Bursting ice dam in Alaska highlights risks of glacial flooding around the globe

JUNEAU, Alaska — The grey, two-story house with white trim toppled and slid, crashing into the river under as speeding waters carried off a bobbing chunk of its roof. Subsequent door, a rental constructing teetered on the sting of the financial institution, its basis already having fallen away as erosion undercut it.

The destruction came visiting the weekend as a glacial dam burst in Alaska’s capital, swelling the degrees of the Mendenhall River to an unprecedented diploma. The bursting of such snow-and-ice dams is a phenomenon known as a jökuhlaup, and whereas it’s comparatively little-known within the U.S., researchers say such glacial floods might threaten about 15 million individuals world wide.

“We sat down there and had been simply watching it, and rapidly bushes began to fall in,” Amanda Arra, whose home continued hanging precariously over the river financial institution Monday, informed the Juneau Empire. “And that’s once I began to get involved. Tree after tree after tree.”

The flooding in Juneau got here from a facet basin of the awe-inspiring Mendenhall Glacier, which acts as a dam for the rain and melted snow that acquire within the basin throughout the spring and summer season. Ultimately, the water gushed out from below the glacier and into Mendenhall Lake, from which it flowed down the Mendenhall River.

Water launched from the basin has triggered sporadic flooding since 2011. However sometimes, the water releases extra slowly, over a lot of days, mentioned Eran Hood, a College of Alaska Southeast professor of environmental science.

Saturday’s occasion was astonishing as a result of the water gushed so rapidly, elevating the river’s flows to about 1 1/2 occasions the very best beforehand recorded — a lot that it washed away sensors that researchers had positioned to review the glacial outburst phenomenon.

“The flows had been simply approach past what something within the river might stand up to,” Hood mentioned.

Two properties had been utterly misplaced and a 3rd partially so, Robert Barr, Juneau’s deputy metropolis supervisor, mentioned Monday. There have been no experiences of accidents or fatalities.

Eight buildings, together with those who fell into the water, have been condemned, however some would possibly be capable to be salvaged by substantial repairs or financial institution stabilization, he mentioned. Others suffered lesser harm.

Whereas local weather change is melting the Mendenhall and different glaciers world wide, its relationship to such floods is sophisticated, scientists say.

The basin the place the rain and meltwater acquire was previously coated by the Suicide Glacier, which used to movement into the Mendenhall Glacier, contributing ice to it. However the Suicide Glacier has retreated because the local weather warms, leaving a lake within the basin dammed by the Mendenhall.

Whereas that half will be linked to local weather change, the unpredictable ways in which these waters can burst by means of the ice dams and create floods downstream shouldn’t be, they mentioned.

“Local weather change triggered the phenomenon, however not the person floods,” Hood mentioned.

The variability within the timing and quantity of such floods makes it arduous to organize for them, mentioned Celeste Labedz, an environmental seismologist on the College of Calgary.

Greater than half of the individuals in danger from glacial outburst floods are in simply 4 nations — India, Pakistan, Peru and China, in keeping with a research revealed this 12 months in Nature Communications.

One of many extra devastating such occasions killed as much as 6,000 individuals in Peru in 1941. A 2020 glacial lake outburst flood in British Columbia, Canada, triggered a surge of water about 330 toes (100 meters) excessive, however nobody was damage.

As a result of the bottom alongside the Mendenhall River is basically made up of unfastened glacial deposits, it is particularly prone to erosion, Hood mentioned. The harm might have been a lot worse if the flood coincided with heavy rains, he mentioned.

Chris and Bob Winter constructed their home about 50 toes (15.2 meters) off the Mendenhall River in 1981. It flooded for the primary time in 2014, an occasion that prompted them to boost their home 3 toes. It flooded once more on Saturday with about 3 inches of standing water, sufficient to soak the carpets, subflooring and drywall.

“You simply bought to tear all of it out,” Chris Winter mentioned. “I simply don’t know what’s going to occur, however we are able to’t dwell in our home proper now.”

She mentioned her largest concern is that they’re each of their mid-70s and can most likely have to maneuver south sooner or later.

“We raised our household, they usually’re gone and no one’s in Juneau,” she mentioned. “And I don’t know that we’ll be capable to promote it.”

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Thiessen reported from Anchorage. Related Press author Gene Johnson in Seattle and researcher Jennifer Farrar in New York contributed to this report.