A new study reveals evidence that much of Greenland melted just about 400,000 years ago, suggesting Greenland may be more sensitive to climate change than previously thought.
the study, Published in Science on July 20 Studies by researchers around the world used decades-old sediments collected from thousands of feet under the ice as part of a covert Cold War-era US military mission.
Previous studies have estimated that Greenland’s ice melted at least once in the last 1.1 million years, but the researchers behind the latest study say Greenland was actually mostly green 416,000 plus or minus 38,000 years ago.
“This is the very first complete evidence that much of the Greenland ice sheet has disappeared due to global warming,” said scientist Paul Biermann, who co-led the study. University of Vermont where he is a professor.
“We always thought the Greenland ice sheet formed about 2.5 million years ago, but we thought it had been there all this time and was very stable,” said study co-author Tammy Littner, a scientist at Utah State University.
“Perhaps the edge melted, or maybe it got a little thicker with more snowfall. But it doesn’t go away, and it doesn’t melt back dramatically. But this paper shows that it did.”
camp century
The sediments were collected at Camp Century in northwest Greenland. Camp Century was a military base in the 1960s that the US military claimed was an Arctic science base.
In fact, this camp was used in an operation called project icewormintended to hide hundreds of nuclear missiles under the ice of Greenland near the Soviet Union.
Although the nuclear missile mission was a “failure,” researchers say scientists on site at the time drilled about a mile deep and collected about 12 feet of soil and rock from under the ice.
This deposit moved from a military freezer to the University of Buffalo in New York in the 1970s and then to a Danish freezer in the 1990s.
sediment research
An ice core rediscovered in 2017 was found to contain leaves, moss and other plants.
Scientists believe that flowing water deposited the sediment during a period of moderate warming called Marine Isotope Stage 11, 424,000 to 374,000 years ago.
Researchers say sea levels rose at least five feet around the world during that period.
Scientists analyzed the cores for “luminescent signals,” in which trapped subatomic particles known as electrons are released during the process of exposing the sediments to blue-green or infrared light.
By measuring the number of electrons emitted, scientists were able to determine when the sediment was last exposed to the sun.
The researchers also studied quartz harvested from deposits. The quartz, they say, contains rare forms, or isotopes, of the elements beryllium and aluminum that accumulate when the ground is exposed to the sun.
This, researchers say, exposed the sediment 14,000 years before it was buried under ice.
They added that understanding Greenland’s history can help predict how quickly the ice sheet will melt in response to climate change.
Greenland’s melting is expected to contribute to about 23 feet of sea level rise, which will pose risks to major coastal cities around the world, researchers say.
“Greenland’s past, preserved in 12 feet of permafrost, hints at a future for a warm, wet, largely ice-free planet unless we can dramatically reduce atmospheric carbon dioxide levels,” Biermann said.
