Articles | Volume 14, issue 10
Research article
04 Oct 2018
Research article |  | 04 Oct 2018

Temperature seasonality in the North American continental interior during the Early Eocene Climatic Optimum

Ethan G. Hyland, Katharine W. Huntington, Nathan D. Sheldon, and Tammo Reichgelt

Abstract. Paleogene greenhouse climate equability has long been a paradox in paleoclimate research. However, recent developments in proxy and modeling methods have suggested that strong seasonality may be a feature of at least some greenhouse Earth periods. Here we present the first multi-proxy record of seasonal temperatures during the Paleogene from paleofloras, paleosol geochemistry, and carbonate clumped isotope thermometry in the Green River Basin (Wyoming, USA). These combined temperature records allow for the reconstruction of past seasonality in the continental interior, which shows that temperatures were warmer in all seasons during the peak Early Eocene Climatic Optimum and that the mean annual range of temperatures was high, similar to the modern value ( ∼ 26 °C). Proxy data and downscaled Eocene regional climate model results suggest amplified seasonality during greenhouse events. Increased seasonality reconstructed for the early Eocene is similar in scope to the higher seasonal range predicted by downscaled climate model ensembles for future high-CO2 emissions scenarios. Overall, these data and model comparisons have substantial implications for understanding greenhouse climates in general, and may be important for predicting future seasonal climate regimes and their impacts in continental regions.

Short summary
Climate equability is a paradox in paleoclimate research, but modeling suggests that strong seasonality should be a feature of greenhouse Earth periods too. Records of temperature from floral assemblages, paleosol geochemistry, clumped isotope thermometry, and downscaled models during the early Eocene show that the mean annual range of temperature was high, and may have increased during warming events. This has implications for predicting future seasonal climate impacts in continental regions.