Topographic control on the recession of the Kokthang glacier and its effect on proglacial lake dynamics

Abstract

We present the preliminary observations about the recession and resultant lake formation of the Kokthang glacier in Sikkim, India. We have analyzed time-series satellite imagery from Corona and Landsat satellites over a span of 55 years to delineate the uncharacteristic recession and its control on the proglacial lake formation. It is seen that the eastern tributary of the glacier has melted and receded at ~ 37 m/yr between 1989 and 2000, which is twice as fast as its western counterpart (~ 18 m/yr). The water spread of the proglacial lake has increased from ~ 11.8 ha to ~ 38.5 ha between 1962 and 2017 with commensurate volume change. The underlying topographic slope possibly controls the differential recession of the tributaries, wherein the eastern slope is significantly steeper (~ 44°) than the western slope (~ 20°). The variation of the slope may have resulted in the differential thickness of ice accumulation (estimated by empirical slope thickness relationship). The eastern tributary is estimated to be less thick than its western counterpart and thus has receded faster.