February 3, 2017

Hinku Nup, Nepal Downwasting Lake Development

Posted by Mauri Pelto

Hinku Nup Glacier in November 2016 Sentinel 2 image.  Yellow arrows indicate three supraglacial lakes that have formed.  

Hinku Nup is a valley glacier in the Dudh Khosi basin in the Mount Everest region of Nepal.  The glacier is heavily debris covered in its lowest 4 km which is a low slope section extending from 5100-4900 m.  In 1992 Landsat images there are only small supraglacial lakes, less than 100 m across on the glacier surface.  In 2000 this remains the case on Hinku Nup proper, though a lake has formed at the terminus of a former tributary, northwest yellow arrow.  By 2013 a lake has formed at the junction of Hinku Nup and Hinku Shar Glacier and a lake near the terminus of the glacier.  By 2016 the terminus lake has expanded to a length of 600 m.  There are a series of lakes that appear ready to coalesce that will extend the lake to 800 m in length, smaller yellow arrow.  The lake at the junction of Hinku Nup and Hinku Shar is 200 m across in 2016.  The proglacial lake at the terminus of the former tributary to Hinku Nup is now 500 m wide and 400 m long.  The coalescing of the lakes near the terminus will lead to the formation of lake large enough to enhance melting and lead to calving.  This should lead soon to a rapid retreat of the terminus, such as occurred on nearby Lumding Glacier.  Glacier lakes have been inventories by ICIMOD, who found little change in glacier lake area from 2001 to 2009 but a sharp decrease in the number of lakes, primarily due to coalescing.  The lake here lacks the clearcut moraine dam that exists on Thulagi Glacier and typifies glaciers that pose a Glacier lake outburst flood hazard.

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 was 32 % more negative than land-terminating, debris-covered glaciers.  This mass loss is what has been driving the widespread glacier retreat in the region.  Bajracharya and Mool (2009) noted the glaciers in the Mount Everest region retreated at a rate of 10–59 m/year from 1976-2009.

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