New research has uncovered evidence that most of Greenland melted only about 400,000 years ago, suggesting the country may be more sensitive to climate change than previously thought.
The study by researchers from around the world, used decades-old sediments that had been gathered from thousands of feet below the ice as part of a secret U.S. military mission during the Cold War.
While previous work has estimated that the ice on Greenland melted at least once in the last 1.1 million years, the researchers behind this latest study say much of the region was in fact green 416,000 years ago, plus or minus 38,000 years.
“It’s really the first bulletproof evidence that much of the Greenland ice sheet vanished when it got warm,” said scientist Paul Bierman who co-let the study.
“We had always assumed that the Greenland ice sheet formed about two and a half million years ago—and has just been there this whole time and that it’s very stable,” said Utah State University scientist Tammy Rittenour,
“Maybe the edges melted, or with more snowfall it got a bit fatter — but it doesn’t go away and it doesn’t dramatically melt back. But this paper shows that it did.”
The sediment was taken in northwestern Greenland at Camp Centuary, a military base from the 1960’s that the U.S. army stated was an Arctic science station.
The researchers say the scientists there at the time drilled down almost a mile deep, collecting 12 feet of soil and rock from beneath the ice.
The ice core was rediscovered in 2017 and was found to contain vegetation such as leaves and moss.
The researchers believe flowing water deposited the sediment during a period of moderate warming called Marine Isotope Stage 11, between 424,000 and 374,000 years ago.
During that time, the sea level rose at least five feet around the globe.
Through analysis, the researchers say the sediment was exposed less than 14,000 years before it was buried under ice.
Thay say that understanding Greenland’s history can help predict how quickly the ice sheet will melt in response to climate change.
With a melting Greenland expected to add about 23 feet to rising sea levels, the researchers say this will pose risks to major coastal cities around the world.