Abrupt changes in Indian summer monsoon strength during the last deglaciation and early Holocene based on stable isotope evidence from Lake Chenghai, southwest China

Quaternary Science Reviews 218 (2019) 1e9

Contents lists available at ScienceDirect

Quaternary Science Reviews journal homepage: www.elsevier.com/locate/quascirev

Abrupt changes in Indian summer monsoon strength during the last deglaciation and early Holocene based on stable isotope evidence from Lake Chenghai, southwest China Weiwei Sun a, Enlou Zhang a, b, *, James Shulmeister c, Michael I. Bird d, e, Jie Chang a, Ji Shen a a State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing, 210008, PR China b Center for Excellence in Quaternary Science and Global Change, Chinese Academy of Science, Xian 710061, China c School of Earth and Environmental Sciences, The University of Queensland, St Lucia, Brisbane, Qld, 4072, Australia d ARC Centre of Excellence for Australian Biodiversity and Heritage, James Cook University, PO Box 6811, Cairns, Queensland, 4870, Australia e College of Science and Engineering, James Cook University, PO Box 6811, Cairns, Queensland, 4870, Australia

a r t i c l e i n f o

a b s t r a c t

Article history: Received 19 February 2019 Received in revised form 24 May 2019 Accepted 5 June 2019 Available online 19 June 2019

Identifying variability and the mechanisms driving variability in the Indian summer monsoon (ISM) since the last deglaciation is critical for understanding past hydroclimatic change. In this study, we present an accelerator mass spectrometry radiocarbon dated record of d18O variations in authigenic carbonates derived from Lake Chenghai in southwest China, a region that receives moisture mainly from the Indian Ocean. The d18O values vary from
11.9 to þ0.1‰, providing a detailed record of variations in ISM precipitation d18O values, and lake hydrological balance. The record shows that the ISM generally strengthened in the post-glacial between 15.6 and 8.8 cal ka BP, but that three centennial to millennialscale drought events were superimposed on the long-term trend. Drought events, as indicated by substantial positive shifts in d18O value, occurred from 15.6 ± 0.2 to 14.4 ± 0.2, 12.5 ± 0.2 to 11.7 ± 0.2 and 10.1 ± 0.1 to 10.0 ± 0.1 cal ka BP, corresponding to the Heinrich 1, Younger Dryas, and Bond 7 cold events in the North Atlantic region, respectively. The timings of these droughts are suggested to be related to meltwater discharge into the North Atlantic. The weakened Atlantic Meridional Overturning circulation, which leads in turn to the southward migration of the intertropical convergence zone and cooling in the tropical Indian Ocean. © 2019 Elsevier Ltd. All rights reserved.

Keywords: Heinrich 1 Younger dryas Bond cold event Stable oxygen isotope Lake chenghai Authigenic carbonates

1. Introduction The Asian summer monsoon (ASM), including the Indian summer monsoon (ISM) and the East Asian summer monsoon, plays a key role in transporting heat and moisture from tropical oceans to the densely populated regions of Asia (An et al., 2000). Variability in the ASM can result in severe flooding or drought events that pose substantial challenges to human activity, both now and in the past (Wu and Liu, 2004; Dixit et al., 2014). In recent years, increasing attention has been paid to the effect of future global warming and anthropogenic changes on the ASM (IPCC, 2013). Precipitation records from China show an overall drying trend in southwest China

* Corresponding author. E-mail address: [email protected] (E. Zhang). https://doi.org/10.1016/j.quascirev.2019.06.006 0277-3791/© 2019 Elsevier Ltd. All rights reserved.

and northern China over the past 50 years, which has resulted in considerable financial loss and threatened the livelihoods of many people (Yao et al., 2012; Ding et al., 2008). Therefore, it is important to understand the possible dynamics and causes of monsoon variability on different time scales. During the last deglaciation and early Holocene (19.0e8.2 cal ka BP), the decay of ice sheets caused a significant rise in global sea level and changes in atmosphere and ocean circulation that affected the global distribution and fluxes of water and heat (Clark et al., 2012). This period encompasses several episodes of abrupt millennial-scale climate change, including the Heinrich 1 (H1) cold event, the Bølling-Allerød (B/A) warm interval; and the Younger Dryas (YD) cold event, all superimposed on a general warming trend across the high-latitude Atlantic and the Greenland Ice Sheet (Bond et al., 1997). Stalagmite stable oxygen isotope (d18O) records

2

W. Sun et al. / Quaternary Science Reviews 218 (2019) 1e9

from parts of India and southwest China, which are influenced by the ISM, are correlated with precipitation amounts and the records are synchronous with the North Atlantic climate events (Dykoski et al., 2005; Sinha et al., 2005; Cai et al., 2015; Dutt et al., 2015; Kathayat et al., 2016). These studies provide evidence that there was a link between North Atlantic climate anomalies and ISM strength. Additionally, some studies have suggested that temperature changes in the Southern Hemisphere high-latitudes and tropical Indian Ocean might also influence millennial scale variability of the ISM during the last glacial period (Cai et al., 2006; Duan et al., 2014; Tierney et al., 2016; Zhang et al., 2017, 2019). However, the establishment of potential links between the ISM and the climate processes of significance during the last deglaciation has proven to be a challenge, in large part because of the scarcity of well-dated highresolution ISM records (Saraswat et al., 2013; Mohtadi et al., 2016). The hydrological balance effect in lake systems is an important driver of isotope fractionation in lake water, and in the d18O of lacustrine carbonates. Therefore the d18O value of lacustrine carbonates represents a powerful tool to infer past hydrological and climatic changes (Leng and Marshall, 2004; Steinman and Abbott, 2013). Carbonate d18O records have been widely used for paleoclimatic evolution in the ASM region (Zhang et al., 2011; An et al., 2012; Hillman et al., 2016, 2017; Rao et al., 2016; Wünnemann et al., 2018). However, high resolution isotopic records from lacustrine sediments covering the hydroclimatic history of southwest China during last deglaciation remain rare. In this study, we present a deglacial to early Holocene sediment record from Lake Chenghai on the Yunnan Plateau, a region that is strongly influenced by the ISM (An et al., 2000). We measured the d18O value of authigenic carbonates in the sediments to reconstruct the hydrological balance of the lake during the last deglacial period. The reconstructed record of environmental change is further compared with other ISM records to test hypotheses about the linkage between North Atlantic and tropical Indian Ocean climate and the ISM

over the deglacial period. 2. Regional setting Lake Chenghai (26 270 -26 380 N, 100 380 -100 410 E, Fig. 1A) is located in Yongsheng County in western Yunnan Province. It is a tectonic lake formed during the early Pleistocene (Wang and Dou, 1998). The lake basin is surrounded by mountains ranging from 2300 to 4000 m above sea level (a.s.l.). The present elevation of the lake is 1503 m a.s.l., and the maximum depth is about 35 m with a mean depth of 20 m. The lake has a surface area of about 77 km2 with a catchment of 318 km2 (Wu et al., 2004). The lake is 19.4 km long with an average width of 4 km. There are no perennial inlets or outflow streams at present, and the lake water is fed by direct precipitation (38.5%), groundwater (42.7%) and surface runoff (18.8%) (Wan et al., 2005). Water residence time is estimated at about 13.5 years (Wan et al., 2005). Previously, Lake Chenghai was linked to the Jinsha River via an outflow (the Haikou River) during the Ming Dynasty (1368-1644 CE), and only became a closed lake since the 1690s CE when a dam (~1540 m a.s.l.) was constructed on its southern side (Wang and Dou, 1998). The temperature of surface water ranges widely from 2.0 to 31.2  C, with an annual mean of 15.9  C (Wan et al., 2005). The lake water is slightly brackish (average ¼ 1.04 g/L) and alkaline (average pH ¼ 8.2). Cations are dominated by Naþ (171.4e193.3 mg/L), Mg2þ (63.6e73.8 mg/L), Kþ (11.0e11.8 mg/L) and Ca2þ (6.5e9.3 mg/L), with bicarbonate (579.9e886.7 mg/L) as the main anion (Whitmore et al., 1997; Wu et al., 2004; Wan et al., 2005). The study region is characterized by distinct dry and wet seasons. The region is mainly affected by a warm-humid monsoonal airflow from the tropical Indian Ocean from June to September and by the southern branch of the westerly airflow between October and May (Wang and Dou, 1998). The observed climatic data spanning the past 30 years from a nearby meteorological station in Yongsheng County (26.68 N, 100.75 E; elevation of 2130 m a.s.l.)

