In-situ measurements reveal significant differences in energy and mass-balance components on monsoon- and westerlies-dominated glaciers in High Mountain Asia

Abstract

Physical interactions between glacier surfaces and atmosphere are crucial to understanding the mechanism and process of glacier ablation but poorly constrained based on measured meteorological data from monitoring glaciers. We investigate how climatic regimes influence glacier mass loss in High Mountain Asia (HMA) from the perspective of glacier energy and mass balance for 30 glaciers with meteorological and mass-balance observations and project their volume loss under various shared socioeconomic pathways (SSPs) by the end of the 21st century. Our study shows that net shortwave (SWnet; 92.7%) and longwave (LWnet; 82.0%) radiation in the monsoon-dominated glaciers during the melt season are 1.08 times higher than those in the westerlies-dominated glaciers. Turbulent fluxes are similar in both regions, so that SWnet and LWnet determine the energy supply and expenditure in the two regions, respectively. Driven by such an energy balance context, melt (94.3%) in monsoon-dominated glaciers is 1.38 times greater than in westerlies-dominated glaciers, while snowfall in monsoon-dominated glaciers decreases, which jointly determines the difference in mass loss between the two regions. Additionally, sublimation and refreezing are the crucial factors contributing to mass balance, but their impact on mass balance is small. Volume-loss differences of approximately 15% also exist between the two regions under three shared socioeconomic pathways (SSPs).