2021
  • Non-ICIMOD publication

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Mass balance and morphological evolution of the dokriani glacier, central himalaya, india during 1999–2014

  • Purushottam Kumar Garg
  • Jairam Singh Yadav
  • Santosh Kumar Rai
  • Aparna Shukla
  • Summary

Glaciological mass balance (MB) is considered as the most direct, undelayed and unfiltered response of the glaciers to the climatic perturbations. However, it may inherit errors associated with stake under-representation, averaging over entire glacier and human error. Therefore, proper validation of glaciological MB with geodetic MB is highly recommended by the World Glacier Monitoring Service (WGMS). Present study focuses on the Dokriani Glacier, central Himalaya which is one of the bench-mark glaciers in the region and has glaciological MB records since 1993 to 2013 with intermittent gaps. In the present study, firstly the glaciological MB series is extended to 2014 i.e., field-based MB for one more year is computed and, to compare with it, the geodetic MB is computed for 1999–2014 period using high resolution Cartosat-1 digital elevation model (DEM) and SRTM DEM. Finally, the study assesses the regional representation of the Dokriani Glacier in terms of MB and evaluates the influence of mass balance regime on its morphological evolution. Results show that the average glaciological MB (−0.34 ±0.2 m water equivalent (w.e.) y−1) is more negative than the geodetic MB (−0.23 ±0.1 m w.e. y−1) for 1999-2014 period. This is likely because of the partial representation of glacier margins in the glaciological MB where melting is strikingly low owing to thick debris cover (>30 cm) whereas geodetic MB considers all marginal pixels leading to a comparatively low MB. A comparative assessment shows that the MB of Dokriani Glacier is less negative (possibly due to its huge accumulation area) than most of other glacier specific and regional MBs restricting it to be a representative glacier in the region. Moreover, continuous negative MB has brought peculiar change in the epiglacial morphology in the lower tongue of the glacier as differential debris thickness-induced differential melting has turned glacier surface into a concave one. This concavity has led to development of a large (10–20 m deep) supraglacial channel which is expanding incessantly. This supraglacial channel is also connected with snout wall and accelerates terminus disintegration. Given the total thickness of about 30-50 m in lower glacier tongue, downwasting at its current pace, deepening/widening of supraglacial channel coupled with rapid terminus retreat may lead to complete vanishing of lower one km glacier tongue.

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