Meteorological conditions play an important role in glacier melt, particularly in the pre-monsoon season. There is, however, another contributor directly related to anthropogenic atmospheric emissions – black carbon (BC). It affects approximately 28% of total glacier melt in the HKH. Understanding this aspect of climate change is vital for informing policies governing water resources management in the region. BC deposition affects cryospheric melt, and therefore the quantity and timing of seasonal melt feeding major river systems. Over the past three-and-a-half years, we have generated invaluable data to improve understanding of how BC relates to the cryosphere. Ground-based remote sensing observations suggest nearly 5% of aerosol pollution from the Indo Gangetic Plain reaches glaciated regions of the central Himalaya in the pre-monsoon season (April–May).

In Yala Glacier, Nepal, approximately 50% of the annual dry deposition of BC occurs in the pre-monsoon season, with 25% of the annual deposition occurring in April. In the pre-monsoon season, BC contribution to melt is approximately 28% of the total melting. While BC generated from biomass burning (forest fires and large-scale open burning) contributes 19% of the total melting in the same season.

Previous studies indicate that BC concentrations are between seven to ten times higher in mid-altitude locations (1000–4000 masl) than high-altitude ones (> 4000 masl). BC concentration in the snow/ice from the surface samples and ice core records we have collected are at levels attributable to decrease in snow/ice albedo and increase in glacier melt. More research is needed to fully understand the variability of BC across the east to west HKH and transport processes.

Our data comes from 29 study sites across the Himalaya – six in Nepal, three in Bhutan, 10 in India, and 10 in the Tibet Autonomous Region, China. Our researchers and scientists are working to gauge future glacier changes across the HKH using a range of data-collection tools – from climate models to ground-based remote sensing techniques, combined with satellite and highaltitude in-situ observations.

Findings from this study are helping quantify the influence of various factors such as climate change, air pollution, emission sources, and geography on glacier melt in the HKH. We rely on our collaboration with our partners – the Indian Institute of Technology, Roorkee; the Department of Environment, Government of Nepal; National Environment Commission (NEC), the Royal Government of Bhutan; and the Chinese Academy of Sciences (CAS) in the HKH; and the Goddard Space Flight Centre, NASA, and Texas A∧M University, USA – for the upkeep of our BC stations as we continue to generate scientific evidence on air pollution impacts on the cryosphere.