Recent research from Newcastle University in the UK shows that glacier melting on the Juneau Icefield, which lies between Alaska and British Columbia, has sped up a lot since 2010. The study found that from 1770 to 1979, glaciers lost between 0.65 and 1.01 km³ of ice per year. This loss increased to between 3.08 and 3.72 km³ per year from 1979 to 2010. From 2010 to 2020, the rate of ice loss doubled to 5.91 km³ per year.
Published in Nature Communications, the study also reported that glacier shrinkage from 2015 to 2019 was five times faster than from 1948 to 1979. The total ice loss on the Juneau Icefield between 1770 and 2020 was just under a quarter of its original volume, about 315.3 ± 237.5 km³. This rapid ice melt could significantly affect sea levels and the icefield's future stability.
The research team, which included scientists from universities in the UK, US, and Europe, documented a significant rise in glacier fragmentation alongside the increased rate of thinning. They observed a dramatic increase in disconnections, where the lower parts of glaciers become separated from the upper sections. By 2019, 100% of the mapped glaciers had receded compared to their positions in 1770, with 108 glaciers disappearing entirely.
Dr. Bethan Davies, Senior Lecturer at Newcastle University, emphasized that the rapid acceleration in glacier loss across the Juneau Icefield since the early 21st century is particularly concerning. She explained that Alaskan icefields, which are predominantly flat plateau icefields, are especially vulnerable to accelerated melting due to the expansive surface area affected by warming temperatures. Unlike steeper glaciers, these flatter icefields cannot retreat to higher elevations to reach a new equilibrium, making them more susceptible to irreversible recession as they continue to thin and retreat.
The melting of Alaskan icefields is a major contributor to current sea level rise, and the processes observed at Juneau are likely to impact other similar icefields across Alaska, Canada, Greenland, Norway, and other high-Arctic locations. The research suggests that current projections for the Juneau Icefield, which predict a linear ice volume loss until 2040 with acceleration only after 2070, may need to be updated to reflect the more immediate acceleration detailed in this study.
Dr. Davies pointed out that the study demonstrates how different processes can accelerate melt, potentially making current glacier projections too conservative. The team utilized a combination of historical glacier inventory records, 20th-century archival aerial photographs, and satellite imagery, along with geomorphological mapping from fieldwork in 2022, to construct a comprehensive 250-year history of changes.
Dr. Robert McNabb from Ulster University highlighted the importance of long-term archives, such as the one created from thousands of archived aerial photographs. These archives provide valuable insights into the long-term behavior of icefields, offering a detailed understanding of the thresholds for accelerating change, as seen on the Juneau Icefield.
