Timing of iceberg scours and massive ice-rafting events in the subtropical North Atlantic

High resolution seafloor mapping shows extraordinary evidence that massive (>300m thick) icebergs once drifted >5,000km south along the eastern United States, with over 700 iceberg scours now identified south of Cape Hatteras. Sediment cores collected from several buried scours show multiple plow marks are ~31,000 years old and align with Heinrich Event 3 (H3). An accompanying set of numerical glacial iceberg simulations performed with an eddy permitting ocean model show that the transport of icebergs to these sites only occurs during massive, but short-lived, periods of elevated meltwater discharge. As H3 was associated with only a modest increase in ice-rafting across the subpolar North Atlantic, we propose that meltwater and icebergs were repeatedly routed to the subtropics during this event. Stratigraphy from subbottom data across the scour marks shows there are additional features that are both older and younger, and may align with other periods of elevated meltwater discharge. Finally, the subtropical iceberg-meltwater pathway identified supports a complex relationship between freshwater forcing and climate change given meltwater may initially be routed far to the south of deep-water formation sites.