Loess deposits in the low latitudes of East Asia reveal the ~20-kyr precipitation cycle

This study examines a high-resolution, approximately 350,000-year record from a low-latitude loess profile in China to understand the dominant cycles of East Asian summer monsoon (EASM) precipitation. Analysis reveals that variations in the ratio of dithionite-citrate-bicarbonate extractable iron to total iron are dominated by the ~20-kyr cycle, reflecting precipitation changes. In contrast, magnetic susceptibility varies with the ~100-kyr cycle, potentially controlled by temperature-induced redox processes or precipitation-induced signal smoothing. The results suggest that EASM precipitation is mainly forced by precession-dominated insolation variations, and precipitation and temperature may have varied with different cycles over the past ~350,000 years.

Xusheng Li, Yuwen Zhou, Zhiyong Han, Xiaokang Yuan, Shuangwen Yi, Yuqiang Zeng, Lisha Qin, Ming Lu, Huayu Lu