An Earth System modeling study of the recent geological history of the global oceanic circulation over the Cenozoic

International audienceThe impact of the Drake Passage (DP) opening on climate is being debated for dozens of years. Indeed, being one of the major geographical changes occurring during the Eocene and at the beginning of a global climate cooling, it has often generated a lot of interest. To date, even though the overall signal remains unclear, it is considered as one of the main potential cause of the contemporaneous climate change. Several model studies have been aiming to assess the importance of this gateway opening through different more or less complex models. However, according to our knowledge on palaeoenvironments, most of them considered unrealistic boundary conditions (notably a low pCO2 or a today-like geography) that might corrupt the transposition of their results to the original deep-time context. In order to better understand if and how climate might have been affected by this gateway opening, the DP question is here evaluated using an up2date IPCC like model, the IPSL-CM5A2. Several simulations have been done using boundary conditions encountered over the Cenozoic from the Early Eocene to the Middle Miocene. For each time period, the role of the atmospheric CO2 level and of the depth and geometry of major marine gateways have been tested. We aim here to better understanding the history of the deep oceanic circulation and its link to the strength of the Antarctic Circumpolar Current. A particular focus will be done on the Eocene-Oligocene transition and on the Early Miocene, a time period during which it has been suggested a narrowing of the Drake Passage. Finally, the impact of the East Tethysian gateway will also be studied both on the global oceanic circulation and on its impact on atmospheric dynamics, specifically over the continents surrounding the Mediterranean region