Western Pacific subtropical high regulated the spatiotemporal pattern of East Asian summer monsoon precipitation during the Holocene

The precipitation delivered by the East Asian summer monsoon (EASM) has significantly influenced the ecological environment, climate, and economy of China. However, the mechanisms responsible for the spatiotemporal pattern of EASM precipitation remain unclear. We present a new Holocene loess-paleosol record from the Hexi Corridor on the EASM margin. Environmental magnetic parameters (χ_lf, χ_fd, χ_ARM/SIRM, and χ_fd/HIRM) indicate that precipitation was low during 14–8 ka and then increased to a maximum during 4–2 ka. Integrated with published records, our results reveal a distinct geographical gradient in the timing of the Holocene precipitation maximum: an early Holocene peak in eastern Inner Mongolia, a mid-Holocene peak in the central and eastern Chinese Loess Plateau (CLP), and a late Holocene peak in the western CLP and central Hexi Corridor. In addition to these zonal differences, we also observed a longitudinal difference in the timing of the Holocene precipitation peak, which occurred later in the southern region than in the northern region. Combined with existing paleoclimate and climate simulation results we propose that this spatial difference in the timing of the Holocene precipitation peak reflects the movement of the EASM rainfall belt related to the westward extension and northward shift of the western Pacific subtropical high. Overall, our findings provide evidence for the location of the westernmost boundary of EASM influence and offer a unified explanation for regional differences in EASM precipitation and its timing.