TULANE (US)—Earth was just coming out of an ice age 9,300 years ago when a cataclysmic event occurred that plunged the planet into a cold “snap” that lasted for centuries.

Scientists have suspected that water melted from snow and ice introduced into the North Atlantic Ocean was the cause—but the source and volume were a mystery.

A new study led by Tulane University researcher Shiyong Yu pinpoints the source.

In the study, published in Science, Yu and coauthors say that a natural dam on the southeast corner of Lake Superior breached, triggering a massive flood.

By dating the age of separation of small basins from Lake Superior, Yu and his research team determined the amount, timeframe and pathway of this flood.

Rapidly—perhaps in a matter of months—Lake Superior dropped 45 meters as its waters spilled into southern Canada to the ocean, raising sea level and dropping temperatures worldwide.

“The ocean circulation might be more sensitive to freshwater perturbation than we thought before,” says Yu. “Today, we are quite concerned about global warming. The accelerated melting of the Arctic ice pack could potentially slow the ocean circulation and push the Earth into a cold snap in a similar manner.”

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