Greenland ice may exaggerate magnitude of 13,000-year-old deep freeze

Ice samples pulled from nearly a mile below the surface of Greenland glaciers have long served as a historical thermometer, adding temperature data to studies of the local conditions up to the Northern Hemisphere's climate.

But the method -- comparing the ratio of oxygen isotopes buried as snow fell over millennia -- may not be such a straightforward indicator of air temperature.

"We don't believe the ice cores can be interpreted purely as a signal of temperature," says Anders Carlson, a University of Wisconsin-Madison geosciences professor. "You have to consider where the precipitation that formed the ice came from."
According to a study published June 25 by the Proceedings of the National Academy of Sciences, the Greenland ice core drifts notably from other records of Northern Hemisphere temperatures during the Younger Dryas, a period beginning nearly 13,000 years ago of cooling so abrupt it's believed to be unmatched since...
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University of Wisconsin-Madison via The Archaeology News Network