A harmonized nitrous oxide (N 2 O) ocean observation network for the 21st century

Abstract

Nitrous oxide (N 2 O) is an important atmospheric trace gas involved in tropospheric warming and stratospheric ozone depletion. Estimates of the global ocean contribution to N 2 O emissions average 21% (range: 10 to 53%). Ongoing environmental changes such as warming, deoxygenation and acidification are affecting oceanic N 2 O cycling and emissions to the atmosphere. International activities over the last decades aimed at improving estimates of global N 2 O emissions, including (i) the MarinE MethanE and NiTrous Oxide database (MEMENTO) for archiving of quality-controlled data, and (ii) a recent large-scale inter-laboratory comparison by Working Group 143 of the Scientific Committee on Ocean Research (SCOR). To reduce uncertainties in oceanic N 2 O emission estimates and to characterize the spatial and temporal variability in N 2 O distributions in a changing ocean, we propose the establishment of a harmonized N 2 O Observation Network (N 2 O-ON) combining discrete and continuous data from various platforms. The network will integrate observations obtained by calibrated techniques, using time series measurements at fixed stations and repeated hydrographic sections on voluntary observing ships and research vessels. In addition to exploiting existing oceanographic infrastructure, we propose the establishment of central calibration facilities in selected international laboratories to improve accuracy, and ensure standardization and comparability of N 2 O measurements. Final data products will include a harmonized global N 2 O concentration and emission fields for use in model validation and projections of future oceanic N 2 O emissions, to inform the global research community and policy makers.