East Antarctic Ice Sheet Could Survive 10-Degree Global Warming... For a Surprising Reason [Reading Science]

IBS Confirms Protective Effects of Snowfall and Clouds in 100,000-Year Climate Simulations
Antarctic Ice Sheet Loss Falls from 70% to 20%... West Antarctica Still Faces Sea-Level Rise Risk

A study has found that a vast mass of ice in East Antarctica could survive largely intact even if the global average temperature rises more than 10 degrees Celsius above preindustrial levels.

This is because the additional water vapor produced by warming brings more snowfall to Antarctica's interior, while increased cloud cover blocks sunlight and slows the rate of ice melt. The scale of ice loss across the Antarctic ice sheet also varied considerably depending on whether these atmospheric changes were taken into account. The findings point to a paradox: global warming melts ice sheets while also creating conditions that help preserve ice in some regions.

The Dibble Ice Shelf in East Antarctica. Researchers at the Institute for Basic Science (IBS) found through climate simulations spanning 100,000 years that increased snowfall and cloud cover driven by global warming could slow the loss of the East Antarctic Ice Sheet. Provided by NASA/JPL-Caltech/UC Irvine.

The Institute for Basic Science (IBS) said on Oct. 30 that a research team led by Axel Timmermann, director of the IBS Center for Climate Physics and a distinguished professor at Pusan National University, confirmed these findings through long-term simulations combining a global climate model with an ice sheet model. The results were published at 7 p.m. that day in the international journal Nature Climate Change.

Previous ice sheet studies applied preset atmospheric and ocean conditions to ice sheet models, making it difficult to fully account for the ways climate and ice sheets influence each other. The research team simulated changes in the climate and the Greenland and Antarctic ice sheets over 100,000 years under varying atmospheric carbon dioxide concentrations. The simulations also calculated how changes in the ice sheets, in turn, affect the climate.

The analysis showed that ice sheet changes due to warming differed substantially by region. When the global average temperature remained more than 2 degrees Celsius above preindustrial levels, the West Antarctic Ice Sheet, much of which rests on bedrock below sea level, experienced substantial ice loss over the long term. The Greenland Ice Sheet also gradually shrank as the climate warmed, and the simulations showed that it could disappear entirely if temperatures rose by more than about 6 degrees Celsius.

By contrast, the East Antarctic Ice Sheet, most of which sits on land, remained relatively stable even when warming exceeded 10 degrees Celsius. This means that continued intense warming does not necessarily lead to the rapid collapse of the East Antarctic Ice Sheet.

More Snowfall and Cloud Cover Blocking Sunlight Slow East Antarctic Ice Loss

Changes in atmospheric circulation were behind the East Antarctic Ice Sheet's greater-than-expected stability. As temperatures rise, the atmosphere can hold more water vapor. Changes in atmospheric circulation in the Southern Hemisphere also increased the amount of water vapor moving toward Antarctica. This vapor fell as snow in the high-altitude interior of East Antarctica, increasing the amount of new ice accumulating on the ice sheet.

Long-term changes in the Greenland and Antarctic ice sheets due to global warming. Circles represent the Antarctic ice sheet, while squares represent the Greenland ice sheet; darker shades of red indicate greater temperature increases. The size of each symbol distinguishes the final state of the simulation. The inset map shows that under high carbon dioxide conditions, most of the East Antarctic Ice Sheet remains, while most of the West Antarctic Ice Sheet disappears. Provided by the research team.

Increased cloud cover also helped curb ice loss. Clouds reduced the sunlight reaching the ice sheet's surface, moderating ice melt. The effects of increased snowfall, which helped ice accumulate, and clouds, which reduced the surface's absorption of energy, worked together.

These effects were most pronounced under the strongest warming conditions. In simulations that did not account for changes in precipitation and solar radiation, the total volume of the Antarctic ice sheets fell by about 70%. In contrast, in a coupled climate-ice sheet model that accounted for warming-driven changes in snowfall and solar radiation, the decline was limited to about 20%.

These figures are results from long-term simulations under different conditions, not observed rates of ice loss in Antarctica. However, they show that ice sheet changes are not determined by rising temperatures alone, and that long-term projections can vary considerably depending on how fully interactions between the atmosphere and ice sheets are represented.

West Antarctic Ice Sheet Remains at Risk as Concerns Over Sea-Level Rise Persist

This does not mean Antarctica is unaffected by warming. Much of the West Antarctic Ice Sheet rests on bedrock below sea level, making it vulnerable to warmer ocean waters. The simulations also showed substantial ice loss in West Antarctica if warming continues. The research team said the risk of sea-level rise should not be underestimated, as ice sheet retreat has also been observed in some parts of East Antarctica.

Yoon Kyungsook, research fellow at the IBS Center for Climate Physics (left, first and corresponding author), and Axel Timmermann, director of the IBS Center for Climate Physics (co-author). Provided by IBS.

The study also has limitations. The coupled model has relatively low spatial resolution, making it difficult to fully reproduce changes beneath floating ice shelves or local processes around the edges of ice sheets. Further research using high-resolution simulations is needed to more accurately predict how these processes affect actual sea-level rise.

Yun Kyungsook, a research fellow at the IBS Center for Climate Physics and the study's first and corresponding author, said, "Our findings show that the long-term future of ice sheets cannot be understood through temperature alone. Changes in snowfall, clouds, wind and ocean temperatures all interact with the changing surfaces of ice sheets."

Axel Timmermann, director of the IBS Center for Climate Physics and a co-author of the study, emphasized, "These findings show why interactions between climate and ice sheets must be considered together when predicting long-term climate instability and sea-level rise. Simplified climate conditions alone can miss regional processes that have a major impact on whether ice sheets retreat, remain stable or disappear."

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