Storms drive outgassing of CO₂ in the subpolar Southern Ocean

The subpolar Southern Ocean is a critical region where CO₂ outgassing influences the global mean air-sea CO₂ flux (F_CO2). However, the processes controlling the outgassing remain elusive. We show, using a multi-glider dataset combining F_CO2 and ocean turbulence, that the air-sea gradient of CO₂ (∆pCO₂) is modulated by synoptic storm-driven ocean variability (20 µatm, 1-10 days) through two processes. Ekman transport explains 60% of the variability, and entrainment drives strong episodic CO₂ outgassing events of 2-4 mol m^-2 yr^-1. Extrapolation across the subpolar Southern Ocean using a process model shows how ocean fronts spatially modulate synoptic variability in ∆pCO₂ (6 µatm² average) and how spatial variations in stratification influence synoptic entrainment of deeper carbon into the mixed layer (3.5 mol m^-2 yr^-1 average). These results not only constrain aliased-driven uncertainties in F_CO2 but also the effects of synoptic variability on slower seasonal or longer ocean physics-carbon dynamics.