| Summary: | Author Posting. © The Author(s), 2016. This is the author's version of the work. It is posted here by permission of American Association for the Advancement of Science for personal use, not for redistribution. The definitive version was published in Science 353 (2016): 470-474, doi:10.1126/science.aaf5529. The most recent ice age was characterized by rapid and hemispherically asynchronous climate oscillations, whose origin remains unresolved. Variations in oceanic meridional heat transport may contribute to these repeated climate changes, which were most pronounced during the glacial interval twenty-five to sixty thousand years ago known as marine isotope stage 3 (MIS3). Here we examine a sequence of climate and ocean circulation proxies throughout MIS3 at high resolution in a deep North Atlantic sediment core, combining the kinematic tracer Pa/Th with the most widely applied deep water-mass tracer, δ13CBF. These indicators reveal that Atlantic overturning circulation was reduced during every cool northern stadial, with the greatest reductions during episodic iceberg discharges from the Hudson Strait, and that sharp northern warming followed reinvigorated overturning. These results provide direct evidence for the ocean's persistent, central role in abrupt glacial climate change. This research was supported in part by a NSF Graduate Research Fellowship to L.G.H, by awards from the Comer Science and Education Foundation and NSF ATM-0936496 to J.F.M., and an award from the LDEO Climate Center to L.G.H. and J.F.M. LDK and WBC were supported by ATM-0836472, and LDK was supported by AGS 1548160.
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