Melting glaciers in Alaska could unleash a ‘mega-tsunami’, an enormously high wall of water with incredible destructive power, scientists have warned.
Glacier retreat in Prince William Sound is destabilising mountain slopes, and a mega-tsunami could be unleashed as early as next year, Science Alert reported.
In an open letter to Alaskan authorities, a group of scientists warned that collapsing mountain slopes in the US state in 2015 had led to waves up to 633 feet in height.
Even 15 miles away, the surge was still 15 feet high, they said.
The researchers wrote: “We, a group of scientists with expertise in climate change, landslides, and tsunami hazards, have identified an unstable mountain slope above the toe of Barry Glacier in Barry Arm, 60 miles east of Anchorage, that has the potential to fail and generate a tsunami.
“This tsunami could impact areas frequented by tourists, fishing vessels, and hunters (potentially hundreds of people at one time).
“We believe that it is possible that this landslide-generated tsunami will happen within the next year, and likely within 20 years.”
The letter was signed by multiple experts including Dr Chad Briggs, of the University of Alaska Anchorage.
Ohio State University researcher Chunli Dai analysed images of the glacier using a high-resolution dataset called ArcticDEM.
Her analysis of the area showed that the entire mountainside was slowly shifting.
If the giant, slow-moving landslide was to suddenly collapse into the narrow fjord below, it would generate an extremely large tsunami because of the way the fjord's shape would amplify the wave.
“It was hard to believe the numbers at first,” said Dai.
“Based on the elevation of the deposit above the water, the volume of land that was slipping, and the angle of the slope, we calculated that a collapse would release 16 times more debris and 11 times more energy than Alaska’s 1958 Lituya Bay landslide and mega-tsunami.”
That event, which was triggered by an earthquake, dropped millions of cubic yards of rock about 2,000 feet into a fjord.
It produced what is thought to be the tallest wave, at 1,700 feet, in modern history.
In an event that eyewitnesses compared to an atomic bomb explosion, the huge wave washed away soil in a wide ring around the bay and obliterated millions of trees.
Lai looked at images from Landsat.
“With the wider perspective from Landsat, the movement of the slope was impossible to miss,” she said.
“You can see a whole section of the mountain between Cascade Glacier and Barry Glacier slumping toward the water.”
Lai coordinated with colleagues to evaluate the risk, and 14 scientists published the open letter.