Eocene Meridional Weather Patterns Reflected in the Oxygen Isotopes of Arctic Fossil Wood

The spectacularly preserved Metasequoia wood excavated from the Fossil Forest site of Axel Heiberg Island (Canadian High Arctic) provides a unique window into the δ 18 O value of Eocene meteoric water via the analysis of fossil cellulose.Seventeen fossilized Metasequoia individuals yielded cellulose with δ 18 O (Vienna standard mean ocean water [VSMOW]) values ranging from 17.1‰ to 21.4‰ and with a mean value of 19.9‰-strikingly low compared to modern trees of all latitudes.Using established biosynthetic relationships for plant cellulose, we reconstructed the δ 18 O (VSMOW) value of Eocene meteoric water to be -15.1‰ on Axel Heiberg Island-a value similar to previous determinations of Eocene terrestrial water using varied paleoenvironmental indicators.A wholly temperature-based interpretation of these isotopic results would predict a mean annual temperature of -2.7 °C, but this is incompatible with extremely high forest productivity.Instead, a calculation of isotopic fractionation in moisture transported from the Pacific Ocean north across North America explains the simultaneous arrival of warm air and isotopically depleted moisture in the Eocene Arctic; we suggest that these meridional weather patterns were caused by the absence of a Polar Front during the ice-free Eocene.