Asynchronous Evolution of Sea Surface Temperature in the Northern and Southern South China Sea During the Holocene

Palaeoceanographic and palaeoclimatic reconstructions, particularly on the spatial and temporal evolution across different regions, can offer valuable insights into global changes. At present, abundant data recorded in sediments indicate a phase asynchrony from land to sea during the Holocene. This has raised great debate about the forcing mechanisms of paleoclimatic evolution. In this study, we reconstructed sea surface temperature and salinity during the Holocene from the northern South China Sea (SCS) by the Mg/Ca ratios and δ¹⁸O values of Globigerinoides ruber sensu stricto (s.s.) in the core SH-CL38. By comparing the results with records from other cores in the SCS, it indicates that during the Holocene, the climatic changes in the SCS are mainly influenced by the East Asian summer monsoon driven by Northern Hemisphere summer insolation. The lower salinity in the early Holocene compared to the mid-late Holocene is mainly controlled by palaeogeographic changes in the SCS Basin related to sea level. The fitted sea surface temperature anomaly results from the northern and southern SCS show that the climate evolution in the entire SCS during the early Holocene was asynchronous. The multi-year mean air mass backward trajectory results indicate that the northern SCS is significantly influenced by moisture originating from the tropical western Pacific, while the southern SCS exhibits notable local or regional contributions. Therefore, the differences in the composition of moisture contributions caused by changes in the strength and path of the summer monsoon may be a factor driving the different spatial climate patterns in the SCS.