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Climate of the Past An interactive open-access journal of the European Geosciences Union
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https://doi.org/10.5194/cp-2020-32
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/cp-2020-32
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 24 Mar 2020

Submitted as: research article | 24 Mar 2020

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This preprint is currently under review for the journal CP.

Paleobotanical proxies for early Eocene climates and ecosystems in northern North America from mid to high latitudes

Christopher K. West1, David R. Greenwood2, Tammo Reichgelt3, Alex J. Lowe4, Janelle M. Vachon2, and James F. Basinger1 Christopher K. West et al.
  • 1Dept. of Geological Sciences, University of Saskatchewan, 114 Science Place, Saskatoon, Saskatchewan, S7N 5E2, Canada
  • 2Dept. of Biology, Brandon University, 270-18th Street, Brandon, Manitoba R7A 6A9, Canada
  • 3Department of Geosciences, University of Connecticut, Beach Hall, 354 Mansfield Rd #207, Storrs, CT 06269, U.S.A.
  • 4Dept. of Biology, University of Washington, Seattle,WA 98195-1800, U.S.A.

Abstract. Early Eocene climates were globally warm, with ice-free conditions at both poles. Early Eocene polar landmasses supported extensive forest ecosystems of a primarily temperate biota, but also with abundant thermophilic elements such as crocodilians, and mesothermic taxodioid conifers and angiosperms. The globally warm early Eocene was punctuated by geologically brief hyperthermals such as the Paleocene-Eocene Thermal Maximum (PETM), culminating in the Early Eocene Climatic Optimum (EECO), during which the range of thermophilic plants such as palms extended into the Arctic. Climate models have struggled to reproduce early Eocene Arctic warm winters and high precipitation, with models invoking a variety of mechanisms, from atmospheric CO2 levels that are unsupported by proxy evidence, to the role of an enhanced hydrological cycle to reproduce winters that experienced no direct solar energy input yet remained wet and above freezing. Here, we provide new estimates of climate, and compile existing paleobotanical proxy data for upland and lowland mid-latitudes sites in British Columbia, Canada, and northern Washington, USA, and from high-latitude lowland sites in Alaska and the Canadian Arctic to compare climatic regimes between mid- and high latitudes of the early Eocene – spanning the PETM to the EECO – of the northern half of North America. In addition, these data are used to reevaluate the latitudinal temperate gradient in North America during the early Eocene, and to provide refined biome interpretations of these ancient forests based on climate and physiognomic data.

Christopher K. West et al.

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Christopher K. West et al.

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Short summary
Fifty-six million years ago during the globally warm early Eocene lush forests extended up to the High Arctic. Fossil plants from the Canadian High Arctic and Pacific Northwest of North America are a window into the past ‘greenhouse world’. We used an improved method for plant fossil climate reconstruction that provides a consensus of all available methods to analyze fossil plant sites from the Pacific Northwest and the Canadian Arctic. Results show climate in northern North America was similar.
Fifty-six million years ago during the globally warm early Eocene lush forests extended up to...
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