Evidence from an ice core more than 600 meters long shows that the West Antarctic ice sheet shrank suddenly and dramatically around 8,000 years ago, according to new research – providing an alarming insight into how quickly Antarctic ice is it could melt and cause sea levels to rise.
Antarctica is vulnerable to global warming PHOTO: Archive
Part of the ice sheet thinned by 450 meters – a height greater than the Empire State Building – in 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 Geosciencem writes edition.cnn .com.
It's the first direct evidence showing such rapid ice loss anywhere in Antarctica, according to the study's authors.
While 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 exactly when that shrinkage occurred, said Eric Wolff, a glaciologist at the University of Cambridge in the Sea. UK and one of the authors of the study.
This study changes that, he told CNN. “We were able to tell exactly when it retreated, but we also managed to tell how quickly it retreated.”
Now that it's clear the ice sheet has retreated and thinned very quickly in the past, Wolff said, the danger is that it could start again. “If he's going to start pulling back, he's going to do it very quickly indeed.” he added.
This could have catastrophic consequences for global sea level rise. The West Antarctic ice sheet contains enough water to raise sea levels by about 5 meters, which would cause devastating flooding in coastal cities around the world.
The study is “excellent detective work” about an important part of the Antarctic ice sheet, said Ted Scambos, a glaciologist at the University of Colorado Boulder.
The key message is that “the amount of ice stored in Antarctica can change very quickly – at a rate that would be difficult for many coastal cities to manage,” he told CNN.
Ice cores are historical archives of the Earth's atmosphere. Made up of layers of ice that 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 change over time. millennia.
The ice core analyzed in the study was drilled from the Skytrain Ice Rise, located at the edge of the ice sheet, near the point where the ice begins to float and become part of the Ronne Ice Shelf.
Scientists extracted it in 2019 in a painstaking process that involved constant drilling for 40 days, removing a thin cylinder of ice a few meters long at a time. They then cut the core into sections, packed them in insulated boxes, kept at minus 20 degrees Celsius, and sent them to Britain by plane, then by ship.
Once in the UK, the scientists measured water isotopes in the ice core, which provide information about past temperature. Warmer temperatures indicate ice at a lower level — think of it like a mountain, Wolff said, the higher you go, the colder it gets.
They also measured the pressure of air bubbles trapped in the ice. Lower, thinner ice contains higher-pressure air bubbles.
It was a surprise when the data revealed how quickly the ice thinned at the end of the last ice age, Wolff said. “In fact, I spent a lot of time checking that I didn't make any mistakes in the analysis.”
The West Antarctic Ice Sheet is particularly vulnerable to climate change because the land beneath it is below sea level and slopes downward. When warm water gets under it, it can melt very quickly. “It may have an escape process, and this obviously happened 8,000 years ago.”Wolff said.
What makes these findings so alarming, said Isobel Rowell, ice core researcher at the British Antarctic Survey and co-author of the study, is that once this runaway phenomenon occurs, “there is very little, if anything, we can do to stop it“, she told CNN.
The crucial thing”is not to test it too far“, Wolff said, and that means addressing 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 said.
David Thornalley, an ocean and climate researcher at University College London, said the study's data “striking”. He cautioned that because the study looked at a period 8,000 years ago, when climate conditions were different, the results are not a direct example of what might happen today. But, he added, they are still capable of providing a “insight into how ice sheets can collapse”.
The study comes as scientists continue to sound the alarm about what is happening to Earth's most isolated continent.
For example, the Thwaites Glacier, also located in West Antarctica, is melting rapidly. A 2022 study said that Thwaites – nicknamed the Apocalypse Glacier for the catastrophic impact its collapse would have on sea level rise – hangs “of nails” as the planet warms.
This new study adds to those concerns, Scambos said. “It shows that exactly the same processes we see, which are just now starting in areas like the Thwaites Glacier, have taken place before in similar areas of Antarctica, and indeed the rate of ice loss has been on par with the greatest our fears of unprecedented ice loss.”