100 k.y. pacing of the East Asian summer monsoon over the past five glacial cycles inferred from land snails

Abstract

Abstract The effects of orbital forcing on the East Asian summer monsoon (EASM) after the mid-Pleistocene transition are controversial. Chinese cave δ18O records only show low-latitude ∼20 k.y. cycles, while pedogenic proxy records from Chinese loess are dominated by highlatitude 100 k.y. cycles. This discrepancy may result from the multicomponent origin of proxies, particularly for pedogenic signals in loess deposits, where the primary climatic signals are modified by pedogenic smoothing, leaching, and changes in sedimentation rate, and the latter are also being forced by 100 k.y. cycles. We present an EASM record spanning the past 470 k.y. from the central Chinese Loess Plateau based on the δ13C values of land snail shells (δ13Cshell), which eliminates the influence of the above processes and exclusively records the local past EASM precipitation. The δ13Cshell record is dominated by the 100 k.y. cycle, with more depleted values during interglacials compared to glacials. At the end of marine isotope stage (MIS) 11, δ13Cshell-based precipitation remained at an interglacial level following the MIS 11 super-interglacial climate in the Northern Hemisphere, although a glacial period had commenced on a global basis. Overall, our δ13Cshell record is highly coupled with high-northern-latitude ice-volume variations, possibly supporting the high-latitude forcing of the EASM.