Nitrous oxide variability at sub-kilometre resolution in the Atlantic sector of the Southern Ocean

The Southern Ocean is an important region for global nitrous oxide (N(2)O) cycling. The contribution of different source and sink mechanisms is, however, not very well constrained due to a scarcity of seawater data from the area. Here we present high-resolution surface N(2)O measurements from the Atlantic sector of the Southern Ocean, taking advantage of a relatively new underway setup allowing for collection of data during transit across mesoscale features such as frontal systems and eddies. Covering a range of different environments and biogeochemical settings, N(2)O saturations and sea-to-air fluxes were highly variable: Saturations ranged from 96.5% at the sea ice edge in the Weddell Sea to 126.1% across the Polar Frontal Zone during transit to South Georgia. Negative sea-to-air fluxes (N(2)O uptake) of up to −1.3 µmol m(−2) d(−1) were observed in the Subantarctic Zone and highest positive fluxes (N(2)O emission) of 14.5 µmol m(−2) d(−1) in Stromness Bay, coastal South Georgia. Although N(2)O saturations were high in areas of high productivity, no correlation between saturations and chlorophyll a (as a proxy for productivity) was observed. Nevertheless, there is a clear effect of islands and shallow bathymetry on N(2)O production as inferred from supersaturations.