3 Results
3.1 Uniform versus spatially varying freshwater fluxes
Compared to the uniform freshwater flux experiment (UNIF ), results from the spatially varying freshwater flux experiment (VARI, Fig 2) show significant salinity anomalies. At the surface, the Amundsen Sea coast becomes 0.5±0.12 PSU fresher inVARI while the remaining Antarctic coast increases in salinity by up to 0.2±0.07 PSU (Fig 2a), thus reflecting the concentration of the freshwater fluxes along the Amundsen Sea (Fig 1d). In the bottom layer, salinity in the Southern Ocean (i.e., poleward of 60oS) increases up to 0.1±0.06 PSU (Fig 2d) inVARI. The average AABW salinity increases by 1.9±0.60×10-3 PSU in VARI compared toUNIF . Thus, the bottom cell of the Southern Ocean’s overturning circulation extends to denser waters, but the transport of the bottom cell stays approximately the same between the UNIF andVARI (Fig 2c).
A transect along the Antarctic shelf shows that positive surface salinity anomalies in the VARI experiment are advected downwards along the shelf to the bottom layer (Fig 2f). The downward advection of high salinity anomalies happens mostly in the Ross Seas where the shelf overflow is parameterized in CESM1 (Fig 2f). Therefore, overflow parameterization has a key role in transmitting surface salinity signals to the deep ocean. Once in the bottom layer, the positive salinity anomalies spread laterally increasing in AABW salinity across the Southern Ocean (Fig 2f).