Abstract
Heterogeneous glacier mass loss has occurred across High Mountain Asia on a multi-decadal timescale. Contrasting climatic settings influence glacier behaviour at the regional scale, but high intra-regional variability in mass loss rates points to factors capable of amplifying glacier recession in addition to climatic change along the Himalaya. Here we examine the influence of surface debris cover and glacial lakes on glacier mass loss across the Himalaya since the 1970s. We find no substantial difference in the mass loss of debris-covered and clean-ice glaciers over our study period, but substantially more negative (−0.13 to −0.29 m w.e.a−1) mass balances for lake-terminating glaciers, in comparison to land-terminating glaciers, with the largest differences occurring after 2000. Despite representing a minor portion of the total glacier population (~10%), the recession of lake-terminating glaciers accounted for up to 32% of mass loss in different sub-regions. The continued expansion of established glacial lakes, and the preconditioning of land-terminating glaciers for new lake development increases the likelihood of enhanced ice mass loss from the region in coming decades; a scenario not currently considered in regional ice mass loss projections.
Highlights
Heterogeneous glacier mass loss has occurred across High Mountain Asia on a multi-decadal timescale
Large intra-regional variability in glacier mass loss is evident along the Himalayan arc[6,9], which suggests factors exist that are capable of exacerbating glacier recession in addition to climatic change here
Glaciers situated in the Himalaya commonly have extensive debris cover[10], and an increasing number terminate into a glacial lake[11]
Summary
Heterogeneous glacier mass loss has occurred across High Mountain Asia on a multi-decadal timescale. The main aim of this study is to examine the influence of a debris mantle and glacial lake development on the long-term evolution of Himalayan glaciers in detail, in order to improve our understanding of the regional variability of ice loss rates. We quantify mass loss and terminus retreat from lake and land-terminating glaciers along the Himalayan arc since the 1970s, using optical and radar based remotely-sensed datasets. We use these data to discuss the role of debris cover and glacial lakes as drivers of glacier mass loss in the Himalaya and consider the future evolution of glaciers in the region
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