Enhanced Ventilation in Energetic Regions of the Antarctic Circumpolar Current

Flow‐topography interactions along the path of the Antarctic Circumpolar Current generate standing meanders, create regions of enhanced eddy kinetic energy (EKE), and modify frontal structure. We consider the impact of standing meanders on ventilation based on oxygen measurements from Argo floats and the patterns of apparent oxygen utilization (AOU). Regions of high‐EKE have relatively reduced AOU values at depths 200–700 m below the base of the mixed layer and larger AOU variance, suggesting enhanced ventilation due to both along‐isopycnal stirring and enhanced exchange across the base of the mixed layer. Vertical exchange is inferred from finite‐size Lyapunov exponents, a proxy for the magnitude of surface lateral density gradients, which suggest that submesoscale vertical velocities may contribute to ventilation. The shaping of ventilation by standing meanders has implications for the temporal and spatial variability of air‒sea exchange. Plain Language Summary The circulation of the Southern Ocean is dominated by the eastward‐flowing Antarctic Circumpolar Current (ACC). The characteristics of the ACC are not uniform around the Southern Ocean. Rather, when the ACC encounters underwater mountain ranges the flow is diverted, which causes these regions to be more energetic through the generation of ocean eddies in a process similar to atmospheric storm tracks. Numerical models have suggested that the exchange of properties, such as heat and carbon dioxide, between the atmosphere and the interior ocean is enhanced in these energetic regions. In this study, data from freely floating robotic floats in the Southern Ocean is used to observe the vertical structure of dissolved oxygen. Transfer of properties between the ocean's surface and the interior ocean preferentially occurs in high energy regions of the ACC. Most previous work has relied on numerical models of the ocean that, due to computational limits, do not represent all aspects of the ACC's energetic regions. This study has implications for how the Southern Ocean's ability to take up excess carbon dioxide from the atmosphere will evolve in the future. Key Points The relationship between apparent oxygen utilization (AOU) and eddy kinetic energy (EKE) is assessed in the Antarctic Circumpolar Current AOU has relatively reduced values below the mixed layer in high‐EKE standing meanders as compared to low‐EKE regions Modification of the density structure and enhanced meso‐ and submesoscale motions enhance ve