Alaska

Glacial lake outburst floods in Alaska and the Himalayas show evolving hazards in a warming world

Published

1 year ago

October 9, 2023

Glacial lake outburst floods in Alaska and the Himalayas show evolving hazards in a warming world

Glacial lakes are common in the Himalayas, as this satellite view shows. Some are dammed by glaciers, other by moraines. Credit: NASA

In August 2023, residents of Juneau, Alaska, watched as the Mendenhall River swelled to historic levels in a matter of hours. The rushing water undercut the riverbank and swallowed whole stands of trees and multiple buildings.

The source for the flood was not heavy rainfall—it was a small glacial lake located in a side valley next to the Mendenhall Glacier.

Glacier-dammed lakes like this are abundant in Alaska. They form when a side valley loses its ice faster than the main valley, leaving an ice-free basin that can fill with water. These lakes may remain stable for years, but often they reach a tipping point, when high water pressure opens a channel underneath the glacier.

The rapid and catastrophic drainage of lake water that follows is called a glacial lake outburst flood, or GLOF for short. The flood waters race downstream over hours or days and often hit unexpectedly.

Suicide Basin, a glacier-dammed lake, has flooded the Mendenhall River before. Scientists with the Alaska Climate Adaptation Science Center examined the glacial lake after an earlier flood.

Glacial lake outburst floods have destroyed homes, infrastructure and human life around the world. They have killed hundreds of people in Europe and thousands of people in both South America and central Asia. Globally, an estimated 15 million people live downstream from these lakes, with those in Asia’s high mountains at greatest risk.

Flooding from a glacial lake in the Himalayas on Oct. 5, 2023, left dozens of people dead in India as water swept away bridges, damaged a hydropower station and flooded small towns. Satellite images showed that the lake level dropped markedly within hours.

I study Alaska’s glacial lakes and the hazards that glacier-dammed lakes in particular can create. Our latest research shows how these lakes are changing as global temperatures rise.

When glaciers hold back lakes

Some glacial lakes are dammed by moraines—mounds of rock and debris that are left behind as a glacier retreats. Too much pressure from extreme rainfall or an avalanche or landslide into the lake can burst these dams, triggering a devastating flood. Officials say that’s likely what happened when the Himalayas’ Lhonak Lake flooded towns in India in October 2023.

Glacier-dammed lakes, like Suicide Basin off of Mendenhall Glacier, are instead dammed by the glacier itself.

These glacial lakes tend to repeatedly fill and drain due to a cyclic opening and closing of a drainage path under the ice. The fill-and-drain cycles can create hazards every couple of years or multiple times a year.

How glacier lake hazards are changing in Alaska

In a new study published in Nature Communications, we identified 120 glacier-dammed lakes in Alaska, 106 of which have drained at least once since 1985.

These lakes have collectively drained 1,150 times over 35 years. That is an average of 33 events every year where a lake drains its contents, sending a pulse of water downstream and creating potentially hazardous conditions.

Many of these lakes are in remote locations and often go undetected, while others are much closer to communities, such as Suicide Basin, which is within 5 miles of the state capital and has frequently drained over the past decade.

Time-lapse video shows how a glacier-dammed lake at Mendenhall Glacier drained over two days in early August 2023.

Our study found that, as a whole, glacier-dammed lakes in Alaska have decreased in volume since 1985, while the frequency of outbursts remains unchanged. This suggests a regional decline in the potential hazards from glacier-dammed lakes because less stored water is available, a trend that has been documented for glacier-dammed lakes worldwide.

To better understand this trend, imagine a bathtub. The higher the sides of the tub, the more water it can hold. For a glacier-dammed lake, the glacier acts as a side of the bathtub. Warming air temperatures are causing glaciers to melt and thin, lowering the tub walls and therefore accommodating less water. That reduces the total volume of water available for a potential glacial lake outburst flood.

Smaller lakes, however, have had less significant change in area over time. As the August 2023 event clearly illustrated, even small lakes can have significant effects downstream.

Drone video shows some of the damage after a glacial lake drained into the Mendenhall River near Juneau, Alaska.

Alaskans witnessed a new record of destruction in Juneau from the flood. The water reached nearly 15 feet at the Mendenhall River gauge—3 feet above its previous record.

In summer 2023 alone, Alaskans saw record or near-record flooding from multiple glacier-dammed lakes near populated areas or infrastructure, such as Suicide Basin, near Juneau; Skilak Glacier-Dammed Lake, which affects the Kenai River; and Snow Lake, which impacts the Snow River. These lakes have remained about the same volume but have produced some larger floods in recent years.

One possible explanation is that with a thinner and weaker ice dam, the water can drain much more quickly, though further research is needed to understand the mechanics. Regardless, it’s a reminder that these lakes and events are unpredictable.

How will rising temperatures affect these lakes?

