New York: Climate change is to blame for a deadly glacier collapse this year in the once stable region of the Tibetan Plateau, says a study.
On July 17, more than 70 million tonnes of ice broke off from the Aru glacier in the mountains of western Tibet and tumbled into a valley below, taking the lives of nine nomadic yak herders living there.
Glacial collapse is unprecedented in western Tibet, which for decades has resisted the effects of climate change while glaciers in southern and eastern Tibet have melted at an accelerating rate.
The most important fact about the avalanche is that it lasted only four or five minutes (according to witnesses), yet it managed to bury 3.7 square miles of the valley floor in that time, said Lonnie Thompson, Professor at The Ohio State University in the US.
Meltwater at the base of the glacier must have lubricated the ice to speed its flow down the mountain, said the study published in the Journal of Glaciology.
"Given the rate at which the event occurred and the area covered, I think it could only happen in the presence of meltwater," Thompson noted.
The researchers used satellite data and GPS to get precise measurements of how much ice fell in the first avalanche and the area it covered.
"We still don't know exactly where the meltwater came from, but given that the average temperature at the nearest weather station has risen by about 1.5 degrees Celsius over the last 50 years, it makes sense that snow and ice are melting and the resulting water is seeping down beneath the glacier," Thompson said.
Increased snowfall has even led to the expansion of some glaciers in western Tibet -- and the extra snowfall likely played some role in the avalanche by creating additional meltwater, said lead author of the paper Lide Tian from the Chinese Academy of Sciences.
Other nearby glaciers may be vulnerable, "but unfortunately as of today, we have no ability to predict such disasters", Thompson added.
Researchers could not have predicted, for example, that a neighbouring glacier in the same mountain range would give way just two months later, but it did in September 2016.
That avalanche appears not to have resulted in any deaths, and the cause is still under investigation.