JUNEAU, Alaska – Individuals in Alaska’s capital have lived for greater than a decade with periodic glacial dam outbursts just like the one which destroyed not less than two houses over the weekend.
However the latest flood was shocking for the way shortly the water moved because the surging Mendenhall River devoured riverbanks, undermining and damaging houses, and prompted some residents to flee.
Listed below are some points surrounding glaciers and the floods that end result from the bursting of snow-and-ice dams.
WHAT CAUSED THE FLOODING IN JUNEAU?
The water got here from a facet basin of the spectacular however receding Mendenhall Glacier that is called the Suicide Basin. The glacier acts as a dam for precipitation and soften from the close by Suicide Glacier that collects within the basin through the spring and summer season. Ultimately the water gushes out from below the Mendenhall Glacier and into Mendenhall Lake, from which it flows down the Mendenhall River.
Such glacial dam outbursts have been occurring within the space since 2011, however typically the water releases extra slowly, sometimes over a number of days, mentioned Eran Hood, a College of Alaska Southeast professor of environmental science.
Lake and streamflow ranges reached report highs throughout Saturday’s flooding in Juneau, which is dwelling to about 30,000 folks and has quite a few houses and in style climbing trails close to the meandering Mendenhall River.
IS CLIMATE CHANGE TO BLAME?
Local weather change is melting glaciers. A research launched this yr advised important melting by the top of this century amid present local weather change developments, and a separate report indicated that glaciers in components of the Himalayas are melting at unprecedented charges.
However the relationship between the altering local weather and glacial outburst floods just like the one in Juneau is difficult, scientists say.
The basin the place the rain and meltwater accumulate was previously coated by Suicide Glacier, which used to contribute ice to the Mendenhall Glacier. Smaller glaciers, like Suicide Glacier, reply extra quickly to modifications in local weather and the retreat of Suicide Glacier uncovered the basin, Hood mentioned.
However the floods that happen “really have nothing to do with climate change and glacier melt directly,” he mentioned.
“The phenomenon itself is caused by climate, but the individual floods don’t have anything to do with climate because they’re basically just the case where water is filling up a basin and then draining at some point during the summer,” he mentioned.
HOW UNUSUAL ARE THESE FLOODS?
These occasions aren’t new and occur in locations around the globe, threatening about 15 million folks globally, in line with researchers. There’s an Icelandic time period for them, jökuhlaups.
However they don’t seem to be one thing many within the U.S. take into consideration — even in Alaska, which is dwelling to the majority of U.S. glaciers, a lot of them distant.
One problem with glacial dam outbursts is that the severity and timing can fluctuate from yr to yr, researchers mentioned.
Celeste Labedz, an environmental seismologist on the College of Calgary, mentioned glaciers are dynamic. For instance, because the long-retreating Mendenhall Glacier continues to soften, a course of aided by the warming local weather, it is attainable it’ll sometime now not block the basin and flooding from that basin will now not be a priority. However there’s additionally potential for brand new basins to type, she mentioned.
“As a glacier is thinning and retreating and changing, you can see some floods are going to stop happening and new ones are going to start happening. It’s a variable system,” Labedz mentioned.
WHAT HAPPENS AS GLACIERS MELT?
Along with flooding dangers, glacial loss can imply diminished water provides in components of the world and will have an effect on things like agriculture and tourism.
Alaska is a bucket-list vacation spot for guests drawn by wild landscapes resembling mountains and craggy glaciers that spectacularly calve into lakes or the ocean.
Glaciers cowl about 33,000 sq. miles (85,000 sq. kilometers) of the state, and annual ice loss from glaciers in Alaska can be sufficient to cowl Texas in 4 inches (10 centimeters) of water, mentioned Christian Zimmerman, director of the U.S. Geological Survey’s Alaska Science Middle.
Retreat of glaciers also can have an effect on ecosystems, together with salmon habitat, one thing researchers are hoping to higher perceive.
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