As much as 1 million cubic meters of freshwater per second  pouring into the Arctic Ocean from northwestern Canada might have triggered the last major cold spell, nearly 13,000 years ago.
     Computer simulations indicate ocean currents would have transported the Arctic floodwaters to the North Atlantic near Greenland, disrupting the ocean's circulation and causing temperatures to plummet.
     The 1,200-year-long cold spell, known as the Younger Dryas, interrupted a warm period 12,900 years ago when the massive ice sheet covering much of Canada was melting. During the cold snap, temperatures in parts of the Northern Hemisphere dropped to about 10 degrees Celsius colder than they are today.
     "Dumping water in the Arctic is a very efficient way to… cool the Northern Hemisphere," says Richard Peltier, a physicist at the University of Toronto. The result fits with previous findings of boulders and gravels in the Mackenzie Valley that suggest a giant flood happened at the onset of the Younger Dryas.
     Co-author Alan Condron, a physical oceanographer at the University of Massachusetts, Amherst (USA), plans to search for more geological clues of a Mackenzie Valley flood. He's also running simulations of what might happen in the future as Greenland's ice sheet melts.

Edited from ScienceNews (5 November 2012)