Scientists report that near the end of the last Ice Age, about 8,000 years ago, an ice dam on North America's east coast broke. This released a torrent of fresh water seven times more voluminous than all the Great Lakes combined. All the water rushed into the Atlantic Ocean over the course of only a few months.
At around the same time, ocean circulation worldwide slowed to a crawl, plunging Europe into a second ice age that lasted centuries.
Scientists have long suspected the two events were linked, and now they have the evidence from sediment core samples to prove it.
The finding, detailed in the June 30 issue of the journal Science, provides the first clear evidence that the so-called North American "lake burst" was the trigger that slowed ocean circulation and cooled the climate about 8,200 years ago.