Particle flux dynamics amplify marine carbon cycle differences between climate states

Abstract. The ocean represents the largest and most rapidly exchanging carbon reservoir on Earth’s surface and the marine carbon cycle response to changing climate is a matter of continuous investigation. Here, we added dynamic environmental controls on the remineralization and dissolution rates of particulate organic matter, carbonate and silicate minerals (Dinauer et al., 2022) to the Earth system model Bern3D to explore feedbacks between biogenic particle fluxes and marine carbon cycling under different climate conditions. The new representation of marine particle dynamics improves the model’s ability to capture the marine biogeochemical response to long-term cooling, almost doubles the sensitivity of global export production, and amplifies the change in marine carbon storage by a factor of about 1.5. In a model configuration where carbon exclusively cycles between the atmosphere and ocean, this corresponds to an additional atmospheric CO₂ drawdown or increase of approximately 20 ppm in response to a -9.1 °C cooling or +6.8 °C warming, respectively.