JUNEAU, Alaska (KTUU/Gray News) – A new study highlighted the shrinking Juneau Icefield in southeast Alaska as an example of how Earth’s glaciers are nearing an “irreversible” tipping point for melting.

“If there are processes in Alaska that are accelerating the melt, they may be relevant to other parts of the world as well,” said Bethan Davies, the paper’s lead author, about the global significance of studying Alaska’s glaciers.

The Juneau Icefield is home to dozens of large glaciers — including the popular Mendenhall Glacier in Juneau — and many more smaller ones. By 2100, many of these glaciers are at risk of disappearing. Experts say if the Earth continues to warm, nearly 70% of the world’s roughly 200,000 glaciers will dry up by the end of the century.

“When we look at the last 10 years worth of glacier change over all of Alaska, we are seeing a real uptick [in melting] that’s faster than in some other parts of the world,” said Davies, who is also the glaciologist and senior lecturer in Physical Geography at Newcastle University. “And it’s very interesting to ask why that’s happening and why these glaciers are not only accelerating but also how they might behave in the future.”

The study, published this month in the journal Nature Communications, showed from the years 1770 to 1979, ice volume loss remained fairly consistent, at roughly 1 kilometer cubed per year.

From 1979 to 2010, there was slightly more melting, but the loss at 3.1 kilometers cubed per year remained fairly consistent.

However, from 2010 through 2020, the Juneau Icefield’s melting rate doubled to almost 6 kilometers cubed per year. That’s the equivalent of 2.4 million Olympic-size swimming pools melting off of the icefield each year.

That icefield thinning led to the formation of Suicide Basin, which saw its first glacial lake outburst in 2011.

“This can only happen because that whole glacier system, as was pointed out in the study, is thinning,” Alaska climate specialist Rick Thoman said. “It’s thinning a lot and it’s thinning rapidly.”

This water release will happen every year, with some years seeing the potential for historic flooding. But as the glacier keeps thinning, Suicide Basin will reach a point where a glacial lake outburst will no longer form.

However, Thoman says newer basins can form.

“It’s entirely possible given the complex nature of the Juneau Icefield, we might see a new glacier dammed lake form in some other part of the system,” Thoman said. “But as last year showed, when there’s a lot of water in these glacier-dammed lakes, and when they release all the water, we get the devastation that we saw last August.”

All of that melting eventually gets dumped into the ocean. According to Davies, glacier melt accounts for about a quarter of the total sea level rise. The remainder comes from the Antarctic ice, Greenland ice sheet and thermal expansion of the ocean.

“A part of the world that’s contributing the most to sea level rise is Alaska,” Davies said. “The Alaskan glaciers are really important in the global context because there’s a large volume of ice.”

She said this study isn’t relevant to just Alaska, because the same processes occurring here in Alaska may be relevant to other parts of the world.

“What’s happening is that the temperature is gradually increasing,” Davies said. “But as that happens, there’s a series of processes that are accelerating melt or amplifying melt.”

One of those processes is the snow line, which continues to dwindle during the summer months.

Davies said the end of summer snow line is actually reaching the top of the low slope, plateau area. This is historically lower than in previous decades when snow was covering the plateau all year round.

Another challenge is that as more of the plateau is exposed, it’s darkening the mountain as more rocks are exposed from the melting ice.

“When we remove the snow, we are reflecting less of the sun’s energy back into space,” Davies said. “Because snow is very bright and white and reflective. So what we’re doing when we raise that end of summer snow line is we expose much more of the glacier to that darker color so it can absorb more of the sun’s energy.”

Thoman said with the summer snow line dwindling, the atmosphere’s snow level rises with atmospheric rivers aiding in transporting warmer air.

“To hold as much water in the air as those atmospheric rivers bring, the air has to be warm,” Thoman said. “If it was colder it wouldn’t be able to hold as much moisture.”

Thoman said it’s both the high precipitation events and warm airmass that are helping to drive snow levels very high into the atmosphere, which can and do occur all winter long, some years.

Climatologically speaking, Juneau temperatures have warmed a few degrees over the last several decades. And while that may not seem like much, when temperatures are hovering around freezing, that can still have large impacts.

“We’re right around that freezing level,” Thoman said. “So an increase of 31 to 33 [degrees], say, as an average temperature is much more significant when you’re talking about snow and ice than say an increase of 40 to 43.”

Davies doesn’t think the Earth’s ice has passed the point of irreversible change but does argue that such a threshold could occur by the end of this century.

And if the feedback loop of melting continues, the icefield will eventually reach a point where it will be difficult to recover from.

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