Dramatic transition of abyssal oceanic carbon reservoir driven by deep ocean overturning circulation during the Cenozoic

The Cenozoic era reflects a discernible global cooling trend attributed to the prolonged decrease in atmospheric pCO₂. Various theories have been proposed to elucidate the mechanisms behind this reduction, with a focus on the substantial carbon exchange between the atmosphere and the global ocean. However, the carbon storage dynamics in the abyssal ocean during the geological past remain enigmatic. Employing a state-of-the-art ocean-biogeochemical model and leveraging recently published paleoceanographic records, this study unveils distinct basin-scale carbon storage patterns in the Pacific and Atlantic in a hypothetical no-Tibetan-Plateau scenario. Through sensitivity experiments, our findings suggest that orographic forcing, specifically the absence of the Tibetan Plateau, may have triggered a significant carbon transition from the Atlantic to the Pacific. This transition appears to be driven by a substantial reorganization of deep ocean overturning circulation. Importantly, this observed phenomenon could be a contributing factor to the long-term reduction in atmospheric pCO₂.