Characterizing the Glacier Mass Change and Water Cycle of High Mountain Asia Rivers Using Satellite Data, Ground Observations, and Model Outputs

As glaciers in High Mountain Asia (HMA) continue to lose mass due to climate change, there are significant effects to river basins and the overall water cycle in the area. More than a billion people rely on these river basins to survive and glacial mass loss will constrict water availability for these large populations. Determining current and future glacial mass loss is difficult due to fluctuations in precipitation, and snow melt in the area as well as due to the geography of the area itself. In addition, components and drivers of the water cycle differ across the region. This further impacts our ability to understand glacier mass balance, its evolution and drivers and to calculate the glacial contribution to river basin hydrology and ecosystem impact.

To improve our understanding of the processes driving the glacial mass changes and their evolution in time, we combine estimates of glacier mass balance and total water storage from the Gravity Recovery and Climate Experiment (GRACE) and GRACE-Follow On (GRACE-FO) missions with ground observations and the outputs of regional climate models, reanalysis, and Earth system models. This allows us to evaluate the model performances during the period for which observational data is available. We then conclude on the main driver of the water cycle and glacier mass changes and how they change in time. We also evaluate the uncertainty of each component based on their spread and we identify key tipping points based on model outputs.