Westerly jet‐East Asian summer monsoon connection during the Holocene

Abstract

[1] The causes of spatial and temporal changes in East Asian summer monsoon (EASM) precipitation on millennial to multimillennial time scales during the Holocene have not yet been resolved. Here, we examine the relationship between spatial variations in EASM precipitation and the westerly jet (WJ) path over East Asia during the Holocene using the provenance of eolian dust in Japan Sea sediments, which we interpret to reflect changes of the WJ path over East Asia and/or surface conditions of desert areas. The contribution of dust from the Mongolian Gobi Desert relative to that from the Taklimakan Desert shows millennial-scale to multimillennial-scale minima at 11.5-10, 7-5, and 3.5-1.5 kyr B.P., which we attribute to earlier seasonal northward progression of the WJ. These dates correlate with precipitation maxima along the present northwestern EASM margin and minima in eastern Northeast China and the Yangtze River Basin, suggesting that the WJ shifted northward earlier in the year, allowing earlier northward migration of the EASM rainband and generating abundant precipitation in the northwestern EASM margin. Therefore, during the Holocene, changes of the WJ path probably contributed to the millennial-scale to multimillennial-scale EASM precipitation changes and its northwest-southeast contrast within China. Our findings suggest that WJ path changes are critical to understand the dynamics of EASM in the past, present, and future.Components: 8,956 words, 4 figures, 1 table.

Orbital control of the western North Pacific summer monsoon

“…3h, the WNP high shifts northward and matures in mid-June, a month ahead of that in the presentday simulation. This earlier break is consistent with a proxy record of Japan Sea sediments that shows an earlyHolocene environment drier than that in the present day (Nagashima et al 2013). …”

“…As the precession-modulated Northern Hemisphere summer insolation decreased after the early Holocene, the "summer optimum" over East Asia (i.e., the timing of peak Holocene rainfall) shifted southwards from northern China in the early Holocene, to central China in the mid-Holocene, and to southern China in the late Holocene . Nagashima et al (2013) furthermore suggested that the path of the westerly jet over East Asia varied over the Holocene, apparently in concert with the spatial-temporal variation in East Asian summer precipitation intensity.…”

“…However, important details associated with the changes in monsoon seasonality remain unclear (Wang et al 2003;Liu et al 2004;Conroy and Overpeck 2011;Chiang et al 2014) Recent work has focused on understanding the impact of precession on the East and South Asian monsoons (Fleitmann et al 2007;Wang et al 2008;Shi et al 2012;Liu et al 2014). This activity has been largely motivated by the introduction of high-resolution paleoclimate records during the Holocene that revealed valuable details on the space spaceregional and seasonal changes Braconnot and Marti 2003;Liu et al 2003;Staubwasser 2006;Jiang et al 2013Jiang et al , 2014Nagashima et al 2013). The summer monsoons in East and South Asia were stronger and penetrated farther north during the early and mid-Holocene compared to today Liu et al 2014).…”

Provenance fluctuations of aeolian deposits on the Chinese Loess Plateau since the Miocene

“…Recently, the application of two single-grain techniques focusing on coarse-grained minerals revealed no apparent provenance shift on the CLP between glacial and interglacial periods (Che and Li, 2013;. However, the ESR signal intensity and crystallinity index (CI) of fine-grained quartz revealed that the provenance of fine dust on the CLP and in the Japan Sea varied at glacial-interglacial timescales (Nagashima et al, , 2013Sun et al, 2008). Different conclusions regarding dust provenance variations are likely due to the different tracers and/or grain-size fractions used in previous work.…”

“…Due to the stable physical and chemical properties of quartz (Xiao et al, 1995), ESR signal intensity and CI, which reflect respectively the formation age and temperature of the host rocks (Murata and Norman, 1976;Toyoda and Naruse, 2002), have been measured intensively in order to trace the provenance of aeolian dust deposits on the CLP and in the Japan Sea (Nagashima et al, , 2011(Nagashima et al, , 2013Sun et al, 2007Sun et al, , 2008Sun et al, , 2013. Previous studies have confirmed that ESR and CI of quartz can effectively distinguish dust provenance.…”