Subantarctic Mode Water and Pycnocline Ventilation

The Subantarctic Mode Water (SAMW) formation region exists on the equatorward edge of the Antarctic Circumpolar Current. It is important for its role in ventilating the permanent pycnocline and is a region of high air-sea gas exchange. Chlorofluorocarbon (CFC) inventories suggest that the Southern Ocean accounts for the majority of air-sea gas fluxes despite lower atmospheric CFC concentrations in the Southern Hemisphere. This air-sea flux exhibits a local maximum in the SAMW formation region. This study employs eddy-resolving configurations of the Coupled-Ocean-Atmosphere-Wave-Sediment Transport Model and the Community Earth System Model to examine (1) the influence of the mesoscale eddy field upon subsurface mixing processes; (2) the combined influence of the seasonal cycle of surface heat flux and subsurface gradients of salinity and potential temperature upon SAMW formation; and (3) the process by which SAMW ventilates the pycnocline, with a particular emphasis on the influence of double-diffusive convection.

Since this session is a special tribute to Prof. Jim McWilliams, this study features a discussion of the models' implementation of the K-profile parameterization (KPP; Large, McWilliams and Doney 1994) and the fidelity it provides relative to other studies that employ models that do not implement KPP.