Short-term changes in the partial pressure of CO2 in Eastern Tropical Atlantic surface seawater and in atmospheric CO2 mole fraction

Continuous monitoring of oceanic and atmospheric CO2 during periods of 8 to 12 days in two particular locations of the tropical Atlantic was carried out during June-August 1986. At the first location (convergence zone; about 5°N, 20°W), the ocean surface was generally slightly undersaturated with respect to the atmosphere, whereas at the second one (Guinea Dome; 12°N, 22°W), the ocean surface was an important source zone of CO2 for the atmosphere. The results of PCO2 in surface seawater, after correction of the temperature effect, show a decrease between morning and evening related to photosynthetic activity ... The net CO2 flux changes considerably during a short periode (8 to 12 days) in the same place, as does the gas transfer coefficient across the sea surface through the variation of the wind speed : the variability is about 80-90 %. The net CO2 flux calculated from mean data is lower (about 30%) than the net CO2 flux calculated from data taken over short time intervals. in the Guinea Dome area in summer, the net CO2 flux can be as hinh (1.8 mmol m-2-d-1) as in the equatorial are