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Estimates and Variability of the Air-Sea CO2 Fluxes in the Gulf of Guinea during the 2005-2007 Period
Measurements of CO2 parameters (i.e. Total Alkalinity (TA) and Dissolved Inorganic Carbon (DIC)) were made from June 2005 to September 2007 in six EGEE ("Etude de la circulation oceanique et de savariabilitedans le Golfe de GuinEE") cruises to better assess air-sea CO2 fluxes in the Gulf of Guinea (6°N - 10°S, 10°E - 10°W). Two empirical relationships TA-Salinity and DIC-Salinity-Temperature were established. These relationships were then used to estimate the monthly fugacity of CO2 (fCO2) and air-sea CO2 fluxes. The monthly mean flux of CO2 reaches 1.76 ± 0.82 mmol·m−2·d−1 (resp. 2.90 ± 1.45 mmol·m−2·d−1) at the north of the Equator (resp. at the South). The north-south gradient observed as the patterns of the air-sea CO2 fluxes was mainly driven by the oceanic fCO2. This gradient was due to the low values of the CO2 parameters flowing by the Guinea Current (6°N - 0°) from the west to the east while the air-sea CO2 fluxes increased in the south (10°S - 0°). In the north, the climatology of Takahashi underestimated the CO2 fluxes in the Gulf of Guinea when comparing to the estimated fluxes. This was due to the north-south gradient, which did not well reproduce by the climatology of Takahashi.
CO2 Fluxes, Total Alkalinity, Dissolved Inorganic Carbon, Gulf of Guinea.
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