Letter | Published:

Antarctic glaciation caused ocean circulation changes at the Eocene–Oligocene transition

Nature volume 511, pages 574577 (31 July 2014) | Download Citation

  • An Erratum to this article was published on 28 January 2015

Abstract

Two main hypotheses compete to explain global cooling and the abrupt growth of the Antarctic ice sheet across the Eocene–Oligocene transition about 34 million years ago: thermal isolation of Antarctica due to southern ocean gateway opening1,2,3,4, and declining atmospheric CO2 (refs 5, 6). Increases in ocean thermal stratification and circulation in proxies across the Eocene–Oligocene transition have been interpreted as a unique signature of gateway opening2,4, but at present both mechanisms remain possible. Here, using a coupled ocean–atmosphere model, we show that the rise of Antarctic glaciation, rather than altered palaeogeography, is best able to explain the observed oceanographic changes. We find that growth of the Antarctic ice sheet caused enhanced northward transport of Antarctic intermediate water and invigorated the formation of Antarctic bottom water, fundamentally reorganizing ocean circulation. Conversely, gateway openings had much less impact on ocean thermal stratification and circulation. Our results support available evidence that CO2 drawdown—not gateway opening—caused Antarctic ice sheet growth, and further show that these feedbacks in turn altered ocean circulation. The precise timing and rate of glaciation, and thus its impacts on ocean circulation, reflect the balance between potentially positive feedbacks (increases in sea ice extent and enhanced primary productivity) and negative feedbacks (stronger southward heat transport and localized high-latitude warming). The Antarctic ice sheet had a complex, dynamic role in ocean circulation and heat fluxes during its initiation, and these processes are likely to operate in the future.

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Acknowledgements

A.G. was funded by a Graduate Assistance in Areas of National Need (GAANN) fellowship through the Computational Sciences and Engineering Program at Purdue University. M.H. and N.H. were supported by National Science Foundation (NSF) P2C2 grants OCE 0902882 and EAR 1049921. Computing was performed on Rosen Center for Advanced Computing resources on the Hansen and Coates cluster at Purdue University. Proxy records were compiled from refs 2, 4, and specific records and references are described in extended data. The CESM model is supported and developed by the National Center for Atmospheric Research, which is supported by the NSF.

Author information

Affiliations

  1. Department of Earth, Atmospheric, and Planetary Sciences, Purdue University, West Lafayette, Indiana 47907, USA

    • A. Goldner
  2. American Geophysical Union, Washington DC 20009, USA

    • A. Goldner
  3. Department of Earth Sciences, University of New Hampshire, Durham, New Hampshire 03824, USA

    • N. Herold
    •  & M. Huber
  4. Earth Systems Research Center, Institute for Earth, Ocean and Space Sciences, University of New Hampshire, Durham, New Hampshire 03824, USA

    • M. Huber

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Contributions

A.G. conducted the EOT simulations, recompiled the proxy record data and wrote the manuscript. N.H. and M.H. helped compile the proxy record data and helped with writing the manuscript.

Competing interests

The authors declare no competing financial interests.

Corresponding authors

Correspondence to A. Goldner or M. Huber.

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https://doi.org/10.1038/nature13597

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