Assessing the sensitivity of modeled air-sea CO₂ exchange to the remineralization depth of particulate organic and inorganic carbon

To assess the sensitivity of surface ocean pC0₂ and air-sea CO₂ fluxes to changes in the remineralization depth of particulate organic and inorganic carbon (POC, PIC), a biogeochemical ocean circulation model (PISCES) was run with different parameterizations for vertical particle fluxes. On the basis of fluxes of POC and PIC, productivity, export, and the distributions of nitrogen (NO3), dissolved inorganic carbon (DIC), and alkalinity, a number of indices defined to estimate the efficiency of carbon transport away from the atmosphere are applied. With differing success for the respective indices the results show that the more efficient the vertical transport of organic carbon toward depth, the lower the surface ocean pC0 ₂, the higher the air-sea CO₂ flux, and the stronger the increase in the oceanic inventory of DIC. Along with POC flux it is important to consider variations in PIC flux, as the net effect of particle flux reorganizations on surface qcean pC0₂ is a combination of changes in DIC and alkalinity. The results demonstrate that changes in the mechanistic formulation of vertical particle fluxes have direct and indirect effects on surface ocean pC0₂ and may thus interact with the atmospheric CO ₂ reservoir.