Greenland sediment shows Camp Century was ice-free 416,000 years ago
A University at Buffalo-led study found that summers at Greenland’s Camp Century were 4.7°C warmer than today during an ice-free period about 416,000 years ago. The ice sheet had retreated more than 97 km from its present edge, and the researchers say the findings suggest the duration of warming matters alongside its intensity.
Bottom line — The study’s authors warn that today’s human-caused warming is more intense than the ancient warm period.
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Researchers reconstructed past summer temperatures from fatty molecules produced by bacteria and preserved in sediment recovered beneath the ice.
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The study authors describe this as the first quantitative estimate of land-based summer temperatures anywhere in Greenland for that ancient warm period.
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Greenland had similarly warm summers 5,000–10,000 years ago, but Camp Century remained ice-covered, the researchers report.
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The authors say the earlier warming may have lasted tens of thousands of years, giving the ice sheet more time to retreat.
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The sediment was drilled from nearly 1.6 km beneath the ice during Project Iceworm, a Cold War US Army effort to hide nuclear missiles under the ice.
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The samples were brought to the University at Buffalo in 1975, later spent more than two decades at the University of Copenhagen, and returned to researchers’ attention in 2018.