Today’s emissions choices could limit Antarctic ice loss and sea-level rise for coastal communities

Cutting greenhouse gas emissions now may limit how much ice Antarctica loses this century and reduce the sea-level rise facing coastal communities, according to findings from a new study.

The research, reported in Nature Geoscience by an international team of scientists, including Rutgers climate scientist Robert Kopp, provides evidence that decisions about emissions today can influence how much water Antarctica adds to the oceans by 2100.

The team found at least an 89% probability that the most ambitious low-emission goal consistent with the objectives of the Paris Agreement, an international treaty on climate change adopted in 2015, would result in less Antarctic ice loss by the end of the century than a scenario with very high emissions.

“Coastal communities need to prepare for rising seas, and the amount of rise they will have to manage still depends on the choices we make today,” said Kopp, a distinguished professor with the Department of Earth and Planetary Sciences in the Rutgers School of Arts and Sciences and an author of the study. “Cutting emissions now can limit the risks facing future generations. Better projections can help communities decide how to protect homes, roads and other essential infrastructure.”

Warming can weaken Antarctica’s ice brakes

The study shows how higher emissions could trigger a series of changes that speed up the movement of Antarctic ice into the ocean.

“What we still control is how much, and whether we set off the chain reaction that takes us to the high end,” said Yucheng Lin, an assistant professor at the City University of Hong Kong and a former postdoctoral associate in the Department of Earth and Planetary Sciences. “Every ton of greenhouse gas we add makes it worse, and the effect lasts for hundreds of years.”

The opportunity to limit future damage comes with a sobering finding: Antarctica is very likely to lose ice overall through the end of this century even if nations sharply cut emissions. The researchers estimated that probability to be at least 92% under the most ambitious scenario, in which the world cuts carbon dioxide emissions to net zero around 2050.

Antarctica holds the world’s largest store of frozen freshwater. Its enormous ice sheet rests on land, and when that ice moves into the ocean, it adds water and raises sea levels. Floating shelves of ice along the continent’s edges help restrain the glaciers behind them, acting somewhat like brakes.

The researchers examined how those brakes could weaken as the climate warms. Warmer ocean water melts ice shelves from below, thinning them, Lin said. As the shelves weaken or break apart, glaciers can flow more quickly into the sea. How easily the ice slides over the ground beneath it also influences the pace of that loss.

Under certain combinations of conditions, these changes can reinforce one another and accelerate the movement of ice into the ocean, he said.

High-end losses could add 10 inches

To explore that possibility, the team examined combinations of assumptions producing the highest projected losses while remaining consistent with satellite observations. Under very high emissions, this selected high-end analysis produced a middle estimate of about 6 inches (15 centimeters) of sea-level rise from Antarctica by 2100, with an upper estimate of about 10 inches (25 centimeters).

Those figures describe a possible high-impact outcome, rather than the study’s central forecast. The 10-inch (25-centimeter) estimate isn’t an absolute ceiling. It also represents Antarctica’s contribution alone, excluding water from melting Greenland ice and mountain glaciers as well as the expansion of seawater as it warms.

The researchers found that additional snowfall in a warmer climate is very unlikely to replace all the ice Antarctica loses. Its response to climate change unfolds slowly, meaning the consequences of today’s emissions can persist long after they enter the atmosphere.

Machine learning narrows the projections

Reaching clearer conclusions about Antarctica has long challenged researchers, Kopp said. Computer models must connect global warming with changes in the surrounding ocean and atmosphere, then calculate how the ice responds. Different assumptions at each step can produce widely different answers.

Running enough detailed simulations to explore all those possibilities would require enormous computing resources. The team instead used machine learning, a subset of artificial intelligence, to analyze an existing collection of ice-sheet simulations, allowing researchers to rapidly explore combinations of assumptions.

The machine-learning tool learned the relationships between the assumptions in those simulations and their results. It could then estimate outcomes much faster than the original models, allowing the researchers to explore possibilities that would otherwise have been too costly to test in detail.

They checked the results against satellite measurements of Antarctic ice loss from 2002 to 2021, giving greater weight to combinations that better matched observations. That comparison narrowed the range of projected outcomes and increased confidence that Antarctica would lose ice overall this century.

Key uncertainties remain in ice-sheet processes

The analysis also helped identify where additional research could make the greatest difference. Three major sources of uncertainty involve how warming ocean water melts ice shelves, how ice slides over bedrock and how the ocean and atmosphere warm around Antarctica.

“We can’t afford to study every detail of an ice-sheet model, so we have to know which details matter,” Lin said.

Better measurements of those processes could sharpen projections and help communities make decisions about coastal development and protection, he said.

But the researchers said their analysis cannot account for processes missing from the original simulations, including some interactions among ice, ocean and atmosphere and changes in water flowing beneath the ice sheet.

Those gaps leave open the possibility of outcomes beyond the study’s projections.

“We still have questions about how quickly Antarctica will change, but communities are making decisions now about buildings and infrastructure that will last for decades,” Kopp said. “Giving them a clearer picture of the risks can help them prepare.”

Who’s behind this story?

Swati Mestri

Swati Mestri holds a bachelor’s degree in Electronics Engineering and has worked as a content editor since 2019. She has experience editing research documents across technology, health care, and materials science, and has a particular interest in technology and space.

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Robert Egan

Bachelor’s in mathematical biology, Master’s in creative writing. Well-traveled with unique perspectives on science and language.

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