Glacier Mass-Balance Modelling: Validation of an Energy-Balance Approach Integrating Debris-Layers Over the Himalayas

Ecosystems and societies are threatened by the significant changes in global glacier mass expected in the coming decades. Temperature-index and energy-balance models coexist to simulate changes in the mass of glaciers. Nevertheless, energy-balance models might overcome temperature-index models in the future as most land surface models are based on energy equations nowadays. New developments showed that the debris-layers over glaciers modify their response to climate forcing by reducing the albedo and creating an insulating layer. However, the glacier response to climate change is not yet well known. In this research, we ran and validated an energy-balance model, for the first time, taking into account the debris-layers over the Himalayas for the period between 1981 and 2013. Overall, we found that glaciers of the Himalayas lost 658 Gt during the period. The model replicated glacier response correctly in Central Asia and South Asia East. Its performance on South Asia West was nonetheless unsatisfactory when compared to another recent model. Our study overestimated mass loss. That discrepancy underlines the already-known misunderstanding of the singular response to climate change of glaciers in South Asia West. Our results validate, on a large spatial and temporal scale, an energy-balance model that incorporates debris-layers. This study aims to open the way for further forecasts on the future response of Himalayan glaciers to climate change.