Fig. 1. (A) Map showing the location of Lake Chenghai in southwest China (triangle) and other sites (circles) mentioned in the text: 1. Core SK237-GC04 (Saraswat et al., 2013); 2. Core SK218/1 (Govil and Divakar Naidu, 2011); 3. Core RC12-344 (Rashid et al., 2007); 4. Core SO188-342 KL (Contreras-Rosales et al., 2014); 5. Mawmluh Cave (Dutt et al., 2015); 6. Bittoo Cave (Kathayat et al., 2016); 7. Timta Cave (Sinha et al., 2005); 8. Chandra valley in northwest Himalaya (Rawat et al., 2015); 9. Lake Tengchongqinghai (Li et al., 2018; Xiao et al., 2015; Zhang et al., 2015, 2017); 10. Lake Tiancai (Xiao et al., 2014a and b); 11. Lake Shudu (Cook et al., 2013); 12. Lake Lugu (Zhang et al., 2018); 13. Lake Xingyun (Chen et al., 2014); 14. Xiaobailong Cave (Cai et al., 2015); 15. Lake Naneng (Kramer et al., 2010); 16. Lake Muge (Sun et al., 2015); 17. Yuexi peatland (Hong et al., 2014); 18. Hongyuan Peatland (Hong et al., 2003); 19. Dongge Cave (Dykoski et al., 2005). Arrows indicate the Indian summer monsoon in the region. (B) The triangle indicates the location of core CH2016 in Lake Chenghai.

W. Sun et al. / Quaternary Science Reviews 218 (2019) 1e9

indicates a mean annual temperature of 13.9  C with maximum mean temperatures in July (18.4  C) and minimum mean temperatures in January (8.0  C, Fig. 2). The region receives an annual precipitation of 660 mm, about 80% of which falls in the wet season. The annual weighted d18O value of modern rainfall for Yongsheng is about
10.2‰ VSMOW with more negative rainfall d18O values during the monsoon season (Fig. 2; Bowen and Revenaugh, 2003). The d18O composition of lake water in summer has increased from
2.9 to
1.6‰ VSMOW since 1994 CE, and is ~8‰ more enriched than that of mean summer precipitation (Whitmore et al., 1997; Hillman et al., 2016). Potential evaporation is approximately 2040 mm/yr (Wan et al., 2005). The geology in the catchment mainly consists of Devonian limestone and dolostone to the north, Permian basalt, sandstones, muddy shale to the west, Jurassic sandstones and muddy shale to the east, and Quaternary alluvium to the south (Ma, 2002). Topsoil types include lateritic red earths and mountain red brown soils (Wang and Dou, 1998).

3. Materials and methods In July 2016 CE, an 874-cm-long sediment core (CH2016, 26 330 29.400 N, 100 390 6.700 E, Fig. 1B) was retrieved from a water depth of 30.0 m, using a UWITEC coring platform system with a percussion corer. In the laboratory, the sediment cores were split longitudinally, photographed and then sectioned at a 1-cm interval. The lacustrine sediment is a generally massive reddish, finegrained silty clay. The samples were stored at 4  C until analysis. A chronology was established using accelerator mass spectrometry (AMS) 14C dating. Bulk organic sediments for AMS dating can be influenced by a reservoir effect from ‘old’ carbon, which may produce a significant uncertainty in the age model (Hou et al., 2012). Therefore, a reliable age model needs to be based on terrestrial plant macrofossils and charcoal (Grimm et al., 2009). Macrofossils of leaves, woody stems and charcoal were handpicked under the microscope. Eight dates covering the period from the last deglaciation to early Holocene were obtained. The analyses were performed at the Beta Analytic Radiocarbon Dating Laboratory in Miami, USA. The age model was developed utilizing Bacon, implemented in R 3.1.0, with the default setting for lake sediments (memory strength of 4, memory mean of 0.7, accumulation mean of 10) at 5-cm intervals (Blaauw and Andres Christen, 2011; R Development Core Team, 2013). All AMS 14C dates were calibrated to calendar years before present (0 BP ¼ 1950 CE) using the program Calib 7.1 and the IntCal13 calibration data set (Reimer et al., 2013).

Fig. 2. Monthly mean rainfall amount (red bars), d18O (cross) and temperature (black dots) in Lake Chenghai. The rainfall and temperature data come from Yongsheng station (26.68 N, 100.75 E; elevation of 2130.5 m a.s.l.), during 1951e2016 AD. The monthly mean rainfall d18O values are modelled from the Online Isotopes in Precipitation calculator (Bowen and Revenaugh, 2003).

3

The core was sub-sampled at 2-cm intervals for carbonate content and stable isotope analysis, and a total of 184 samples were analyzed. Prior to analysis, samples were disaggregated with 7% H2O2 and sieved through a 63-mm screen to remove biogenic carbonates derived from ostracod and gastropod shells, following the method of Hillman et al. (2016). The fine fraction was retained, freeze-dried and ground in an agate mortar to homogenize the samples. Total carbonate content was measured by Thermo Nicolet 6700 Fourier transform infrared spectroscopy (FTIR) with a diffuse reflectance attachment at the Key Laboratory of Surficial Geochemistry, Nanjing University. For FTIR analysis, ~0.2 g of sample was placed in a cylindrical sample cup that is 12 mm in diameter and 3 mm deep (Ji et al., 2009; Meng et al., 2015). The limits of detection in Lake Chenghai sediments were ~1.5% for total carbonate and relative errors were 5%. The dried samples were reacted in 100% phosphoric acid and the d18O composition was measured using a Thermo-Fisher MAT 253 mass spectrometer equipped with a Gas Bench-II carbonate preparation device at the Nanjing Institute of Geology and Paleontology, Chinese Academy of Sciences. The d18O results are expressed as per mil (‰) deviation from the Vienna Pee Dee Belemnite (VPDB) standard. The calibration and assessment of the reproducibility and accuracy of the isotopic analysis were based on replicate analyses of laboratory standard materials (GBW-04405 calcite standard) and the analytical precision is better than 0.1‰. The mineralogical composition of the <63 mm fraction was determined using a Rigaku D/MAXe2400 X-ray diffractometry (XRD) equipped with a graphite monochromator at Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences. The XRD employs Cu radiation at 40 KV, 60 mA to generate X ray that irradiates a sample at a 2q scanning angle of 3 e90 . Mineralogical composition was determined by comparison of the sample's characteristic diffraction peaks with the standard XRD mineral spectrum. Sediment samples were also imaged using a Zeiss Sigma 500 field emission scanning electron microscope (SEM) at the Key Laboratory of Surficial Geochemistry, Nanjing University, to examine carbonate mineral shape and form. 4. Results Radiocarbon ages are generally in stratigraphic order (Table 1). Only one date on charred material is reversed, which is likely due to the longer terrestrial residence time of charcoal in the catchment (Oswald et al., 2005; Bird and Ascough, 2012). Therefore, this date was excluded from the age model. The relationship between age and depth in the core is plotted in Fig. 3A. The basal mean weighted age is ~15.6 cal ka BP, and the mean age uncertainty is about ±0.2 ka, with a maximum uncertainty of ±0.4 ka at the depth of 800-cm. Based on the age-depth model, the average sedimentation rate is ~41 cm/ka, with minimum values (~6.6 cm/ka) between 13.1 and 12.1 cal ka BP, and maximum values (~115.2 cm/ka) between 9.8 and 8.5 cal ka BP (Fig. 3B). Therefore, the temporal resolution for the isotope record ranges from 17 to 303 years per sample, with a mean of 49 years per sample. Total carbonate content through the record generally shows a decreasing trend, ranging from 2.4 to 22.9% with a mean of 9.2% (Table S1 and Fig. 3C). Total carbonate contents are divided into distinct episodes: higher contents of about 17.4% during the period from 15.6 ± 0.2 to 14.4 ± 0.2 cal ka BP, ~9.8% from 14.4 ± 0.2 to 8.8 ± 0.1 cal ka BP, and a decline to 3.1% from 8.8 ± 0.1 to 6.9 ± 0.3 cal ka BP. Total carbonate content from 8.8 to 6.9 cal ka BP was too low to enable the analysis of d18O values, but where analyses were possible, the d18O values vary from
11.9 to 0.1‰ with a mean value about
7.7‰ from 15.6 to 8.8 cal ka BP (Table S1 and Fig. 3D). The d18O values also exhibit millennial and centennial-scale

