Spatial and temporal changes in aerosol radiative forcing on glaciers in the eastern Himalaya

Glacial meltwater is a valuable resource for many mountain communities, but can also impact billions living downstream, particularly in regions such as High Mountain Asia (HMA). Due to the rapid and near global retreat of glaciers, including most regions of HMA, scientists and stakeholders are interested in understanding the major drivers of glacier melt. Several studies have shown that aerosols, in particular dust and black carbon (BC), can significantly alter the radiation budget at the surface of snow and glacier ice, causing enhanced melt. Glaciers respond to anthropogenic forcing on a global level, however local drivers can also have an impact. Rising population and development can significantly increase local aerosol concentrations over a given region. We compare the aerosol radiative forcing between two regions in the eastern Himalaya to improve our understanding of local and regional aerosol influences on glacier mass balance. The two regions of focus were centered on the glacierized areas of Bhutan and Nepal. Although Bhutan and Nepal are culturally similar, the population and economies are quite different. The added populace and industry in Nepal creates more local aerosol sources, which in turn may increase the radiative forcing for glaciers and snow in that region as compared to Bhutan. We analyze the spatial and temporal variability of radiative forcing by aerosols in snow and ice using the MODIS dust radiative forcing in snow (MODDRFS) product, available near daily over the entire Himalaya since 2000 from NASA's Snow Data System Portal. We also adapt the dust radiative forcing algorithm for Landsat in order to assess changing aerosol concentrations over a longer period of time. This data will be used to improve our understanding of the impact of dust and BC on snow and glacier melt in monsoon-dominated regions of HMA.