Formation and spreading of Antarctic deep and bottom waters inferred from a chlorofluorocarbon (CFC) simulation

Abstract

The formation of deep and bottom waters along Antarctica's perimeter is determined by ocean interaction with the atmosphere, sea ice, ice shelves, and bottom topography. It initiates a chain of processes that contribute to the ventilation of the global abyss. To identify the formation sites and investigate the combined effects of the local forcing mechanisms on water mass transformation and spreading in the Southern Ocean, chlorofluorocarbon (CFC) simulations with the regional ocean circulation model (BRIOS‐1) were performed. The model uses terrain‐following vertical coordinates to better represent both near‐bottom and mixed layer processes, and includes an explicit formulation of the ice shelf–ocean interaction. In agreement with observations, the results show the main deep and bottom water formations sites to be located in the Ross Sea, Prydz Bay, and southwestern Weddell Sea. The Ross Sea ventilates the South East Pacific and Australian Antarctic Basins. Both Ross Sea and Prydz Bay ventilate via the Antarctic Coastal Current the Weddell‐Enderby Basin. The latter signal is overprinted by sources in the Weddell Sea which ventilate the south Scotia Sea and also the Weddell‐Enderby Basin. Despite the general agreement between observed and simulated quantities like bottom layer CFC distribution and inventories along the Greenwich Meridian, the model tends to underestimate the ventilation of the abyssal ocean like other models with coarse resolution.