Low Oxygen Zone Water Masses and Their Link to Nitrous Oxide Production in the Eastern Pacific Ocean

Nitrous Oxide, a potent greenhouse and ozone depleting gas, is produced in large quantities over oceanic oxygen minimum zones as a result of nitrification and denitrification. A majority of oceanic N₂O is produced at O₂ concentrations of less than 30 μmol/L, which are primarily located below the mixed layer. As a result, the time scales and pathways over which N₂O effluxes into the atmosphere are poorly understood. Subsurface N₂O data collected at five stations by Alyson Santoro during a 2010 research cruise over the Eastern Tropical South Pacific low oxygen zone were analyzed in this study. In order to better understand the mid-depth ocean circulations that transport N₂O rich waters to the surface over this region, we used the Hybrid Coordinate Ocean Model (HYCOM) in conjunction with a Lagrangian float model. We found that the combination of coastal upwelling and horizontal advection of N₂O rich waters was responsible for both spatial distributions of atmospheric N₂O effluxes and their magnitudes. Station analyses also uncovered denitrification as the primary method for N₂O production in oxygen minimum zones.