Alaska’s Juneau Icefield Is Melting at an ‘Incredibly Worrying’ 50,000 Gallons per Second, Researchers Find

Between 2010 and 2020, the icefield lost 1.4 cubic miles of ice each year, according to a new studyGilkey Trench, in the Juneau Icefield

The Juneau Icefield, which extends for some 1,500 square miles from northwest British Columbia, Canada, into southeast Alaska, is composed of more than 1,000 glaciers, and it has been for millennia. But now, perhaps more than ever, the landscape’s longevity is in question.

A new study published Tuesday in the journal Nature Communications highlights the icefield’s unprecedented and accelerating melting. Its snow-covered area is shrinking 4.6 times faster than it was prior to the 1980s, researchers say—and between 2010 and 2020, it lost roughly 1.4 cubic miles of ice per year. Now, meltwater is flowing from the icefield at 50,000 gallons per second, reports Seth Borenstein of the Associated Press (AP).Amid human-caused climate change, driven largely by carbon dioxide emissions from burning fossil fuels, the Arctic is warming nearly four times faster than anywhere else in the world. Alaska itself has seen the average temperature increase 2.6 degrees Fahrenheit since 1980.

“If we reduce carbon, then we have more hope of retaining these wonderful ice masses,” Bethan Davies, a glaciologist at Newcastle University and lead author of the study, tells the New York Times Raymond Zhong. “The more carbon we put in, the more we risk irreversible, complete removal of them.”

A map shows the location of the Juneau Icefield, along the U.S.-Canadian border.
The Juneau Icefield straddles the border between Alaska and Canada. USGS

Since the late 18th century, which saw a period of global cooling and glacial formation known as the Little Ice Age, one quarter of the icefield’s total volume has melted. But the rate of this melting has rapidly increased in recent years, a trend that is “incredibly worrying,” Davies says in a statement from Newcastle University.

Between 1948 and 2005, only four glaciers on the icefield melted completely. But between 2005 and 2019, another 64 melted away—including the Antler glacier, reports the AP, which once stretched 3.5 miles long.

This acceleration might be aided by a few feedback loops in which melting leads to more melting. Thinner ice, for instance, warms more easily. And dark-colored rocks revealed by melting glaciers can retain more heat than white snow does, prompting even more snow to liquify.

“The feedback processes this sets in motion is likely to prevent future glacier regrowth, potentially pushing glaciers beyond a tipping point into irreversible recession,” Davies says in the statement.

A map shows the Juneau Icefield's glacial area change from the Little Ice Age to 2019
A map shows the Juneau Icefield's glacial area change from the Little Ice Age to 2019. Davies et al., Nature Communications, 2024

To complete their study of how the icefield is changing, the team analyzed historical and contemporary aerial photographs, past records of glaciers, satellite imagery and geomorphological mapping.

“Putting together this archive of photographs, collected 70 and 50 years ago, was a little like doing the world’s hardest jigsaw puzzle,” Robert McNabb, an environmental scientist at Ulster University in Northern Ireland and a co-author of the study, says in the statement. “But the quality of the imagery meant we were able to reconstruct the icefield elevation in the pre-satellite era for the first time.”

Researchers walk near crevasses on the Juneau Icefield in northern British Columbia.
Researchers walk near crevasses on the Juneau Icefield in northern British Columbia, Canada. NSIDC under CC BY 2.0

Some of the differences revealed in the research are also visible to the naked eye. Mauri Pelto, an environmental scientist at Nichols College and a co-author of the study, first arrived on the icefield more than four decades ago—as a competitive skier.“In 1981, it wasn’t too hard to get on and off the glaciers,” Pelto tells the Associated Press. “You just hike up and you could ski to the bottom or hike right off the end of these glaciers.” Now, however, lakes have formed on the edges of glaciers from melted snow, and new crevasses could pose hazards to skiers.

Between 1770 and 2019, every single glacier in the icefield receded, the team found, giving rise to at least 50 new lakes.

Research published last year in the journal Science projects that even if global temperature rise is kept below the 1.5 degree Celsius warming threshold compared to pre-industrial temperatures, roughly 104,000 glaciers—or about half the world’s total—could disappear by the end of the century

No comments:

Powered by Blogger.