A Colder Earth: Modelling carbon cycle perturbations to assess the course of the Eocene-Oligocene Transition

Abstract

Using an adapted version of the model LOSCAR, which simulates the carbon cycle over long time scales, I studied the course of the Eocene-Oligocene Transition (EOT), ca. 34 Ma. Various hypotheses, which try to explain the course of the carbon cycle (d13C, CCD position, CO2, and more) during the EOT, were tested against actual proxy records. They varied from a shelf-to-basin fractionation change, to more biological production, and more. Furthermore, the possibility of an ocean circulation change (better, shift in deep water source) as "initiator" of the EOT was explored. Eventually, two "synthesis scenarios" were formed, which are the best fit, according to the results, with the course of the EOT. They can be divided into one giving more importance to shelf-to-basin fractionation change, and the other giving more importance to increased biological production. The research into a possible ocean circulation change as instigator of the EOT proved less fruitful, due to limitations of the model used.