Experts published evidence on Friday to support a popular theory that rising temperatures caused a big melt of polar ice 8200 years ago, causing a freshwater flood into the salty North Atlantic. 

This would have changed the flow of the balmy Gulf Stream and, in just a few years, average temperatures plummeted, ushering in a deep freeze that lasted a century or more, researchers have proposed. 

Writing in the 11 December issue of Geophysical Research Letters, Torbjorn Tornqvist, an assistant professor of earth and environmental sciences at the University of Illinois at Chicago, says he has evidence that this happened. 

"Few would argue it's the most dramatic climate change in the last 10,000 years," Tornqvist said. "We're now able to show the first sea-level record that corresponds to that event." 

Evidence found

Tornqvist and some graduate students found the evidence along the Gulf of Mexico off the southern US coast. 

They found peat deposits that would have been formed under rising sea levels. Working with researchers in the Netherlands, they dated the material to 8200 years ago. 

Their composition suggested they were made when a saltwater marsh was abruptly flooded and turned into a lagoon. 

"Climatologists urgently need this type of information to run their climate models in order to understand the conditions that can produce such an abrupt climate change," Tornqvist said.