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

Aug 8, 2023, 4:25 PM

JUNEAU, Alaska (AP) — People in Alaska’s capital have lived for more than a decade with periodic glacial dam outbursts like the one that destroyed at least two homes over the weekend.

But the most recent flood was surprising for how quickly the water moved as the surging Mendenhall River devoured riverbanks, undermining and damaging homes, and prompted some residents to flee.

Here are some issues surrounding glaciers and the floods that result from the bursting of snow-and-ice dams.


The water came from a side basin of the spectacular but receding Mendenhall Glacier that is known as the Suicide Basin. The glacier acts as a dam for precipitation and melt from the nearby Suicide Glacier that collects in the basin during the spring and summer. Eventually the water gushes out from under the Mendenhall Glacier and into Mendenhall Lake, from which it flows down the Mendenhall River.

Such glacial dam outbursts have been occurring in the area since 2011, but often the water releases more slowly, typically over a few days, said Eran Hood, a University of Alaska Southeast professor of environmental science.

Lake and streamflow levels reached record highs during Saturday’s flooding in Juneau, which is home to about 30,000 people and has numerous homes and popular hiking trails near the meandering Mendenhall River.


Climate change is melting glaciers. A study released this year suggested significant melting by the end of this century amid current climate change trends, and a separate report indicated that glaciers in parts of the Himalayas are melting at unprecedented rates.

But the relationship between the changing climate and glacial outburst floods like the one in Juneau is complicated, scientists say.

The basin where the rain and meltwater collect was formerly covered by Suicide Glacier, which used to contribute ice to the Mendenhall Glacier. Smaller glaciers, like Suicide Glacier, respond more rapidly to changes in climate and the retreat of Suicide Glacier exposed the basin, Hood said.

But the floods that occur “really have nothing to do with climate change and glacier melt directly,” he said.

“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 said.


These events aren’t new and happen in places around the world, threatening about 15 million people globally, according to researchers. There’s an Icelandic term for them, jökuhlaups.

But they’re not something many in the U.S. think about — even in Alaska, which is home to the bulk of U.S. glaciers, many of them remote.

One challenge with glacial dam outbursts is that the severity and timing can vary from year to year, researchers said.

Celeste Labedz, an environmental seismologist at the University of Calgary, said glaciers are dynamic. For example, as the long-retreating Mendenhall Glacier continues to melt, a process aided by the warming climate, it’s possible it will someday no longer block the basin and flooding from that basin will no longer be a concern. But there’s also potential for new basins to form, she said.

“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 said.


In addition to flooding risks, glacial loss can mean diminished water supplies in parts of the world and could affect such things as agriculture and tourism.

Alaska is a bucket-list destination for visitors drawn by wild landscapes such as mountains and craggy glaciers that spectacularly calve into lakes or the ocean.

Glaciers cover about 33,000 square miles (85,000 square kilometers) of the state, and annual ice loss from glaciers in Alaska would be enough to cover Texas in 4 inches (10 centimeters) of water, said Christian Zimmerman, director of the U.S. Geological Survey’s Alaska Science Center.

Retreat of glaciers can also affect ecosystems, including salmon habitat, something researchers are hoping to better understand.

United States News


KTAR Video

Video: Do Phoenix Police officers do an excellent job? Mike Broomhead thinks so

Do Phoenix Police officers do an excellent job? Mike Broomhead thinks so

1 hour ago

Associated Press

North Carolina judges consider if lawsuit claiming right to ‘fair’ elections can continue

RALEIGH, N.C. (AP) — North Carolina judges deciding whether a redistricting lawsuit claiming a state constitutional right to “fair” elections can go to trial questioned Thursday their ability to scrutinize district boundaries that way or to define what “fair” means. A panel of three trial judges listened to arguments on a motion by Republican legislative […]

1 hour ago


KTAR Video

Video: Why reform is needed on Arizona highways- by the numbers #commentary

Jim Sharpe breaks down the numbers to explains why the Arizona State Troopers Association is fighting for reform on state highways in Thursday’s Sharper Point commentary.

1 hour ago


KTAR Video

Video: Reaction to DOJ findings on Phoenix Police Department

Mike Broomhead reacts to the Department of Justice’s findings about the Phoenix Police Department. Video: Jeremy Schnell and Felisa Cárdenas/KTAR News

2 hours ago

Associated Press

UN adopts a resolution demanding that Sudan’s paramilitary force halt its siege of a Darfur city

UNITED NATIONS (AP) — The U.N. Security Council adopted a resolution Thursday demanding that Sudan’s paramilitary force halt its siege of the only capital in the vast western region of Darfur that it doesn’t control where more than a million people are reportedly trapped. The resolution, which was approved by a vote of 14-0 with […]

2 hours ago

Follow @ktar923...

Sponsored Content by Collins Comfort Masters

Here's how to be worry-free when your A/C goes out in the middle of summer

PHOENIX -- As Arizona approaches another hot summer, Phoenix residents are likely to spend more time indoors.

Sponsored Articles


Day & Night Air Conditioning, Heating and Plumbing

Beat the heat, ensure your AC unit is summer-ready

With temperatures starting to rise across the Valley, now is a great time to be sure your AC unit is ready to withstand the sweltering summer heat.



Here are 5 things Arizona residents need to know about their HVAC system

It's warming back up in the Valley, which means it's time to think about your air conditioning system's preparedness for summer.


Collins Comfort Masters

Here’s 1 way to ensure your family is drinking safe water

Water is maybe one of the most important resources in our lives, and especially if you have kids, you want them to have access to safe water.

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