Global significance of nitrous-oxide production and transport from oceaniclow-oxygen zones: A modeling study

Recent studies of marine nitrous oxide have focused attention on the suboxi c and low-oxygen zones associated with ocean basin eastern boundaries. It h as been suggested that complex N2O cycling mechanisms in these regions magi provide a net source to the oceanic interior and a significant portion of the ocean-atmosphere flux. In this study we evaluate the global significanc e of N2O formation in these regions. N2O is treated as a nonconserved trace r in an ocean general circulation model; a simple source function is develo ped which models NaO production as a function of organic matter remineraliz ation and local oxygen concentration. Model results are evaluated against b oth surface and deep observational data sets. The oceanic oxygen minimum zo nes are predominantly found in the upper water column of tropical latitudes and overlain by regions of strong: upwelling in the surface ocean. Simulat ions of increased N2O production under low-oxygen conditions indicate that the majority of the N2O thus formed escapes directly to the atmosphere and is not subject to significant meridional transport. Results indicate that w hile enhanced N2O production in these regions cannot be held accountable fo r the majority of the sea-air flux and interior distribution, it may, howev er, have significance for the local distribution anti provide as much as 25 -50% of the global oceanic source.