4

W. Sun et al. / Quaternary Science Reviews 218 (2019) 1e9

Table 1 AMS radiocarbon dates from CH2016. All of the AMS14C dates obtained were calibrated to calendar years before present using the IntCal13 calibration dataset (Reimer et al., 2013). Lab. number

Composite depth (cm)

Material

Beta-455295 Beta-450609 Beta-450605a Beta-450606 Beta-450607 Beta-455296 Beta-450608 Beta-450611

550 586

Plant material Plant material Charred material Plant material Plant material Plant material Plant material Plant material

a

699 722 741 792 806 866

Age (14C yr BP± 1s)

Calibrated age (cal yr BP): 2 s

6990 ± 30 7990 ± 30 8900 ± 30 8740 ± 30 8910 ± 30 10310 ± 40 12230 ± 40 12900 ± 40

7745e7925 8655e8995 9905e10180 9565e9885 9910e10185 11990-12380 14045-14195 15265-15560

Median age (cal yr BP) 7830 8877 10036 9707 10037 12108 14127 15400

Ignored in the age model.

fraction exhibit small and prismatic idiomorphic low-Mg calcite crystals, and spherulitic high-Mg calcite, indicating that the carbonate crystals are of authigenic origin and rapidly precipitated in Lake Chenghai sediments (Fig. S2).

5. Discussion 5.1. Source and climatic interpretation of carbonates Carbonate minerals in lacustrine sediments can be either allocthonous or autochthonous. There are some outcrops of limestone in the northern part of the Lake Chenghai catchment. However, the previous study has suggested that sedimentary carbonates in the <63 mm fraction in deep water sediments of Lake Chenghai were dominated by autochthonous aragonite during the last millennium (Hillman et al., 2016). It is generally considered that authigenic carbonates precipitate in summer (Leng and Marshall, 2004; Hillman et al., 2016, 2017). We determined the equilibrium precipitation of aragonite in lake water over the temperature range of 0e40  C (Kim et al., 2007):

. 103  lna ¼ 17:88  ð103 TÞ
31:14

Fig. 3. (A) Age-depth model for the Lake Chenghai sediment core produced by Bacon software (Blaauw and Andres Christen, 2011). Dotted lines indicate the 95% confidence range and the solid line indicates the weighted mean ages for each depth, error bars indicate the standard deviation range (2s) of the calibrated radiocarbon dates; (B) estimated sedimentation rate; (C) contents and (D) d18O values of carbonate finer in grain size than 63 mm.

fluctuations. Significantly enriched values (averaging
0.8‰) are present during the interval from 15.6 ± 0.2 to 14.4 ± 0.2 cal ka BP. Carbonate d18O values then rapidly decrease to
4.4‰ and then more gradually to
8.5‰ at about 12.5 ± 0.2 cal ka BP. During the period from 12.5 ± 0.2 to 11.7 ± 0.2 cal ka BP, the d18O values significantly increase to
4.1‰. In contrast, the d18O values from 11.7 ± 0.2 to 8.8 ± 0.1 cal ka BP are relatively depleted, ranging from
11.9 to
6.9‰ with a mean of
9.8‰. The largest positive excursion of about ~þ2.8‰ occurs between 10.1 ± 0.1 and 10.0 ± 0.1 cal ka BP. XRD results show that the major minerals in Lake Chenghai consist of quartz, illite, smectite, calcite, albite, kaolinite, hematite and anorthite. Other carbonate minerals such as aragonite and dolomite were not detected (Fig. S1). SEM images of the <63 mm

(1)

where a is the fractionation factor between aragonite and lake water, and T is the temperature in Kelvin. Assuming the maximum water temperature is 31.2  C, the estimated equilibrium d18O value of aragonite ranged from
6.0 to
4.8‰ VPDB over the last two decades. The mean is þ0.2‰ higher than the measured surface sediment value of
5.6‰ (Hillman et al., 2016). Factors such as temperature of formation, Ca/Mg ratio and primary productivity can influence the difference between the estimated and measured d18O values of carbonates in lacustrine sediments (Leng and Marshall, 2004). The coefficient of ~
0.24‰  C
1 defines the relationship between temperature and the d18O values of carbonates (O'Neil et al., 1969). The d18O value of magnesian calcite is ~0.06‰/mol% MgCO3 more positive than that of calcite formed under the same conditions (Leng and Marshall, 2004). Photosynthesis of phytoplankton can also result in slight isotopic disequilibrium with the surface water of the lake (Leng and Marshall, 2004). The blooming of phytoplankton not only controls the carbonate saturation state by photosynthetic removal of CO2, but also provides nucleation sites for carbonate crystallization. Although there has not been direct observation of carbonates precipitating in Lake Chenghai, higher temperatures and increased primary productivity in the epilimnion in summer should decrease the solubility of CO2 and increase water pH, both promoting the precipitation of carbonates with minor disequilibrium. In addition, precipitation of carbonates in lakes is also influenced by the salinity of the lake water (Shen et al., 2005; Xiao et al., 2008; Haberzettl

W. Sun et al. / Quaternary Science Reviews 218 (2019) 1e9

5

et al., 2009; Jouve et al., 2013). When evaporation exceeds water input to the lake, and Ca2þ and Mg2þ in the lake water become saturated, that results in a higher carbonate precipitation rate and this should be reflected in the carbonate content of the sediment. The absence of dolomite in Lake Chenghai during the last deglaciation and early Holocene is consistent with the sediments deposited during the last millennium. Clay minerals are mostly detrital and are formed from the weathering and erosion of the surrounding soils. Kaolinite is the product of pedogenetic weathering of feldspar, mica and other aluminosilicate minerals in warm and humid conditions. The carbonates are more reactive than silicate minerals during pedogenesis (Nesbitt et al., 1980), so the presence of kaolinite in the sediments indicates that the soils in the catchment were generally highly weathered. Recent studies have suggested that the mountainous red soils in northwest Yunnan Plateau have not formed under present climate conditions, suggesting these minerals are the result of uplift since the midPleistocene (Wang and Lu, 2014; Lu et al., 2015). In addition, detrital carbonates would be expected to be completely dissolved in the acid catchment soils because of the relative high the mean annual precipitation (>610 mm) (Meng et al., 2015). Detrital carbonates derived from the physical weathering of bedrock should have been chemically weathered in situ before being transported into the lake. Furthermore, aragonite would be likely to form in high Mg/Ca lake water, whereas calcite precipitates in low Mg/Ca lake water (Shen et al., 2005). The carbonate in the sediment of Lake Chenghai is mainly calcite, indicating that the lake water has maintained a relative low level of salinity during the last deglaciation and early Holocene. Therefore, the carbonate content and d18O value of carbonates precipitated in the Lake Chenghai sediments should provide proxies for past changes in hydrological balance and water d18O. 5.2. Comparison of d18O records from the Indian summer monsoon domain The d18O signals in precipitation can serve as proxies for panregional moisture source dynamics and/or regional-local rainfall amount in the ISM region, although source, seasonality and upstream rainout also influence isotopic composition (Maher, 2008; Pausata et al., 2011; Liu et al., 2015). Speleothem's d18O values can record d18O variations in rainfall when they grow under conditions close to isotopic equilibrium. (Lachniet, 2009; Cheng et al., 2012; Wong and Breecker, 2015). Recent model simulations suggested that modern 850 hPa elevation wind trajectories in the ISM region during summer are similar to those of the Last Glacial Maximum and the mid-Holocene. Net moisture convection over the tropical Indian Ocean was reduced during the last deglaciation but enhanced during the early and mid-Holocene (Pausata et al., 2011; Contreras-Rosales et al., 2014; Cai et al., 2015). This indicates a relatively stable moisture transport from the Bay of Bengal to southwest China. Therefore, d18O variability of precipitation in the ISM region likely derives from changes in the precipitation regime, and speleothem d18O records from this region can be used as a rainfall amount proxy. Comparing speleothem d18O records from the ISM domain with our signal, the overall trend observed in our d18O record of authigenic carbonates from Lake Chenghai generally tracks changes in monsoonal precipitation d18O values and rainfall amount within the dating uncertainty (Fig. 4). However, the amplitude of isotopic changes in Lake Chenghai sediments is much larger than that in speleothem d18O records, with the exception of the record from Bittoo Cave in north India (Fig. 4D; Kathayat et al., 2016). For example, the d18O values decreased by 8.6‰ in Lake Chenghai record from 15.5 to 12.5 cal ka BP, while the stalagmite d18O record

