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

In the present paper we report partial pressure of CO2 (pCO2) data obtained off
the Belgian coast during 24 cruises. The temporal and spatial resolution of this data set allows
us to discuss satisfactorily seasonal and inter-annual variability of pCO2 in the study area.
The dynamics of pCO2 are described using two approaches: fixed reference stations and area
survey cruises. The air-water fluxes of CO2 in the Scheldt estuarine plume and in the outerplume
region are estimated quantitatively, showing that these areas correspond respectively to
a net annual source and sink of atmospheric CO2. The annually integrated air-water fluxes for
the Scheldt estuarine plume range between +1.1 and +1.9 mol m−2 year−1 as a function of
the formulation of the exchange coefficient of CO2. The annual net emission of CO2 from the
estuarine plume to the atmosphere is estimated to be between +2.3 to +4.0 Gmol year−1 which
represents 17 to 29% of the estimate reported in the literature for the Scheldt inner estuary.