When we think of icebergs, we usually picture the cold, wind-chilled expanses of the Arctic and Antarctic, but new research has shown that these massive slabs of ice once drifted as far south as sunny south Florida.
Using a first-of-its-kind, high-resolution climate model, researchers discovered iceberg scour marks on the sea floor along the entire continental shelf. It seems that during the last ice age about 21,000 years ago, icebergs and meltwater from the North American ice sheet would have regularly reached South Carolina and even southern Florida.
This finding, described in the journal Nature Geoscience, exposes just how abrupt and complex the effects of climate change can be.
"Our study is the first to show that when the large ice sheet over North America known as the Laurentide ice sheet began to melt, icebergs calved into the sea around Hudson Bay and would have periodically drifted along the east coast of the United States as far south as Miami and the Bahamas in the Caribbean, a distance of more than 3,100 miles, about 5,000 kilometers," lead researcher and oceanographer Alan Condron of the University of Massachusetts Amherst said in a press release.
Condron, in collaboration with Jenna Hill of Coastal Carolina University, analyzed high-resolution images of the sea floor from Cape Hatteras to Florida, identifying about 400 scour marks on the seabed left behind from dragging icebergs. As the bergs moved into more shallow waters, their rough bottoms scraped along the ocean bottom, leaving behind obvious pits and grooves.
"The depth of the scours tells us that icebergs drifting to southern Florida were at least 1,000 feet, or 300 meters thick," Condron said. "This is enormous. Such icebergs are only found off the coast of Greenland today."
So how could these massive slabs have made it as far south as Florida? According to the researchers' ocean circulation model, which simulated the release of a series of glacial meltwater floods, a catastrophic flood event would have had to occur, releasing enormous volumes of meltwater into the ocean from the Laurentide ice sheet, from either Hudson Bay or the Gulf of St. Lawrence.
This, is turn, would have caused the surface ocean current to undergo a complete 180, "so that the warm, northward flowing Gulf Stream would have been replaced by a cold, southward flowing current," the researchers write. This would make waters off Florida only a few degrees above freezing, however, this event wouldn't have lasted for long, maybe less than a year.
Condron and Hill say this discovery could be useful in future research on abrupt climate change.