Fig. 4. Comparison of the d18O record from Lake Chenghai (A) with the stalagmite d18O records from the ISM domain. B. Mawmluh Cave (Dutt et al., 2015); C. Timta Cave (Sinha et al., 2005); D. Bittoo Cave (Kathayat et al., 2016); E. Xiaobailong Cave (Cai et al., 2015); F. Dongge Cave (Dykoski et al., 2005). The shading represents the Heinrich 1 (H1) and Younger Dryas (YD) ‘cold’ events in the North Atlantic.

decreased by only 4.3‰ in speleothems from Mawmluh Cave in northeast India (Fig. 4B, Dutt et al., 2015) and 4.8‰ in speleothems from Xiaobailong Cave in southwest China (Fig. 4E, Cai et al., 2015). Even smaller variations in speleothems d18O values are recorded during this interval from Dongge Cave in southwest China (Fig. 4F, Dykoski et al., 2005). Therefore, the large amplitude of Lake Chenghai d18O record requires explanation. Large fluctuations in isotope composition of authigenic carbonates are usually a function of long-term changes in precipitation-evaporation balance (Leng and Marshall, 2004). Lake water d18O values are always higher than those of the mean weighted annual precipitation as the lighter isotopes are preferentially lost to evaporation. With no outflow in closed lakes, enhanced isotopic enrichment in 18O is generally associated with reduced precipitation and/or increased evaporation. In contrast, surface outflow is significant in open lakes, where the water isotope composition is not substantially influenced by evaporation and generally more similar to precipitation. In the modern Lake Chenghai area, the negative precipitationevaporation balance results in d18O values in the lake water that are much higher than that of summer precipitation. In addition, the construction of a dam during the Ming Dynasty should have caused a positive shift in the isotopic composition of the lake water and

6

W. Sun et al. / Quaternary Science Reviews 218 (2019) 1e9

carbonates (Hillman et al., 2016). The isotopic composition of carbonates in Lake Chenghai predominantly reflects changes in residence time for the lake water, which is largely determined by variations in precipitation and evaporation. A chironomid record from Lake Tiancai in Yunnan Province indicates that summer temperature in the region might have been 5  C cooler during the last glacial maximum than the present day in the tropical mountain regions, and the summer temperature generally shows a warming trend during the last deglaciation (Zhang et al., 2019). This line of evidence suggests that the effect of temperature dependent evaporation and isotopic fractionation on the water d18O composition is negligible compared to the amplitude (up to 12‰) of the isotopic changes observed in the Lake Chenghai sedimentary record during the last deglaciation and early Holocene. Therefore, the d18O composition of carbonates is most likely influenced by changes in ISM precipitation. When the ISM weakened, precipitation and runoff decreased, the lake level was lower and, as a result, outflow stopped. The net result was greater water losses through evaporation, leading to more positive d18O values in the carbonates. Conversely, when the ISM intensified, more precipitation was delivered to the lake, increasing lake level until the lake discharged into the Jinsha River through the Haikou River. As a result, the d18O value of the lake water more closely approximated the d18O value of monsoonal precipitation at times of a strong monsoon. 5.3. Millennial scale droughts during the last deglaciation Climate change in southwest China as inferred from the carbonate content and d18O record from Lake Chenghai during the period from the last deglaciation to the early Holocene is illustrated in Figs. 4 and 5. The records generally show increasing lake levels and a strengthening ISM during the deglacial and early Holocene. Superimposed on this long-term trend, however, are pronounced millennial-scale hydroclimate fluctuations. The most positive d18O values from 15.6 ± 0.2 to 14.4 ± 0.2 cal ka BP suggest that the driest period in the record occurred during this interval; a wet interval occurred from 14.4 ± 0.2 to 12.5 ± 0.2 cal ka BP followed by a further dry interval from 12.5 ± 0.2e11.7 ± 0.2 cal ka BP. These abrupt millennial-scale changes during the last deglacial period are consistent in timing with the H1 cold event, B/A warm interval; and the YD cold event in higher latitude Atlantic and Greenland (Andersen et al., 2004; Bond et al., 1997). Similar millennial-scale oscillations of ISM intensity during the last deglacial period are also observed in the speleothem d18O records from Mawmluh Cave, Bittoo Cave and Timta Cave in north India (Fig. 4B, C and D, Sinha et al., 2005; Dutt et al., 2015; Kathayat et al., 2016), and Donnge Cave in southwest China (Fig. 4F, Dykoski et al., 2005). In addition, stable hydrogen isotope (dD) record of leaf wax n-alkane from the northern Bay of Bengal indicate relatively dry conditions during the H1 and YD events (Fig. 5D, Contreras-Rosales et al., 2014). However, the millennial-scale oscillation of ISM precipitation during the YD event is not recorded by the carbonate content, possibly because the precipitation of carbonates was also influenced in the past by factors such as cooler summer temperature and/or lower biological productivity, resulting in less carbonate precipitation and preservation after deposition (Shen et al., 2005; Zhang et al., 2019). Findings from several recent studies of lacustrine sediments suggest that the H1, B/A and YD events were also recorded across southwest China. Multi-proxy records including pollen, diatom, grain-size, charcoal and black carbon content were analyzed in Lake Tengchongqinghai (Fig. 5B, Xiao et al., 2015; Zhang et al., 2015; Zhang et al., 2017; Li et al., 2018). The results from these studies show a significant increase in drought resistant plant taxa such as Artemisia and Chenopodiaceae, an increase in black carbon and

Fig. 5. A comparison of millennial scale dry events recorded around Lake Chenghai (A) with other ISM precipitation records. B. Ti counts from Lake Tengchongqinghai (Zhang et al., 2017); C. d13C values of pyrogenic carbon from Lake Lugu (Zhang et al., 2018); D. dD of n-alkanes data from Core SO188-342 KL (Contreras-Rosales et al., 2014); E. d18O of sea water of Core RC12-344 (Rashid et al., 2007).

