New climate model shows icebergs off the Miami coast


A map showing the pathway taken by icebergs from Hudson Bay, Canada, to Florida. The more blue the color the less salty it is than normal. In this case, blue all the way along the coast shows that very fresh, cold waters flow along the entire east coast from Hudson Bay to Florida.
UMASS AMHERST

A new climate model suggests that during the last ice age, around 20,000 years ago, icebergs were drifting off the coast of Miami.

Oceanographer Alan Condron of the University of Massachusetts Amherst used a first-of-its-kind, high-resolution numerical model to describe ocean circulation during the ice age.

It shows that icebergs and meltwater from the large ice sheet that sat over North America would have regularly reached South Carolina and even southern Florida. The models are supported by the discovery of iceberg scour marks on the sea floor along the entire continental shelf.

His work, conducted with Jenna Hill of Coastal Carolina University, is described in the current advance online issue of Nature Geosciences.

Hill analysed high-resolution images of the sea floor from Cape Hatteras in North Carolina to Florida and identified about 400 scour marks on the seabed that were formed by enormous icebergs plowing through the mud on the sea floor.

These icebergs weren't small, either:

"The depth of the scours tells us that icebergs drifting to southern Florida were at least 1,000 feet, or 300 meters thick," says Condron. "This is enormous. Such icebergs are only found off the coast of Greenland today."

The research has implications for future scenarios:

"This new research shows that much of the meltwater from the Greenland ice sheet may be redistributed by narrow coastal currents and circulate through subtropical regions prior to reaching the subpolar ocean. It's a more complicated picture than we believed before," Condron says. He and Hill say that future research on mechanisms of abrupt climate change should take into account coastal boundary currents in redistributing ice sheet runoff and subpolar fresh water.

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