The Xiamen Symposium on Marine Environmental Sciences (XMAS 2025)

The East Asian summer monsoon (EASM) system influences 10% of the world's population. Yet debates exist regarding the past spatio-temporal patterns of rainfall amount/isotopic composition in different areas of the EASM region and the underlying forcing mechanisms. The southern part of the EASM region has the highest annual rainfall but paleo-records of rainfall amount/isotopic composition remain limited. In this study we use the stable hydrogen isotope (δD) of leaf wax lipids from a marine sediment core in the northern South China Sea to reconstruct the changes in rainfall isotopes in Taiwan throughout the last deglaciation. We also simulate deglacial changes in rainfall amount and isotopes using the isotope-enabled Transient Climate Evolution (iTRACE) experiment. Contrary to the previously proposed coherent continental-scale pattern shown by speleothem records, our δD record is negatively correlated with both simulated and proxy-derived annual rainfall amount in Taiwan on the millennial timescale, suggesting a distinct 'amount effect' in the southern part of the EASM region.