Glacier loss in Alaska is accelerating as temperatures rise. Due to the large volume of glaciers and the many intersecting valleys filled with ice in Alaska, there is a high probability that new lakes will develop as side valleys deglaciate, introducing new potential hazards.

Many of these lakes are likely to develop in remote locations, and their presence may only be noticed in satellite images that reveal changes over time.

Given the abundance of glacial lakes and their potential threat to human lives, early warning and monitoring systems are worryingly sparse. Efforts are underway, such as those in the Himalayas and Chile, but further research is needed to develop reliable, low-cost monitoring systems and to improve our understanding of these evolving hazards.

More information:
B. Rick et al, Unchanged frequency and decreasing magnitude of outbursts from ice-dammed lakes in Alaska, Nature Communications (2023). DOI: 10.1038/s41467-023-41794-6

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Alaska

Short-lived cold snap, with another warming trend this weekend

Published

5 hours ago

January 14, 2025

Press Room

Short-lived cold snap, with another warming trend this weekend

ANCHORAGE, Alaska (KTUU) – Temperatures across the state are cooling off, as our strong low from the weekend moves into the Chukchi Sea. This will set up for colder air to spread across the state this week, as another short-lived cold snap is expected. While some light snow is possible for the Interior, areas of the Slope and Western Alaska, Southcentral will stay on the drier side until the night. Meanwhile, Southeast will continue to hold onto moderate rain with gusty conditions.

SOUTHCENTRAL:

Temperatures this morning are 10 to 20 degrees colder than yesterday, as colder air has settled back into Southcentral. Clear skies and calm winds are evident this morning for parts of the region, with light snow falling through the Copper River Basin. We’ll see fairly quiet conditions today, outside of Kodiak which will see increasing snow and rain into the afternoon and evening hours. This comes as our next area of low pressure moves up the Alaska Peninsula.

We’ll see light snow spreading north across the Kenai overnight into Wednesday, with light snow expected through Prince William Sound. Several inches are likely through the Kenai and Chugach Mountains, with the pass expected to see a couple of inches of accumulation. Western parts of the Kenai will see the potential for a few inches, while inland areas of Southcentral largely stay dry. If Anchorage and surrounding locations see any accumulation, it’ll amount to less than half an inch.

As snow tapers off Wednesday, we’ll see the return to colder and drier conditions into Thursday. Thursday may be the coldest day this week across the region, before another warming trend carries us into next week. Right now holding with snow through early next week, but areas of wintry mix are possible as highs warm above freezing.

SOUTHEAST:

The winter storm warning for Skagway and higher elevations expired at 6am this morning. While some light snow showers are still possible, little accumulation will occur the rest of the day. Scattered to periodic showers are occurring elsewhere across Southeast today, with less than half an inch of rainfall through the day. Any moisture available into the evening will see a transition to some wintry mix or snow into Wednesday morning. However, the better chance will come from another low lifting north into the panhandle. Any snow and wintry mix we see for Wednesday will primarily stay confined to the central and southern panhandle. We’ll see much cooler weather taking hold this week for Southeast.

INTERIOR:

Some areas of light snow are possible this morning, with less than half an inch to be expected. While temperatures are still warm for much of the Interior, highs will steadily fall throughout the day. Many areas will see lows bottom out near or below zero by tomorrow morning. We’ll see high pressure keep things dry and sunny through the next couple of days, with the coldest stretch of weather from Wednesday morning into Thursday morning. Much like the rest of the state will experience, a warming trend arrives this weekend. We’ll see the return to highs in the 20s, with some snow in the forecast. Be prepared for some gusty conditions through the Alaska Range by the close of this week.

SLOPE/WESTERN ALASKA:

Areas of light snow and blowing winds will continue to impact the Slope, with a winter weather advisory remaining in place for the Central Brooks Range and the Beaufort Sea Coast. Both locations will see up to 1 inch of snow and gusty winds up to 35 mph. While the winter weather advisory will expire for the Central Brooks Range this afternoon, the Beaufort Sea Coast will see the alert continue into Tuesday evening. Snow and blowing snow will be the primary impact today, with a return to colder weather through the rest of this week, this comes as high pressure settles into the area.

The storm responsible for the damaging winds for Southcentral over the weekend, has pushed north into the Chukchi Sea. We’ll still see some light snow accumulations for Western Alaska, with 1 to 3 inches expected. Some fo the heaviest snow will fall across the Seward Peninsula and the Western Brooks Range.

An area of low pressure in the Bering Sea will keep gusty winds and snow in the forecast for Gambell/St. Lawrence. Be prepared for heavy snow at times and areas of reduced visibility. Overall, colder weather will settle into Western Alaska, with the possibility of morning fog in the valleys over the next few mornings.

