Melting glacier threatens to trigger a catastrophic tsunami in Alaska – CNET

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The dangerous slope as of June 2019.

NASA/Valisa Higman

A glacier in Alaska is threatening to trigger a potentially deadly and historic tsunami as it retreats under the overheated stress of climate change. 

A glacier flowing into the Barry Arm of Prince William Sound has been receding rapidly in recent years, and the result is that some adjacent slopes held in place by the glacier for centuries have been destabilized. One in particular has been slumping downward in slow motion since at least 2010. Researchers fear that if it were to completely collapse into the sound, it could trigger a mega-tsunami.

“If the slope fails at once, it would be catastrophic,” said Bretwood Higman, a geologist with Ground Truth Alaska and co-author of a study published Oct. 29 in Geophysical Research Letters.

In the study, researchers modeled different scenarios to find that such a collapse could produce a tsunami moving at up to 90 miles per hour (145 kilometers per hour) across the sound, which is frequented by large cruise and cargo ships as well as fishing boats and kayakers. They report that waves could reach heights of 33 feet (10 meters) in the nearby town of Whittier. 

“It was hard to believe the numbers at first,” said lead author Chunli Dai from Ohio State University. “We calculated that a collapse would release sixteen times more debris and eleven times more energy than Alaska’s 1958 Lituya Bay landslide and mega-tsunami.” 

That event was set off by a 7.8 earthquake and produced what is thought to be the tallest wave in modern history at 1,700 feet (about a third of a mile or half a kilometer) that destroyed millions of trees around the remote bay. 

A similar quake, significant rain or other factors could trigger a slide at Barry Arm at just about any time. In 2017, a similar but smaller situation yielded a tsunami in western Greenland that killed four people.

“People are working on early-detection warnings, so if a landslide happens, people in nearby communities might at least get a warning,” said hydrologist Anna Liljedahl, another co-author.

It’s just one of the many less obvious ways the warming of the planet threatens to damage or destroy lives and property.  In the Andes of Peru, landslides into glacial lakes threaten to cause outburst floods that can devastate large cities downstream. 

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“These are fairly unusual events, and scientists have only started studying the connections between glacial retreat and landslide tsunamis in the past few decades,” Higdon said. “We don’t have a very long or deep record to look at yet.”

New data continues to come in from Prince William Sound, however. On Tuesday, the Alaska Department of Natural Resources reported satellite images showed renewed movement of the unstable slope in the form of “eight inches of downslope creep between October 9 and October 24.”     

State officials are asking everyone to avoid the area of Prince William Sound near the Barry Arm.

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