After a glacial dam outburst destroyed homes in Alaska, a look at the risks of melting ice masses

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 a minimum of two properties over the weekend.

However the latest flood was stunning for a way rapidly the water moved because the surging Mendenhall River devoured riverbanks, undermining and damaging properties, and prompted some residents to flee.

Listed here are some points surrounding glaciers and the floods that outcome from the bursting of snow-and-ice dams.

WHAT CAUSED THE FLOODING IN JUNEAU?

The water got here from a aspect basin of the spectacular however receding Mendenhall Glacier that is named 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. Finally the water gushes out from underneath 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, usually 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 properties 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 12 months steered vital melting by the tip of this century amid present local weather change traits, 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 sophisticated, scientists say.

The basin the place the rain and meltwater gather was previously lined 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 “actually don’t have anything to do with local weather change and glacier soften instantly,” he mentioned.

“The phenomenon itself is brought on by local weather, however the person floods haven’t got something to do with local weather as a result of they’re principally simply the case the place water is filling up a basin after which draining sooner or later through the summer season,” he mentioned.

HOW UNUSUAL ARE THESE FLOODS?

These occasions aren’t new and occur in locations world wide, threatening about 15 million folks globally, in keeping 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, lots of them distant.

One problem with glacial dam outbursts is that the severity and timing can differ from 12 months to 12 months, 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 potential it would sometime not block the basin and flooding from that basin will 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 altering, you’ll be able to see some floods are going to cease taking place and new ones are going to begin taking place. It is 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 comparable 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, mentioned Christian Zimmerman, director of the U.S. Geological Survey’s Alaska Science Heart.

Retreat of glaciers may have an effect on ecosystems, together with salmon habitat, one thing researchers are hoping to raised perceive.