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Persistent near-tropical warmth on the Antarctic continent during the early Eocene epoch

Abstract

The warmest global climates of the past 65 million years occurred during the early Eocene epoch (about 55 to 48 million years ago), when the Equator-to-pole temperature gradients were much smaller than today1,2 and atmospheric carbon dioxide levels were in excess of one thousand parts per million by volume3,4. Recently the early Eocene has received considerable interest because it may provide insight into the response of Earth’s climate and biosphere to the high atmospheric carbon dioxide levels that are expected in the near future5 as a consequence of unabated anthropogenic carbon emissions4,6. Climatic conditions of the early Eocene ‘greenhouse world’, however, are poorly constrained in critical regions, particularly Antarctica. Here we present a well-dated record of early Eocene climate on Antarctica from an ocean sediment core recovered off the Wilkes Land coast of East Antarctica. The information from biotic climate proxies (pollen and spores) and independent organic geochemical climate proxies (indices based on branched tetraether lipids) yields quantitative, seasonal temperature reconstructions for the early Eocene greenhouse world on Antarctica. We show that the climate in lowland settings along the Wilkes Land coast (at a palaeolatitude of about 70° south) supported the growth of highly diverse, near-tropical forests characterized by mesothermal to megathermal floral elements including palms and Bombacoideae. Notably, winters were extremely mild (warmer than 10 °C) and essentially frost-free despite polar darkness, which provides a critical new constraint for the validation of climate models and for understanding the response of high-latitude terrestrial ecosystems to increased carbon dioxide forcing.

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Figure 1: Site location and continental setting of Antarctica during early Eocene times.
Figure 2: Data from Site U1356 for the early Eocene to mid-Eocene.
Figure 3: Climate reconstruction for the Wilkes Land sector of Antarctica during the early and mid-Eocene derived from Site U1356.

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Acknowledgements

This research used samples and data provided by the Integrated Ocean Drilling Program (IODP). The IODP is sponsored by the US National Science Foundation and participating countries under the management of Joint Oceanographic Institutions, Inc. Financial support for this research was provided by the German Research Foundation, to J.P. (grant PR 651/10) and U.R. (grant RO 1113/6); the Biodiversity and Climate Research Center of the Hessian Initiative for Scientific and Economic Excellence, to J.P.; the Netherlands Organisation for Scientific Research, to H.B. and S.S. (VICI grant); the Natural Sciences and Engineering Research Council of Canada, to D.R.G. (grant DG 311934); the Natural Environment Research Council, to S.M.B. (grant Ne/J019801/1), J.A.B. (grant Ne/I00646X/1) and T.v.d.F. (grant Ne/I006257/1); the US National Science Foundation, to L.T. (grant OCE 1058858); and the New Zealand Ministry of Science and Innovation, to J.I.R.. We thank J. Francis, S. Gollner and M. Huber for discussions, and B. Coles, E. Hopmans, K. Kreissig, A. Mets, J. Ossebaar, B. Schminke, J. Treehorn and N. Welters for technical support.

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J.P., H.B. and S.S. designed the research. L.C., J.P. and J.I.R. analysed the sporomorphs, D.R.G. and L.C. conducted the quantitative climate reconstructions, and P.K.B. and S.S. carried out the MBT/CBT analyses. All authors contributed to the interpretation of the data. J.P. wrote the paper with input from all authors.

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Correspondence to Jörg Pross or Jörg Pross.

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Supplementary information

Supplementary Information

This file contains Supplementary Text, Supplementary Figures 1-7, Supplementary Table 1 and additional references. (PDF 8516 kb)

Supplementary Data

This file contains Supplementary Data, including all sporomorph data, sporomorph-based climate estimates and MBT/CBT data. (XLS 390 kb)

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Pross, J., Contreras, L., Bijl, P. et al. Persistent near-tropical warmth on the Antarctic continent during the early Eocene epoch. Nature 488, 73–77 (2012). https://doi.org/10.1038/nature11300

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