Folks in Alaska’s capital have lived for greater than a decade with periodic glacial dam outbursts just like the one which destroyed at least two homes over the weekend.
However the most recent flood was stunning for a way rapidly 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 consequence from the bursting of snow-and-ice dams.
What prompted the flooding in Juneau?
The water got here from a aspect 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 in the course of the spring and summer season. Finally 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 usually the water releases extra slowly, usually over a couple of days, stated 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 standard mountaineering trails close to the meandering Mendenhall River.
Is local weather change in charge?
Local weather change is melting glaciers. A study released this year recommended vital melting by the top of this century amid present local weather change developments, and a separate report indicated that glaciers in elements of the Himalayas are melting at unprecedented rates.
However the relationship between the altering local weather and glacial outburst floods just like the one in Juneau is sophisticated, scientists say.
The basin the place the rain and meltwater acquire was previously lined by Suicide Glacier, which used to contribute ice to the Mendenhall Glacier. Smaller glaciers, like Suicide Glacier, reply extra quickly to adjustments in local weather and the retreat of Suicide Glacier uncovered the basin, Hood stated.
However the floods that happen “actually don’t have anything to do with local weather change and glacier soften instantly,” he stated.
“The phenomenon itself is attributable to local weather, however the person floods don’t have something to do with local weather as a result of they’re mainly simply the case the place water is filling up a basin after which draining in some unspecified time in the future in the course of the summer season,” he stated.
How uncommon are these floods?
These occasions aren’t new and occur in locations around the globe, threatening about 15 million people globally, in keeping with researchers. There’s an Icelandic time period for them, jökuhlaups.
However they’re not 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 range from yr to yr, researchers stated.
Celeste Labedz, an environmental seismologist on the College of Calgary, stated glaciers are dynamic. For instance, because the long-retreating Mendenhall Glacier continues to soften, a course of aided by the warming local weather, it’s potential it should sometime now not block the basin and flooding from that basin will now not be a priority. However there’s additionally potential for brand spanking new basins to kind, she stated.
“As a glacier is thinning and retreating and altering, you may see some floods are going to cease occurring and new ones are going to start out occurring. It’s a variable system,” Labedz stated.
What occurs as glaciers soften?
Along with flooding dangers, glacial loss can imply diminished water provides in elements 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 akin to 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, stated Christian Zimmerman, director of the U.S. Geological Survey’s Alaska Science Heart.
Retreat of glaciers can even have an effect on ecosystems, together with salmon habitat, one thing researchers are hoping to higher perceive.