Lagged variation of moisture conditions in central Asia compared with monsoonal Asia during the last four interglacials

Previous research has indicated that variations in moisture conditions in 15 arid central Asia (ACA) were out-of-phase with those of monsoonal Asia during the Holocene. In order to investigate this phenomenon, we compared the pattern of moisture variations in ACA and the region dominated by the East Asia summer monsoon (EASM) during the last four interglacials. The results indicate that moisture variations (pre) in ACA lagged those in the EASM region by 3 kyr during MIS 5, by 0 20 kyr during MIS 7, by 2 kyr during MIS 9, and by 5 kyr during MIS 11. We suggest that this lagged pattern in three out of four interglacials was the result of a zonal climatic teleconnection, westerly wind intensity, and evaporation upstream. Overall, our results shed new light on the climatic variability of central Asia and its origins during the Holocene. 25


Introduction
Asia can be climatically divided into two regions: monsoon-dominated Asia which is had similar boundary conditions to the modern Holocene interglacial and for this reason they were selected for detailed investigation. 60 2. Geological setting and the studied section ACA is far from oceanic moisture sources and is therefore an arid environment. The western part of ACA contains widespread sandy desert, while the eastern part is characterized by a basin-mountain topography (Fig. 1). Precipitation occurs mainly in 65 the mountains and adjacent areas and rarely in the basins. In the Junggar Basin, the mean annual precipitation (MAP) is less than 50 mm, but gradually increases to more than 1000 mm on the northern slopes of the North Tienshan Mountains. The rivers rise in the high mountains and flow into the lakes in the arid basins. Today ACA is climatically dominated by the westerlies with precipitation in most regions predominantly in winter-spring; only in the northern part is the precipitation predominantly in summer-autumn. Notably, carbon isotope records indicate that a 75 continental dry summer climate was established by at least 1.77 Ma (Yang and Ding, 2006).
Loess deposits are one of the most important geological archives in the region (e.g. Ding et al., 2002;Yang et al., 2006;Chen et al., 2016;Jia et al., 2018b). They are widespread on alluvial fans, river terraces, and on the piedmont slopes of the Tienshan 80 and Pamir mountains (Frechen and Dodonov, 1998;Sun et al., 2002;Li et al., 2018), and they have preserved paleoclimatic records from the early-to the late Pleistocene (Frechen and Dodonov, 1998;Ding et al., 2002;Wang et al., 2018;Li et al., 2019).
The most complete published loess record was obtained from Tajikistan (Frechen and Dodonov, 1998;Ding et al., 2002). In the present study, the Darai Kalon (DK) section 85 was selected to retrieve a record of moisture variations of the last four interglacials.
The Holocene (modern interglacial) was excluded from the study, since this interval may be eroded or partly eroded, as suggested by Frechen and Dodonov (1998). upper four paleosols were selected in the present study. Paleosols S1, S2, and S3 are pedocomplexes, which comprise 3, 2 and 2 soil layers, respectively. S4 consists of a single soil layer. The soil layers are separated from the underlying less-weathered parent material by a thin carbonate horizon. A detail stratigraphic description is given elsewhere (Dodonov et al., 2006;Jia et al., 2018b).

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It is widely observed that the loess of the Chinese Loess Plateau (CLP) provides a continuous and long-term record of fluctuations in moisture conditions in the EASM-dominated region during the Quaternary (e.g. Ding et al., 1995;Guo et al., 2009;Lu et al., 2018). The Xifeng (XF) section (35º 45′31″N, 107º 41′45″E, 1345 a.m.s.l.; Fig. 1), located on the northwest edge of the EASM-dominated region, is 100 acknowledged as preserving the most complete Quaternary record (e.g. Guo et al., 2009;Hao et al., 2012;Lu et al., 2018). In this study, the upper four loess-paleosol alternations were investigated for comparison with the loess record from Tajikistan.

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Grain size analysis was conducted on all of the samples using the methods of Lu and An (1997). After sequential removal of organic matter with 10% H2O2 and carbonate with 10% HCl, and dispersal using 0.05 N (NaPO3)6, the samples were measured using a Mastersizer 2000 laser diffraction particle size analyzer with size range of 0.02-2000 m.

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The eolian mineral dust comprising the loess of the CLP is transported by the East Asian winter monsoon (Guo et al., 2009). Investigations of Chinese loess have revealed a close link between the grain size of loess to variations in Northern Hemisphere ice sheets effected via the Siberian High anticyclone (e.g. Ding et al., 1995;Guo et al., 2009;Hao et al., 2012Hao et al., , 2015. Hao et al. (2012) confirmed that this 115 close coupling between high northern latitude cooling and increased dust activity in the deserts of the Asian interior deserts operated on timescales ranging from decadal to Earth orbital. Therefore, the grain size of Chinese loess provides independent Hemisphere ice volume. Therefore, the chronology of the DK and XF loess sections can be established using the accepted correlation scheme between the loess grain-size record of loess and the benthic  18 O record of marine sediments.

