Early on July 17, 2016, the Aru Range of Tibet experienced a massive, unexpected glacier avalanche that propelled ice and rock down into the surrounding valley. The glacier collapse of roughly 60-70 million cubic meters killed nine herders and hundreds of animals within 40 square kilometers. Controversy remains among glaciologists about what caused the avalanche in July.
According to the record, in the months prior to the avalanche, temperatures in western Tibet, west of the Aru Co Lake, had been normal, with an ordinary amount of rainfall. Equally perplexing was the fact that the part of the glacier that collapsed sat on fairly flat terrain.
There has only been one other region, Kolka/Karmadon in the Russian Caucasus, where similar events have occurred, according to a publication by the scientific commission GAPHAZ. In the article by GAPHAZ, researchers from the International Association of Cryospheric Sciences (IACS) and the International Permafrost Association (IPA) report that the last Kolka/Karmadon event occurred on September 20, 2002 and “led to a rock and ice avalanche of 120 million cubic meters in volume, killing more than 100 people.”
Whats even stranger about the Tibet avalanche is that on September 20, only two months after the first avalanche, a second massive glacier avalanche occurred just 4.8 kilometers to the south of the first collapse. According to Wanqin Guo, an associate professor at CAREERI (Cold and Arid Regions Environmental and Engineering Research) in China and an expert in avalanches, the glacier slide totaled an area of 6.4 square kilometers. The Tibetan Armed Police Force conducted the rescue for the second avalanche, but the casualty count remains unknown.
Guo talked to GlacierHub about what he believes caused the rare glacier avalanches in the region, explaining: “As the remote sensing shows, the avalanche that happened in July was mainly caused by glacier surges. The glacier had been moving slowly since 2013. It significantly accelerated moving in May 2016.” The second avalanche that happened in September was also suspected to be caused by a surge from the same glacier.
“Because the first avalanche generated a concussion wave (a shock wave or type of propagating disturbance), it stimulated the southern glacier,” Guo explained. “Though it is hard to predict avalanches, there were clues detected by scientists and warnings.” But, unfortunately, says Guo, the warnings for the glacier collapse came too late, only several hours before the second avalanche struck the region.
“This is very unusual,” added Jeffrey Kargel, a senior associate research scientist and adjunct professor at the University of Arizona, who spoke to GlacierHub about the twin avalanches. “The cause is still not known,” he said.
To date, there are multiple opposing viewpoints about the source of the avalanches among scholars, causing controversy within the scientific community. Guo, for example, believes the two massive avalanches are linked to climate change. “No matter what kind of glacier surges happen, there is always the effect of the meltwater inside of or at the bed of the glaciers,” Guo told GlacierHub. “Climate change caused the melt of the Tibet glacier, consequently causing more melt water to smooth the glacier. This meant the glacier was able to surge further at a higher speed. Without climate change, the glacier surges could happen but would not cause such massive avalanches.”
One speculation is that a geothermal anomaly is involved. But researchers studying the avalanches don’t see eye to eye. Kargel disagrees with Guo’s assessment: “If it is correct, it may explain why two neighboring glaciers experienced the same thing, but it would also make it less likely that this will happen elsewhere any time soon,” he explained to GlacierHub.
Another possibility, according to Kargel, is that seasonal meltwater (originating at the surface) worked its way down to the bed. But this is also not a very satisfactory explanation.
“Why are there just two glaciers? If this is the correct explanation, then other glaciers may experience something similar in coming summers,” said Kargel.
For now, everything is as Kargel put it to GlacierHub: “Honestly, it is a mystery.”