Volume Budget of Antarctic Intermediate Water in the Southern Ocean from an Eddy-Resolving Ocean Simulation

The volume budget of Antarctic Intermediate Water (AAIW) in the Southern Ocean was examined using a 0.1 degrees ocean model output, from 1955 to 2017. Results show that AAIW volume has significant seasonal variation, with the maximum volume occurring in September and the minimum volume occurring in March, as a result of air-sea buoyancy fluxes. Comparing the AAIW on an interannual time scale, the volume appears to be driven by interior diapycnal mixing and air-sea buoyancy fluxes. While the diapycnal mixing dominates the interannual variation of AAIW in the Indian Ocean, the air-sea formation dominates the interannual variation of AAIW in the Pacific Ocean. The AAIW volume in the Southern Ocean decreased by approximately 7.2% from 1955 to 2017, due to a consistent increase of oceanic buoyancy gain over the outcropping area around 27.1 kg m(-3) and, thus, more AAIW being transformed into lighter water.