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Og det kan skje fort. Dersom Nord-Atlanterens strømmer forstyrres, kan den nordlige halvkule bli forandret til is i løpet av måneder, ikke engang tiår. Den siste istiden skyldtes nettopp at det rant mye ferskvann ut i havet i løpet av kort tid. En rask nedsmelting av isbreene på Grønland kunne gi samme effekten.

William Patterson, from the University of Saskatchewan in Canada, and his colleagues have shown that switching off the North Atlantic circulation can force the Northern hemisphere into a mini 'ice age' in a matter of months. Previous work has indicated that this process would take tens of years.

Around 12,800 years ago the northern hemisphere was hit by a mini ice-age, known by scientists as the Younger Dryas, and nicknamed the 'Big Freeze', which lasted around 1300 years. Geological evidence shows that the Big Freeze was brought about by a sudden influx of freshwater, when the glacial Lake Agassiz in North America burst its banks and poured into the North Atlantic and Arctic Oceans. This vast pulse, a greater volume than all of North America's Great Lakes combined, diluted the North Atlantic conveyor belt and brought it to a halt.

- Science Daily