yarlung tsangpo glacier retreat – From a Glaciers Perspective

Jiemayangzong Glacier in 1991 and 2020 Landsat images. The red arrow is the 1991 terminus location, yellow arrow is the 2020 terminus location and purple dots mark the snowline. Point A indicates a tributary that has disconnected, while bedrock expanded at Point B.

Jiemayangzong Glacier drains east from 6200 m peaks along the Nepal-China border. The glacier ends in a lake- Jiemayangzong Tso. Ren et al (2016) identify this as the headwaters of the Yarlung Tsangpo (Zangbo), which becomes the Brahmaputra River. The Zangmu hydropower project was completed on the river in 2015, it is a 510 MW project. Here we examine Landsat and Google Earth imagery from the 1991-2014 period. This is a region where Li et al (2011) noted that increasing temperature during the 1961-2008 period, especially at altitude, led to the retreat of glaciers and expansion of glacial lakes in this region. Liu et al (2011) noted that this glacier’s area has decreased 5%, retreating 768m ( 21 m/year), leading to lake expansion of ~64% during the 1974-2010 period.

In 1991 the lake was 1.1 km long, the snowline was at 5500 m near the elevation where the northern tributary joined at Point A. In 1998 the snowline was at 5600 m, the glacier had not retreated appreciably. In 2017 tributary A no longer is connected to the main glacier, the snowline is at 5600 m and the lake has expanded to a length of 1.9 km. In 2020 the snowline in mid-September, with the melt season still going, is at 5700 m. The glacier has retreated 1000 m from 1991-202o a rate of ~33 m/year. The lake is now 2.1 km long and has an area of 1.3 km². The glacier has a wide stable moraine belt (M) and does not pose a GLOF threat. Immediately downstream of the lake is a 10 km² braided valley/wetland area as well that would mitigate any potential flood hazard. This glaciers retreat is similar to many others draining north into Tibet from the Himalayan crest, Chako Glacier, West Ganglung Glacierand Asejiaguo Glacier

Jiemayangzong Glacier in 1998 and 2017 Landsat images. The red arrow is the 1991 terminus location, yellow arrow is the 2020 terminus location and purple dots mark the snowline. Point A indicates a tributary that has disconnected, while bedrock expanded at Point B.

Jieayangzong Glacier (JG) in 2015 Digital Globe image indicating the expanding proglacial lake (JL), moraine belt (M) and large wetland

The Yemayundrung Glacier flows northeast from the Nepal-China border to end in lake at the headwaters of the Khugpi Chu River. This river is one of the source rivers of the Yarlung Tsangpo (Zangbo) in China which becomes the Brahmaputra in India. This is a region where Li et al (2011) noted that increasing temperature, especially at altitude, the fronts of 32 glaciers have retreated, mass losses of 10 glaciers have been considerable, glacial lakes in six regions have expanded and melt water discharge of four basins has also increased. This is further documented by an inventory of 308 glaciers in the Nam Co Basin, Tibet, where an increased loss of area for the 2001-2009 period, 6% area loss (Bolch et al., 2010) was observed. Here we examine Landsat imagery of changes in this glacier from 1998 to 2014.

In each image the yellow arrow indicates the 1998 terminus and the red arrow the 2014 terminus. The purple arrows indicate a pair of tributary glaciers from the south and the green arrow a tributary after it has joined the main glacier separated by a lateral moraine. In 1998 the glacier terminates at the yellow arrow and the maximum length of the proglacial lake at the terminus is 1 km. The two tributaries from the south join the main glacier. The tributary at the green arrow has a blue ice tongue that extends down glacier to the main glacier junction. In 2000 the terminus has retreated a short distance, but there is little change in the tributaries. By 2013 the lake has lengthened to 1.8 km with glacier retreat. In 2014 the two southern tributaries at the purples arrows no longer connect to the main glacier. The tributary at the green arrow no longer has blue glacier ice extending past the arrow to the main glacier junction. The glacier has retreated 750 m from 1998-2014. The thinning of several tributaries is indicative of less volume flux toward the terminus, which will lead to continued retreat of this glacier and lake expansion. The retreat is similar to that of Durung Drung Glacier, India, Reqiang Glacier, China and Matsang Tsanpo Glacier, China and Ribuktse Glacier, China, which are in a similar climate setting. This area did get an unusual heavy October snowfall from Cyclone Hudhud this week.

1998 Landsat image

2000 Landsat image

2013 Landsat image
2014 Landsat image