Evidence from a 600-meter-long ice core reveals that the West Antarctic Ice Sheet suddenly and dramatically shrank about 8,000 years ago, according to new research; This gives an alarming insight into how quickly Antarctic ice may melt and how quickly sea levels may rise.
Over a period of just 200 years at the end of the last Ice Age, part of the ice sheet was thinned by 450 meters (1,476 feet) – a height higher than the Empire State Building, according to research published Wednesday in the journal Nature Geoscience. .
According to the study’s authors, this is the first direct evidence of such rapid ice loss anywhere in Antarctica.
While scientists know that the ice sheet was larger at the end of the last Ice Age than it is today, much less is known about exactly when this shrinkage occurred, said Eric Wolff, a glaciologist at the University of Cambridge in the United Kingdom and author of the study.
This study changes that, he told CNN. “We were able to tell exactly when it retreated, but we were also able to tell how quickly it retreated.”
Wolff said it is now clear that the ice sheet has retreated and thinned so quickly in the past that the danger is that it could start again. “If he starts to pull back, he will do it really quickly,” he added.
This could have devastating consequences for global sea level rise. The West Antarctic Ice Sheet holds enough water to raise sea levels by nearly 5 meters (more than 16 feet); This will cause devastating flooding in coastal towns and cities around the world.
Ted Scambos, a glaciologist at the University of Colorado Boulder, said the study was “an excellent detective study” of a large portion of the Antarctic ice sheet.
The main message is that “the amount of ice stored in Antarctica can change very quickly, at a rate that is difficult for many coastal cities to cope with,” he told CNN.
Ice cores are historical archives of the Earth’s atmosphere. Formed from layers of ice that form when snow falls and compacts over thousands of years, these layers 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 the Skytrain Ice Rise, located at the edge of the ice sheet near the point where the ice begins to float and becomes part of the Ronne Ice Shelf.
Scientists figured it out in 2019 through a painstaking process that involved 40 days of continuous drilling and pulling a thin cylinder of ice up a few meters at a time. They then cut the core into sections, packaged it in insulated boxes stored at minus 20 degrees Celsius, and shipped it to England by plane, then shipped it by ship.
Once in the UK, scientists measured the ice core’s water isotopes, which provide information about past temperature. Higher temperatures are indicative of lower-lying 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 and thinner ice contains higher pressure air bubbles.
Wolff said it was surprising that the data revealed how rapidly the ice thinned at the end of the last Ice Age. “We actually spent a lot of time checking whether we had 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. It can melt very quickly when put under hot water. “It may have been a process that got out of control, and it’s clear that this happened 8,000 years ago,” Wolff said.
What makes the findings so worrying is that once this escape occurs, “there’s really very little, if anything, that we can do to stop it,” said Isobel Rowell, an ice core scientist at the British Antarctic Survey and co-author of the study. she told CNN.
The important thing, Wolff said, is “not to test too much,” which means tackling climate change. “We can still avoid these tipping points,” he said.
The new data will help improve the accuracy of 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 from University College London, said the study’s data was “striking”. He cautioned that because the study looked at a period 8,000 years ago when climatic conditions were different, the results were not a direct example of what might happen today. But he added that they could still offer “some insight into how ice sheets might collapse.”
The research comes as scientists continue to sound the alarm about what is happening on the world’s most isolated continent.
For example, Thwaites Glacier, also in West Antarctica, is melting rapidly. A 2022 study said Thwaites, dubbed the Doomsday Glacier because of the devastating impact its collapse would have on sea level rise, is hanging on “by its fingernails” as the planet warms.
This new study raises those concerns, Scambos said. “(This) shows that the processes we are seeing, which are just beginning in areas like the Thwaites Glacier, have occurred before in similar parts of Antarctica, and indeed the rate of ice loss is on par with our worst fears about ice getting out of control.” loss.”
For more CNN news and newsletters, create an account at CNN.com