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The global sea level will rise higher than previously expected if the West Antarctic Ice Sheet collapses, according to a new study from Harvard researchers.

The study, published in the journal Scientific Advances on April 28, was led by graduate students Linda Pan and Evelyn Powell.

Pan and Powell found the ocean level would rise an additional meter, about 3 feet, higher than previously predicted over the next 1,000 years if the ice sheet collapses entirely.

Their conclusions came from new “water expulsion mechanism” calculations, the university said in a statement.

Water expulsion occurs “when the solid bedrock the West Antarctic Ice Sheet sits on rebounds upward as the ice melts and the total weight of the ice sheet decreases.” The bedrock lies below the ocean’s surface and when it lifts it “pushes water from the surrounding area into the ocean” which contributes to sea-level rise, the statement said.

Prior research into sea-level rise had dismissed the water expulsion mechanism as “small and slowly accumulating,” Pan said.


An illustration depicting water expulsion.
An illustration depicting water expulsion.Courtesy of Linda Pan

Being an integral part of a major discovery was exciting, Pan said, especially considering the paper published last week was the first she was a lead author on.

“It was basically very unbelievable at first,” she said in a telephone interview. “I’m still like ‘Wow, people actually care!’ ”

Pan said she developed an interest in earth sciences at an early age and, as an undergraduate student at McGill University, found sea level and geophysics particularly engrossing.

“If the West Antarctic Ice Sheet collapsed, the most widely cited estimate of the resulting global mean sea-level rise that would result is 3.2 meters,” Powell said. “What we’ve shown is that the water-expulsion mechanism will add an additional meter, or 30 percent, to the total” over a 1,000-year period.

A 20 percent increase is possible by the end of the 21st century, according to one simulation, the researchers said.


Jerry X. Mitrovica, the Frank B. Baird Jr. Professor of Science in the Department of Earth and Planetary Sciences at Harvard who is a senior author on the paper, said “every published projection of sea-level rise due to melting of the West Antarctic Ice Sheet ... is going to have to be revised upward because of their work.”

Pan and Powell, who are researchers in Mitrovica’s lab, began their research on the West Antarctic Ice Sheet while working on another project. After noticing more water expulsion from the ice sheet than anticipated, they realized they were on to something and switched their focus.

“No matter what scenario we used for the collapse of the West Antarctic Ice Sheet, we always found that this extra one meter of global sea-level rise took place,” Pan said.

A 2020 study found that ancient melting of the ice sheet contributed to the sea level’s rise more than 100,000 years ago. Another study published in 2020 found the ocean’s temperatures were the highest they had ever been in 2019. And, in 2016, researchers found melting on the East Antarctic Ice Sheet during summer months — in an area that was thought to be too cold for ice loss to be perceivable.

Charlie McKenna can be reached at charlie.mckenna@globe.com. Follow him on Twitter @charliemckenna9.