Paleoclimate Changes and the Evolution of Atmospheric Circulation in Selin Co on the Central Tibetan Plateau Since the Mid–Late Holocene

Paleoclimate Changes and the Evolution of Atmospheric Circulation in Selin Co on the Central Tibetan Plateau Since the Mid–Late Holocene | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Paleoclimate Changes and the Evolution of Atmospheric Circulation in Selin Co on the Central Tibetan Plateau Since the Mid–Late Holocene Hailei Wang, Chengjun Zhang, Gao Song, Mianping Zheng This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9194728/v1 This work is licensed under a CC BY 4.0 License Status: Under Revision Version 1 posted 9 You are reading this latest preprint version Abstract Selin Co, the largest lake on the Central Tibetan Plateau, is located at the junction of the Asian summer monsoon and the Westerlies, making it an ideal site for investigating the evolution of atmospheric circulation. In this study, variations in total organic carbon (TOC) and total carbonate contents, carbon and oxygen isotopic compositions of authigenic carbonates, together with grain-size parameters and changes in ostracod assemblages from lake sediments, are used to reconstruct the advance and retreat of the Asian summer monsoon and the Westerlies circulation since 6.20 ka. The regional climate evolution and the characteristics of specific climatic events in the Selin Co area are also discussed. The results indicate that from 6.20 to 2.21 ka, the Selin Co region was mainly dominated by the Westerlies. Lake level remained relatively high as it inherited from the highstand during the Holocene Megathermal, the supply of glacial meltwater also contributed. Between 3.32 and 2.21 ka, the regional climate experienced pronounced fluctuations. After 2.21 ka, the Indian summer monsoon became the dominant controlling factor. Nevertheless, weakened solar radiation led to reduced moisture transport by the monsoon, resulting in a gradual trend toward aridification and a progressive decline in lake level. The widely recognized 4.2 ka cold-dry event began at approximately 4.25 ka in the central Tibetan Plateau and persisted for about 370 years. It was characterized by predominantly cold conditions during its initial phase, followed by pronounced aridity during the middle to late stages, with superimposed temperature fluctuations. The Medieval Warm Period (MWP) was relatively short-lived, occurring between 1.15 and 0.79 ka, and was marked by a distinct early temperature increase followed by gradual cooling. After 0.68 ka, regional temperatures declined further, with modest cooling initially and a more pronounced temperature decrease after 0.39 ka, corresponding broadly to the Little Ice Age (LIA). Selin Co mid–late Holocene organic and inorganic carbon contents carbon and oxygen isotopes atmospheric circulation shifts climate evolution Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Introduction As the “Third Pole of the Earth,” the Tibetan Plateau (TP) has been a major focus of international geoscientific research over recent decades. Holocene climate and environmental changes on the TP have been widely documented using various archives, including ice cores (Yao et al., 1996 ; Thompson et al., 1997 ), lake sediments (Mischke et al., 2010; An et al., 2012a ; Ahlborn et al., 2017 ; Conroy et al., 2017 ; Hou et al., 2017 ; Du et al., 2019 ; Gao et al., 2024 ; Ma et al., 2024a , b ), as well as speleothem (Han et al., 2017 ) and tree ring (Yang et al., 2021 ). Atmospheric circulation plays a crucial role in transporting water vapor and dust, thereby exerting a strong influence on regional moisture conditions, lake-level fluctuations, and aeolian material transport. The Tibetan Plateau is located at the intersection of the East Asian summer monsoon, the Indian summer monsoon, and the Westerlies (Chen et al., 2020 ). The southeastern and southern parts of the Plateau are primarily influenced by the Indian summer monsoon (Tian et al., 2001 ; Tong et al., 2016 ). The East Asian summer monsoon, however, was able to extend to the northeastern margin of the Plateau, especially the eastern Qaidam Basin, during certain periods (An et al., 2012b ; Qiang et al., 2017 ; Song et al., 2020; Wu et al., 2026). The Westerlies, as a high-altitude airflow system, can either cover the Plateau directly or split