Assessing the state, parameter-interlinkages and dynamic shift of glaciers in the western Himalaya

The present study remotely investigates multiple parameters of 25 well-distributed glaciers in the western Himalaya (WH) for similar to 1990-2015 period to understand their state. Glacier changes for 1990-2000 (pre-2000) and 2000-2015 (post-2000) were analysed separately to assess the shift in glacier dynamics. Results reveal a clear glacier terminus retreat (13.4 +/- 2.1 m/y), deglaciation (0.2 +/- 0.1%/y), surface velocity slowdown (21%) and increase in number of glacial lakes (28 to 38) as well their area (5%/y) during 1990-2015. Notably, average terminus retreat and deglaciation rates were reduced post-2000 (retreat: 12.5 +/- 3.2 m/y; deglaciation: 0.1 +/- 0.1%/y) compared to pre-2000 (retreat: 15.3 +/- 6.8 m/y; deglaciation: 0.2 +/- 0.2%/y). Further, the average surface velocity was found to be increasing (0.9%/y) over 1990-2000. This can be linked with suggested less negative or slightly balanced condition of the WH glaciers over 1990s by previous studies. Present study also finds low downwasting during pre-2000 (-0.24 +/- 0.14 m/y). Post-2000, studied glaciers downwasted (-0.50 +/- 0.06 m/y) and slowed down (2%/y) significantly showing a decadal time lag in geometrical adjustment. Supraglacial debris, largely influenced by slope characteristics, increased with a uniform rate of 0.9%/y during pre- and post-2000 periods. Systematic analysis of interlinkages among various glacier parameters reveals a large interdependency. Further, presence of debris cover and pro- and supra-glacial lakes modify the glacier response to a great extent. Overall, the present study shows that (a) studied glaciers were in overall depleting phase over 1990-2015, (b) balanced conditions during 1990s prevailed over the studied glaciers, followed by accelerated mass wastage, (c) topography and local surface conditions introduce the intraregional heterogeneity in glacier response to climate.

Automated summary

This study remotely investigates 25 well-distributed glaciers in the western Himalaya and finds that these glaciers were in an overall retreating phase from 1990 to 2015. The study also reveals changes in glacier dynamics before and after 2000, including reduced terminus retreat and deglaciation rates, increased surface velocity, and the presence of more glacial lakes and supraglacial debris. The study highlights the importance of topography and local surface conditions in the heterogeneity of glacier response to climate.