Debris-cover impact on glacier melting in the Upper Indus Basin

Out of 4530 glaciers covering similar to 4770 km(2) in the Upper Indus Basin, viz., Chenab, Zanaskar and Suru sub-basins, we selected topographically and morphologically homogeneous set of 98 glaciers; 56 debris-covered and 42 clean to assess the impact of debris-cover on glacier melting. Satellite data analysis from 2000 to 2017 showed that the debris-covered glaciers have melted slower (2.49 +/- 0.05%; 0.15%a(-1)) than the clean glaciers (4.07 +/- 0.03%; 0.24%a(-1)). The intra-basin analysis revealed that clean and debris-covered glaciers in the Chenab have melted 2.34 +/- 0.17% and 1.1 +/- 0.30% (0.14%a(-1) and 0.06%a(-1)) and retreated 8.82 +/- 2.67ma(-1) and 5.7 +/- 2.67ma(-1) respectively. Similarly, clean and debris-covered glaciers in the Zanaskar have melted at similar rates of 4.58 +/- 0.07% and 4.55 +/- 0.21% (0.27%a(-1) and 0.25%a(-1)) and retreated 10.0 +/- 2.67ma(-1) and 8.4 +/- 2.67ma(-1) respectively. Clean and debris-covered glaciers in the Suru have melted 5.56 +/- 0.09% and 4.53 +/- 0.14% (0.33%a(-1) and 0.27%a(-1)) and retreated 9.6 +/- 2.67ma(-1) and 7.0 +/- 2.67ma(-1) respectively. Extensive debris-cover of similar to 32.3% modulates glacier loss in the Chenab and sparse debris-cover of 11.4% and 6.4% in the Suru and Zanaskar enhances the melting of the debris-covered glaciers. Overall, debris-covered glaciers melted slower than the clean glaciers, with inter- and intra-basin variations, suggesting that debris-cover plays a complex but significant role in modulating glacier melting under climate change.