OLIVEIRA, A.P.; CABEÇADAS, G., and PILAR-FONSECA, T., 2012. Iberia coastal ocean in the CO₂ sink/source context: Portugal case study.

Carbon fluxes were calculated for the Portuguese western inner continental shelf region (adjacent waters off Douro, Tagus, and Sado estuaries, and Tagus estuary) and the southern outer shelf (Algarve). The role played by the described ecosystems in terms of CO₂ source/sink functioning is compared with other coastal Atlantic systems off the Iberian Peninsula. Overall, the Portuguese western near-shore ecosystems emit 0.3 Tg C yr⁻¹ to the atmosphere, which corresponds to an additional source of approximately 0.1% to the CO₂ emissions of worldwide near-shore ecosystems. In these systems the CO₂ water–air fluxes varied temporal and spatially. From 1999 to 2007, a trend of decreasing fluxes was observed. While annually the Iberia continental shelf is a sink for atmospheric CO₂, roughly at a rate between −2.9 and −0.2 mol C m⁻² yr⁻¹, the Iberia near-shore ecosystems are sources of CO₂ to the atmosphere, displaying fluxes from 0.01 to 76 mol C m⁻² yr⁻¹. An insight into the controlling factors and mechanisms for the CO₂ flux variability for the distinct coastal ecosystem is provided. The Portuguese water–air CO₂ fluxes presented in this work are a contribution to the European CO₂ budgets.