Alaska’s Glaciers Near Irreversible Tipping Point, Study Finds

A recent study published in Nature Communications reveals that the Juneau Icefield, a major icefield spanning Alaska in the United States and British Columbia in Canada, is approaching an irreversible tipping point faster than previously predicted. The glaciers in this region have been receding rapidly since 2005.

Historical Context

The Juneau Icefield, which consisted of 1,050 glaciers covering 3,816.3 square kilometers in 2019, has experienced significant shrinkage. The rate of glacier shrinkage from 2015 to 2019 was five times faster than between 1948 and 1979. This alarming trend is part of a broader pattern of glacial retreat that has been ongoing since the end of the Little Ice Age, a period of cooling that lasted from 1303 to 1850.

Key Findings

• Sea Level Rise Contribution: Alaska’s glaciers are a major contributor to global sea level rise, accounting for about 25% of global glacier ice loss. The region loses approximately 66.7 billion tonnes of ice annually, which could raise global sea levels by 46.4 millimeters if melted entirely.
• Acceleration of Glacier Mass Loss: The study highlights that glacier mass loss in Alaska is accelerating. Researchers lack a long-term timeframe to fully understand this trend, prompting further studies to predict future responses to climate change.
• Historical Glacier Changes: From the Little Ice Age to 2020, the Juneau Icefield has shrunk by about 30%. Between 1770 and 2019, 108 glaciers disappeared, and all remaining glaciers have receded compared to their positions during the Little Ice Age.
• Temperature Rise and PDO Influence: The temperature at Juneau Airport rose by 1.39°C from 1941 to 2020, with a significant shift in the 1970s linked to the Pacific Decadal Oscillation (PDO). The PDO, a long-term ocean fluctuation, brought increased precipitation and warmer temperatures to the region.
• Glacier Volume Loss Rates: Glacier volume loss increased from 1.0 cubic kilometers per year (1948-1979) to 5.9 cubic kilometers per year (2010-2020). The rising Equilibrium Line Altitude (ELA), where snow and ice accumulation balance out with loss, is a significant factor in this accelerated melt.

Future Research

The research team aims to examine longer-term records of icefield changes, especially during previous periods of rapid climate change, such as the last glacial-interglacial transition 19,000 to 11,000 years ago.

Summary in Bullet Points

• Study Focus: Juneau Icefield in Alaska and British Columbia.
• Glacier Shrinkage: Rapid since 2005, five times faster from 2015-2019 compared to 1948-1979.
• Sea Level Rise: Alaska’s glaciers contribute 25% of global glacier ice loss.
• Historical Context: Shrinkage since the Little Ice Age (1303-1850).
• Temperature Rise: 1.39°C increase at Juneau Airport from 1941-2020.
• PDO Influence: Positive PDO values since 1976 increased precipitation and temperatures.
• Glacier Volume Loss: Increased from 1.0 km³/year (1948-1979) to 5.9 km³/year (2010-2020).
• Equilibrium Line Altitude (ELA): Rising ELA accelerates icefield mass loss.
• Future Research: Focus on longer-term records of icefield changes during past climate transitions.

This comprehensive understanding of glacier dynamics is crucial for students preparing for competitive exams, as it integrates historical context with current scientific findings on climate change and its impacts.