Juneau's iconic icefield faces an irreversible melting crisis

Juneau's icefield is one of the largest in North America. It contains vast expanses of glaciers. According to new research, these glaciers are melting faster and may soon reach an "irreversible" tipping point.

An international team of scientists analyzed information about the icefield, which covers an area of over 1,500 square miles. Data was reviewed from as far back as 1770, during the "Little Ice Age," up to 2020, and the volume of the glacier over this period was compared.

- 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 Dr. Robert McNabb, the study's author, as quoted by iflscience.com.

By combining photo imagery with historical inventory records, maps, and satellite images, the team found that the ice volume in the icefield dropped by at least 25 percent over 250 years.

However, the rate of ice loss has not always been the same. From 1770 to 1979, the volume loss of ice was stable. It only began to increase at the end of the 20th century, with the most significant acceleration occurring from 2010 to 2020. During this period, the rate of ice loss doubled, resulting in the loss of 108 glaciers since 1770.

- 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 – says Dr. Berthan Davies, the study leader.

- 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, potentially pushing glaciers beyond a tipping point into irreversible recession – adds Davies.