Association between Changes in Glacier Mass and Climate Seasonality Revealed from GRACE/FO in High Mountain Asia.

The mass balance of High Mountain Asia (HMA) glaciers have a significant impact on water resources of neighboring watersheds and it is sensitive to a changing climate. Some studies have emphasized the impact of climate seasonality, i.e., timing and amplitude of annual and seasonal variability in precipitation and temperature, on glacier mass balance at a local scale. In this study, we investigate how glacier mass changes may associate with changes in climate seasonality for greater glacier areas in HMA. We apply satellite gravimetric observations of the Gravity Recovery and Climate Experiment (GRACE) and its follow-on mission (GRACE-FO) for 2002-2020 to quantify glacier mass changes. We isolate their effect of total water storage changes, as provided from satellite gravimetry, by removing the influence of non-glaciological processes, including in-situ groundwater changes in northern India and changes in soil and snow, and surface waters. We investigate changes in climate seasonality by analyzing precipitation and temperature records from the HAR V2 (The high Asia Refined analysis V2) dataset with 10 km spatial resolution. We quantify long-term changes for all datasets and investigate correlations between inter-annual changes of GRACE-based ice mass changes and climate sensitivity parameters through a wavelet spectrum coherence analysis. We further study the association of the monsoon and westerlies with glacier mass changes. We observe a total mass loss of -23 gt/year over the entire area of high mountain Asia from 2002 to 2016. Our analysis showed the highest mass loss in Central, Eastern and Western Himalayas and mass gain in Karakoram and Tibetan plateau region from 2002 to 2016. We observed the mass loss slowed, in 2019, leading to an overall smaller mass loss in High Mountain Asia of -16.51 gt/year till 2020, by including the GRACE-FO dataset. We compare our results for mass change from GRACE/FO with geodetic measurement of glacier mass change of HMA. Lastly, we present a detailed analysis of how glacier mass changes may be associated with observed changes in climate seasonality. The results provide insight into potential mechanisms for glacier mass changes on inter-annual and long-term temporal scales.