Alaskan glacier melt is accelerating — and the effects could be irreversible: Study

The melt rate of a major Alaskan icefield is accelerating and could reach a point of no return much sooner than previously anticipated, a new study has found.

The thawing of glaciers in the Juneau icefield, which connects Alaska and British Columbia, has surged dramatically since 2010, according to the study, published on Tuesday in Nature Communications.

Across the icefield, rates of glacier shrinkage were five times greater from 2015 to 2019 than they were from 1948 to 1979, the researchers observed. Total ice loss across the entire Juneau field from 1770 to 2020 was equivalent to nearly a quarter of the original ice volume, per the study.

“It’s incredibly worrying that our research found a rapid acceleration since the early 21st century in the rate of glacier loss across the Juneau icefield," lead author Bethan Davies, a senior lecturer at England's Newcastle University, said in a statement. 

The flat, plateau-like structure of most Alaskan icefields — and their large, exposed surface area — makes them "particularly vulnerable to accelerated melt as the climate warms," Davies explained. These types of icefields are also unable to retreat and rebalance at higher elevations, she added.

Instead, the ice shifts to lower levels, where warmer air and the associated feedback processes "prevent future glacier regrowth, potentially pushing glaciers beyond a tipping point into irreversible recession," according to Davies.

To draw their conclusions, Davies and her colleagues — from universities in the U.K., the U.S. and Europe — identified three distinct periods between 1770 and the current day in which icefield volumes underwent tangible changes.

They sharpened their understanding of these eras by combing through historical glacier inventory records, aerial photographs and satellite imagery, while also conducting fieldwork and mapping the area’s geological features.

The researchers described glacier loss as relatively consistent from 1770 to 1979 — with a melt rate of about 0.65 to 1.01 square kilometers per year. But that annual rate increased to 3.08-3.72 square kilometers from 1979 to 2010 and then spiked to 5.91 square kilometers in the following decade.

In addition to observing a surge in glacier thinning rates, the scientists also found evidence of increased glacier fragmentation — or when lower and upper parts of these ice masses separate.

All the Juneau icefield glaciers that the scientists studied receded relative to their position in 1770, while 108 disappeared entirely.

Co-author Robert McNabb, a lecturer in remote sensing at Ulster University in Northern Ireland, likened their work to solving "the world's hardest jigsaw puzzle" with high-quality imagery from the pre-satellite era — while ultimately gaining a valuable window into future climate-driven changes. 

The researchers expressed concern about their findings, with a particular eye on the fact that Alaska contains some of the world's largest plateau icefields. The melting of such massive fields could have major impacts on sea level rise, they warned.

Similar effects, the authors concluded, could also apply to plateau icefields across Alaska, Canada, Greenland, Norway and other high-Arctic locations.

The scientists also suggested that current melt rate projections, which have indicated that ice volume loss would be linear through 2040, might require an update.

"Current glacier projections may be too small and underestimate glacier melt in the future," Davies said.