The contribution of storm-induced outgassing to the CO2 air-sea flux in the Southern Ocean in a high-resolution, atmosphere-ocean simulation with ICON

The global ocean uptake of anthropogenic CO2 is sensitive to the uptake in the Southern Ocean, which accounts for 40-50% of the total uptake. At the same time, the Southern Ocean is the windiest region on the planet and experiences storms all year round. These storms, in turn, play an important role for the CO2 uptake in the Southern Ocean, because they can trigger outgassing of CO2 to the atmosphere. Storms induce outgassing by stirring the mixed layer via wind forcing, which leads to entrainment of waters rich in dissolved inorganic carbon into the mixed layer and elevates ocean pCO2 at the air-sea interface. However, since storms occur on synoptic time scales, such outgassing events are highly localised and short lived. Recent work based on in-situ measurements suggests that the magnitude of storm-induced outgassing and its contribution to the total Southern Ocean CO2 air-sea flux may have been severely underestimated by previous modelling studies, which do not sufficiently resolve storms and outgassing events. In this study, we take advantage of a cutting-edge simulation conducted with a fully-coupled, global, atmosphere-ocean model (ICON) with ocean biogeochemistry. Running on the assumption that the smaller grid spacing of 5 km better resolves storms and variability in wind forcing, we analyse the simulated contribution of storm-induced outgassing to the Southern Ocean uptake of CO2.