Ocean circulation sensitivity to tectonic gateways changes during the latest Cretaceous

Ocean circulation is a fundamental driver of the Earth's climate, exerting a critical control on the distribution of heat over the globe. Yet in some past warm periods, including the Cretaceous, there is still no consensus on the modes of ocean circulation. During the latest Cretaceous, observational evidence, notably using neodymium isotopes, has inferred that significant reorganizations of the ocean circulation occurred but large discrepancies exist among the results obtained from these studies. The progressive decrease in bottom water epsilon-Nd values in the Atlantic and Southern Ocean during the Campanian and Maastrichtian has for example been explained by the initiation of deep-water formation in the South Atlantic and South Indian Oceans, which then bathed the North Atlantic. However, other data point to deep-water formation in the low-latitude Atlantic and initiation in the North Atlantic during the Maastrichtian. In fact, deep-water production has hitherto been proposed for most of the high-latitudes regions of the latest Cretaceous. As a consequence the locations of deep-water formation and pathways of water masses in the latest Cretaceous remain elusive.

Here we present climate model simulations of the Maastrichtian stage (~ 70 Ma) using the NCAR CESM1 Earth system model to investigate the role of major oceanic gateways on the shape of the global oceanic circulation. Long integrations of CESM (> 3000 years) allow us to focus on the changes driven by the gateways on the intermediate and deep ocean circulation and on the structure of the meridional overturning circulation. The simulated circulation patterns are then compared to the published literature of proxy-based data to improve our understanding of how the ocean engine functioned during the latest Cretaceous.