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.