September 6, 2016

West Hongu Glacier Retreat-Ablation Extending into January, Nepal

Posted by Mauri Pelto

hongo compare

Landsat comparison of West Hongu Glacier snowline, purple dots from October 2015 to January 2016. The red arrow indicates the 1993 active terminus location and the yellow arrow the 2015 active terminus location. 

West Hongu Glacier is a small glacier in the Dudh Khosi Basin of Nepal. The glacier drains the east side of Ama Dablam Peak. Shea et al (2015) noted that glaciers in the Dudh Khosi Basin of Nepal lost 16% of total volume and 20% of area from 1961-2007. Shea et al (2015), in an ICIMOD project, modeled future changes in glaciers with various climate scenarios, finding a minimum projected volume change by 2050 of −26 % and maximum of −70 %. This glacier is a short distance from Mera Glacier where mass balance is measured.  Both are summer accumulation type glaciers with 80% of annual precipitation occurring during the summer monsoon season. Salerno et al (2015)  found that the main and most significant increase in temperature is concentrated outside of the monsoon period, leading to more ablation favoured during winter and spring months, and year around close to the glacier terminus. The lake at the end of the glacier is unnamed and not listed as one of 20 lakes recorded as potentially unstable and warranting further investigation in Nepal (Ives et al., 2010). ICIMOD has continued to inventory and assess the hazards from glacier lakes and their capacity to induce outburst floods.  ICIMOD notes the area of the lake is 0.366 square kilometers.

Here we examine the snowline from fall into winter in 2015/16. Above is the comparison indicating the rise of the snowline from October into January. This has been a common occurrence in recent years, indicating that ablation though limited, continues in the post-monsoon into the mid-winter period. The snowline rises from 5550-5600 m in October to 5650-5700 m in January. Besides ongoing ablation into January, the high snowline illustrates the lack of significant accumulation at any elevation on the glacier in the post Monsoon period extending into January. The snowline remained high on Jan.20, 2016, but the image has considerable cloud cover. This tendency has been noted at Nup La-West Rongbuk Glacier, on the Nepal-China border, Chutanjima Glacier, China and Lhonak Glacier, Sikkim.

Below the active ice terminus change from 1993-2013 is noted.  The active ice ended on the shore of the lake in 1993, red arrow.  By 2013 the active ice has retreated 500 m from the lake, yellow arrow. There is still debris covered stagnant ice in this zone. The inactive ice is dissected by significant stream channels that cannot develop in an area of active ice. Some of the stream channels have cut to the base of the glacier.

hongu terminus

Comparison of active terminus location from 1993-2013 in Landsat images. The red arrow indicates the 1993 active terminus location and the yellow arrow the 2015 active terminus location.hongu glaceri terminus 2013

Terminus of West Hongu Glacier inn 2013. Yellow arrows indicate the stream channels cutting through the debris covered inactive ice.Map below indicates glacier ending in the lake.

west hongu map