Melting of Juneau Icefield Accelerates Toward Potentially Irreversible Tipping Point
Melting of Juneau Icefield Accelerates Toward Potentially Irreversible Tipping Point

Melting of Juneau Icefield Accelerates Toward Potentially Irreversible Tipping Point

The melting of the Juneau Icefield, one of North America’s largest icefields located near Juneau, Alaska, is accelerating and approaching a potentially irreversible tipping point. This conclusion comes from recent research published in Nature Communications, based on observations and measurements taken by researchers during the summer of 2022.

The icefield comprises around 40 large interconnected glaciers and numerous smaller ones. The study reveals a climate feedback loop where rising temperatures result in less summer snow, exposing more ice to melt, which in turn leads to even less snow retention.

Juneau’s glaciers, like many in Alaska, are top-heavy with significant ice and snow at high altitudes. Historically, this sustained the glaciers’ lower tongues. However, as the end-of-summer snowline rises, more of the upper glacier areas are exposed to melting, accelerating the loss of ice.

Melting of Juneau Icefield Accelerates Toward Potentially Irreversible Tipping Point
Melting of Juneau Icefield Accelerates Toward Potentially Irreversible Tipping Point

Each summer, the glaciers now melt faster, causing the icefield to thin and the plateau to lower. Once a critical threshold is reached, these feedback mechanisms can perpetuate the loss of snow and ice, continuing even if global warming halts.

The research utilized satellite images, photographs, and historical rock formations to measure the icefield’s ice loss from the end of the Little Ice Age (around 250 years ago) to today. It was found that the glaciers began shrinking after the Little Ice Age ended around 1770, with a significant acceleration in ice loss since 1979, and a further doubling of this rate around 2010.

Between 2015 and 2019, the glaciers shrank five times faster than from 1979 to 1990. As the snow cover decreases and the summer melt season lengthens, the ice field darkens, absorbing more solar energy and exacerbating the melting process.

As the icefield plateau thins, higher altitude ice and snow reserves diminish, lowering the plateau’s surface and making stabilization or recovery increasingly difficult. This results in warmer air at lower elevations driving further melt, pushing the icefield towards an irreversible tipping point.

The complexity of these processes poses challenges in predicting future glacier behavior, highlighting the importance of long-term data in understanding glacier dynamics and tipping points.

To reconstruct the glacier’s historical behavior beyond the past 50 years of satellite records, researchers mapped moraine ridges and other geological features, spent time on the icefield and in the surrounding rainforest, and utilized aerial photographs from the 1940s and 1970s.

This work, though challenging, is crucial as glaciers worldwide are melting rapidly, with thinning rates doubling over the past two decades. Understanding the feedback mechanisms driving accelerated glacier melt is essential for making accurate predictions of future changes in such critical regions.

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