Between 20,000 and 10,000 years ago, icebergs released from the ice sheet covering the eastern region of North America drifted as far south as Florida, reports a paper published online in Nature Geoscience.
Jenna Hill and Alan Condron used maps of the seafloor to the south of Cape Hatteras, North Carolina, to identify numerous long, narrow grooves that were carved out by icebergs. The shape and distribution of the scars implies they were made by icebergs up to 300 metres thick. Based on a numerical model of ocean circulation, the authors argue that the icebergs were carried there by a narrow cold coastal current formed during periods when water from the melting North American ice sheet was discharged to the ocean. Relatively small pulses of meltwater could have transported icebergs as far south as South Carolina, but icebergs only reached the Florida coast during periods of intense meltwater discharge.