Dayna Collins 

Title: On the Ice: Learning from the field

Sina Wallschuss 

Title: Nitrous oxide in the Southeast Atlantic

Summary: Nitrous oxide (N₂O) is a climate‑active trace gas, and the global ocean is estimated to account for roughly one‑third of natural N₂O emissions to the atmosphere. In the troposphere, N₂O acts as a strong greenhouse gas with a 100‑year global warming potential about 300 times greater than that of carbon dioxide (CO₂), while in the stratosphere its long lifetime allows it to participate in photochemical reactions that deplete ozone. In the marine environment, N₂O is generated primarily through microbial nitrification and denitrification associated with the nitrogen cycle, and redistributed by horizontal circulation and vertical transport in regions of upwelling and intense mesoscale and submesoscale activity. Where N₂O-rich subsurface waters reach the surface, these regions can act as local hotspots of N₂O outgassing to the atmosphere. In this talk, I first focus on the Southern Benguela upwelling system, where recent work has shown that N₂Ois produced predominantly in situ, and sea–air fluxes are seasonal. I then extend this framework to the Northern Benguela upwelling system, where physical transport plays an equal role to in situ biogeochemical production in shaping N₂Odistributions. Finally, I look ahead to an upcoming project in the Cape Basin, where energetic meso‑ and submesoscale dynamics are expected to strongly modulate N₂O inventories in the water column and control the timing and magnitude of its flux to the atmosphere.

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