![]() ![]() The team brought up its first core this summer. The project will drill four new bedrock cores from around Greenland, which will be intensively studied in order to better document the recent melt history of Greenland. National Science Foundation-funded effort aimed at doing just that. He is currently helping lead Project GreenDrill, a massive U.S. ![]() Still, he believes more work is needed to really prove the case. “Clearly we have considered MIS 11 a contender, because it was one of the warmest periods,” he said. Joerg Schaefer, a geochemist at Lamont-Doherty Earth Observatory who helped lead the previous two studies but was not involved with the current paper, said he was not surprised that the researchers zeroed in on this time period. “It’s really the first bulletproof evidence that much of the Greenland ice sheet vanished when it got warm,” says University of Vermont scientist Paul Bierman, who co-led the new study with Drew Christ, a post-doctoral geoscientist who worked in Bierman’s lab. Army-ERDC-CRREL, courtesy AIP Emilio Segrè Visual Archives)īut how long ago were those plants growing there, where today there is an ice sheet three times the size of Texas and as much as two miles thick? The new study presents evidence that the sediment just beneath the ice sheet was deposited by flowing water in an ice-free environment during a moderate warming period called Marine Isotope Stage 11 lasting from 424,000 to 374,000 years ago, when temperatures were slightly warmer than today. The findings, published in 2021, showed it held not just sediment but leaves, moss and other detritus of things living on the surface-remnants of an ice-free landscape, perhaps a boreal forest.ĭrilling rig that brought up a sediment core at the secret Camp Century military installation, 1961. There it was forgotten, until it was examined in 2017. ![]() The scientists at the time took little interest in the sediments the core was moved in the 1970s from a military freezer to the University at Buffalo, then to a freezer in Denmark in the 1990s. Then they kept going, to pull out a 12-foot-long tube of soil and rock from below the ice. The missile mission was a bust, but a science team there completed important research, including drilling an ice core 4,560 feet deep. As cover, the Army claimed it was a science station. One purpose of the Cold War camp was to secretly station hundreds of nuclear missiles near the Soviet Union. ![]() The study site, called Camp Century, is in northwest Greenland, 138 miles inland from the coast and only 800 miles from the North Pole. It was a serendipitous opportunity to probe the history recorded in the sediments.” “A big remaining question following was when was the most recent exposure?” said study coauthor Sidney Hemming, a geochemist at the Columbia Climate School’s Lamont-Doherty Earth Observatory. The Greenland ice is thought to have largely melted at least once in recent geologic time. They applied advanced luminescence and isotope techniques to provide direct evidence of the timing and duration of the ice-free period. military base in the 1960s, to make the discovery. The scientists, from the University of Vermont, Columbia University and other institutions, used sediment from the bottom of a long-lost ice core, collected at a secret U.S. This indicates that the Greenland ice may be more sensitive to human-caused climate change than previously understood, and could be vulnerable to irreversible, rapid melting in coming centuries. They calculate that the melting caused at least five feet of sea level rise-and maybe as much as 20 feet-at a time when temperatures were only slightly warmer than today, even though atmospheric levels of heat-trapping carbon dioxide were far lower. A new study in the journal Science says a large portion of Greenland turned to ice-free tundra about 416,000 years ago, plus or minus 38,000 years-quite recent in geologic time. Researchers now say they have more precise timing for at least one such melting event. It also strengthened the prospect that human-induced warming could eliminate the ice sheet, which holds some 23 feet of potential sea-level rise. The pair of studies helped overturn a previous view that the ice sheet has been stable for millions of years, even during naturally warm periods. In 2021, a study of another core containing sub-ice sediments laden with plants from a site 500 miles away reached a similar conclusion. In 2016, a groundbreaking study of a unique bedrock core drilled from under the center of the Greenland Ice Sheet suggested that most or all of the ice covering the landmass had melted away at least once during the last 1.1 million years. ![]()
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