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

The effects of orbital forcing on the East Asian summer monsoon (EASM) after the mid -Pleistocene transition are controversial. Chinese cave 618O records only show low-latitude similar to 20 k.y. cycles, while pedogenic proxy records from Chinese loess are dominated by high -latitude 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 613C values of land snail shells (613Cshell), which eliminates the influence of the above processes and exclusively records the local past EASM precipitation. The 613Cshell 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, 613Cshell-based precipitation remained at an interglacial level following the MIS 11 super-interglacial climate in the Northern Hemisphere, although a gla-cial period had commenced on a global basis. Overall, our 613Cshell record is highly coupled with high-northern-latitude ice-volume variations, possibly supporting the high-latitude forcing of the EASM.

Automated summary

The effects of orbital forcing on the East Asian summer monsoon after the mid-Pleistocene transition are controversial. A study based on the 613C values of land snail shells provides a record of the past 470 k.y., which suggests that the EASM is dominated by a 100 k.y. cycle with higher values during glacials. The study also reveals that precipitation remained at an interglacial level following the end of the MIS 11 super-interglacial climate in the Northern Hemisphere.