Juneau Icefield is one of North America’s largest, home to swathes of glaciers – but, according to new research, those glaciers are melting at a dramatically increased rate and the loss seen could reach an “irreversible” tipping point far earlier than previously thought.
An international team of researchers analyzed records of the 3,885-square kilometer (1,500-square mile) icefield, all the way back from 1770 – a time when the planet underwent the “Little Ice Age” – through to 2020, looking at how the volume of the icefield had changed over that time.
“Putting together this archive of photographs, collected 70 and 50 years ago, was a little like doing the world's hardest jigsaw puzzle but the quality of the imagery meant we were able to reconstruct the icefield elevation in the pre-satellite era for the first time,” said study author Dr Robert McNabb in a statement.
Combining these photos with historical inventory records, mapping, and satellite imagery, the team found that over the course of those 250 years, just under a quarter of the icefield’s original ice volume was lost.
However, the rate at which that ice was lost hasn’t always stayed the same. While glacier volume loss was relatively stable between 1770 to 1979, it began ramping up in the late 20th century and sharply accelerated between 2010 and 2020, with the rate of ice loss doubling in those 10 years.
The result of all that loss is the disappearance of 108 glaciers since 1770 and for those that were still there when they were last mapped in 2019 – a total 1,050 – every single one had receded over 250 years.
“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,” said study lead Dr Bethan Davies, who attributed the increase to climate change.
“Alaskan icefields – which are predominantly flat, plateau icefields – are particularly vulnerable to accelerated melt as the climate warms since ice loss happens across the whole surface, meaning a much greater area is affected. Additionally, flatter ice caps and icefields cannot retreat to higher elevations and find a new equilibrium.”
With this in mind, what does the future hold for the Juneau Icefield? Prior to this study, estimates had suggested that the rate of ice volume loss wouldn’t increase anymore until after 2070 – but those estimates might now be in need of change. Not just for the Juneau Icefield, the team argues, but for others too, as Davies explained.
“This work has shown that different processes can accelerate melt, which means that current glacier projections may be too small and underestimate glacier melt in the future.”
And the predictions for the Juneau Icefield are concerning in light of the study’s findings. “As glacier thinning on the Juneau plateau continues and ice retreats to lower levels and warmer air, the feedback processes this sets in motion is likely to prevent future glacier regrowth,” said Davies, “potentially pushing glaciers beyond a tipping point into irreversible recession.”
The study is published in Nature Communications.
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