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Ventilation Changes Drive Orbital‐Scale Deoxygenation Trends in the Late Cretaceous Ocean

Mechanisms that drive cyclicity in marine sediment deposits during hothouse climate periods in response to Earth's orbit variations remain debated. Orbital cycles fingerprint in the oceanographic records results from the combined effect of terrestrial (e.g., Weathering derived nutrient supply, freshwater discharge) and oceanic (e.g., productivity, oxygenation) processes, whose respective contribution remains to be clarified. Here we investigate the effect of extreme orbital configurations on the oxygenation state of the ocean using marine biogeochemistry simulations with the IPSL‐CM5A2 Earth System Model under Cenomanian‐Turonian boundary conditions. Our simulations show that small changes in ocean ventilation triggered by orbitally induced variations in deep water formation have a strong impact on the spatial distribution of dissolved oxygen. This phenomena is amplified in enclosed and already poorly oxygenated basins, such as the proto‐Atlantic ocean, where up to 50% of the water volume become anoxic for some of the configurations.