Constraining the early Eocene climatic optimum: A terrestrial interhemispheric comparison

The early Eocene climatic optimum was a period of major climatic and environmental change that was caused by perturbations to the global carbon cycle. Recent work from terrestrial sections in the Northern Hemisphere demonstrates that the period was characterized by different responses in the terrestrial and marine realms, suggesting that traditional causal mechanisms may not adequately explain the dynamics of the early Eocene climatic optimum. Here, we present a new high-resolution multiproxy record of terrestrial climatic and environmental conditions during the early Eocene climatic optimum from the Southern Hemisphere and compare this reconstruction to other marine and terrestrial records. Similar to Northern Hemisphere terrestrial records, there is a transient peak period of atmospheric carbon isotope enrichment as well as increased temperatures and precipitation, which indicate that terrestrial environmental responses to the early Eocene climatic optimum were broadly consistent in temperate settings worldwide. This global consistency in terrestrial records demonstrates differences in peak warming time scales and carbon isotope responses between marine and terrestrial systems, which further constrain potential causes for the early Eocene climatic optimum to multiple-system or nontraditional mechanisms and highlight the importance of paired records for understanding past climate.