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Deep Atlantic Ocean carbon storage and the rise of 100,000-year glacial cycles

Nature Geoscience volume 12, pages 355–360 (2019)Cite this article

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Abstract

Over the past three million years, Earth’s climate oscillated between warmer interglacials with reduced terrestrial ice volume and cooler glacials with expanded polar ice sheets. These climate cycles, as reflected in benthic foraminiferal oxygen isotopes, transitioned from dominantly 41-kyr to 100-kyr periodicities during the mid-Pleistocene 1,250 to 700 kyr ago (ka). Because orbital forcing did not shift at this time, the ultimate cause of this mid-Pleistocene transition remains enigmatic. Here we present foraminiferal trace element (B/Ca, Cd/Ca) and Nd isotope data that demonstrate a close linkage between Atlantic Ocean meridional overturning circulation and deep ocean carbon storage across the mid-Pleistocene transition. Specifically, between 950 and 900 ka, carbonate ion saturation decreased by 30 µmol kg−1 and phosphate concentration increased by 0.5 µmol kg−1 coincident with a 20% reduction of North Atlantic Deep Water contribution to the abyssal South Atlantic. These results demonstrate that the glacial deep Atlantic carbon inventory increased by approximately 50 Gt during the transition to 100-kyr glacial cycles. We suggest that the coincidence of our observations with evidence for increased terrestrial ice volume reflects how weaker overturning circulation and Southern Ocean biogeochemical feedbacks facilitated deep ocean carbon storage, which lowered the atmospheric partial pressure of CO2 and thereby enabled expanded terrestrial ice volume at the mid-Pleistocene transition.

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Fig. 1: Location of sediment cores and modern Atlantic Ocean hydrography.
Fig. 2: Site 1267 and 607 circulation and trace element records across the MPT.
Fig. 3: Changes in ocean CO2 feedbacks and climate across the MPT.
Fig. 4: Schematics of proposed coupling between the cryosphere, Atlantic MOC and carbon cycle responses across the MPT.

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Data availability

The datasets generated during the current study are available as Supplementary Tables 2–5, and are publicly accessible at the National Centers for Environmental Information (NCEI): https://www.ncdc.noaa.gov/paleo-search/study/26310.

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Acknowledgements

We thank L. Bolge, J. Falsetta, K. Esswein and A. Dial for laboratory assistance, and D. Sigman for discussions. This research was supported by NSF grant no. OCE 14-36079. J.R.F. acknowledges support from NSF grant no. DGE 16-44869. L.P. acknowledges support from the Ramón y Cajal program and grant no. CTM2016-75411-R (MINECO, Spain).

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  1. J. R. Farmer

    Present address: Department of Geosciences, Princeton University, Princeton, NJ, USA

  2. J. R. Farmer

    Present address: Max-Planck Institut für Chemie, Mainz, Germany

Authors and Affiliations

  1. Department of Earth and Environmental Sciences, Columbia University, New York, NY, USA

    J. R. Farmer, B. Hönisch, L. L. Haynes, M. E. Raymo, S. L. Goldstein & M. Yehudai

  2. Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY, USA

    J. R. Farmer, B. Hönisch, L. L. Haynes, H. L. Ford, M. E. Raymo, M. Jaume-Seguí, S. L. Goldstein, M. Yehudai & J. Kim

  3. School of GeoSciences, University of Edinburgh, Edinburgh, UK

    D. Kroon, S. Jung & D. B. Bell

  4. School of Geography, Queen Mary University of London, London, UK

    H. L. Ford

  5. Department of Earth and Ocean Dynamics, University of Barcelona, Barcelona, Spain

    M. Jaume-Seguí & L. D. Pena

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Contributions

J.R.F., L.D.P., B.H., M.E.R. and S.L.G. designed the study. J.R.F., D.K., S.L.J. and D.B.B. designed the sampling strategy. J.R.F., L.L.H. and H.L.F. performed trace element analyses. M.J.-S., M.Y. and J.K. performed Nd sample processing and isotopic analyses. All authors contributed to the interpretation of results and manuscript preparation.

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Farmer, J.R., Hönisch, B., Haynes, L.L. et al. Deep Atlantic Ocean carbon storage and the rise of 100,000-year glacial cycles. Nat. Geosci. 12, 355–360 (2019). https://doi.org/10.1038/s41561-019-0334-6

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