East Asian monsoon variability over the last seven glacial cycles recorded by a loess sequence from the northwestern Chinese Loess Plateau

Abstract

A 180‐m‐thick loess‐paleosol sequence from the northwestern Chinese Loess Plateau was investigated to construct a high‐resolution record of the East Asian monsoon variability over the last seven glacial‐interglacial cycles. The low‐field magnetic susceptibility (χ, mass‐specific) and the mean grain size are used as proxies for changes in the intensity of the East Asian summer and winter monsoon, respectively. Because of the weaker pedogenesis at the northwestern Chinese Loess Plateau compared to the central Chinese Loess Plateau, our χ and mean grain size records show a muted glacial‐interglacial contrast for the Asian summer monsoon but an enhanced contrast for the Asian winter monsoon. Although better resolved, most orbital‐scale East Asian monsoon variations captured by our χ and grain size records are similar to those reported from the central Chinese Loess Plateau. Nevertheless, variations in χ exhibit clear precessional cycles in three paleosol layers (i.e., S1, S2, and S3), corresponding with solar insolation maxima. Furthermore, unlike χ records at the central Chinese Loess Plateau where χ is dramatically enhanced at paleosol S5SS1 (corresponding to marine isotope stage 13), our new χ record shows a major enhancement at paleosol S4 (corresponding to marine isotope stage 11), which indicates geographic differences in the timing of local monsoon precipitation in the two regions.