Investigating Antarctic Intermediate Water Changes in the Southern Ocean Under RCP 8.5 Using CESM-BGC

Antarctic Intermediate Water (AAIW), formed primarily in the Southern Ocean, is an important water mass responsible for nutrient transport, heat storage, and uptake of anthropogenic CO₂ throughout the global oceans.  AAIW is thought to be the most important global source of O² and nutrient transfer to the equatorial regions.  In this study we investigate changes in the surface properties of AAIW in the South Pacific, under historical (1970-1990) and RCP8.5 (2080-2100) scenarios, using CESM-BGC. These surface properties will then be subducted within intermediate water and distributed throughout the subtropical gyre. AAIW within the South Pacific is identified based on a low salinity of 34.2 psu.  We investigate changes in AAIW surface properties (e.g., salinity, O₂, NO₃) under the RCP 8.5 (+8.5 W/m² from pre-industrial values) scenario. Initial results indicate a decrease in surface oxygen levels of < 0.02 mol/m³ between 1970 to 2100.  Identifying changes in AAIW can be valuable in diagnosing a changing climate.