Monthly insolation linked to the time-transgressive nature of the Holocene East Asian monsoon precipitation maximum

Abstract

More than 10% of the world’s population lives in the East Asian monsoon (EAM) region, where precipitation patterns are critical to agricultural and industrial activities. However, the dominant forcing mechanisms driving spatiotemporal changes in the EAM remain unclear. We selected Holocene records tracking monsoon precipitation in the EAM region reconstructed from pollen data to explore the spatiotemporal patterns of monsoon precipitation changes. Our analysis shows a time-transgressive pattern of maximum precipitation, with earlier occurrence in the southern area and later occurrence in the northern area. The monthly insolation changes force monsoon precipitation in different parts of the EAM region through a shift in the Western Pacific Subtropical High. We conclude that low-latitude monthly insolation changes (rather than average summer insolation changes) were the main forcing mechanisms of the spatiotemporal patterns of the monsoon precipitation maximum during the Holocene.

Millennial‐ to centennial‐scale anti‐phase relationship between the Westerlies and the East Asian summer monsoon and its cultural response along the Silk Roads after a great earthquake in southern Altay ~ 3500 cal a BP

“…Cai et al 2021, Zhang et al 2021c. Modern observations showed a northward migration of the EASM rain belt from late May to early August (Xiao et al 2018), in response to a northward movement of the WPSH (Zhou et al 2022). The position and intensity of the WPSH were closely related to sea surface temperature (SST) in the Tropical Pacific.…”

“…In the EASM region, relatively low/high tree pollen percentages in Hulun Lake (Figs 1a and 6g) (Zhang, Xiao and Xu, 2022b), low/high mean annual precipitation (MAP) reconstructed from pollen assemblages in Moon Lake (Figs 1a and 6h) (Zhou et al 2022), Daihai Lake (Figs 1a and S4k) (Xiao et al 2004, Xu et al 2010 and Gonghai Lake (Figs 1a and 6i) (Chen et al 2015a), low/high values of the summer monsoon index (SMI) inferred from Qinghai Lake (Figs 1a and S4m) (An et al 2012), high/low values of anhysteretic remanent magnetization/saturation isothermal remanent magnetization (ARM/SIRM) ratio of a stalagmite from Heshang Cave (indicating decreasing/increasing transport of coarse magnetic particles associated with weak/ heavy rainfall) (Figs 1a and 6j) (Xie et al 2013), and low/high TOC contents (indicating low/high water levels) in Emerald Peak (EP) Lake (Figs 1a and S4o) (Selvaraj et al 2012) indicated a generally weak/strong EASM intensity from 3500 to 2300/2300 to 1000 cal a BP. The MWP/LIA was generally characterized by a strong/weak EASM intensity (Figs 6i,j and S4o), which was also supported by a large amount of paleoclimatic evidence from the northeastern Tibetan Plateau (e.g.…”

“…It was not widely considered that such a complicated EASM system could result in a uniform precipitation pattern (Shi et al 2012); however, this study focuses on consistent changes in the EASM intensity and precipitation, because it was widely accepted by a large number of previous studies that EASM precipitation could be used to infer EASM intensity, especially in the marginal areas of the EASM (e.g. An et al 2000, Chen et al 2015a, Gao et al 2022, Mao et al 2021, Xiao et al 2004, Yang et al 2015, Zhou et al 2022. Overall, EASM intensity was strong/weak during the MWP/LIA, showing opposed trends to the Westerlies (Chen et al 2015b, Yan et al 2017this study).…”

“…The above two factors would trigger the northward movement of the WPSH (e.g. Tan et al 2018, Xiao et al 2006, Zhou et al 2022, resulting in more EASM precipitation in northern China (Fig. 6g-i) (Chen et al 2015a, Zhang, Xiao and Xu, 2022b, Zhou et al 2022.…”

“…Paleoclimatologists have made great efforts to characterize Holocene climatic changes within the Westerlies and the EASM regions (e.g. An et al 2012, Cai et al 2017, Chen et al 2008, Xu et al 2019, Zhang and Feng 2018, Zhou et al 2022. Several previous studies suggested an in-phase relationship between the Westerlies and the EASM during the Holocene, resulting from an incursion of summer monsoon moisture into Westerlies-dominated regions of Central Asia during periods of high boreal solar insolation (Cheng et al 2012, Rudaya et al 2009, Zhang 2021.…”