charcoal content, coarser grain-size of mineral particles, and a decrease in acidophilous diatom species occurred from 18.5 to 15.0 and from 12.8 to 11.1 cal ka BP, suggesting that increased fire activity, decreased lake levels and increased alkalinity resulted from reduced monsoonal precipitation. In contrast, proxies during the period from 15.0 to 12.8 cal ka BP indicate significantly decreased proportions of Pinus, Chenopodiaceae and Artemisia, reduced fire activity, higher lake levels and acidified water in Lake Tengchongqinghai, suggesting a relatively humid climate during the B/A interval. The late glacial pollen record from Lake Xingyun shows that drought resistant broadleaved tree pollen percentages increased to their maximum during the H1 cold event, indicating that the climate was the driest and the summer monsoon was the weakest during this part of the last deglaciation (Chen et al., 2014). Relatively abundant C4 biomass inferred from the d13C record of pyrogenic carbon from Lake Lugu also suggests dry intervals during the H1 and YD cold events (Fig. 5C, Zhang et al., 2018). The deglacial pollen records from alpine lakes such as Lake Tiancai and Naleng in southeast margin of the Qinghai-Tibetan Plateau also indicate low effective moisture related to the H1 and YD cold events (Kramer et al., 2010; Xiao et al., 2014). In addition, a dry climate related to the YD cold event in southwest China was revealed by the pollen record from Lake Erhai (Shen et al., 2006), the Yuexi peat cellulose record (Hong et al., 2014), and a d13C record of black carbon from

W. Sun et al. / Quaternary Science Reviews 218 (2019) 1e9

7

Lake Muge (Sun et al., 2015). The climate history of Lake Chenghai inferred in this study is also compatible with records from the tropical Indian Ocean. The d18O values of sea water and salinity changes in the Bay of Bengal and Andaman Sea are strongly controlled by the ISM precipitation and associated river discharge. Increased d18O values of sea water and salinity of the north Indian Ocean during the H1 and YD cold events suggest reduced ISM rainfall during these intervals (Fig. 5E, Rashid et al., 2007; Govil and Divakar Naidu, 2011; Saraswat et al., 2013). 5.4. Weak centennial-scale changes in the ISM during the early Holocene The gradual decrease in the d18O values of carbonates from the Lake Chenghai record during the early Holocene (11.7 ± 0.2 to 8.8 ± 0.1 cal ka BP) indicates gradually increasing precipitation and generally wetter conditions, consistent with the speleothem d18O records from Mawmluh Cave in north India (Dutt et al., 2015), Donnge Cave in southwest China (Dykoski et al., 2005), and dD record of leaf wax n-alkane from the northern Bay of Bengal (Contreras-Rosales et al., 2014). Previous studies have suggested that the timing of the maximum effective precipitation recorded in the ISM region centered on the early Holocene, much earlier than in other regions in China (Wang et al., 2010). The ISM variability reconstructed from Lake Chenghai is also characterized by a few apparent centennial-scale periods of reduced ISM intensity in the early Holocene. The most pronounced drought occurred at between 10.1 ± 0.1 and 10.0 ± 0.1 cal ka BP as evidenced by high d18O values that coincide roughly with Bond 7 event at about 10.3 cal ka BP (Bond et al., 1997). Reduced ISM intensity during Bond event 7 is also indicated by several previous paleoclimate reconstructions from adjacent regions within the uncertainties of the age models. Lower organic matter and reduced total pollen concentrations from Shudu Lake in northwest Yunnan Province suggest a dry climate from 10.7 to 10.1 cal ka BP (Cook et al., 2013). An increase in d13C values is widely reported in records from the Qinghai-Tibetan Plateau, such as Muge Co, Yuexi and Hongyuan peatland on the eastern margin of the plateau, and Chandra Peatland in northwest Himalaya at about 10.0 cal ka BP, indicating increased C4 plants biomass and/or closing of C3 plants leaf stomata in response to a dry period (Hong et al., 2003, 2014; Rawat et al., 2015; Sun et al., 2015). The slight difference in timing and duration has been ascribed to dating uncertainties, due to the fact that AMS 14C dating of bulk sediments often suffers from the carbon reservoir problem (Sun et al., 2015). 5.5. Global teleconnections of the ISM Millennial scale failures of ISM precipitation generally follows periods of intense cooling of the North Atlantic and rapid warming of the Southern Hemisphere (Fig. 6, Cai et al., 2006; An et al., 2011). The potential links between the ISM and high latitude climate in both the Southern and Northern Hemisphere are in part due to the monsoon system being driven by seasonal temperature differences and the resulting pressure gradient between Asia and the Indian Ocean. The North Atlantic climate anomalies have been explained by variability in the strength of the Atlantic Meridional Overturning circulation (AMOC), resulting in changing amount of heat and moisture transport to the high latitudes (Bond et al., 1997; McManus et al., 2004). A period of reduced ocean thermohaline circulation should be associated with extended winter Eurasian snow cover and cooling in the Northern Hemisphere (Broccoli et al., 2006; Shakun et al., 2012). The intertropical convergence zone (ITCZ) and Eurasian snow cover responses to asymmetric cooling would lead to a delayed or weakened ISM, and enhanced

Fig. 6. A comparison of the precipitation record from Lake Chenghai (A) with potential forcing factors. B. The NGRIP d18O record from Greenland (Andersen et al., 2004); C. Pa/ Th record from the North Atlantic (McManus et al., 2004); D. EDML Antarctic ice core dD record (EPICA Community Members, 2006); E. Reconstruction of hemispheric surface temperature difference (Shakun et al., 2012); F. Stalagmite d18O record from Liang Luar Cave (Ayliffe et al., 2013).

monsoonal precipitation in south Indonesia and northwest Australia (Fig. 6F, Ayliffe et al., 2013; Denniston et al., 2013; Mohtadi et al., 2016). In addition, the southward displacement of the ascending branch of the Hadley circulation would also lead to the cooling of surface water in the northern tropical Indian Ocean during the H1 cold event, further weakening convection and thereby ISM strength (Mohtadi et al., 2016). The decoupling of an intensified ISM from decreasing temperatures in Greenland during the BA cannot be totally explained by the interhemispheric bipolar seesaw mechanism (Shen et al., 2010; Zhang et al., 2017). However, the increasing strength of the ISM through the BA event revealed by our d18O record and the stalagmite records follows closely observed increases in Northern Hemisphere insolation and warming in the tropical Indian Ocean (Tierney et al., 2016; Zhang et al., 2017, 2019). This suggests a progressive increase in the influence of sea surface temperature in the tropical Indian Ocean on the ISM intensity during the last deglaciation. Ocean-atmospheric interactions in the northern tropical Indian Ocean are the main heat and water vapor source for the ISM. Rising sea surface temperatures in the northern tropical Indian Ocean during the BA event would increase the meridional

