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.