Dust dominates high-altitude snow darkening and melt over high-mountain Asia

Abstract

Westerly driven, long-range transportation of dust particles in elevated aerosol layers (EALs) is a persistent phenomenon during spring and summer over the Indian subcontinent. During the snow accumulation season, EALs transport substantial amounts of dust to the snow-covered slopes of high-mountain Asia (HMA). Here we use multiple satellite-based estimates to demonstrate a robust physical association between the EALs and dust-induced snow darkening over HMA. Results from a fully coupled atmosphere–chemistry–snow model support these observations, revealing across HMA a signature of increasing dust-induced snow darkening with surface elevation that peaks near 4,500 m. Moreover, the influence of dust on snow darkening is greater than that of black carbon above 4,000 m. Our findings suggest a discernible role of dust in the observed spatial heterogeneity of snowmelt and snowline trends over HMA and highlight an increasing contribution of dust to snowmelt as the snowline rises with warming. Dust deposition in high-mountain Asia lowers snow albedo and hastens melt. Satellite data and models show that dust arrives via transport in elevated aerosol layers and outweighs black carbon impacts at high altitudes, suggesting a growing importance of dust on snowmelt as snowlines rise with warming.