December 22, 2012

Changsang Glacier Retreat and Lake Formation, Sikkim

Posted by Mauri Pelto

Changsang Glacier is a valley glacier just north of Kanchengjunga, the third highest peak, in Sikkim. A comparison of Landsat imagery from 1989 to 2012 identifies the formation of a lake at the end of the glacier. The red arrow indicates the downvalley end of the lake that will develop, the green arrow the upvalley end. In 1989 there is no evidence of a lake either on top of the glacier, supraglacial or proglacial, at the end of the glacier. In 2000 there are a several small lakes beginning to develop. In the 2006 Google Earth imagery the lake is 700 meters long with several other developing smaller lakes. By 2011 the main lake is 1000 meters long and has one debris covered ridge that separates it from a second lake. By 2012 the lake has expanded incorporated the second lake and is now 1500 meters long. The Changsang Glacier was reported to be retreating 22 m/year from 1976 to 2005 (Raina, 2009). In Sikkim 26 glaciers examined were retreating at an average rate of 13.02 m per year from 1976 to 2005 (Raina, 2009) is following the same path as South Lhonak Glacier just to the north and Zemu Glacier just to the south. Zemu Glacier to the south is fed by a higher accumulation zone, and has not been retreating as fast, but it should be anticipated that a lake will form near its terminus.

changsang 2000

changsang 2006 ge

changsang 2011
changsang 2012

A closeup view of the terminus area in 2006 indicates the main lake and several smaller lakes that will join the main lake by 2012. The purple arrow indicates the outlet river from beneath stagnant debris covered ice. The orange arrows indicate the extent of the developing lake by 2012.
changsang terminus