Modeling present-day spatial and seasonal variability of carbon dioxide in surface waters of the Southern Bight of the North Sea

The 3D ecological MIRO&CO-CO2 model is used to describe the spatial and seasonal variations of air-sea CO2 exchanges in the English Channel and the Southern Bight of the North Sea receiving important nutrient and carbon river loads. Runs are performed for years 2003 and 2004 using actual sea water temperature, light, wind speed and river forcings. MIRO&CO-CO2 simulations show large spatial and seasonal variations of surface pCO2 (range 100 - 600 ppm). Significant under- (and over-) saturation are simulated in spring (and summer) due to the dominance of auto- (and heterotrophic) activities. The highest pCO2 values are simulated in the vicinity of river mouths. Similarly, the computed annual air-sea CO2 fluxes varies spatially, predicting sources of CO2 to the atmosphere near estuaries but moderate sinks (or neutral) in offshore waters. Sensitivity studies are further performed to estimate the contribution of organic and inorganic carbon and nutrient river loads on the air-sea CO2 flux simulated in the area.