ALEUTIANS:

Some light areas of snow will occur for the Pribilof Islands and into parts of the Alaska Peninsula today, as a weak low moves up the Peninsula. This will be the main focus for snow into Wednesday for Southcentral. This low will bring heavy precipitation and gusty winds for the Eastern Aleutians and the Alaska Peninsula. Looking ahead through the rest of the week, we can expect to see more a ridge beginning to build into the region. This ridge will slowly shift east, keeping several upper level disturbances traversing the Aleutians. Temperatures will remain fairly warm in the 30s and 40s.

OUTLOOK AHEAD:

Model consensus continues to agree on another warming trend heading our way into next week. This stretch of warmth will likely lead to many spots cementing themselves within the top warmest January’s on record. While we’ll spend the rest of this week on the colder side, highs steadily climb this weekend into next week. We’ll see highs in Southcentral climbing back above freezing, with areas of the Interior climbing back into the 20s.

Have a safe and wonderful Tuesday!

See a spelling or grammar error? Report it to web@ktuu.com

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Alaska

Anchorage, Alaska hit by hurricane-force winds, structures damaged across city

Published

13 hours ago

January 14, 2025

Press Room

Anchorage, Alaska hit by hurricane-force winds, structures damaged across city

Associated Press

Hurricane-force winds cause widespread damage in Alaska’s largest city

Thousands of residents across Alaska’s largest city were still without power Monday, a day after a powerful storm brought hurricane-force winds that downed power lines, damaged trees, forced more than a dozen planes to divert, and caused a pedestrian bridge over a highway to partially collapse. A 132-mph (212-kph) wind gust was recorded at a mountain weather station south of Anchorage. A large low-pressure system in the Bering Sea brought the high winds, moisture and warmer than average temperatures — in the low 40s Fahrenheit (slightly over 4.4 degrees Celsius) — to Anchorage on Sunday, said National Weather Service meteorologist Tracen Knopp.

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Alaska

Thousands without power in Alaska after hurricane-force winds hit

Published

20 hours ago

January 13, 2025

Press Room

Thousands without power in Alaska after hurricane-force winds hit

Thousands of residents in Anchorage, Alaska, faced widespread devastation and power outages Monday after hurricane-strength winds battered the city on Sunday.

Why It Matters

This latest incident comes as power outages across the United States have become a growing concern as extreme weather events increase in frequency and intensity, often leaving millions of Americans in precarious situations. Hurricanes, wildfires, ice storms and heatwaves have caused widespread disruptions, highlighting the vulnerability of aging electrical grids to severe conditions.

Prolonged outages not only hinder daily life by cutting off access to heating, cooling and essential appliances but also pose significant risks to public health, particularly for the elderly and those with medical conditions reliant on powered devices.

What To Know

The Anchorage storm, which began Sunday, delivered gusts reaching 132 mph at a mountain weather station south of the city, according to the National Weather Service. Within Anchorage itself, winds hit 75 mph, toppling trees, scattering debris and partially collapsing a pedestrian bridge over the Seward Highway, the city’s main southern thoroughfare.

At the height of the storm, 17,500 customers were without power, according to Julie Hasquet, spokesperson for Chugach Electric Association. As of Monday, roughly 5,700 homes remained offline with full restoration expected to stretch into Tuesday.

Dick Powell cuts a birch tree blocking Steeple Drive in South Anchorage during the windstorm on January 12, 2025. A powerful storm in Anchorage left thousands without power.

Bill Roth/Anchorage Daily News/ AP

The storm’s chaos wasn’t limited to neighborhoods. Anchorage’s airport, a vital hub for passenger and cargo traffic, saw significant disruptions. Winds forced 13 aircraft, including a U.S. Air Force plane, to divert to Fairbanks, which sits nearly 360 miles away.

On the ground, emergency crews scrambled to clear bridge debris, which had obstructed traffic on the highway. However, no injuries were reported when the side fencing and roof of the bridge fell onto the four-lane divided highway on Sunday. Traffic was rerouted and crews removed the debris.

Alaska Department of Transportation spokesperson Shannon McCarthy pointed to the winds as the probable cause of the bridge failure. However, structural engineers are investigating to determine the full extent of the damage.

Meanwhile, the storm marked a rare convergence of high winds, warmer-than-average temperatures and moisture from a low-pressure system in the Bering Sea, said National Weather Service meteorologist Tracen Knopp. Anchorage saw temperatures in the low 40s Fahrenheit, unusual for mid-winter.

What People Are Saying

Alaska Department of Transportation spokesperson Shannon McCarthy said: “The winds were the leading cause, but our bridge engineers will be out there today and may be able give us a more comprehensive analysis of what happened.”

Julie Hasquet, a spokesperson for Chugach Electric Association, said some customers may not have power back on until Tuesday. She said: “When our crews show up for repairs, they don’t know what they’re going to find.”

Resident Steven Wood told Anchorage television station KTUU about how he and his family was watching the winds blow things around the yard Sunday morning when they saw their neighbor’s roof partially blow off and head right toward them.

“All of a sudden, I see the roof start to peel off, and all I can yell is, ‘Incoming! Everybody run!’” Wood said.