Atmospheric intertropical convergence impacts surface ocean carbon and nitrogen biogeochemistry in the western tropical Pacific

Concentrations of inorganic and organic carbon and organic nitrogen, as well as other hydrographic and biogeochemical variables, were measured in the oligotrophic waters of the western South Pacific Ocean (5-35°S; 170°W). With those data, we assess the impact of the intertropical convergences of the western tropical Pacific Ocean on surface ocean biogeochemistry. Low salinity, oligotrophic waters of the western tropical Pacific underlying regions of high net precipitation are characterized by concentrations of organic carbon and nitrogen that are elevated relative to higher salinity (lower net precipitation) zones. We hypothesize that water column stratification, forced by high net precipitation, favors enhanced rates of N₂ fixation, with resultant elevation of organic carbon and nitrogen concentrations in the region. An effect of anthropogenic ocean warming and the associated increased hydrologic cycle in the tropical Pacific may be to alter the biogeochemical cycling of carbon and nitrogen through enhancement of N₂ fixation.