Sign In
International
Media release
From:
Accelerating glacier loss on the Juneau Icefield
The Juneau Icefield, Alaska, lost ice at an accelerated rate after 2005, relative to the past 250 years, according to a study in Nature Communications. Rates of area shrinkage were found to be 5 times faster from 2015–2019 than from 1979–1990. The authors suggest that a continuation of this trend could push glacial retreat beyond the point of possible recovery.
Climate-driven ice loss from glaciers and icefields has been shown to contribute to rising sea-levels, with Alaska expected to remain the largest regional contributor to this effect up to the year 2100. Alaskan glaciers are particularly vulnerable to changes in the climate because they are often top-heavy (with more area at a higher altitude) and located on plateaus. In addition, these factors make Alaskan glaciers more prone to threshold behaviour, in which exceeding a tipping point could result in an irreversible recession. Longer-term records of Alaskan glacier change are needed to understand how climate change impacts these glaciers.
Bethan Davies and colleagues used historical records, aerial photographs, 3D terrain maps, and satellite imagery to reconstruct Juneau Icefield glacier behaviour over the past 250 years. They observed steady glacier volume loss at a rate of approximately 0.65 km3 per year between 1770–1979. This rate accelerated to approximately 3 km3 per year between 1970–2010 and then nearly doubled to 5.9 km3 per year between 2010–2020. This ice loss acceleration between 2010–2020 was accompanied by a glacial thinning rate 1.9 times higher than that from 1979–2000 and increased icefield fragmentation. The authors suggest that this reduction in icefield accumulation area is contributing to a positive feedback loop, wherein surfaces such as darker rock are exposed, reducing solar reflectivity, and further contributing to the recession.
The findings suggest that a physical mechanism could be contributing to this icefield moving towards an irreversible tipping point in glacier recession. This greater understanding of Alaskan glacier ice loss mechanisms could improve projections of near-future sea level rise, the authors suggest.
