The Bay of Marseille (BoM), located in the northwestern Mediterranean Sea, is affected by various hydrodynamic processes (e.g., Rh & ocirc;ne River intrusion and upwelling events) that result in a highly complex local carbonate system. In any complex environment, the use of models is advantageous since it allows us to identify the different environmental forcings, thereby facilitating a better understanding. By combining approaches from two biogeochemical ocean models and improving the formulation of total alkalinity, we develop a more realistic representation of the carbonate system variables at high temporal resolution, which enables us to study air-sea CO2 fluxes and seawater pCO(2) variations more reliably. We apply this new formulation to two particular scenarios that are typical for the BoM: (i) summer upwelling and (ii) Rh & ocirc;ne River intrusion events. In both scenarios, our model was able to correctly reproduce the observed patterns of pCO(2) variability. Summer upwelling events are typically associated with a pCO(2) decrease that mainly results from decreasing near-surface temperatures. Furthermore, Rh & ocirc;ne River intrusion events are typically associated with a pCO(2) decrease, although, in this case, the pCO(2) decrease results from a decrease in salinity and an overall increase in total alkalinity. While we were able to correctly represent the daily range of air-sea CO2 fluxes, the present configuration of Eco3M_MIX-CarbOx does not allow us to correctly reproduce the annual cycle of air-sea CO2 fluxes observed in the area. This pattern directly impacts our estimates of the overall yearly air-sea CO2 flux as, even if the model clearly identifies the bay as a CO2 sink, its magnitude was underestimated, which may be an indication of the limitations inherent in dimensionless models for representing air-sea CO2 fluxes.
