Preliminary Study on Estimation of Volume of Eastern Himalayan Glaciers Using Remote Sensing Methods

The volume of glaciers in Sikkim with specific reference to East Rathong glacier is estimated. The variability in the results from different methods of volume estimation is also studied. Volume of East Rathong glacier is estimated using on-field and off-field methods. Then volume of other 424 glaciers is estimated using off-field methods. Using the glacier outline from Randolph Glacier Inventory 5.0, a total of 424 Sikkim glaciers are analysed in this study. The area estimated is 509 km². Total volume of glaciers estimated using volume-area scaling method is 35 km³. Estimates of the total volume and average thickness of these glaciers using slope-dependent method in 2008 are 51 km³ and 100 m respectively. Estimates of the total volume (average thickness) of these glaciers using ice-flow velocity method in 2010 and 2014 are 48 km³ (95 m) and 47 km³ (93 m) respectively. The glaciers of Sikkim Himalaya seem to show annual mass balance of –0.44±0.2 m w.e. using ice-flow velocity method during the period of 2010-2014.

Slope of Sikkim glaciers is calculated from Cartosat-1 DEM 2008. Cartosat-1 DEM is validated with Global Positioning System (GPS) points. The volume of the ablation (Ab) zone of East Rathong glacier using GPS data is found to be 0.054 km³. Its volume calculated using slope-dependent method is ~0.037 km³ and using ice-flow velocity method is ~0.038 km³. Volumes estimated for East Rathong glacier using field and off-field methods are comparable. The negative mass balance of Sikkim glaciers could be attributed to an increase in air temperature (0.23 °C/decade) at higher altitude (~5500 m a.s.l.) and reduction of precipitation as reported in Agrawal et al. (2014).