Evidence from a 2,000-foot-long ice core suggests that the West Antarctic Ice Sheet dramatically shrank around 8,000 years ago, according to a new study. The research offers insight into how quickly Antarctic ice could melt and cause a significant rise in sea levels.
The study, published in the journal Nature Geoscience, reveals that part of the ice sheet thinned by 450 meters (1,476 feet) in a mere 200 years, at the end of the last Ice Age – a height greater than the Empire State Building.
According to the study’s authors, this is the first direct evidence showing such a rapid loss of ice in Antarctica.
Eric Wolff, a glaciologist at the University of Cambridge and a study author, stated that while scientists knew the ice sheet was larger at the end of the last Ice Age than today, little was known about the exact timing of its shrinking. This study changes that by pinpointing both the time and speed of the ice’s retreat.
Wolff explains that now it’s evident the ice sheet retreated and thinned rapidly in the past, the concern is that it could happen again. “If it does start to retreat, it really will do it very fast,” he added.
This could have devastating consequences for global sea level rise, as the West Antarctic Ice Sheet holds enough water to raise sea levels by about 5 meters (more than 16 feet).
According to Ted Scambos, a glaciologist at the University of Colorado Boulder, the study is “an excellent piece of detective work” about a major part of the Antarctic ice sheet. He emphasized that the key message is that “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.”
Ice cores are historical records of the Earth’s atmosphere, containing layers of ice that formed as snow fell and compacted over thousands of years. They also hold ancient air bubbles and contaminants that provide a record of environmental changes over millennia.
The ice core analyzed in the study was drilled from Skytrain Ice Rise at the edge of the ice sheet, near the point where the ice starts to float and become part of the Ronne Ice Shelf.
The extraction process, completed in 2019, involved drilling constantly for 40 days, pulling up a thin cylinder of ice a few feet at a time. The core was then cut into sections, packed in insulated boxes kept at minus 20 degrees Celsius, and sent to the UK via plane then ship.
In the UK, the scientists measured the ice core’s water isotopes to glean information about temperature in the past. They also measured the pressure of trapped air bubbles in the ice, as lower-lying and thinner ice contain higher pressure air bubbles.
Wolff expressed his surprise at how quickly the ice had thinned at the end of the last Ice Age, stating that they spent a lot of time verifying the analysis to ensure its accuracy.
The West Antarctic Ice Sheet is particularly vulnerable to climate change due to the land under it being below sea level and sloping downward, making it more susceptible to fast melting when warm water gets underneath it. This runaway process is what occurred 8,000 years ago, according to Wolff.
Isobel Rowell, an ice core scientist at the British Antarctic Survey and a study co-author, emphasized that once such a runaway process happens, “there’s really very little, if anything, that we can do to stop it.”
Wolff stressed the importance of addressing climate change to prevent reaching such tipping points, stating that “we can avoid these tipping points still.”
The new data from the study will help improve the accuracy of the models used by scientists to predict how the ice sheet will respond to future global heating, the report notes.
David Thornalley, an ocean and climate scientist at University College London, termed the study’s data “striking.” While he cautioned that the study looked at a period 8,000 years ago, when climate conditions were different, he also emphasized that the results offer valuable “insight into the way that ice sheets can collapse.”
This study adds to the concerns raised by scientists about the changes happening in Antarctica, such as the rapid melting of the Thwaites Glacier, also in West Antarctica, which is often referred to as the Doomsday Glacier due to its potential catastrophic impact on sea level rise. The study underscores the urgency of addressing the situation, as the pace of ice loss observed is equal to worst-case scenarios about runaway ice loss, according to Scambos.
