Ocean Deoxygenation Conference | Kiel 2018

The largest uncertainty and inconsistency in global marine N2O emission estimate appear in the euphotic zone where physical disturbances prevents N2O accumulation if any. Here we presented high vertical resolution N2O profiles in the euphotic zone with distinctive peaks near the oxycline in the oligotrophic Western Pacific, where the maximum of Chl-a and nitrite appeared correspondingly. Production term is required to support such N2O deviation from the vertical mixing curve. The intimate association between N2O excursion and biological parameters suggests that some biological processes, though unclear, must involve. Dual isotope signature of N2O around these peaks affirmed in-situ biological N2O production. More high-resolution observation and process studies are urgently needed to explore the spatial-temporal distribution of euphotic zone N2O production and its controlling mechanisms to fill the knowledge gap. The coupling of the addition of anthropogenic nitrogen and expansion of deoxygenated area in the upper ocean is likely to enhance N2O in euphotic layer due to the sensitivity of N2O release to deoxygenation. Unlike N2O generation in deep ocean, such kind of production in shallow ocean will be more effective in short-term climate feedback according to frequent physical disturbances.