8

W. Sun et al. / Quaternary Science Reviews 218 (2019) 1e9

heat and water vapor transport from tropical regions to high latitudes, strengthening the ISM. Another observation is that our d18O record during the cold YD event shows a less marked signature than that occurring during the H1 event, which also contrasts with the Greenland ice core records. The reconstructed and modelled sea surface temperature in the northern tropical Indian Ocean shows only a small cooling during the YD event (Saraswat et al., 2013; Tierney et al., 2016). Therefore, this lesser weakening in the ISM is likely modulated by processes in the tropical Indian Ocean. 6. Conclusions The content and d18O values of carbonates finer than 63 mm in size from a sediment core derived from Lake Chenghai on the Yunnan Plateau were analyzed. The carbonates represent authigenic calcite precipitation within the water body of the lake. The large amplitude (up to 12‰) of the d18O record provides a detailed record of variations in precipitation d18O values, and lake hydrological balance. These changes were driven by changes in the balance between precipitation, influenced by the strength of the ISM, and evaporation during the last deglaciation and early Holocene (15.6 ± 0.2 to 8.8 ± 0.1 cal ka BP). Abrupt increases in the d18O values of authigenic carbonates during the H1, YD and Bond 7 cold events suggest severe droughts in the ISM region at these times. Anomalies in ISM intensity during the last deglaciation and early Holocene were mainly driven by a weakened AMOC, southward migration of the ITCZ and cooling in the tropical Indian Ocean. Our findings highlight the interplay between climatic processes occurring in the high and low latitudes, which in combination play an important role in modulating ISM intensity. Acknowledgements We would like to express our gratitude to two anonymous reviewers for their insightful comments. We thank Dr. Q. Jiang, R. Chen and D. Ning for field assistance. The research was supported by the found from the program of Global Change and Mitigation (2016YFA0600502), the National Natural Science Foundation of China (Grants. 41702183, 41572337 and 41430530). Appendix A. Supplementary data Supplementary data to this article can be found online at https://doi.org/10.1016/j.quascirev.2019.06.006. References An, Z., Clemens, S.C., Shen, J., Qiang, X., Jin, Z., Sun, Y., Prell, W.L., Luo, J., Wang, S., Xu, H., Cai, Y., Zhou, W., Liu, X., Liu, W., Shi, Z., Yan, L., Xiao, X., Chang, H., Wu, F., Ai, L., Lu, F., 2011. Glacial-Interglacial Indian summer monsoon dynamics. Science 333, 719e723. An, Z., Colman, S.M., Zhou, W., Li, X., Brown, E.T., Jull, A.J.T., Cai, Y., Huang, Y., Lu, X., Chang, H., Song, Y., Sun, Y., Xu, H., Liu, W., Jin, Z., Liu, X., Cheng, P., Liu, Y., Ai, L., Li, X., Liu, X., Yan, L., Shi, Z., Wang, X., Wu, F., Qiang, X., Dong, J., Lu, F., Xu, X., 2012. Interplay between the westerlies and asian monsoon recorded in lake Qinghai sediments since 32 ka. Sci. Rep. 2. An, Z., Porter, S.C., Kutzbach, J.E., Wu, X., Wang, S., Liu, X., Li, X., Zhou, W., 2000. Asynchronous holocene optimum of the east asian monsoon. Quat. Sci. Rev. 19, 743e762. Andersen, K.K., Azuma, N., Barnola, J.M., Bigler, M., Biscaye, P., Caillon, N., Chappellaz, J., Clausen, H.B., DahlJensen, D., Fischer, H., Fluckiger, J., Fritzsche, D., Fujii, Y., Goto-Azuma, K., Gronvold, K., Gundestrup, N.S., Hansson, M., Huber, C., Hvidberg, C.S., Johnsen, S.J., Jonsell, U., Jouzel, J., Kipfstuhl, S., Landais, A., Leuenberger, M., Lorrain, R., Masson-Delmotte, V., Miller, H., Motoyama, H., Narita, H., Popp, T., Rasmussen, S.O., Raynaud, D., Rothlisberger, R., Ruth, U., Samyn, D., Schwander, J., Shoji, H., Siggard-Andersen, M.L., Steffensen, J.P., Stocker, T., Sveinbjornsdottir, A.E., Svensson, A., Takata, M., Tison, J.L., Thorsteinsson, T., Watanabe, O., Wilhelms, F., White, J.W.C., Project, N.G.I.C., 2004. High-resolution record of Northern Hemisphere climate extending into the last interglacial period. Nature 431, 147e151.

Ayliffe, L.K., Gagan, M.K., Zhao, J.-x., Drysdale, R.N., Hellstrom, J.C., Hantoro, W.S., Griffiths, M.L., Scott-Gagan, H., Pierre, E.S., Cowley, J.A., Suwargadi, B.W., 2013. Rapid interhemispheric climate links via the Australasian monsoon during the last deglaciation. Nat. Commun. 4, 2908. Bird, M.I., Ascough, P.L., 2012. Isotopes in pyrogenic carbon: A review. Org. Geochem. 42, 1529e1539. Blaauw, M., Andres Christen, J., 2011. Flexible paleoclimate age-depth models using an autoregressive gamma process. Bayesian Analysis 6, 457e474. Bond, G., Showers, W., Cheseby, M., Lotti, R., Almasi, P., deMenocal, P., Priore, P., Cullen, H., Hajdas, I., Bonani, G., 1997. A pervasive millennial-scale cycle in North Atlantic holocene and glacial climates. Science 278, 1257e1266. Bowen, G.J., Revenaugh, J., 2003. Interpolating the isotopic composition of modern meteoric precipitation. Water Resour. Res. 39. Broccoli, A.J., Dahl, K.A., Stouffer, R.J., 2006. Response of the ITCZ to northern Hemisphere cooling. Geophys. Res. Lett. 33, L01702. Cai, Y., An, Z., Cheng, H., Edwards, R.L., Kelly, M.J., Liu, W., Wang, X., Shen, C.-C., 2006. High-resolution absolute-dated Indian Monsoon record between 53 and 36 ka from Xiaobailong Cave, southwestern China. Geology 34, 621e624. Cai, Y., Fung, I.Y., Edward, R.L., An, Z., 2015. Variability of stalagmite-inferred Indian monsoon precipitation over the past 252,000 y. Proc. Natl. Acad. Sci. U. S. A 112 (10), 2954e2959. Chen, X., Chen, F., Zhou, A., Huang, X., Tang, L., Wu, D., Zhang, X., Yu, J., 2014. Vegetation history, climatic changes and Indian summer monsoon evolution during the Last Glaciation (36,400e13,400 cal yr BP) documented by sediments from Xingyun Lake, Yunnan, China. Palaeogeogr. Palaeoclimatol. Palaeoecol. 410, 179e189. Cheng, H., Sinha, A., Wang, X., Cruz, F.W., Edwards, R.L., 2012. The global paleomonsoon as seen through speleothem records from Asia and the americas. Clim. Dyn. 39, 1045e1062. Clark, P.U., Shakun, J.D., Baker, P.A., Bartlein, P.J., Brewer, S., Brook, E., Carlson, A.E., Cheng, H., Kaufman, D.S., Liu, Z., Marchitto, T.M., Mix, A.C., Morrill, C., OttoBliesner, B.L., Pahnke, K., Russell, J.M., Whitlock, C., Adkins, J.F., Blois, J.L., Clark, J., Colman, S.M., Curry, W.B., Flower, B.P., He, F., Johnson, T.C., LynchStieglitz, J., Markgraf, V., McManus, J., Mitrovica, J.X., Moreno, P.I., Williams, J.W., 2012. Global climate evolution during the last deglaciation. Proc. Natl. Acad. Sci. U. S. A 109, E1134eE1142. Contreras-Rosales, L.A., Jennerjahn, T., Tharammal, T., Meyer, V., Lückge, A., Paul, A., Schefuß, E., 2014. Evolution of the Indian Summer Monsoon and terrestrial vegetation in the Bengal region during the past 18 ka. Quat. Sci. Rev. 102, 133e148. Cook, C.G., Jones, R.T., Turney, C.S.M., 2013. Catchment instability and Asian summer monsoon variability during the early Holocene in southwestern China. Boreas 42, 224e235. Denniston, R.F., Asmerom, Y., Lachniet, M., Polyak, V.J., Hope, P., An, N., Rodzinyak, K., Humphreys, W.F., 2013. A Last Glacial Maximum through middle Holocene stalagmite record of coastal Western Australia climate. Quat. Sci. Rev. 77, 101e112. Ding, Y., Wang, Z., Sun, Y., 2008. Inter-decadal variation of the summer precipitation in East China and its association with decreasing Asian summer monsoon. Part I: Observed evidences. Int. J. Climatol. 28, 1139e1161. Dixit, Y., Hodell, D.A., Petrie, C.A., 2014. Abrupt weakening of the summer monsoon in northwest India ~4100 yr ago. Geology 42, 339e342. Duan, F., Liu, D., Cheng, H., Wang, X., Wang, Y., Kong, X., Chen, S., 2014. A highresolution monsoon record of millennial-scale oscillations during Late MIS 3 from Wulu Cave, south-west China. J. Quat. Sci. 29, 83e90. Dutt, S., Gupta, A.K., Clemens, S.C., Cheng, H., Singh, R.K., Kathayat, G., Edwards, R.L., 2015. Abrupt changes in Indian summer monsoon strength during 33,800 to 5500 years B.P. Geophys. Res. Lett. 42, 2015GL064015. Dykoski, C.A., Edwards, R.L., Cheng, H., Yuan, D., Cai, Y., Zhang, M., Lin, Y., Qing, J., An, Z., Revenaugh, J., 2005. A high-resolution, absolute-dated Holocene and deglacial Asian monsoon record from Dongge Cave, China. Earth Planet. Sci. Lett. 233, 71e86. EPICA Community Members, 2006. One-to-one coupling of glacial climate variability in Greenland and Antarctica. Nature 444, 195e198. Govil, P., Divakar Naidu, P., 2011. Variations of Indian monsoon precipitation during the last 32 kyr reflected in the surface hydrography of the Western Bay of Bengal. Quat. Sci. Rev. 30, 3871e3879. Grimm, E.C., Maher Jr., L.J., Nelson, D.M., 2009. The magnitude of error in conventional bulk-sediment radiocarbon dates from central North America. Quat Res. 72, 301e308. Haberzettl, T., Anselmetti, F.S., Bowen, S.W., Fey, M., Mayr, C., Zolitschka, B., Ariztegui, D., Mauz, B., Ohlendorf, C., Kastner, S., Lücke, A., Sch€ abitz, F., Wille, M., 2009. Late Pleistocene dust deposition in the Patagonian steppe - extending and refining the paleoenvironmental and tephrochronological record from Laguna Potrok Aike back to 55ka. Quat. Sci. Rev. 28, 2927e2939. Hillman, A.L., Abbott, M.B., Finkenbinder, M.S., Yu, J., 2017. An 8,600 year lacustrine record of summer monsoon variability from Yunnan, China. Quat. Sci. Rev. 174, 120e132. Hillman, A.L., Abbott, M.B., Yu, J., Steinman, B.A., Bain, D.J., 2016. The isotopic response of Lake Chenghai, SW China, to hydrologic modification from human activity. Holocene 26, 906e916. Hong, B., Hong, Y., Uchida, M., Shibata, Y., Cai, C., Peng, H., Zhu, Y., Wang, Y., Yuan, L., 2014. Abrupt variations of Indian and East Asian summer monsoons during the last deglacial stadial and interstadial. Quat. Sci. Rev. 97, 58e70. Hong, Y.T., Hong, B., Lin, Q.H., Zhu, Y.X., Shibata, Y., Hirota, M., Uchida, M., Leng, X.T.,

