SOURCES AND SINKS OF CARBON-MONOXIDE IN THE MIXED-LAYER OF THE TROPICAL SOUTH-PACIFIC OCEAN

The magnitude of the oceanic source of carbon monoxide (CO) to the atm osphere depends on the concentration of CO in ocean surface waters. To ascertain the relative importance of the processes controlling this c oncentration, depth profiles of CO concentrations in the oceanic mixed layer and upper thermocline were made at two time series stations in the tropical Pacific Ocean during 1993. The two stations were chosen t o contrast an oligotrophic region of low CO water concentrations (RITS 93) with a biologically productive region of high seawater CO concentr ations (RITS94). The column burden of CO in the upper 75 m of the wate r column averaged 53 mu mole m(-2) at the RITS93 station and 240 mu mo le m(-2) at the RITS94 station. From the observed diurnal cycle of the CO column burden, production and loss rates at each site were estimat ed. The factor of 4.5 difference in the column burden is primarily due to a smaller in situ oxidation rate constant at the RITS94 site.