Seven Decades of Dimensional and Mass Balance Changes on Dokriani Bamak and Chhota Shigri Glaciers, Indian Himalaya, Using Satellite Data and Modelling

In the present study, dimensional (glacier area and snout position) and mass balance changes of Dokriani Bamak (central Himalaya) and Chhota Shigri (western Himalaya) glaciers have been investigated over the last seven decades using satellite data and modelling. Dimensional changes were investigated using satellite data from Corona (1968–1971), Landsat TM/ETM+ (1993–2010) and Sentinel-MSI (2020) along with limited field checks, while annual and seasonal mass balances on both the glaciers were reconstructed using a simple temperature-index model since 1950. Dokriani Bamak and Chhota Shigri glaciers showed deglaciation and retreat over 1968–2020 with limited areal and snout changes up to 1990s, and then accelerated rates in the twenty-first century, especially after ~ 2010. The mean annual glacier-wide mass balances were computed as − 0.09 ± 0.35 m w.e./y and − 0.12 ± 0.28 m w.e./y with equivalent cumulative mass wastage of − 6.33 m w.e. and − 8.61 m w.e. on Dokriani Bamak and Chhota Shigri glaciers over 1950–2020, respectively. Both the glaciers showed decadal positive mass balances over 1950–1980s followed by a limited wastage over 1980–2000, and an accelerated decadal mass wastage post-2000, in agreement with decreasing glacier velocities. As a result of an accelerated post-2000 wastage, a western tributary glacier detached from the Chhota Shigri Glacier, providing much higher deglaciation rate on Chhota Shigri Glacier compared to Dokriani Bamak Glacier. The present study revealed that mass balance exerts significant control on deglaciation and retreat of both the glaciers. Though the mass wastage patterns were roughly similar on both the glaciers, Chhota Shigri Glacier showed consistently lower terminus retreat than that of the Dokriani Bamak Glacier because of the presence of thick debris cover and local steep topographic settings around glacier snout.