The South China Sea Throughflow (SCSTF) serves as a critical oceanic conveyor belt for heat and freshwater, mediating water exchanges between the South China Sea (SCS) and the Pacific and Indian oceans while regulating key processes such as heat and salt budgets, eddy activities, and marine biogeochemical cycles. It also plays a pivotal role in modulating the Indonesian Throughflow (ITF) and shaping climate variability across the Indo-Pacific. However, long-term direct observational data of the SCSTF have long been scarce, leaving its long-term changes under climate change and associated driving mechanisms poorly understood.

The researchers also highlighted important questions for future research. The 35% reduction in transport has increased the SCS water renewal time from 2.6 to 3.5 decades, which could alter the basin’s thermocline and halocline structures and reshape air–sea interactions related to the East Asian monsoon. The weakening Kuroshio intrusion has already been linked to decreasing chlorophyll-a concentrations and phytoplankton growth in the SCS, threatening marine productivity and fish habitats. Furthermore, the slowdown of the SCSTF may act as a compensatory mechanism for the strengthening ITF, potentially restructuring inter-basin ocean circulation in the Indo-Pacific.