W. Sun et al. / Quaternary Science Reviews 218 (2019) 1e9 Jiang, H.B., Xu, H., Wang, H., Yi, L., 2003. Correlation between Indian ocean summer monsoon and north atlantic climate during the holocene. Earth Planet. Sci. Lett. 211, 371e380. Hou, J., D'Andrea, W.J., Liu, Z., 2012. The influence of 14C reservoir age on interpretation of paleolimnological records from the Tibetan Plateau. Quat. Sci. Rev. 48, 67e79. IPCC, 2013. Climate Change 2013 Working Group I Contribution to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge, United Kingdom and New York. Ji, J., Ge, Y., Balsam, W., Damuth, J.E., Chen, J., 2009. Rapid identification of dolomite using a Fourier Transform Infrared Spectrophotometer (FTIR): A fast method for identifying Heinrich events in IODP Site U1308. Mar. Geol. 258, 60e68. Jouve, G., Francus, P., Lamoureux, S., Provencher-Nolet, L., Hahn, A., Haberzettl, T., Fortin, D., Nuttin, L., 2013. Microsedimentological characterization using image analysis and m-XRF as indicators of sedimentary processes and climate changes during Lateglacial at Laguna Potrok Aike, Santa Cruz, Argentina. Quat. Sci. Rev. 71, 191e204. €tl, C., Edwards, R.L., Zhang, H., Li, X., Yi, L., Kathayat, G., Cheng, H., Sinha, A., Spo Ning, Y., Cai, Y., Lui, W.L., Breitenbach, S.F.M., 2016. Indian monsoon variability on millennial-orbital timescales. Sci. Rep. 6, 24374. Kim, S.-T., O'Neil, J.R., Hillaire-Marcel, C., Mucci, A., 2007. Oxygen isotope fractionation between synthetic aragonite and water: Influence of temperature and Mg2þ concentration. Geochem. Cosmochim. Acta 71, 4704e4715. Kramer, A., Herzschuh, U., Mischke, S., Zhang, C., 2010. Late glacial vegetation and climate oscillations on the southeastern Tibetan Plateau inferred from the Lake Naleng pollen profile. Quat Res. 73, 324e335. Lachniet, M.S., 2009. Climatic and environmental controls on speleothem oxygenisotope values. Quat. Sci. Rev. 28, 412e432. Leng, M.J., Marshall, J.D., 2004. Palaeoclimate interpretation of stable isotope data from lake sediment archives. Quat. Sci. Rev. 23, 811e831. Li, Y., Chen, X., Xiao, X., Zhang, H., Xue, B., Shen, J., Zhang, E., 2018. Diatom-based inference of Asian monsoon precipitation from a volcanic lake in southwest China for the last 18.5 ka. Quat. Sci. Rev. 182, 109e120. Liu, J., Chen, J., Zhang, X., Li, Y., Rao, Z., Chen, F., 2015. Holocene East Asian summer monsoon records in northern China and their inconsistency with Chinese stalagmite d18O records. Earth Sci. Rev. 148, 194e208. Lu, S., Wang, S., Chen, Y., 2015. Palaeopedogenesis of red palaeosols in Yunnan Plateau, southwestern China: Pedogenical, geochemical and mineralogical evidences and palaeoenvironmental implication. Palaeogeogr. Palaeoclimatol. Palaeoecol. 420, 35e48. Ma, L., 2002. Geological Atlas of China, pp. 1e384. Maher, B.A., 2008. Holocene variability of the East Asian summer monsoon from Chinese cave records: A re-assessment. Holocene 18, 861e866. McManus, J.F., Francois, R., Gherardi, J.M., Keigwin, L.D., Brown-Leger, S., 2004. Collapse and rapid resumption of Atlantic meridional circulation linked to deglacial climate changes. Nature 428, 834e837. Meng, X., Liu, L., Balsam, W., Li, S., He, T., Chen, J., Ji, J., 2015. Dolomite abundance in Chinese loess deposits: A new proxy of monsoon precipitation intensity. Geophys. Res. Lett. 42 (10), 310e391. Mohtadi, M., Prange, M., Steinke, S., 2016. Palaeoclimatic insights into forcing and response of monsoon rainfall. Nature 533, 191e199. Nesbitt, H.W., Markovics, G., price, R.C., 1980. Chemical processes affecting alkalis and alkaline earths during continental weathering. Geochem. Cosmochim. Acta 44, 1659e1666. O'Neil, J.R., Clayton, R.N., Mayeda, T.K., 1969. Oxygen isotope fractionation in divalent metal carbonates. J. Chem. Phys. 51, 5547e5558. Oswald, W.W., Anderson, P.M., Brown, T.A., Brubaker, L.B., Hu, F.S., Lozhkin, A.V., Tinner, W., Kaltenrieder, P., 2005. Effects of sample mass and macrofossil type on radiocarbon dating of arctic and boreal lake sediments. Holocene 15, 758e767. Pausata, F.S.R., Battisti, D.S., Nisancioglu, K.H., Bitz, C.M., 2011. Chinese stalagmite d18O controlled by changes in the Indian monsoon during a simulated Heinrich event. Nat. Geosci. 4, 474e480. R Development Core Team, 2013. R: A Language and Environment for Statistical Computing. R Foundation for Statistical Computing, Vienna, Austria. Rao, Z., Li, Y., Zhang, J., Jia, G., Chen, F., 2016. Investigating the long-term palaeoclimatic controls on the dD and d18O of precipitation during the Holocene in the Indian and East Asian monsoonal regions. Earth Sci. Rev. 159, 292e305. Rashid, H., Flower, B.P., Poore, R.Z., Quinn, T.M., 2007. A ~25 ka Indian Ocean monsoon variability record from the Andaman Sea. Quat. Sci. Rev. 26, 2586e2597. Rawat, S., Gupta, A.K., Sangode, S.J., Srivastava, P., Nainwal, H.C., 2015. Late pleistoceneeholocene vegetation and Indian summer monsoon record from the Lahaul, northwest Himalaya, India. Quat. Sci. Rev. 114, 167e181. Reimer, P.J., Bard, E., Bayliss, A., Beck, J.W., Blackwell, P.G., Ramsey, C.B., Buck, C.E., Cheng, H., Edwards, R.L., Friedrich, M., 2013. IntCal13 and Marine13 radiocarbon age calibration curves 0e50,000 years cal BP. Radiocarbon 55, 1869e1887. Saraswat, R., Lea, D.W., Nigam, R., Mackensen, A., Naik, D.K., 2013. Deglaciation in the tropical Indian Ocean driven by interplay between the regional monsoon and global teleconnections. Earth Planet. Sci. Lett. 375, 166e175. Shakun, J.D., Clark, P.U., He, F., Marcott, S.A., Mix, A.C., Liu, Z., Otto-Bliesner, B.,

