Assessment of Volume Change in East Rathong Glacier, Eastern Himalaya

An estimate of change in volume of East Rathong glacier in Eastern Himalayas has been made, vis-a-vis changes in its surface area over the period 1962-2011. The change in the area and volume of the glacier has been estimated using remote sensing (CORONA and Landsat images) and GIS techniques, field methods and certain empirical relationships and scaling laws. Bruckl's thickness-area relationship and volume-area scaling methods are used to estimate the volume and change in the volume of the glacier from 1962 to 2011. Nye's glacier flow mechanics equation gave the volume of the glacier for 2002. The volume of the glacier in the year 2002 calculated (using the value of = 150 kPa), has been found to be almost equal to the volume of glacier estimated using other methods for 2002. From 1962 to 2011, surface area of East Rathong glacier decreased by 15 % whereas the estimated total volume loss is ~20%.Total retreat of the glacier during 1962-2011 is 740 m. AAR has been observed to show an almost constant value ~0.6 throughout the study period. Though AAR is nearly constant, the decrease in surface area, the rate of retreat and the rate of % volume loss, all have been observed to be consistently positive. This shows that for a three-zone glacier like East Rathong, AAR is not a very good measure of the glacier health. Hence, while assessing the health of a glacier, it is important to look into parameters like surface area, length and the thickness parameters along with AAR.