March 1, 2016
Thong Wuk Glacier comparison in 1988 and 2015 Landsat image. Red arrow is the 1988 terminus location, yellow arrow the 2015 terminus location and orange arrow indicates expanding lake of Yanglang Glacier.
There are two glaciers that drain the north side of Sepu Kangri Peak in the Eastern Nyainqêntanglha Mountains of Tibet in China. Thong Wuk to the east and Yanglang Galcier to the west. Most of the peaks in East Nyainqêntanglha Mountains are unclimbed, Sepu Kangri the highest peak was not climbed until 2002. The Sepu Kangri glaciers drain into the Salween River. In a study by Tobias Bolch et al (2010) in the western Nyainqêntanglha Mountains glacier area decreased by 6% between 1976 and 2001 and continued to shrink during the period 2001–2009. Li et al (2010) examined glacier change over the last several decades in China and found ubiquitous glacier retreat and commonly lake formation as glaciers retreated.
In this case we compare Landsat images from 1988, 2003, 2010 and 2015 and Google Earth images from 2011. In 1988 the lake at the end of the two glaciers are both 500-700 m long. By 2003 there is limited terminus change for the eastern side of the Thong Wuk terminus and the western side of the terminus has retreated 200 meters. By 2010 the terminus tongue is breaking up with many icebergs filling the lake. In 2011 the lake has expanded from a length of 600 meters in 1988 to 1300 meters. A closeup view in Google Earth of the eastern tongue indicates that this narrow tongue is not stable and the lake will lake quickly develop to an area of 1.7 km long and 0.8 km wide. In 2015 the glacier has retreated 1050 m since 1988, and the lake has an area of 2.4 square kilometers. Based on an increase in surface slope 500 m from the current terminus the lake will not expand more than this. This glacier remains heavily crevassed and has a vigorous accumulation zone indicating that it is not in danger of disappearing with current climate. In fact images from the first ascent of Sepu Kangri in 2002 indicate the annual layering in a crevasse, illustrating the considerable accumulation. The formation of lakes at the end of the glaciers as they retreat is quite common, including in the Tibetan glaciers.
Thong Wuk Glacier comparison in 2003 and 2010 Landsat image. Red arrow is the 2003 terminus location and orange arrow indicates expanding lake of Yanglang Glacier.
2011 Google Earth image. Note the heavy crevassing indicating considerable accumulation and flow.
2011 Google Earth image indicatint narrow tongue that has broken up by 2015.
Crevasse with annual layers on upper Thong Wuk Glacier from the Sepu Kangri Expedition in 2002.