Orbital- and suborbital-scale changes in the East Asian summer monsoon since the last deglaciation

Abstract

The variability of the East Asian summer monsoon (EASM) has far-reaching effects on the global climate system and the environment, and full understanding of the variability and dynamics of the EASM contributes to predictions of its future behavior. Here, we present a well-dated mineralogical and total organic carbon record from a saline inland lake in northern China which provides a robust archive of the EASM evolution since 16.0 cal. ka BP. Our record reveals a series of rapid and frequent millennial-scale climatic fluctuations during the last deglaciation; these fluctuations are documented by changes in the abundances of mirabilite, bloedite, and gypsum, which appear to record the Oldest Dryas, the Bølling-Allerød warm period, and the Younger Dryas. The peak EASM moisture occurred in the early and middle Holocene, which was punctuated by a prominent and abrupt weak monsoon interval that occurred synchronously with the 8.2 cal. ka BP cold event. This moisture maximum was terminated at 6.9–5.9 cal. ka BP by a warm-dry event marked by the deposition of gaylussite. Subsequently, the EASM gradually weakened over the late Holocene. The EASM moisture patterns reconstructed from Anguli-nuur Lake display good consistency with records from northern China, as revealed by a regional comparison; moreover, the recorded changes are synchronous with those of the Indian summer monsoon moisture patterns, as revealed by a comparison with the stalagmite records of southern China. Our reconstruction shows that the EASM has responded broadly to Northern Hemisphere summer insolation forcing on orbital time scales since the last deglaciation; thus, insolation is the primary factor that controls regional hydrological variations in the Asian monsoonal domain. The suborbital-scale events are related to the Atlantic meridional overturning circulation, and a slowdown of this circulation would lead to a southward shift of the intertropical convergence zone and a weakening of the EASM.