Greenland ice sheet retreated 60 miles during warmer period
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Researchers studying sediment from a former U.S. military base in Greenland determined that the area was ice-free around 416,000 years ago when summer temperatures were warmer than today.
A team led by the University at Buffalo examined samples collected during the Cold War’s Project Iceworm, a plan to conceal nuclear missiles under the ice at Camp Century.
They discovered that summer temperatures were 4.7 degrees Celsius (8.5 degrees Fahrenheit) higher than current summers to allow the Greenland Ice Sheet to retreat more than 97 kilometers from its present location. The scientists reconstructed these ancient temperatures by analyzing fatty molecules left by bacteria in the sediment. They found that the duration of warmer periods may be as important as the degree of warming, as similar temperatures during a more recent period did not cause the same ice retreat.
However, the researchers caution that current human-caused warming is occurring at a faster rate than the warming 416,000 years ago and may last for centuries. The sediment samples originally came to the University at Buffalo in 1975, but were largely forgotten for over two decades until a cleanup in Denmark brought them back to scientists’ attention in 2018.
Elizabeth Thomas and John Michael Aguilar then began a multi-year analysis to account for changes in land elevation and accurately interpret the results, producing the first quantitative estimate of land-based summer temperatures in Greenland from that ancient period.