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The age control points are shown in Figure 2, which are locating the boundary of Marine Isotope Stage (MIS). By determine the sample location with mean value between peak and valley around soil/loess boundary, we obtained the age control points in DK and XF section. The Linear interpolation between age control points was then used to generate a final timescale. The depths and age control points are listed in     susceptibility was measured at 470 Hz and 4700 Hz (lf and hf, respectively) using a Bartington Instruments MS2B sensor. Frequency-dependent magnetic susceptibility 150 (fd) was calculated as fd = lf -hf.
The four major magnetic minerals in loess are hematite, goethite, magnetite, and maghemite (e.g. Maher, 1998;Liu et al., 2007). It had been widely observed that weakly magnetic hematite and goethite only make a small contribution to the magnetic susceptibility, while in contrast strongly magnetite and maghemite, although 155 present in trace contents, make a large contribution (e.g. Liu et al., 2007;Wang et al., 2018). fd is extremely sensitive to the fine-grained ferrimagnetic component of loess (Liu et al., 2007), which is 20-30 nm maghemite (Liu et al., 2007;Chen et al., 2010b).
According to magnetic and mineralogical evidence, it has been proposed that the fine-grained maghemite is pedogenic, and its content can be used as proxy of

Results
The fd of the DK section varies within the range of 0.0-18.5×10 -8 m 3 kg -1 and of the XF section it varies within the range of 0.8-26.2×10 -8 m 3 kg -1 (Fig. 5a). Three peaks are evident in both fd records during MIS 5, and one poorly defined peak is evident during 130-120 ka in the XF section; however, at least three soil units can be readily 170 distinguished in the field. Since loess is also a typical eolian dust, pedogenesis must be influenced by the processes of dust deposition (such as dust accumulate rate) as well as by the local climate. In order to minimize the influence of dust deposition and make the pedogenic signal more obviously, the FFT filtering analysis has been applied on the fd curves. Due to the development of soil units contains strongly precession XF records. The resulting curve exhibits three peaks which have an out-of-phase pattern of variation compared with the DK loess record (Fig. 6a). Cross-correlation 180 analysis of loess records reveals that during 130-75 ka the precipitation variations in ACA lagged that of the EASM-dominated region by 3 kyr (Fig. 6e). Similarly, from the KS loess record, it can be seen that: the moisture variations lagged those of the EASM-dominated region by ~3-5 kyr during MIS 5 (Jia et al., 2018a).
Both loess records exhibit two peaks during MIS 7 (Fig. 5b). In the DK section fd 185 varies within the range of 0.4-10.5×10 -8 m 3 kg -1 , and in the XF section it varies within the range of 0.8-26.2×10 -8 m 3 kg -1 . The filtering curve exhibited that, during this period, precipitation change in the DK section shows synchronous variation with that in XF section (Fig. 6b), which supported by cross-correlation analysis (Fig. 6f).
Unlike MIS 5 and MIS 7, which span one and a half obliquity cycles or three 190 precession cycles, the duration of MIS 9 and 11 are much shorter, and they only include one obliquity cycle or two precession cycles. During MIS 9, the fd in the DK section varies within the range of 1.4-18.5×10 -8 m 3 kg -1 , and within the XF section within the range of 8.7-25.9×10 -8 m 3 kg -1 (Fig. 5c). According to cross-correlation analysis, the precipitation variations in the DK section during 290-345 ka lag those of 195 the XF record by 2 kyr (Fig. 6g). During MIS 11, the fd in the DK section varies within the range of 0.7-9.2×10 -8 m 3 kg -1 , and in the XF section within the range of 9.0-21.6×10 -8 m 3 kg -1 (Fig. 5d). The variations of fd curves are dominated by obliquity (Fig. 5d). After application of 19-23 kyr band-pass FFT filtering, two peaks are evident in both curves during (during the period 424-379 ka) (Fig. 6d).

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Cross-correlation analysis of the loess records suggests that during 430-385 ka in ACA, precipitation variations lagged those of the EASM-dominated region by 5 kyr (Fig. 6g). Earth orbital (e.g. Ding et al., 1995;Guo et al., 2009;Kang et al., 2018). In contrast, stalagmite records from South China, which have a robust chronology, document that the glacial termination of the Asian summer monsoon occurred 3 kyr earlier than that is evident in the global ice volume record (Cheng et al., 2009). In a review of previous research, Wang and Liu (2016) proposed that stalagmite oxygen isotope record was 235 dominated by variations in the ratio of moisture from the Indian Ocean and from the Pacific Ocean, rather than by precipitation. In a comparison with the Holocene moisture pattern in the East Asian monsoon margin, it was suggested that a major The lagged response of Northern Hemisphere ice volume to insolation variations may be the major cause of the lagged response of climate change in high and mid-latitudes to insolation (e.g. Ding et al., 1995).
Combining the foregoing modelling and geological evidence, an out-of-phase 250 variation of moisture conditions between ACA and the EASM-dominated region is indicated during interglacials. This scenario is supported by the results of the present study, which indicate that during the last three out of four interglacials there was a lag in moisture changes in ACA compared to the EASM-dominated region. In addition, our results contribute to an improved understanding of climate change in ACA.

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During MIS 9, which was a relatively cool interglacial during which the ASM was relatively weak (e.g. Guo et al., 2009;Hao et al., 2012), there was a relatively brief 2 kyr delay in moisture change. In contrast, during MIS 11, a warm interglacial with a relatively strong ASM (e.g. Guo et al., 2009;Hao et al., 2012), there was a much longer delay of 5 kyr. Our results indicate that the length of the lag was variable and 260 related to the intensity of the ASM, with a stronger ASM corresponding to longer lag and a weaker ASM corresponding to a short lag. This phenomenon is well explained by the foregoing model.
Among the studied interglacials, MIS 7 is distinguished by synchronous moisture variations on precession component. As illustrated in Figure 7, an interglacial climate 265 is normally characterized by a rapid increase of precipitation at the beginning with a subsequent gradual decrease (Fig. 7a-d). However, the records from the CLP indicate the reverse pattern of climatic variation: a gradual increase from the beginning of the interglacial and a rapid decrease at the end (Fig. 7d). Furthermore, the MIS 7 is the coolest interglacial among past four interglacials. According to the conceptual model, 270 a gradually strengthening ASM and the relatively weak ASM in MIS 7 are both beneficial to westerlies staying in ACA during the early stage, rather than northward movement. For this reason, the moisture record in ACA exhibits a synchronous humidity variation compared to the EASM-dominated region.