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Melting of the Antarctic ice sheet due to global warming has long-term, irreversible societal impacts with important implications for people around the world. Spatial patterns of sea level change from ice sheet mass loss vary in cause, and have worldwide impacts.

Despite the importance of understanding global impacts of ice sheet mass loss, imperfect understanding of ice sheet-climate interactions poses challenges for projecting the impacts it has on the world's future climate and sea levels.

Ambarish Karmalkar, an assistant professor in the University of Rhode Island's Department of Geosciences, has partnered with lead author Shaina Sadai and colleagues to better simulate ice sheet-climate interactions and their evolution over the next century. The team their findings in the recent issue of Nature Communications, reporting that sea level and climate projections are significantly different from simulations that lack interactive ice sheets and realistic Antarctic meltwater discharge.

To study the effects of Antarctic ice sheet melting, the team designed an experiment depicting simultaneous interactions between the ice sheet, ocean, and atmosphere. Their results show that while cold Antarctic meltwater will slow human-induced warming, it will also cause uneven sea level rise and significant climatic changes worldwide, highlighting the importance of lowering greenhouse gas emissions.

Working in collaboration with other modelers, Sadai set up and ran simulations on a supercomputer and assembled a team of sea level, ocean, and atmosphere experts, including Karmalkar, to analyze the simulation results. "We predict higher regional sea levels for low-lying islands in the Pacific due to melting in Antarctica," says Karmalkar. "Simulating ice-sheet-climate interactions also indicates higher Northern Hemisphere temperatures and altered precipitation patterns worldwide."

"Doing this kind of modeling work is challenging but critical to understanding the full impact of global warming on ice sheets, and how the ice sheets, in turn, affect the climate," says Karmalkar, who is part of URI's new specialization in water and climate science. He studies changes in atmospheric and oceanic conditions and their impact.

A key focus of his research looks at climate trends, variability, and extremes in different parts of the world, with an emphasis on understanding the atmospheric and oceanic drivers of regional climate change. His career has brought him into varied terrain, from studying fire-climate-vegetation dynamics in the eastern U.S. and climate extremes in the Arctic to working on climate projects across the Americas.

Assessing climate and sea level changes

The team's research predicts that while Antarctic meltwater will dampen temperature rise in the Southern Hemisphere, it can lead to warming in the North Atlantic and surrounding regions, including in eastern North America.

The paper also notes that insufficient global mitigation could lead to large-scale ice sheet mass loss, exposing people and ecosystems around the world to substantial sea level rise. By 2060, over one billion people could be living in low elevation coastal areas, increasing the risk of sea level rise impacts for socially and geographically vulnerable populations.

Understanding the interactions between ice sheets and the broader climate system is key to constraining future Antarctic ice sheet stability, global climate, and sea level. The group notes that current pledges submitted by parties to the United Nations Framework Convention on Climate Change are insufficient for meeting the Paris Agreement's long-term temperature goal of limiting global mean surface temperature rise. Robust mitigation will be crucial for preventing Antarctic ice sheet mass loss and resulting sea level rise.

Their modeling experiment predicts a contribution to sea level rise from the East Antarctic Ice Sheet in a very high emissions scenario. This is especially noteworthy because the ice sheet in East Antarctica is enormous but is currently more stable than its counterpart in West Antarctica. The study shows that the Antarctic contribution to sea level rise by 2200 is over 3m (10 feet) in a very high emissions scenario and about 1m (3 feet) in a medium emissions scenario, underscoring the importance of reducing greenhouse gas emissions.

Consistent with prior research, the team found that regions of the world far away from Antarctica will experience higher sea level rise due to gravitational and Earth deformational effects. They predict that regional sea level rise of up to 1.5m (5 feet) will occur in the Pacific and Indian Ocean basins and Caribbean Sea.

In other words, the loss of ice sheet mass will drive substantial sea level rise. Even with a slower rate of warming, any continued increase in sea level poses risks to island and coastal communities, raising wide-ranging issues of intergenerational inequity and injustice, as the lead author Sadai has shown in her previous research. Last week's destruction in the Caribbean caused by Hurricane Melissa shows how storm surge can devastate vulnerable coastal communities.

"Rising sea levels makes these impacts worse, which is why studies like this that quantify the uneven future rise in sea level are absolutely critical," says Karmalkar.