Carbon dioxide fluxes in the Benguela upwelling system during winter and spring: A comparison between 2005 and 2006

Abstract

The distributions of fCO2 in surface seawater and in the atmosphere were studied in the Benguela Province (14–33°S) during the austral winter and spring 2005 and 2006. High fCO2sw variability was observed due to the effect of upwelled and derived meso-scale structures such as filament water. The complexity of the system, dominated by the upwelling dynamics, produces both a general decrease in fCO2sw with temperature (16 μatm/°C) and negative temperature–fCO2sw relationship due to the presence of upwelling, filaments, and frontal zones. Multiple linear regressions are unable to capture the resulting variability in fCO2 in the area. CO2 fluxes over the cruise track varied from Northern Namibia to the Southern Benguela regions. The northern system (14–20°S) is oversaturated in CO2 relative to the atmosphere, and presents an average flux of 0.56 mol m−2 yr−1. The southern part (20°S–33°S) of the Benguela system is undersaturated in CO2, and the average flux is −1.62 mol m−2 yr−1. This study describes an intensive upwelling area, acting as a sink for CO2 in winter and spring.