Impact of marine gateways on oceanic circulation and carbon cycle in the Late Eocene

The Late Eocene is a period of global cooling and high-latitude tectonic changes culminating in the Eocene Oligocene Transition (34 Ma ago), one of the major climatic shifts of the Cenozoic. Across the Late Eocene, the Earth went from a largely ice-free greenhouse during the early Eocene climatic optimum to an icehouse with the ice sheet inception over Antarctica. This long-term cooling happened simultaneously with a decrease in the atmospheric content in carbon dioxide whose causes are still unclear. During the same period, marine gateways surrounding Antarctica (Drake Passage and Tasman Gateway) opened and deepened and Atlantic-Artic gateways changed configurations, thereby allowing the onset of oceanic currents such as the circumpolar current isolating Antarctica.

Here, we investigate how coupled changes in the configuration of these gateways impact the oceanic circulation and carbon cycle, in particular the distribution of δ¹³C. Applying for the first time the carbon isotopes-enabled version of PISCES (Buchanan et al. 2021) to the Late Eocene,  we present and analyze a set of experiments with different gateways configurations with a specific focus on the reorganization of ocean circulation and its consequence on carbon isotopes distribution and gradients. We then compare our model results to available proxy data and discuss hypotheses regarding Late Eocene δ¹³C changes.