According to a new study, evidence from a 6,000-foot-long ice core reveals that the West Antarctic ice sheet shrank suddenly and dramatically about 8,000 years ago, showing how Antarctic ice It provides surprising insight into how fast it will melt and sea levels will rise.
In just 200 years at the end of the last Ice Age, parts of the ice sheet rose 450 meters (450 meters) tall, higher than the Empire State Building, according to a study published Wednesday in the journal Nature Geoscience. 1,476 feet). .
According to the study authors, this is the first direct evidence of such rapid ice loss anywhere in Antarctica.
Study author Eric Woolf, a glaciologist at the University of Cambridge in the UK, said scientists knew the ice sheet was larger at the end of the last ice age than it is today, but they weren’t sure exactly when that shrinkage occurred. said it was little known.
This study changes that, he told CNN. “We could tell exactly when we were going backwards, but we could also tell how fast we were going backwards.”
It is now clear that ice sheets have retreated and thinned very quickly in the past, and the danger is that they could start again, Wolff said. “If the withdrawal starts, it will come out really quickly,” he added.
That could have a devastating effect on global sea level rise. The West Antarctic ice sheet holds enough water to raise sea levels by about 5 meters (more than 16 feet), potentially causing devastating flooding in coastal towns and cities around the world .
Ted Scambos, a glaciologist at the University of Colorado Boulder, said the study was “a great piece of detective work” on a large portion of the Antarctic ice sheet.
Inside the SkyTrain Ice Rise drilling tent, scientists prepare a drill for the next drop in the borehole. (University of Cambridge/British Antarctic Survey)
The key message: “The amount of ice stored in Antarctica can change very rapidly, and the pace will be difficult for many coastal cities to cope with,” he told CNN.
Ice cores are historical archives of Earth’s atmosphere. It is made up of layers of ice formed by falling snow and compacting over thousands of years, and contains ancient air bubbles and pollutants that provide a record of environmental change over thousands of years.
The ice cores analyzed in the study were drilled from the SkyTrain Ice Rise, located at the edge of the ice sheet, near the point where the ice begins to rise and become part of the Ronne Ice Shelf.
Scientists extracted this ice in 2019 by drilling continuously for 40 days and painstakingly pulling up thin cylinders of ice several feet at a time. The core was then cut into sections, packaged in insulated boxes kept at -20 degrees Celsius, and shipped by plane to the UK and then by ship.
Once in the UK, scientists measured water isotopes in the ice cores, which provide information about past temperatures. Warmer temperatures indicate that there is a lower layer of ice. If you compare the ice to a mountain, Wolfe said, the higher you go, the colder it gets.
They also measured the pressure of air bubbles trapped in the ice. Thin ice at lower altitudes contains bubbles of higher pressure.
Wolff said he was surprised when the data revealed how quickly the ice thinned at the end of the last ice age. “In fact, we spent a lot of time making sure there were no mistakes in our analysis.”
The West Antarctic Ice Sheet is particularly vulnerable to climate change because the land beneath it is below sea level and slopes downward. If warm water gets under it, it will quickly dissolve. “A runaway process can occur, and that’s clearly what happened 8,000 years ago,” Wolff said.
An insulated box filled with ice cores is loaded onto a Twin Otter aircraft on SkyTrain Ice Rise in Antarctica. (Eric Wolf)
Isobel Lawwell, an ice core scientist at the British Antarctic Survey and a co-author of the study, said what makes the findings so worrying is that once a runaway occurs, “there’s nothing we can do to stop it.” That means there are very few, if any, cases.” ” she told CNN.
The key, Wolff said, is “not to experiment too much,” and that means tackling climate change. “These tipping points can still be avoided,” he said.
The new data will help improve the accuracy of models scientists use to predict how ice sheets 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 “astonishing”. He cautioned that the study looked at a time 8,000 years ago when climate conditions were different, so the results are not a direct example of what could happen today. But they can still provide “insight into how ice sheets break up,” he added.
The study comes as scientists continue to sound the alarm about what is happening to Earth’s most isolated continent.
For example, Thwaites Glacier, also in West Antarctica, is melting rapidly. A 2022 study said Thwaites Glacier (dubbed the “terminal glacier” because of the devastating effects its collapse would have on rising sea levels) is holding on “by its claws” as the planet warms.
This new study adds to those concerns, Scambos said. “[It]shows that the very same processes that we are now beginning to see in areas like Thwaites Glacier have been occurring before in similar areas of Antarctica, and that the pace of ice loss is, in fact, Our worst fears about ice spills were the same as “losses”. “
