1. Shell Exploration and Production UK Ltd, 1 Altens Farm Road, Nigg, Aberdeen, AB12 3FY, UK
2. Biology Department, Brandon University, 270 18th Street, Brandon, Manitoba, R7A 6A9, Canada
3. School of Ocean and Earth Science, National Oceanography Centre, University of Southampton, European Way, Southampton, SO14 3ZH, UK
4. Earth and Atmospheric Sciences Department, Purdue Climate Change Research Center, Purdue University, 550 Stadium Mall Drive, West Lafayette, Indiana 47906, USA

Correspondence to: James S. Eldrett¹ Correspondence and requests for materials should be addressed to J.S.E. (Email: james.eldrett@shell.com).

Abstract

A profound global climate shift took place at the Eocene–Oligocene transition (33.5 million years ago) when Cretaceous/early Palaeogene greenhouse conditions gave way to icehouse conditions^{1, 2, 3}. During this interval, changes in the Earth's orbit and a long-term drop in atmospheric carbon dioxide concentrations^{4, 5, 6} resulted in both the growth of Antarctic ice sheets to approximately their modern size^{2, 3} and the appearance of Northern Hemisphere glacial ice^{7, 8}. However, palaeoclimatic studies of this interval are contradictory: although some analyses indicate no major climatic changes^{9, 10}, others imply cooler temperatures¹¹, increased seasonality^{12, 13} and/or aridity^{12, 13, 14, 15}. Climatic conditions in high northern latitudes over this interval are particularly poorly known. Here we present northern high-latitude terrestrial climate estimates for the Eocene to Oligocene interval, based on bioclimatic analysis of terrestrially derived spore and pollen assemblages preserved in marine sediments from the Norwegian–Greenland Sea. Our data indicate a cooling of 5 °C in cold-month (winter) mean temperatures to 0–2 °C, and a concomitant increased seasonality before the Oi-1 glaciation event. These data indicate that a cooling component is indeed incorporated in the ¹⁸O isotope shift across the Eocene–Oligocene transition. However, the relatively warm summer temperatures at that time mean that continental ice on East Greenland was probably restricted to alpine outlet glaciers.

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