Nitrous oxide (N₂O) is a potent greenhouse gas, with a global warming potential ~300 times higher than CO₂ and is currently the dominant ozone-depleting substance emitted to the atmosphere. Oceanic waters are generally viewed as being oversaturated in N₂O, and the ocean contributes ~30% of global N₂O emissions. Intriguingly, repeated observations suggest that high-latitude waters can also act as N₂O sinks under specific conditions, such as vertical mixing, sea-ice melt, glacial meltwater influence, or N₂ fixation. The coexistence of offshore N₂O sinks and shelf N₂O sources, although not consistently observed, together with the limited number of available observations precludes a robust assessment of whether the Arctic Ocean is a net source or a net sink of atmospheric N₂O. This uncertainty is critical, as Arctic warming, sea-ice decline, glacier retreat, and increasing meltwater discharge are already reshaping the physical and biogeochemical functioning of coastal marine systems. As a result, both the magnitude and direction of Arctic N₂O feedback to the atmosphere remain poorly quantified.
Within the GreenFeedBack project, an EU-funded Research and Innovation Action running from 2023 to 2026, we collected an extensive dataset of N₂O observations across the European sector of the Arctic, from Davis Strait to the Barents Sea. The study area includes three fjord systems in Greenland, the southwestern fjords of Svalbard, and the central Arctic Ocean. N₂O concentrations were measured continuously in surface waters and/or discretely at selected depths throughout the water column, providing a unique dataset to assess spatial variability in Arctic N₂O distributions across contrasted coastal and open-ocean environments.
This effort will contribute to future Arctic N₂O budget assessments by providing observations that can be combined with existing datasets across spatial and temporal scales. Here, we describe the spatio-temporal variability of N₂O concentrations across a broad range of Arctic environments, from open-ocean waters to glacier-influenced fjord systems. Preliminary results reveal contrasting spatial patterns, particularly between fjords and open waters, highlighting the strong heterogeneity of Arctic N₂O distributions.

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