Investigating the Influence of Climate Seasonality on Glacier Mass Changes in High Mountain Asia via GRACE Observations

Recent global warming has caused a rapid melting of High Mountain Asia (HMA) glaciers. The impact of warming on glacier mass decline is undisputed. However, the influence of precipitation changes and their seasonal distribution on glacier mass remains uncertain. Here, using observations from satellite gravimetry complemented by hydrological data for seven glacier regions, we investigate the relationship between net glacier mass budget changes and seasonal precipitation patterns by applying time series and wavelet-based signal decomposition approaches. For a total HMA glacier mass loss of -22.23±8.61 Gt/yr during 2002-2016, the highest portions are contributed by the glacier regions Central Himalaya, Eastern Himalaya, and Tien Shan with -11.99±1.24 Gt/yr, -8.62±0.99 Gt/yr, and -6.93±0.97 Gt/yr, respectively. We found a high association between glacier mass loss and increased rainfall during Western Himalaya's monsoon season, decreased snowfall during post-monsoon months in Eastern Himalaya, and increased rainfall during the pre-monsoon season for Central Himalaya. These associations partly derive from frequency bands at 3–4.5-year and 5-8-year periods, which conform with typical repeat patterns of the South Asian Monsoon (SAM). Since precipitation seasonality of several HMA regions is strongly influenced by SAM, this raises the question of which role a climate change-induced SAM alteration would play in glacier melting. We conclude that especially summer-fed and SAMdominated HMA glacier regions are vulnerable to accelerated melting from changes in precipitation seasonality driven by SAM alterations. We call for denser and more accurate spatial monitoring of meteorological variables to accurately predict the impact of monsoon alterations on future melting rates.