Scientists from the Scripps Institution of Oceanography have explained a sudden, 200-year cooling in Europe that occurred 13,000 years ago and has implications for the melting glaciers of today.
The existence of the cold snap, called the Younger Dryas after a flower that flourished in Europe during the period, had been known for a century but the physical cause for its origin had eluded researchers.
In 2013, Scripps Geologist Neal Driscoll and colleagues set sail to the eastern Beaufort Sea in search of evidence for the flood offshore of the Mackenzie River.
From aboard the U.S. Coast Guard icebreaker Healy, the team gathered sediment cores bearing fossil shells of microscopic organisms known as foraminifera from along the continental slope 135 miles north of the mouth of the river. Preserved in the shells were isotopes of oxygen with a ratio that is consistent with a large incursion of glacially derived freshwater.
“The signature of oxygen isotopes recorded in foraminifera shells preserved in the sediment allowed us to fingerprint the source of the glacial lake discharge down the Mackenzie River 13,000 years ago,” said Driscoll, an author of the study. “Radiocarbon dating on the shells provided the age constraints. How exciting when the pieces of a more than 100-year puzzle come together.”
The abrupt climate change triggered by the freshwater inundation ended more than 2,000 years of warming, said Lloyd Keigwin, an oceanographer at Woods Hole and lead author of the National Science Foundation-funded study, which appeared online this week in the journal Nature Geoscience.
“Events like this are really important, and we have to understand them better,” said Keigwin. “It certainly calls further attention to the warming we’re seeing in the Arctic today, and the accelerated melting of Greenland ice.”