Spatial debris-cover effect on the maritime glaciers of Mount Gongga, south-eastern Tibetan Plateau

Abstract. The Tibetan Plateau and surroundings contain a large number of debris-covered glaciers, on which debris cover affects glacier response to climate change by altering ice melting rates and spatial patterns of mass loss. Insufficient spatial distribution of debris thickness data makes it difficult to analyze regional debris-cover effects. Mount Gongga glaciers, maritime glaciers in the south-eastern Tibetan Plateau, are characterized by a substantial reduction in glacier length and ice mass in recent decades. Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER)-derived thermal property of the debris layer reveals that 68% of the glaciers have extensive mantles of supraglacial debris in their ablation zones, in which the proportion of debris cover to total glacier area varies from 1.74% to 53.0%. Using a surface energy-mass balance model accounting for the debris-cover effect applied at a regional scale, we find that although the presence of supraglacial debris has a significant insulating effect on heavily debris-covered glaciers, it accelerates ice melting on ~ 10.2% of the total ablation area and produces rapid wastage of ~ 25% of the debris-covered glaciers, resulting in the similar mass losses between debris-covered and debris-free glaciers. Widespread debris cover also facilitates the development of active terminus regions. Regional differences in the debris-cover effect are apparent, highlighting the importance of debris cover for understanding glacier status and hydrology in both the Tibetan Plateau and other mountain ranges around the world.