North Atlantic production of nitrous oxide in the context of changing atmospheric levels

We use transit time distributions calculated from tracer data together with in situ measurements of N₂O to estimate the concentration of biologically produced N₂O ([N₂O]_xs) and N₂O production rates in the central North Atlantic Ocean. Our approach to estimation of N₂O production rates integrates the effects of potentially varying production and decomposition mechanisms along the transport path of a water mass. We find that previously used approaches overestimate the oceanic equilibrium N₂O concentrations by 8-13% and thus underestimate the strength of N₂O sources in large parts of the water column. Thus the quantitative characteristics of the [N₂O]_xs/AOU relationship used as an indicator of nitrification are distorted. We developed a new parameterization of N₂O production during nitrification depending linearly on AOU and exponentially on temperature and depth, which can be applied to calculate N₂O production due to nitrification in the entire ocean including oxygen minimum zones.