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 may impact oceanic circulation and carbon cycle using climate simulations performed with the IPSL-CM5A2 model, an Earth System Model equipped with the biogeochemical model PISCES. Our reference simulation uses the paleogeography from Poblete et al (2021), based on the paleobathymetry of Straume et al (2020). Several sensitivity experiments with different gateway configurations are then presented and discussed, with specific focus on global ocean circulation changes and implications for the carbon cycle.