Temperature - carbon cycle interactions during the Early Eocene Climatic Optimum (ODP Site 1263, Walvis Ridge)

The Late Paleocene to Early Eocene warming trend is characterized by a gradual temperature rise culminating in the Early Eocene Climatic Optimum “EECO”. This warming trend was punctuated by several hyperthermals, which were geologically brief (<200kyr) episodes of extreme warmth. Recently, Lauretano et al. (2016) published a new high-resolution benthic foraminiferal stable isotope record of ODP Site 1263, which encompasses the EECO. This record confirms the presence of hyperthermals during and at the termination of the EECO as was previously found for ODP Site 1258 (Kirtland-Turner et al., 2014). Also, the record reveals a highly significant linear relationship between ∂18O and ∂13C for these events, similar to the PETM and ETM2. This indicates a strong coupling between global warming and the release of isotopically light carbon into the ocean-atmosphere system during these events. However, whilst the coupling between temperature changes and perturbations in the exogenic carbon pool remain stable on short-term time scales, they do not for the long-term trend. At ~52 Ma a rapid 13C enrichment in carbon data occurs that is not accompanied by changes in the oxygen record. It was hypothesized that enhanced carbonate and organic carbon burial rates might be responsible for this shift in average isotopic values during a temporary reduced efficiency of the biological pump. To test this hypothesis, additional records over various water depths are necessary to create a depth-transect. We will present our new stable isotopic results of two planktic foraminiferal species derived from the same samples as Lauretano et al. (2016), which portray changes in surface (Acarinina ssp.) and thermocline (Subbotina ssp.) waters. Since high-resolution planktic foraminiferal records covering the EECO are still scarce, these records will also help confirm the presence of the “new” hyperthermals during the peak and termination of the EECO, as one would expect for global events.