CNN
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Evidence from a 2,000-foot-long ice core reveals 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 could melt and send sea levels soaring.
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 Wednesday in the journal Nature Geoscience.
It’s the first direct evidence that shows such a rapid loss of ice anywhere in Antarctica, according to the study’s authors.
While scientists knew the ice sheet was bigger at the end of the last Ice Age than today, much less was known about when exactly that shrinking happened, said Eric Wolff, a glaciologist at the University of Cambridge in the UK and a study author.
This study changes that, he told CNN. “We’ve been able to say exactly when it retreated, but we’ve also been able to say how fast it retreated.”
Now it’s clear the ice sheet retreated and thinned very rapidly in the past, Wolff said, the danger is that it could begin again. “If it does start to retreat, it really will do it very fast,” he added.
That could have catastrophic 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 — which would cause devastating flooding in coastal towns and cities around the world.
The study is “an excellent piece of detective work” about a major part of the Antarctic ice sheet, said Ted Scambos, a glaciologist at the University of Colorado Boulder.
The key message is “the amount of ice stored in Antarctica can change very quickly — at a pace that would be hard to deal with for many coastal cities,” he told CNN.
University of Cambridge/British Antarctic Survey
Map showing the location of the Skytrain Ice Rise, part of the Ronne Ice Shelf, from where the ice core was taken.
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 bubbles of ancient air as well as contaminants that provide a record of environmental 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 starts 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, pulling up a thin cylinder of ice a few feet 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 the UK via plane then ship.
Once in the UK, the scientists measured the ice core’s water isotopes, which provide information on temperature in the past. 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 trapped air bubbles in the ice. Lower-lying and thinner ice contains higher pressure air bubbles.
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