According to a team of scientists led by Dr Joseph Shea of the International Centre for Integrated Mountain Development in Kathmandu, Nepal, if greenhouse-gas emissions continue to rise, glaciers in the Dudh Kosi basin in the Nepal Himalaya, which is home to some of the world’s highest mountain peaks, including Mt Everest, could experience dramatic change in the decades to come.
Everest and Khumbu glacier in the Dudh Koshi basin. Image credit: Patrick Wagnon.
The glacier model used by Dr Shea and his colleagues in their study shows that glacier volume in the region could be reduced between 70 and 99 percent by 2100.
The results depend on how much greenhouse-gas emissions continue to rise, and on how this will affect temperature, snowfall and rainfall in the area.
“Our results indicate that these glaciers may be highly sensitive to changes in temperature, and that increases in precipitation are not enough to offset the increased melt,” explained Dr Shea, who is the lead author on the paper published in the journal Cryosphere.
Increased temperatures will not only increase the rates of snow and ice melt, but can also result in a change of precipitation from snow to rain at critical elevations, where glaciers are concentrated.
Together, these act to reduce glacier growth and increase the area exposed to melt.
“Apart from the significance of the region, glaciers in the Dudh Kosi basin contribute meltwater to the Kosi River, and glacier changes will affect river flows downstream,” Dr Shea said.
Changes in glacier volume can impact the availability of water, with consequences for agriculture and hydropower generation.
While increased glacier melt initially increases water flows, ongoing retreat leads to reduced meltwater from the glaciers during the warmer months, with greatest impact for the local populations before the monsoon when rainfall is scarce.
Glacier retreat can also result in the formation and growth of lakes dammed by glacial debris. Avalanches and earthquakes can breach the dams, causing catastrophic floods that can result in river flows 100 times greater than normal in the Dudh Kosi basin.
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Shea, J. M. et al. 2015. Modelling glacier change in the Everest region, Nepal Himalaya. Cryosphere, 9, 1105-1128; doi: 10.5194/tc-9-1105-2015
