A high-resolution sediment record of East Asian summer monsoon from the northern South China Sea spanning the past 7500 years

Abstract

High-resolution Holocene marine sediment records are limited, which hampers our understanding of paleomonsoon evolution. Continental shelf sediment records are derived mainly from terrestrial weathering products and are thus often sensitive to paleoclimate variations. In this study, the grain size and magnetic mineral composition of a well-dated sediment core (YJ Core) from the northern inner shelf of the South China Sea (SCS) were analyzed to provide a high-resolution record of the Holocene evolution of the East Asian summer monsoon (EASM). These magnetic and grain size records indicate that EASM intensity followed a general declining trend between approximately 6800 and 2000 cal yr BP. This general pattern is synchronous with other geologic archives from monsoon regions, and can be attributed to solar radiation forcing in the Northern Hemisphere. On centennial timescales, a weak EASM closely coincides with periods of weak solar activity. In addition, spectral analysis of clays reveals five prominent cycles, with periodicities of approximately 364, 202, 158, 119, and 104 years, which correspond to solar activity cycles. The similarities between the cyclicities of the Asian monsoon signal in sedimentary records and those of solar activity demonstrate that solar forcing has a relatively large influence on the centennial-scale variability of the EASM.