https://doi.org/10.5194/cp-2020-32 Preprint. Discussion started: 24 March 2020 c Author(s) 2020. CC BY 4.0 License. 1 Paleobotanical proxies for early Eocene climates and ecosystems in northern North 2 America from mid to high latitudes 3 4 Christopher K. West1, David R. Greenwood2, Tammo Reichgelt3, Alexander J. Lowe4, Janelle M. 5 Vachon2, and James F. Basinger1. 6 1 Dept. of Geological Sciences, University of Saskatchewan, 114 Science Place, Saskatoon, 7 Saskatchewan, S7N 5E2, Canada. 8 2 Dept. of Biology, Brandon University, 270-18th Street, Brandon, Manitoba R7A 6A9, Canada. 9 3 Department of Geosciences, University of Connecticut, Beach Hall, 354 Mansfield Rd #207, 10 Storrs, CT 06269, U.S.A. 11 4 Dept. of Biology, University of Washington, Seattle, WA 98195-1800, U.S.A. 12 13 Correspondence to: C.K West (
[email protected]) 14 15 Abstract. Early Eocene climates were globally warm, with ice-free conditions at both poles. Early 16 Eocene polar landmasses supported extensive forest ecosystems of a primarily temperate biota, 17 but also with abundant thermophilic elements such as crocodilians, and mesothermic taxodioid 18 conifers and angiosperms. The globally warm early Eocene was punctuated by geologically brief 19 hyperthermals such as the Paleocene-Eocene Thermal Maximum (PETM), culminating in the 20 Early Eocene Climatic Optimum (EECO), during which the range of thermophilic plants such as 21 palms extended into the Arctic. Climate models have struggled to reproduce early Eocene Arctic 22 warm winters and high precipitation, with models invoking a variety of mechanisms, from 23 atmospheric CO2 levels that are unsupported by proxy evidence, to the role of an enhanced 24 hydrological cycle to reproduce winters that experienced no direct solar energy input yet remained 25 wet and above freezing.