Prehistoric currents brought icebergs to Florida

Pensioners flock to Florida from colder North American climes to spend their days basking in the sun and soaking in the warm subtropical waters. Now researchers say that thousands of years ago, icebergs did the same thing.

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Alan Condron, a climate modeller at the University of Massachusetts in Amherst, and Jenna Hill, a marine geologist at Coastal Carolina University in Conway, South Carolina, used a computer climate model to map the icebergs’ path with higher spatial resolution than previous simulations. As the massive North American ice sheet began to melt 20,000 years ago, fresh water pooled into lakes dammed by glaciers and debris. When those lakes burst, floods carried icebergs into the northern Atlantic Ocean. Modelling studies have suggested that these hulking masses drifted east, past Greenland and towards Europe. But a study published on 12 October in Nature Geoscience reports evidence that the icebergs took a southerly route — a finding that offers a glimpse of how the changing climate can affect ocean circulation.

Their results show that some of the glacial floodwater running off North America formed a narrow current some 100 kilometres wide that flowed south along the continental shelf from the tip of present-day Newfoundland. Icebergs carried along by these flows would have reached South Carolina within a few months — and in some larger floods, would have reached Florida. The bergs would have been as large as some that calve from Greenland today, extending as far as 300 metres below the surface.

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