Subtropical iceberg scours and meltwater routing in the deglacial western North Atlantic
Hill, J.C.; Condron, A. (2014). Subtropical iceberg scours and meltwater routing in the deglacial western North Atlantic. Nature Geoscience 7(11): 806–810. http://dx.doi.org/10.1038/ngeo2267
In: Nature Geoscience. Nature Publishing Group: London. ISSN 1752-0894; e-ISSN 1752-0908, more
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| Abstract |
Abrupt centennial-to-millennial shifts in Northern Hemisphere climate during the last deglaciation are thought to have been triggered by the discharge of large volumes of meltwater and icebergs to the subpolar North Atlantic. Here we show that meltwater and icebergs were also transported directly from the Laurentide ice margin to the subtropical North Atlantic in a narrow coastal current. We present high-resolution bathymetric data from south of Cape Hatteras showing numerous scours that we interpret as relict iceberg keel marks. This indicates that icebergs up to 300 m thick drifted to southern Florida (24.5° N). In simulations with an ocean circulation model, during deglaciation, fresh water and icebergs routinely reached as far south as 32.5° N, in a period of less than four months. The southernmost scours formed only during periods of high meltwater discharge from the Northern Hemisphere ice sheets. In the simulations, such extreme periods of meltwater release led to a reversal of the typically northward surface flow in the nearshore subtropical western North Atlantic. We therefore suggest that significant volumes of iceberg-laden meltwater routinely bypassed subpolar regions and spread across the subtropical North Atlantic. |
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