by Evidence from a 2,000-foot-long ice core shows that the West Antarctic Ice Sheet shrank suddenly and dramatically around 8,000 years ago, according to new research – providing alarming insight into how quickly Antarctic ice and sea levels could melt to raise.
Part of the ice sheet thinned by 450 meters (1,476 feet) – a height greater than the Empire State Building – over a period of just 200 years at the end of the last Ice Age, according to the study published on Wednesday in the journal Nature Geoscience.
This is the first direct evidence showing such rapid ice loss anywhere in Antarctica, according to the study authors.
Although scientists knew that the ice sheet was larger at the end of the last Ice Age than it is today, much less was known about when exactly that shrinkage occurred, said Eric Wolffglaciologist at the University of Cambridge in the UK and author of a study.
This study changes that, he told CNN. “We were able to tell exactly when it took off, but we were also able to tell how quickly it took off.”
Now that the ice sheet has retreated and thinned so rapidly in the past, Wolff said, there is a risk it could start again. “If it starts to back off, it’s going to do it really quickly,” he said.
This could have disastrous consequences for global sea level rise. The West Antarctic Ice Sheet holds enough water to raise sea levels by about 5 meters – more than 16 feet – causing catastrophic flooding in coastal towns and cities around the world.
The study of much of the Antarctic ice sheet is a “remarkable piece of detective work,” said Ted Scambos, a glaciologist at the University of Colorado Boulder.
The main message is that “the amount of ice stored in Antarctica can change very quickly — at a pace that would be difficult to deal with in many coastal cities,” he told CNN.
Ice cores are a historical archive of the Earth’s atmosphere. They are made up of layers of ice formed as snow fell and compacted over thousands of years, they contain ancient air bubbles as well as contaminants that provide a record of environmental changes over thousands of years.
The ice core analyzed in the study was drilled from Skytrain Ice Rise which is located at the edge of the ice sheet, near the point where the ice begins to float and is part of the Ronne Ice Shelf.
Scientists achieved it in 2019, as part of a painstaking process that involved drilling continuously for 40 days, pulling up a thin cylinder of ice a few feet at a time. They then cut the heart into sections, packed them in insulated boxes kept at minus 20 degrees Celsius, and sent them to the UK by plane and then by ship.
Once in the UK, the scientists measured the ice core’s water isotopes, which provide information on past temperatures. Warmer temperatures indicate lower-lying ice — think of it like a mountain, Wolff said, the higher up you go, the colder it gets.
They also measured the pressure of air bubbles trapped in the ice. Lower and thinner ice has air bubbles under higher pressure.
It was a big surprise when the data showed how fast the ice was thinning at the end of the last Ice Age, Wolff said. “We spent a lot of time checking that we hadn’t made a mistake with the analysis.”
The West Antarctic Ice Sheet is particularly vulnerable to climate change, because the land is below sea level and slopes down. When warm water comes from below, it can melt very quickly. “It can have a runaway process, and that’s what happened 8,000 years ago,” Wolff said.
What is worrying about the results, said Isobel Rowell, an ice core scientist with the British Antarctic Survey and co-author of the study, is that such escape occurs “very little, if at all, we can to stop it,” she told CNN.
The key is “not to test it too far,” Wolff said, and that means tackling climate change. “We can still avoid these tipping points,” he said.
The new data will help improve the accuracy of the models scientists use to predict how the ice sheet will respond to future global warming, the report says.
David Thornalley, an ocean and climate scientist at University College London, said the study’s data were “conquering”. He cautioned that since the study looked at a period 8,000 years ago, when climate conditions were different, the results are not a direct example of what could happen today. But, he said, they are still able to “give insight into how icebergs can collapse.”
The study comes as scientists continue to call out what is happening on Earth’s most remote continent.
For example, the Thwaites Glacier, also in West Antarctica, is melting rapidly. A 2022 study said Thwaites – known as the Doomsday Glacier because of the catastrophic impact it would have on rising sea levels – was hanging “on its toes” as the planet grew.
This new study adds to these concerns, Scambos said. “(It) shows that the same processes that we are seeing, which are just starting now in areas like the Thwaites Glacier, have already taken place in similar areas in Antarctica and in fact, the speed of ice loss has been equal to the our worst concern was about running ice. loss.”
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