A Himalayan glacier collapse killed hundreds. One in Alaska could look different.
Listen to this story:
A massive chunk of a Himalayan glacier and underlying rock broke off and led to catastrophic flooding in parts of Nepal and Tibet last Wednesday, leaving hundreds dead and thousands missing. Scientists who study glacier hazards in Alaska said that glacier collapses have happened here, but they’ve looked a bit different.
Researchers are still working to understand the chain of events that caused a slurry of ice, rock and water to destroy entire villages near the Nepal-Tibet border. Science Magazine reported that a landslide likely triggered a glacier collapse. Nature Magazine reported that it could have also happened the other way around.
But scientists say one thing is clear: human-caused climate change is destabilizing glaciers around the world.
“I think with climate warming, that it is likely to see more glacier collapses,” said Eran Hood, a professor of environmental science at the University of Alaska Southeast.
Hood is one of the primary researchers who studies glacial lake outburst floods in Juneau. Those types of floods on the Mendenhall, Taku and Snow rivers in Alaska are well-documented. Glacial outburst floods happen when a large pool forms and builds up enough water pressure to bore through the ice until it all rushes out.
But the flood in the Himalayas was triggered differently.
A key ingredient is ice perched precariously on steep terrain. That’s according to Joanna Young, a research assistant professor at the International Arctic Research Center and the University of Alaska Fairbanks.
“You also need typically to have a large amount of water getting into that ice, and so that can either be through heavy rains, or it can be after a really prolonged hot period where there’s a lot of meltwater getting into the ice,” Young said.
In the case of the Himalayan disaster, the soil was saturated and river levels were high from monsoon rains. Plus, it was a hot summer.
Finally, Young said stress has to build up in the rock or ice until gravity brings it all down at once.
So, could a glacier collapse in Alaska?
In Wrangell-St. Elias National Park, it already has.
The Flat Creek Glacier had two large collapses in 2013 and 2015. That’s according to a study by Mylène Jacquemart and her colleagues, published in 2020. She’s a glaciologist at the Swiss Federal Institute of Technology in Zurich, Switzerland.
“It was, you know, this entire glacier that had collapsed and run like 11 kilometers out the valley down into the White River,” she said.
That’s about 6.8 miles. It’s a remote area, and no one was killed.
In the first collapse, Jacquemart said the ice bulged out on the very steep Flat Creek Glacier, which had loose, fine-grained sediment beneath it. Then, meltwater built up behind the bulge over a particularly hot summer, until finally, more than 1,600 feet from the toe of the glacier collapsed.
“So that’s roughly the scale of the Blatten rock avalanche and glacial collapse that we had last year in Switzerland,” Jacquemart said.
That collapse buried much of the village of Blatten. But because the village had an early warning system in place, all 300 residents evacuated beforehand.
Jacquemart said the glacier collapses in Alaska and Switzerland were much smaller than what happened in the Himalayas.
“What we just saw in Nepal is going to end up being, you know, five to 10 times the larger event at Flat Creek,” she said.
She said a catastrophe of that level isn’t as likely in Alaska.
“There’s just not the population density and the infrastructure concentrated along these river corridors the way that it exists in the Himalayas,” Jacquemart said.
Hood, the researcher in Juneau, said if something similar happened in Southeast Alaska, it would probably look quite different from Nepal, where there are steep river canyons.
“We tend to have relatively wide glacially carved valleys, and so if you put a flood like that into a wide glacially carved valley, it’s going to behave very differently,” Hood said.
Floodwater moves faster when it’s constricted than when it can spread out.
Hood said he doesn’t expect this disaster scenario to strike from the Mendenhall or other glaciers nearby.
“The glacier collapse part is much less likely in the Coast Mountains,” he said.
Although the mountains of Southeast Alaska are known for being steep, Hood said glaciers that flow from the Juneau Icefield don’t perch thousands of feet above areas where people live, like they do in the Himalayas.
But he said there’s a related hazard that locals already know about.
“The landslide part of that equation is very likely around Juneau, in some places because of glacier retreat,” Hood said.
He said the permafrost that glues rock together melts when glaciers pull back, making it susceptible to crumbling.
Landslides in Southeast Alaska have grown more destructive with climate change, according to research published last year. Fatal landslides hit Ketchikan, Wrangell, Haines and Sitka in recent years.
Jacquemart said that although it’s difficult to tie single disasters to human-caused climate change, people should generally expect to see more glacier disasters as a result.
“Overall, we are creating conditions where these kinds of hazardous events are more likely to happen, and I think we need to really understand this responsibility,” she said. “We should be really concerned about the changes that are going on and do our utmost to really stop the warming.”