Acceleration of ice loss across the Himalayas over the past 40 years

Himalayan glaciers supply meltwater to densely populated catchments in South Asia, and regional observations of glacier change over multiple decades are needed to understand climate drivers and assess resulting impacts on glacier-fed rivers. Here, we quantify changes in ice thickness during the intervals 1975-2000 and 2000-2016 across the Himalayas, using a set of digital elevation models derived from cold war-era spy satellite film and modern stereo satellite imagery. We observe consistent ice loss along the entire 2000-km transect for both intervals and find a doubling of the average loss rate during 2000-2016 [-0.43 +/- 0.14 m w.e. year(-1) (meters of water equivalent per year)] compared to 1975-2000 (-0.22 +/- 0.13 m w.e. year(-1)). The similar magnitude and acceleration of ice loss across the Himalayas suggests a regionally coherent climate forcing, consistent with atmospheric warming and associated energy fluxes as the dominant drivers of glacier change.