Climate change may be to blame for the deadly avalanche in Tibet this year which claimed the nine lives, a new study has found.
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.
The most important fact about the July 17 avalanche is that it lasted only four or five minutes, yet it managed to bury 3.7 square miles of the valley floor in that time, researchers said.
Something – likely meltwater at the base of the glacier – must have lubricated the ice to speed its flow down the mountain, said Lonnie Thompson research scientist at Ohio State University's Byrd Polar and Climate Research Centre (BPCRC) in the US.
“Given the rate at which the event occurred and the area covered, I think it could only happen in the presence of meltwater,” Thompson said.
“Other nearby glaciers may be vulnerable, but unfortunately as of today, we have no ability to predict such disasters,” he said.
Researchers could not have predicted, that a neighboring 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.
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.
They have since pieced together more answers by working with computer modelers who were able to replicate the avalanche virtually.
In those simulations, the only condition that led to an avalanche was the presence of meltwater.
“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.
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.
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 Lide Tian, a glaciologist at the Institute of Tibetan Plateau Research of the Chinese Academy of Sciences.
The research was published in the the Journal of Glaciology.