Evolution of Glacial and High-Altitude Lakes in the Sikkim, Eastern Himalaya Over the Past Four Decades (1975–2017)

Aparna Shukla,Purushottam K. Garg,Smriti Srivastava

doi:10.3389/fenvs.2018.00081

Abstract

Global climate change is significantly triggering the dynamic evolution of high-mountain lakes which may pose a serious threat to downstream areas, warranting their systematic and regular monitoring. This study presents the first temporal inventory of glacial and high-altitude lakes in the Sikkim, Eastern Himalaya for four points in time i.e., 1975, 1991, 2000 and 2017 using Hexagon, TM, ETM+ and OLI images, respectively. First, a baseline data was generated for the year 2000 and then the multi-temporal lake changes were assessed. The annual mapping of SGLs was also performed for four consecutive years (2014-2017) to analyze their nature and occurrence pattern. The results show an existence of 463 glacial and high-altitude lakes (>0.003 km2) in 2000 which were grouped into four classes: supraglacial (SGL; 50) pro/peri glacial lake in contact with glacier (PGLC; 35), pro/peri glacial lake away from glacier (PGLA; 112) and other lakes (OL; 266). The mean size of lakes is 0.06 km2 and about 87% lakes have area 80%) are persistent in nature, followed by drain-out (15-20%) and recurring type lakes (7-8%). The new-formed lakes (9-17%) were consistently noticed in all the years (2014-2017). The results of this study underline that regional climate is accelerating the cryosphere thawing and if the current trend continues, further glacier melting will likely occur. Therefore, formation of new lakes and expansion of existing lakes is expected in the study area leading to increase in potential of glacial lake outburst floods. Thereby, persistent attention should be paid to the influences of climatic change in the region.

Highlights

The global climate changed at an accelerated rate and by an unprecedented magnitude in the last century which significantly influenced the cryosphere (IPCC, 2007; Bolch et al, 2012)
These lakes have severe implications related to the glacier health and human well-being because- (i) proglacial lakes may instigate the calving process leading to an increased terminus disintegration and higher retreat (Warren and Kirkbride, 1998; Benn et al, 2001, 2012; Sakai, 2012), (ii) supraglacial lakes (SGL), have a lower albedo than that of the surrounding snow and ice, and become hotspot of enhanced melting
There are a total of 463 glacial and high-altitude lakes (>0.003 km2) in the Sikkim Himalaya based on 2,000 ETM+ image, covering an area of 29.30 ± 2.21 km2 (Figure 5A)

Summary

Introduction

The global climate changed at an accelerated rate and by an unprecedented magnitude in the last century which significantly influenced the cryosphere (IPCC, 2007; Bolch et al, 2012). The supraglacial lakes occur on low sloping glacier tongues, where active downwasting had led to decrease in driving stresses and glacier velocity causing stagnation (Benn et al, 2001, 2012; Westoby et al, 2014) These lakes have severe implications related to the glacier health and human well-being because- (i) proglacial lakes may instigate the calving process leading to an increased terminus disintegration and higher retreat (Warren and Kirkbride, 1998; Benn et al, 2001, 2012; Sakai, 2012), (ii) supraglacial lakes (SGL), have a lower albedo than that of the surrounding snow and ice, and become hotspot of enhanced melting. At least 20 GLOF events have been recorded in Himalaya in the last 7 decades causing heavy loss of human lives and property, destruction of infrastructure besides damages to agriculture land and forests (Mool et al, 2001)

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