Distribution and air-water exchange of carbon dioxide in the Scheldt plume off the Belgian coast

In the present paper we report partial pressureof CO₂ (pCO₂) data obtained off theBelgian coast during 24 cruises. The temporaland spatial resolution of this data set allowsus to discuss satisfactorily seasonal andinter-annual variability of pCO₂ in thestudy area. The dynamics of pCO₂ aredescribed using two approaches: fixed referencestations and area survey cruises. The air-waterfluxes of CO₂ in the Scheldt estuarineplume and in the outer-plume region areestimated quantitatively, showing that theseareas correspond respectively to a net annualsource and sink of atmospheric CO₂. Theannually integrated air-water fluxes for theScheldt estuarine plume range between +1.1 and+1.9 mol m^–2 year^–1 as a function ofthe formulation of the exchange coefficient ofCO₂. The annual net emission of CO₂from the estuarine plume to the atmosphere isestimated to be between +2.3 to +4.0 Gmolyear^–1 which represents 17 to 29% of theestimate reported in the literature for the Scheldtinner estuary.