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A glacier that has held an Alaskan slope in place for centuries is melting, releasing the ground below in what can be described as a slow-motion landslide, the researchers say. But there is also the possibility of a real landslide that could cause a devastating tsunami.
In a study published last week, scientists noted that the slope of Barry Arm Fjord on Prince William Sound in southeast Alaska slipped about 120 meters from 2010 to 2017. These are some of the first measurements to quantify how the slope is falling there.
“We are measuring this land loss before the tsunami occurs,” said Chunli Dai, lead author of the article and a researcher at Ohio State University’s Byrd Polar and Climate Research Center.
The study was published in Geophysical Research Letters.
Landslides on slopes near glaciers generally occur when glacial ice melts, a phenomenon that occurs more rapidly around the world due to climate change. Landslides can cause tsunamis by sending huge amounts of earth and rocks into nearby bodies of water. A similar landslide occurred in 2017 in western Greenland, resulting in a tsunami that killed four people.
Scientists estimate that a landslide in Barry Arm Fjord could be about eight times larger than that of Greenland.
If the entire slope collapsed at once, the researchers found that the tsunami waves could reach communities across the sound, which are home to hundreds of people and visitors, including fishermen, tourists, and members of an indigenous Alaskan group called Chugach.
For this study, the researchers used satellite data to measure and monitor the size of the glacier that had covered the Barry Arm slope and to measure the amount of land that had already been displaced, which appears to be directly related to the melting of the Glacier Barry Arm. Then, they built models to identify the potential landslide risk.
The data showed that, from 1954 to 2006, the Barry Glacier thinned by less than one meter per year. But after 2006, melting increased rapidly, so much so that the glacier was thinning about 40 meters per year. The glacier retreated rapidly from 2010 to 2017, the researchers found. The “tip” of the ground – the lowest point of the falling slope – had hit the glacier in 2010. By 2017, that tip was exposed and bumped into the water in Prince William Sound.
The researchers modeled potential tsunami scenarios and found that if the land along that slope collapsed immediately, the resulting tsunami would send currents between 25 and 40 meters per second, enough to cause significant damage to large cruise and cargo ships and fishing vessels. . , as well as overwhelming kayakers, who frequent Prince William Sound.
Waves could reach 10 meters in the nearby town of Whittier. The tsunami could disrupt fiber optic service in parts of Alaska, the researchers noted: Two of five fiber optic undersea lines for Alaska run under Prince William Sound. And the oil from the 1989 Exxon Valdez oil spill still lingers in sediments in Prince William Sound, meaning it’s possible a tsunami could send that oil back into the environment.
“If the slope fails immediately, it would be catastrophic,” said Dr. Bretwood Higman, a geologist at Ground Truth Alaska and co-author of the study.
When and if that massive landslide occurs depends on geology, climate and luck. An earthquake, prolonged rains, melting permafrost or melting snow could trigger one, the researchers said. (A 2018 earthquake in Alaska did not trigger a landslide, the researchers noted.)
“People are working on early detection alerts, so if a landslide occurs, people in nearby communities could at least get a warning,” said Anna Liljedahl, an Alaska-based hydrologist with the Woodwell Climate Research Center, and a other co-author. “This kind of research could help build those early warning systems.”
Source of the story:
Materials provided by Ohio State University. Original written by Laura Arenschield. Note: The content can be changed by style and length.
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