9

Schmittner, A., Bard, E., 2012. Global warming preceded by increasing carbon dioxide concentrations during the last deglaciation. Nature 484, 49. Shen, C.-C., Kano, A., Hori, M., Lin, K., Chiu, T.-C., Burr, G.S., 2010. East Asian monsoon evolution and reconciliation of climate records from Japan and Greenland during the last deglaciation. Quat. Sci. Rev. 29, 3327e3335. Shen, J., Liu, X., Wang, S., Ryo, M., 2005. Palaeoclimatic changes in the Qinghai Lake area during the last 18,000 years. Quat. Int. 136, 131e140. Shen, J., Jones, R.T., Yang, X., Dearing, J.A., Wang, S., 2006. The Holocene vegetation history of Lake Erhai, Yunnan province southwestern China: The role of climate and human forcings. Holocene 16, 265e276. Sinha, A., Cannariato, K.G., Stott, L.D., Li, H.C., You, C.F., Cheng, H., Edwards, R.L., Singh, I.B., 2005. Variability of Southwest Indian summer monsoon precipitation during the Boiling-Allerod. Geology 33, 813e816. Sun, W., Zhang, E., Jones, R.T., Liu, E., Shen, J., 2015. Asian summer monsoon variability during the late glacial and Holocene inferred from the stable carbon isotope record of black carbon in the sediments of Muge Co, southeastern Tibetan Plateau, China. Holocene 25, 1857e1868. Steinman, B.A., Abbott, M.B., 2013. Isotopic and hydrologic responses of small, closed lakes to climate variability: Hydroclimate reconstructions from lake sediment oxygen isotope records and mass balance models. Geochem. Cosmochim. Acta 105, 342e359. Tierney, J.E., Pausata, F.S.R., deMenocal, P., 2016. Deglacial Indian monsoon failure and North Atlantic stadials linked by Indian Ocean surface cooling. Nat. Geosci. 9, 46e50. Wan, G.J., Chen, J.A., Wu, F.C., Xu, S.Q., Bai, Z.G., Wan, E.Y., Wang, C.S., Huang, R.G., Yeager, K.M., Santschi, P.H., 2005. Coupling between 210Pbex and organic matter in sediments of a nutrient-enriched lake: An example from Lake Chenghai, China. Chem. Geol. 224, 223e236. Wang, S., Dou, H., 1998. Lakes in China. Science Press, Beijing, China (in Chinese). Wang, S., Lu, S., 2014. A rock magnetic study on red palaeosols in Yun-Gui Plateau (Southwestern China) and evidence for uplift of Plateau. Geophys. J. Int. 196, 736e747. Wang, Y., Liu, X., Herzschuh, U., 2010. Asynchronous evolution of the Indian and East Asian summer monsoon indicated by holocene moisture patterns in monsoonal central Asia. Earth Sci. Rev. 103, 135e153. Whitmore, T.J., Brenner, M., Jiang, Z., Curtis, J.H., Moore, A.M., Engstrom, D.R., Wu, Y., 1997. Water quality and sediment geochemistry in lakes of Yunnan Province, southern China. Environ. Geol. 32, 45e55. Wong, C.I., Breecker, D.O., 2015. Advancements in the use of speleothems as climate archives. Quat. Sci. Rev. 127, 1e18. Wu, J., Gagan, M.K., Jiang, X., Xia, W., Wang, S., 2004. Sedimentary geochemical evidence for recent eutrophication of Lake Chenghai, Yunnan, China. J. Paleolimnol. 32, 85e94. Wu, W., Liu, T., 2004. Possible role of the “holocene event 3” on the collapse of Neolithic Cultures around the central plain of China. Quat. Int. 117, 153e166. Wünnemann, B., Yan, D., Andersen, N., Riedel, F., Zhang, Y., Sun, Q., Hoelzmann, P., 2018. A 14 ka high-resolution d18O lake record reveals a paradigm shift for the process-based reconstruction of hydroclimate on the northern Tibetan Plateau. Quat. Sci. Rev. 200, 65e84. Xiao, J.L., Si, B., Zhai, D.Y., Itoh, S., Lomtatidze, Z., 2008. Hydrology of dali Lake in central-eastern inner Mongolia and holocene East Asian monsoon variability. J. Paleolimnol. 40, 519e528. Xiao, X., Haberle, S.G., Yang, X., Shen, J., Han, Y., Wang, S., 2014. New evidence on deglacial climatic variability from an alpine lacustrine record in northwestern Yunnan Province, southwestern China. Palaeogeogr. Palaeoclimatol. Palaeoecol. 406, 9e21. Xiao, X., Shen, J.I., Haberle, S.G., Han, Y., Xue, B., Zhang, E., Wang, S., Tong, G., 2015. Vegetation, fire, and climate history during the last 18 500 cal a BP in southwestern Yunnan Province, China. J. Quat. Sci. 30, 859e869. Yao, T., Thompson, L., Yang, W., Yu, W., Gao, Y., Guo, X., Yang, X., Duan, K., Zhao, H., Xu, B., Pu, J., Lu, A., Xiang, Y., Kattel, D.B., Joswiak, D., 2012. Different glacier status with atmospheric circulations in Tibetan Plateau and surroundings. Nat. Clim. Change 2, 663e667. Zhang, E., Chang, J., Shulmeister, J., Langdon, P., Sun, W., Cao, Y., Yang, X., Shen, J., 2019. Summer temperature fluctuations in Southwestern China during the end of the LGM and the last deglaciation. Earth Planet. Sci. Lett. 509, 78e87. Zhang, E., Sun, W., Chang, J., Ning, D., Shulmeister, J., 2018. Variations of the Indian summer monsoon over the last 30 000 years inferred from a pyrogenic carbon record from south-west China. J. Quat. Sci. 33, 131e138. Zhang, E., Sun, W., Zhao, C., Wang, Y., Xue, B., Shen, J., 2015. Linkages between climate, fire and vegetation in southwest China during the last 18.5 ka based on a sedimentary record of black carbon and its isotopic composition. Palaeogeogr. Palaeoclimatol. Palaeoecol. 435, 86e94. Zhang, E., Zhao, C., Xue, B., Liu, Z., Yu, Z., Chen, R., Shen, J., 2017. Millennial-scale hydroclimate variations in southwest China linked to tropical Indian Ocean since the Last Glacial Maximum. Geology 45, 435e438. Zhang, J., Chen, F., Holmes, J.A., Li, H., Guo, X., Wang, J., Li, S., Lü, Y., Zhao, Y., Qiang, M., 2011. Holocene monsoon climate documented by oxygen and carbon isotopes from lake sediments and peat bogs in China: A review and synthesis. Quat. Sci. Rev. 30, 1973e1987.