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Researchers warn that ancient Antarctic ice melt fueled sea-level rise — and it could happen again

Researchers who studied ice core samples from Antarctica warned of melting that could raise sea levels around the world.
Researchers who studied ice core samples from Antarctica warned of melting that could raise sea levels around the world.Turney et al (custom credit)/Courtesy of the researchers

A new study finds that melting of the West Antarctic Ice Sheet during a warm period more than 100,000 years ago may have caused sea levels to rise more than 12 feet, and the study’s authors are warning that it is a “deeply worrying” finding at a time of human-driven global warming.

“This underlines the urgent need to reduce and control greenhouse gas emissions that are driving warming today," Professor Christopher Fogwill of the UK University of Keele, one of the co-authors, said in a statement.

An international team of researchers led by Professor Chris Turney of the University of New South Wales published their research in the Proceedings of the National Academy of Sciences.

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The study looked at melting of the ice sheet during the Last Interglacial period, which was 129,000 to 116,000 years ago. Ice ages occur about every 100,000 years. Warm interglacial periods happen in between. The Last Interglacial is the most recent warm period except for the current period, which is called the Holocene.

The researchers believe the ocean temperature at the time was about the same as it was in preindustrial times, around the mid-19th century. When it heated up, the ice began to melt and the oceans began to rise. They’re warning that the same thing could happen today — with a boost from human-generated global warming.

“This happened in the past under very natural warming,” Fogwill said in a telephone interview. “It gives us that real analogue for the future.”

The melting was likely caused by an increase of less than 3.6 degrees Fahrenheit in ocean warmth, “and that’s something that has major implications for the future, given the ocean temperature increase and West Antarctica melting that’s happening today,” Turney said in the statement, which was released by his university.

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“This study shows that we would lose most of the West Antarctic Ice Sheet in a warmer world,” Turney said.

“We’re already on that trajectory,” Fogwill said.

During the Last Interglacial period global sea level is believed to have been 20 to 30 feet higher than the present day. That cannot be fully explained by the Greenland ice sheet melting, thermal expansion of the ocean, and the melting of mountain glaciers. Scientists decades ago theorized that West Antarctica might have played a role.

“We now have some of the first major evidence that West Antarctica melted and drove a large part of this sea level rise,” said Professor Turney.

The study used methods including horizontal ice core analysis and ice sheet modeling.

The study comes at a time of worrying reports about Antarctic warming and ice melting.

—A recent study found that the world’s oceans were the warmest in recorded human history in 2019

—An iceberg about twice the size of the District of Columbia broke off Pine Island Glacier in West Antarctica sometime between Feb. 8 and 9, satellite data shows, confirming yet another in a series of increasingly frequent calving events in this rapidly warming region.

—The Antarctic for the first time in history logged a temperature of more than 68 degrees Fahrenheit on Sunday, almost a full degree higher than the previous record, the Guardian reported Thursday.






Martin finucane can be reached at martin.finucane@globe.com.