Experts: ‘Big Freeze’ about 12,800 years ago happened within months

In the film, "The Day After Tomorrow,” the world gets gripped in ice within the span of just a few weeks. Now research now suggests an eerily similar event might indeed have occurred in the past.

Looking ahead to the future, there is no reason why such a freeze shouldn’t happen again — and in ironic fashion it could be precipitated if ongoing changes in climate force the Greenland ice sheet to suddenly melt, scientists say.

Starting roughly 12,800 years ago, the Northern Hemisphere was gripped by a chill that lasted some 1,300 years. Known by scientists as the Younger Dryas and nicknamed the”Big Freeze,” geological evidence suggests it was brought on when a vast pulse of fresh water — a greater volume than all of North America’s Great Lakes combined — poured into the Atlantic and Arctic Oceans.

This abrupt influx, caused when the glacial Lake Agassiz in North America burst its banks, diluted the circulation of warmer water in the North Atlantic, bringing this "conveyer belt” to a halt.

Without this warming influence, evidence shows that temperatures across the Northern Hemisphere plummeted.
No time to react

Previous evidence from Greenland ice samples had suggested this abrupt shift in climate happened over the span of a decade or so. Now researchers say it surprisingly may have taken place over the course of a few months, or a year or two at most.

"That the climate system can turn on and off that quickly is extremely important,” said earth system scientist Henry Mullins at Syracuse University, who did not take part in this research. "Once the tipping point is reached, there would be essentially no opportunity for humans to react.”

For two years, isotope biogeochemist William Patterson at the University of Saskatchewan in Canada and his colleagues investigated a mud core — a tube of mud — taken from the ancient lake Lough Monreach in Ireland.

Because this sediment was deposited slowly over time, each layer from this core effectively represents a snapshot of history, with slices just a half-millimeter thick presenting one to three months.

"Basically, I drive around in western Ireland looking for the right conditions — bedrock, vegetation and lake — to obtain the most complete record of climate,” Patterson explained.

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