South China Sea Annual Meeting 2023 (SCSAM)

21 / 2023-07-24 15:04:47

Thermohaline impacts of the South China Sea throughflow on the Indonesian throughflow

Indonesian throughflow, South China Sea throughflow, Thermohaline

The thermohaline impacts of the South China Sea (SCS) throughflow interannual variability on the Indonesian Throughflow (ITF) are investigated based on a high-resolution (0.1° × 0.1°) regional ocean model, Lagrangian particle tracking model- Connectivity Modeling System (CMS), as well as several reanalysis datasets. The Lagrangian particle tracking results show that the average proportion of thermocline water mass from the SCS to the Makassar Strait is about 13.3%, while increasing to 23.3% during El Niño events and decreasing to 6.9% during La Niña event. The quantitatively water proportion from SCS exhibits a strong positive correlation (correlation coefficient of 0.718) with Niño 3.4 index, and the mainly passage is Mindoro–Sibutu pathway via the Sulu Sea and Sulawesi Sea. Upon closing the Mindoro–Sibutu passage in high-resolution regional model sensitivity experiments, the transport of Luzon Strait into the SCS is reduced by 75%. The Mindoro–Sibutu pathway is fundamental in governing the SCS’s low salinity, buoyancy, and upper layer injection into the Makassar Strait, which is the primary component of the ITF, thus inhibiting the transport within the upper 200 m of the throughflow. The impact of closing the Karimata Strait is limited to the Sunda Shelf and the Java Sea. The shallow Sunda Shelf of the southern SCS is primarily driven by local monsoon winds. Influenced by winds anomalies, more SCS water flows into the Makassar Strait through the Karimata Strait during La Niña events.