1. Department of Geology and Geophysics, Yale University, PO Box 208109, New Haven, Connecticut 06520, USA
2. Earth and Atmospheric Sciences Department and the Purdue Climate Change Research Center, Purdue University, 550 Stadium Mall Drive, West Lafayette, Indiana 47906, USA
3. Palaeoecology, Institute of Environmental Biology, Utrecht University, Laboratory of Palaeobotany and Palynology, Budapestlaan 4, 3584 CD, Utrecht, The Netherlands
4. Royal Netherlands Institute for Sea Research (NIOZ), Department of Marine Biogeochemistry and Toxicology, PO Box 59, 1790 AB, Den Burg, Texel, The Netherlands
5. Faculty of Geosciences, Department of Earth Sciences, Utrecht University, Budapestlaan 4, 3584 CD, Utrecht, The Netherlands
6. Department of Earth Sciences, Rice University, 6100 Main Street, Houston, Texas 77005, USA
7. *These authors contributed equally to this work
8. †A list of authors and affiliations appears at the end of the paper
9. Department of Geology and Geochemistry, Stockholm University, Stockholm, SE-10691, Sweden
10. Geological Sciences, Brown University, 324 Brook Street, PO Box 1846, Providence, Rhode Island 02912-1846, USA
11. US Geological Survey, Eastern Earth Surface Processes Team, 926A USGS National Center, Reston, Virginia 20192, USA
12. Department de Géologie et Océanographie, Université Bordeaux 1, Avenue des facultés, c/o Bernei Housen, 33405 Talence Cedex, France
13. Department of Geophysics, CEREGE (CNRS)/University of Aix-Marseille 3, BP80, 13545 Aix-en-Provence Cedex 4, France
14. Department of Geology and Geochemistry, Stockholm University, 10691 Stockholm, Sweden
15. Department of Earth and Environmental Sciences, Faculty of Science, Yamagata University, 1-4-12 Kojirakawa-machi, Yamagata 990-8560, Japan
16. Department of Earth Sciences, University College London, Gower Street, London WC1E 6BT, UK
17. Graduate School of Oceanography, University of Rhode Island, Narragansett Bay Campus, South Ferry Road, Narragansett, Rhode Island 02882, USA
18. Norwegian Polar Institute, Polar Environmental Center, N-9296 Tromsø, Norway
19. Department of Earth Sciences, Boston University, 685 Commonwealth Avenue, Boston, Massachusetts 02215, USA
20. British Geological Survey, Murchison House, West Mains Road, Edinburgh EH9 3LA, UK
21. Geological Sciences, University of Michigan, Ann Arbor, Michigan 48109-1063, USA
22. Department of Earth and Planetary Sciences, Graduate School of Sciences, Kyushu University, Hakozaki 6-10-1, Higashi-ku, Fukuoka 812-8581, Japan
23. School of Ocean and Earth Science, University of Southampton, Southampton Oceanography Centre, European Way, Southampton SO14 3ZH, UK
24. Department of Geography and Environment, School of Geosciences, University of Aberdeen, Elphinstone Road, Aberdeen AB24 3UF, UK
25. Department of Geology, Paleontology and Geophysics, University of Padova, Via Giotto 1 I-35137 Padova, Italy
26. Institute for Research on Earth Evolution (IFREE), Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Natsushima-cho 2-15, Yokosuka 237-0061, Japan
27. Department of Geology and Environmental Science, MSC7703, James Madison University, Harrisonburg, Virginia 22807, USA
28. Institute of Life and Environmental Science, University of Tsukuba, Tennoudai 1-1-1, Tsukuba, Ibaraki 305-8572, Japan
29. Institute of Geology and Paleontology, Graduate School of Science, Tohoku University, Aramaki, Aoba, Aoba-ku, Sendai City 980-8578, Japan
30. Institute of Geoscience, National Institute of Advanced Industrial Science, and Technology (Geological Survey of Japan), AIST Tsukuba Central 7, Higashi-1-1-1, Tsukuba, Ibaraki 305-8567, Japan
31. Graduate School of Environmental Earth Science, Hokkaido University, Kita-10, Nishi-5, Kita-ku, Sapporo 060-0810, Japan

Correspondence to: Mark Pagani^1,7 Correspondence and requests for materials should be addressed to M.P. (Email: mark.pagani@yale.edu).

Abstract

The Palaeocene/Eocene thermal maximum represents a period of rapid, extreme global warming 55 million years ago, superimposed on an already warm world^{1, 2, 3}. This warming is associated with a severe shoaling of the ocean calcite compensation depth⁴ and a >2.5 per mil negative carbon isotope excursion in marine and soil carbonates^{1, 2, 3, 4}. Together these observations indicate a massive release of ¹³C-depleted carbon⁴ and greenhouse-gas-induced warming. Recently, sediments were recovered from the central Arctic Ocean⁵, providing the first opportunity to evaluate the environmental response at the North Pole at this time. Here we present stable hydrogen and carbon isotope measurements of terrestrial-plant- and aquatic-derived n-alkanes that record changes in hydrology, including surface water salinity and precipitation, and the global carbon cycle. Hydrogen isotope records are interpreted as documenting decreased rainout during moisture transport from lower latitudes and increased moisture delivery to the Arctic at the onset of the Palaeocene/Eocene thermal maximum, consistent with predictions of poleward storm track migrations during global warming⁶. The terrestrial-plant carbon isotope excursion (about -4.5 to -6 per mil) is substantially larger than those of marine carbonates. Previously, this offset was explained by the physiological response of plants to increases in surface humidity². But this mechanism is not an effective explanation in this wet Arctic setting, leading us to hypothesize that the true magnitude of the excursion—and associated carbon input—was greater than originally surmised. Greater carbon release and strong hydrological cycle feedbacks may help explain the maintenance of this unprecedented warmth.

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