Century-long coral records of the South China Sea throughflow slowdown

The South China Sea throughflow (SCSTF) serves as a heat and freshwater conveyor, playing a pivotal role in regulating physical processes and biogeochemical cycles in the SCS. Because of limited observations, the long-term changes of the SCSTF under a warming climate and underlying dynamics remain unclear. In this study, we reconstructed centennial-scale variability of the SCSTF (1894-2022) using coral oxygen isotope (δ¹⁸O) and satellite observations. Besides prominent interannual and decadal variabilities, there exists a marked long-term decreasing trend at -0.14 ± 0.02 Sv (1 Sv = 10⁶ m³ s^-1) per decade for the total SCSTF volume transport. Consequently, the SCSTF transport decreased by 35 ± 5% over the past 129 years in comparison with the mean value of 5.15 Sv. Using the Time-dependent Island Rule theory, we further reveal that the intensified trade wind in the tropical western Pacific drives the SCSTF slowdown. The findings substantially contribute to investigating the physical, ecological, and biogeochemical changes in the SCS and the Indo-Pacific Oceans.