Air‐Sea CO2 Fluxes Localized by Topography in a Southern Ocean Channel.

Air‐sea exchange of carbon dioxide (CO2) in the Southern Ocean plays an important role in the global carbon budget. Previous studies have suggested that flow around topographic features of the Southern Ocean enhances the upward supply of carbon from the deep to the surface, influencing air‐sea CO2 exchange. Here, we investigate the role of seafloor topography on the transport of carbon and associated air‐sea CO2 flux in an idealized channel model. We find elevated CO2 outgassing upstream of a seafloor ridge, driven by anomalous advection of dissolved inorganic carbon. Argo‐like Lagrangian particles in our channel model sample heterogeneously in the vicinity of the seafloor ridge, which could impact float‐based estimates of CO2 flux. Plain Language Summary: The Southern Ocean, the ocean surrounding Antarctica, contributes significantly to carbon exchange between the global ocean and the atmosphere, which in turn matters for climate change. Here, we use a simplified model of the Southern Ocean to see how mountain ranges on the sea floor influence the carbon exchange at the ocean‐atmosphere interface. We find that the seafloor mountain ranges lead to more carbon exchange. Floating carbon sensors in our model ocean may under or over sample the water near the mountains and this can affect the carbon exchange that they report. Key Points: We examine the localized patterns of air‐sea carbon dioxide (CO2) fluxes in an idealized Southern Ocean‐like model with simple biogeochemistryWe find intense sea‐air CO2 fluxes upstream of seafloor topography driven by anomalous advection of inorganic carbonDue to the topography, uncertainty in the flux is highly sensitive to sampling network design [ABSTRACT FROM AUTHOR]