February 8, 2017

Lumding Glacier Rapid Retreat, Nepal 1992-2016

Posted by Mauri Pelto

Landsat comparison of Lumding Glacier terminating in Lumding Tsho. Red arrow on each Landsat image indicates 1992 terminus and yellow arrow 2016 terminus location.

Lumding Glacier, Nepal terminates in Lumding Tsho, a proglacial lake, in Dudh Khosi Valley in the Mount Everest region of Nepal. This lake poses a hazard for a glacier lake outburst flood in the Dudh Khosi valley. The lake expansion results from retreat of the Lumding Glacier. International Centre for Integrated Mountain Development (ICIMOD) study examined the changes in Lumding Tsho from 1962-2000 and found the lake grew from 0.2 km2 in 1962 to 0.77 km2 in 2000. ICIMOD has an ongoing specific focus on assessing glacier lake outburst flood potential. The lake growth was the result of a retreat of 40 meters/year from 1976-2000 and 35 meters/year from 1962-2007, as noted in figure below from Bajracharya  & Mool (2009). Here we update the changes to 2016 using Landsat imagery.

The lake begins at the end of the heavily debris covered Lumding Glacier draining east from Numbur Himal . Red arrow on each Landsat image indicates 1992 terminus and yellow arrow 2016 terminus location. The lake was 1675 meters long in 1992, 1950  meters long in 2000, 2350 meters long in 2009 and 2800 meters in 2016. This 1100 m retreat in 25 years is a retreat rate of 45 meters/year. The lake at 2.8 km in length now has an area of over 1 square kilometer. The glacier is fed largely by avalanching off the flanks of Numbur, blue arrows. King et al (2017) noted a mean mass balance of all 32 glaciers examined in the Mt. Everest region from 2000-15 was  −0.52  water equivalent per year. The mean mass balance of nine lacustrine terminating glaciers, like Lumding Glacier, was 32 % more negative than land-terminating debris-covered glaciers.  An additional problem for the glacier in the future is the retreat of the terminus of the tributary glaciers that avalanche onto the lower Lumding Glacier. The yellow letter A in the 2016 Sentinel images indicates the retreat of a feeder glaciers, 300 m since 1992.  The lower section of the Lumding Glacier is heavily debris covered, noted best in Google Earth image, which insulates the underlying ice, reducing melting and retreat. This also indicates the avalanche source of much of the accumulating snow and ice. The increased distance to the feeding snow and ice slopes will reduce this input.  The two blue arrows indicate plumes of glacier runoff into the lake.  This glacier loss in mass driving the retreat is like that on Hinku Nup Glacier and Middle Lhonak Glacier

A 2016 Sentinel image of Lumding Glacier with avalanche paths shown by blue arrows, and retreating tributary above Point A.

Google Earth image of Lumding Glacier front.  This illustrates the debris cover and also meltwater plumes entering lake.