| Summary: | Nitrous oxide (N2O) is one of the most important long-lived greenhouse gases (GHG) responsible for the overall warming of the Earth system, and the strongest ozone-depleting compound in the stratosphere. While the ocean is thought to be a net source of N2O to the atmosphere, at regional and basin-scales there is a large range of variability in terms of its mid-depth water production and consumption, as well as a wide range of physical processes which impact the pool of this GHG in surface waters, posing a significant challenge to both observational and model-based estimates of the annual emissions. Furthermore, although environmental changes such as warming, eutrophication and decrease in sea ice coverage are expected to affect the cycling of N2O, the particular direction of the projected trends is highly uncertain, mostly due to the paucity of measurements in strong source regions and areas of difficult access due to their remote location or extreme weather conditions. In this talk I will present an overview of the current state of knowledge with respect to the exchanges of N2O across the sea-air-ice interfaces, and discuss their relevance in the context of ongoing climate change. To this end, I will use examples from ship-based observations in Eastern Boundary Upwelling Systems (EBUS), the subpolar North Atlantic and the Arctic Ocean. By looking at the contrasting features of these ecosystems and how they affect the marine budget of N2O, I aim to highlight the need of new approaches and priority areas for research on GHGs such as N2O.
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