In the Himalayas, which are home to more than one quarter of the world’s total, glaciers are beginning to recede as a result of climate change. According to a new study of 32 glaciers in the area, Himalayan glaciers which terminate in lakes are losing ice especially quickly. This raises serious concerns about the stability of debris dams, which could collapse and flood nearby valleys as these lakes glacial lakes fill with meltwater.
With decreasing snowfall and increasing air temperatures, the Himalaya’s many existing glaciers are beginning to melt. Owen King, a glaciologist at the University of Leeds in the United Kingdom and lead author of the study, highlighted how “The landscape is primed for lake development.”
As these lakes swell with runoff from glaciers, the risk of dam collapse rises. In 1985, a debris dam at a glacial lake in eastern Nepal collapsed, and millions of cubic meters of water poured into the nearby village of Ghat. Bridges, houses, and a newly built hydroelectric plant were destroyed. Just last year, the Nepalese government drained a portion of Imja Tsho, which is among the most rapidly growing lakes in Nepal.
King, along with other members of his team, utilized satellite data to examine a 15 year history of 9 glaciers that terminated in lakes, and 23 that terminated on land, in Nepal and Tibet. They used digital elevation maps created in 2000 and 2015 to determine changes in ice mass, ice area, and height. The team found that glaciers melting into lakes had been melting 32 percent faster than glaciers which terminate on land. The glaciers melting into lakes had lost more height and area than their landlocked counterparts. Their study appeared this month in the journal The Cryosphere.
The team think that lake water has eroded the underside of these glaciers, leading them to split into icebergs. Such a process would rapidly reduce ice mass, they said. However, other experts said the issue is still unresolved.
According to Patrick Wagnon, a glaciologist at the French National Research Institute for Sustainable Development in Marseille, not involved in the research:
“It’s still unclear why lake-terminating glaciers are losing more mass than land-terminating glaciers.”
New data may hold more information about these processes. King and his team recently returned from more expeditions to the region to examine the relationship between glacial lakes and glaciers. “I’m knee-deep in field data,” said King. The team also plans to examine a broader timeline of data, including satellite images going as far back as the 70s.