Estimates of the Fugacity of CO2 in the Vridi Channel (Côte d’Ivoire)

Abstract

From July to November 2023 and in April 2024, surface waters were collected at three separate sampling sites within the Vridi channel, to measure physical and chemical parameters such as salinity, temperature, pH, Dissolved Inorganic Carbon (DIC). The fCO2 and Total Alkalinity were calculated from pH and DIC. These surface waters were sampling during 4 seasons to study the variability of the carbonate system parameters. Low salinity and low temperature were observed in July -August because this period corresponded to high precipitation inducing salinity dilution and the appearance of coastal upwelling. High salinity and temperature were observed in a great dry season. In the whole, salinity and temperature have same trends of variability. Whatever the season, surface waters were oversaturated in fCO2 with respect to atmospheric equilibrium in the Vridi channel except in dry season. On average the fCO2 decreased from the great cold season to the hot season following marine season. Indeed, the high coastal upwelling appeared in July and disappeared in October. The variability of the channel fCO2 followed the upwelling events along the coastal areas. Moreover, parameters such as Total Alkalinity (TA), Dissolved Inorganic Carbon and pH undergone the influence of coastal upwelling as fCO2 in the Vridi channel.