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This study calculates N2O production rates (N2OPR) based on concentration measurements and Transit Time Distribution (TTD) calculations. New parameterisations of N2OPR based on an apparent oxygen consumption rate (AOUR and temperature or depth, respectively, are developed and applied to calculate N2O production the entire ocean. A global annual subsurface N2O production of ~3±1 Tg N and a global annual organic carbon remineralisation rate of 17.6 Pg are estimated. The N2O flux to the mixed layer (F_grad) and the N2O emissions to the atmosphere via gas exchange (F_gasex) are calculated or the central North Atlantic. The mean F_grad is found to be significantly smaller than the mean F_gasex. A possible reason for this is the seasonality of surface pN2O/F_gasex, as a seasonally-resolved, integrated estimate of F_gasex significantly reduces the difference between the two flux estimates. There is no conclusive evidence for a biological N2O source in the mixed layer. In dieser Studie werden, basierend auf Konzentrationsmessungen und Transit Time Distributions (TTD) N2O Produktionsraten (N2OPR) berechnet. Neue Parameterisierungen für N2OPR abhängig von einer Sauerstoffverbrauchsrate (AOUR) und der Temperatur bzw. der Tiefe werden entwickelt und zur Berechnung der N2O-Produktion im Weltozean verwendet. Dabei wird die globale jährliche N2O-Produktion auf ~3±1 Tg N und die jährliche Remineralisationsrate von organischem Kohlenstoff auf 17.6 Pg geschätzt. Der N2O-Fluss in die Mischungsschicht (F_grad) und der N2O-Fluss in die Atmosphäre (F_gasex) werden für den zentralen Nord-Atlantik berechnet. Der mittlere F_grad ist signifikant kleiner als der mittlere F_gasex. Ein möglicher Grund ist der zyklische Jahresgang von pN2O/F_gasex, da eine integrierte Schätzung die Differenz zwischen den verschiedenen Flüssen deutlich reduziert. Es gibt keine zwingenden Hinweise auf biologische N2O-Produktion in der Mischungsschicht.

We use transit time distributions calculated from tracer data together with in situ measurements of N(2)O to estimate the concentration of biologically produced N(2)O ([N(2)O](xs)) and N(2)O production rates in the central North Atlantic Ocean. Our approach to estimation of N(2)O 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 N(2)O concentrations by 8-13% and thus underestimate the strength of N(2)O sources in large parts of the water column. Thus the quantitative characteristics of the [N(2)O](xs)/AOU relationship used as an indicator of nitrification are distorted. We developed a new parameterization of N(2)O production during nitrification depending linearly on AOU and exponentially on temperature and depth, which can be applied to calculate N(2)O production due to nitrification in the entire ocean including oxygen minimum zones.

Berichte - Reports, Institut f��r Geowissenschaften