During the last deglaciation (19,000–9,000 years ago), atmospheric CO2 increased by about 80 ppm. Understanding the mechanisms responsible for this change is a central theme of palaeoclimatology, relevant for predicting future CO2 transfers in a warming world. Deglacial CO2 rise hypothetically tapped an accumulated deep Pacific carbon reservoir, but the processes remain elusive as they are underconstrained by existing tracers. Here we report high-resolution authigenic neodymium isotope data in North Pacific sediment cores and infer abyssal Pacific overturning weaker than today during the Last Glacial Maximum but intermittently stronger during steps of deglacial CO2 rise. Radiocarbon evidence suggestive of relatively ‘old’ deglacial deep Pacific water is reinterpreted here as an increase in preformed 14C age of subsurface waters sourced near Antarctica, consistent with movement of aged carbon out of the deep ocean and release of CO2 to the atmosphere during the abyssal flushing events. The timing of neodymium isotope changes suggests that deglacial acceleration of Pacific abyssal circulation tracked Southern Hemisphere warming, sea-ice retreat and increase of mean ocean temperature. The inferred magnitude of circulation changes is consistent with deep Pacific flushing as a significant, and perhaps dominant, control of the deglacial rise of atmospheric CO2.
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We thank J. Muratli for assistance with bulk sediment digestion and A. Ungerer for assistance with elemental and isotope analyses at the W. M. Keck Collaboratory for Plasma Spectrometry at Oregon State University. We thank the OSU Marine and Geology Repository and the International Ocean Discover Program for providing sediment samples. IODP-U1418 samples were provided by C. Belanger. This study was supported by NSF grant MGG-1357529 (A.C.M. and B.A.H.).
The authors declare no competing interests.
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Du, J., Haley, B.A., Mix, A.C. et al. Flushing of the deep Pacific Ocean and the deglacial rise of atmospheric CO2 concentrations. Nature Geosci 11, 749–755 (2018). https://doi.org/10.1038/s41561-018-0205-6
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