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Evidence from a 2,000-foot-long ice core reveals that the West Antarctic ice sheet shrank suddenly and dramatically about 8,000 years ago, according to new research, providing insight. alarming vision about how quickly Antarctic ice could melt and raise sea levels.
Part of the ice sheet thinned by 450 meters (1,476 feet), taller 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 Wednesday in the journal Nature Geoscience.
It is the first direct evidence showing such rapid ice loss anywhere in Antarctica, according to the study’s authors.
While scientists knew the ice sheet was larger at the end of the last Ice Age than it is today, much less It is known exactly when that contraction occurred, said Eric Wolff, a glaciologist at the University of Cambridge in the United Kingdom and an author of the study.
This study changes that, he told CNN. “We could tell exactly when it retreated, but we could also tell how quickly it retreated.”
Now that it’s clear that the ice sheet retreated and thinned very rapidly in the past, Wolff said, the danger is that it could start again. “If it starts to go backwards, it will go really fast,” 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 (more than 16 feet), which would cause devastating flooding in coastal towns and cities around the world.
The study is “excellent detective work” on an important part of the Antarctic ice sheet, said Ted Scambos, a glaciologist at the University of Colorado at Boulder.
The key message is that “the amount of ice stored in Antarctica can change very rapidly, at a rate that would be difficult for many coastal cities to cope with,” he told CNN.
Cambridge University/British Antarctic Survey
Map showing the location of the Ice Rise Skytrain, part of the Ronne Ice Shelf, where the ice core was taken.
Ice cores are historical archives of the Earth’s atmosphere. Formed by layers of ice that formed when snow fell and compacted Over thousands of years, they contain bubbles of ancient air as well as contaminants that provide a record of environmental pollution. changes over millennia.
The ice core analyzed in the study was drilled from 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 drilling constantly for 40 days, extracting a thin cylinder of ice a few meters at a time. They then cut the core into sections, packed them in insulated boxes kept at -20 degrees Celsius and shipped them to the UK by plane and then by ship.
Once in the UK, scientists measured water isotopes from the ice core, which provide information about temperature in the past. Warmer temperatures indicate lower ice; 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.
Cambridge University/British Antarctic Survey
Inside the drill shop at Skytrain Ice Rise, scientists prepare the drill for its next drop into the shaft.
Eric Wolff
Isolated boxes full of ice cores loaded onto Twin Otter aircraft, Skytrain Ice Rise, Antarctica.
It was a surprise when the data revealed how quickly the ice had thinned at the end of the last Ice Age, Wolff said. “In fact, we spent a lot of time checking that we hadn’t made a mistake 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 underneath, it can melt very quickly. “You can have a runaway process, and that’s evidently what happened 8,000 years ago,” Wolff said.
What makes the findings so alarming, said Isobel Rowell, a scientist at the British Antarctic Center and co-author of the study, is that once runaway occurs “there’s really very little, if anything, we can do to stop it.” “he told CNN.
The crucial thing “is not to test it too much,” 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 that scientists use to predict how the ice sheet will respond to future global warming, according to the report.
David Thornalley, an ocean and climate scientist at University College London, said the study’s data was “surprising.” 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 could happen today. But, he added, they can still offer “insight into how ice sheets can collapse.”
The study comes as scientists continue to sound the alarm about what is happening on Earth’s most isolated continent.
For example, the Thwaites Glacier, also in West Antarctica, is melting quickly. A 2022 study said Thwaites, nicknamed the Doomsday Glacier for the catastrophic impact its collapse would have on sea level rise, was hanging “by the nails” as the planet warms.
This new study adds to these concerns, Scambos said. “(This) shows that the same processes we are now seeing beginning, in areas like the Thwaites Glacier, have played out before in similar areas of Antarctica and, in fact, the rate of ice loss was equal to our worst fears about uncontrolled ice. loss.”