A global high-resolution map of debris on glaciers derived from multi-temporal ASTER images

Abstract. Supraglacial debris affects the response of glaciers to climate change by altering the reflectivity of solar radiation and conductive heat flux. To accurately assess the contribution of glacier melts to sea level rise, water resources and natural hazards, it is important to account for the effects of debris. However, due to the practical difficulties of global-scale field measurements, information regarding the spatial distribution of the thickness and thermal properties of debris on glaciers is limited; hence, the effects of debris on glacier melting are not explicitly taken into account in current global glacier models. In this study, we developed a dataset of the thermal resistance of debris on glaciers at 90-m resolution derived from multi-temporal satellite images and satellite-derived radiation data at the global scale, excluding Greenland, Antarctica, and some of the Arctic. We found that supraglacial debris covered 16.8 % of the entire analyzed glacial area. The highest debris cover percentage occurred in New Zealand, and the lowest was in Iceland. The area of thick debris (which suppresses glacier melting) was about two times that of thin debris (which accelerates glacier melting), indicating that the insulation effect of debris to inhibit glacier melting may dominate at the global scale. The distribution of debris was also related to the slope aspect of glaciers. Despite the limitations of this study, the resulting global distribution of the thermal resistance of debris can be incorporated into global glacier models, and hence it provides a solid basis for evaluating the effects of debris on glacial melting.