alone. Therefore, a method to estimate debris thickness from an ASTER thermal band surface temperature image, based on a physical solution of the energy balance at the debris surface, has been developed. The model performs well in comparison to previous empirical methods showing good agreement with measured debris thicknesses.