June 2, 2015

Midui Glacier, Tibet, China: Retreat and Terminus Collapse 1995-2014

Posted by Mauri Pelto

Midui Glacier is 7 km from the G318 National Highway in China and 2 km from Midui village, hence the lake near the terminus is often visited. The glacier is near the headwaters of Yarlung Tsangpo. Glaciers in this region have experienced significant retreat and area loss as noted by the second China Glacier inventory. This compared glacier area from the 1950’s, 2002 and 2010, Liu et al (2013) noted that glacier area has declined 13%. The Midui Glacier was advancing as recently as 1964 when it emplaced an advance moraine (Xu et al, 2012).  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. The nearby Yemayundrung Glacier retreat is similar. Here we examine changes in this glacier using Landsat imagery and Google Earth from 1995-2014.

midui glacier 1995
1995 Landsat image

midui glacier 2014 landsat
2014 Landsat image

In the Landsat images above in 1995 the glacier terminates in a proglacial lake at the red arrow. A ridge separates two tributaries each with an icefall creating ogives, purple arrow. There are ogives below a pair of icefalls at the yellow arrow. The tributaries are separated by a medial moraine orange arrow. By 2014 retreat has led to expansion of the lake at the terminus. The retreat is 300 meters during this 20 year period. The icefall on the right, east side of the glacier, is no longer producing significant ogives and the bare glacier ice has been replaced with extensive debris cover, yellow arrow. Both the ridge and medial moraine separating the tributaries have expanded in width as the glacier has thinned.

A series of comparison images from Google Earth in 2001 and 2014 further illustrate the changes noted above.

In the first pair the terminus change and lake expansion is evident at the red arrow. Debris cover expansion at the lateral moraine area with thinning of the eastern tributary is notable at the yellow arrow.

The second pair is the terminus reach. A series of depressions are noted with each yellow arrow, indicated by concentric crevassing. This indicates collapse due to a subglacial basin/lake. Further this indicates a stagnant collapsing terminus area in the lower 1.5 km of the glacier.

The last pair is the icefall region indicating reduced crevassing below the lefthand icefall, pink arrow and the expanding medial moraine yellow arrow. It is clear that this glacier is going to continue to retreat in the coming decades, and the rate is going to increase in the near future as the collapsing sections of the terminus melt away. There is still considerable glacier area that remains snowcovered each year, and it can survive current climate and some additional warming. The snowline on the glacier is at 5000-5100 m and the head of the glacier is at 6100 m.
midui glacier comp
Midui Glacier comparison from Google Earth

midui terminus comp
Midui Terminus comparison from Google Earth

midui icefall
Midui Icefall comparison from Google Earth