The CO2 partial pressure in the eastern Ezquatorial Pacific (1991 to 1994): Empirical relationships with other oceanic variables and with carbon luxes in the mixed layer

Abstract

In order to better understand the processes which control the pCO2 variability in the Equatorial Pacific, a monitoring program between Panama and New Caledonia collects pCO2 both in air and sea surface, sea surface temperature (SST), nitrate concentration, satinity, chlorophyll and temperature at depth using expendable bathythermographs. These measurements cover the 1991–1994 warm episode. A multiple linear regression selects the nitrate concentration as the best predictor for CO2 partial pressure (r=0.78). The information given by the chlorophyll concentration is already contained in the nitrate concentration. A principal component analysis, between 1°N and 7°S, has been realized with the set of data to which we added TOPEX/POSEIDON zonal current anomalies. 60 % of the pCO2 variance of large scale anomalies could be explained by the first eigenvector which represents the influence of the upwelling on pC02. An anomaly characterized by high pCO2 and high SST in April 1994 is related to the general circulation as shown by the third eigenvector. An attempt was made to estimate new production and airsea exchange using mesoscale anomalies. The influence of biocalcification and of the C:N ratio on the results is examined.