into northern and southern branches that bypass the Plateau (Schiemann et al., 2009 ; Molnar et al., 2010 ; An et al., 2012a ; Günther et al., 2015). Paryal et al. (2026) recently summarized the current understanding of the East Asian summer monsoon, the Indian summer monsoon, and the Westerlies on the Tibetan Plateau since the Last Glacial Maximum based on lake sediment records. Chen et al. ( 2008 ) divided the southeastern Eurasian continent into three climatically distinct regions: humid Asia, mainly controlled by summer monsoonal circulation; arid central Asia (ACA), dominated by the Westerlies; and a transitional zone encompassing semi-arid northwestern China and the southern Mongolian Plateau. Selin Co, located in the central Tibetan Plateau, lies precisely within this transitional zone. Its lacustrine sediments therefore provide valuable insights into the advance–retreat history of the summer monsoon and the Westerlies. Selin Co is currently the largest lake in Tibet, with a surface area exceeding 2200 km² and a maximum water depth of nearly 60 m (Zhu et al., 2019 ). These characteristics make it an ideal site for Holocene climate studies, as it preserves continuous sedimentary records without significant depositional hiatuses. In recent decades, numerous paleoclimate studies have been conducted in the Selin Co region, primarily focusing on climatic and environmental changes and lake-level fluctuations since the Last Glacial Maximum (Morinaga et al., 1993 ; Wang et al., 2014; Shi et al., 2017; Du et al., 2019 ; Guo et al., 2019 ; Wang et al., 2019 ; Zhu et al., 2019 ; Hou et al., 2021; Song et al., 2022; Kou et al., 2023 , 2024 ; Zhu et al., 2026). Morinaga et al. ( 1993 ) and Zhu et al. (2026) reconstructed records spanning the past 14 ka and 25.1 ka, respectively, whereas this study focuses on the period since 6.20 ka, providing higher-resolution insights. In addition, multiple proxy indicators-including total organic carbon (TOC), carbonate content, the 10–70 µm fraction of grain-size, and ostracod assemblages-are integrated in this study, resulting in a different interpretative emphasis. This study focuses on shifts of the Asian monsoon and the Westerlies, as well as associated climatic events in the Selin Co region since 6.20 cal ka BP. By employing higher-resolution records, we aim to provide a more detailed reconstruction of the advance and retreat of major atmospheric circulation systems and the characteristics of key climatic events. Such high-resolution paleoclimate records not only improve our understanding of past climate dynamics but also offer an essential baseline for numerical climate modeling and for assessing future hydrological responses. This is particularly relevant given the rapid rise in Selin Co lake level in recent decades, which has already exerted significant impacts on local ecosystems, infrastructure, and socioeconomic activities. Materials and Methods Study Area Selin Co is a brackish lake located in the west of Bange county in Naqu district (88°32´-89°22´E, 31°32´-32°07´N)(Fig. 1 ). Selin Co consists of two sub-basins: an eastern basin and a western basin. The eastern basin is larger but relatively shallow, whereas the western basin is smaller, deeper, and characterized by steeper lake-floor topography. Selin Co is a terminal lake fed by several inflowing rivers, including the Zajia Zangbu (Zangbu is river in Tibetan), Zagen Zangbu, Ali Zangbu, and Boqu Zangbu, etc. Among these, the Zajia Zangbu, with a total length of approximately 409 km, is the longest inland river in Tibet. It enters the northern part of the eastern basin and serves as the primary perennial river supplying water and sediments to Selin Co. Its catchment originates from the glaciated Geladandong Mountains, providing substantial glacially derived sediment input. The Selin Co region is located in the cold semi-arid climatic zone of the Tibetan Plateau, characterized by strong solar radiation and long sunshine duration. Mean annual precipitation ranges from 290 to 321 mm, with most rainfall occurring between June and September. In contrast, annual evaporation is extremely high, reaching approximately 2176 mm. The mean annual air temperature ranges from 0.8 to 1.0°C, and the number of gale days per year is between 103 and 132 (Dasang, 2011 ). Core Sampling and Chronology In 2014, a 2.78 m long sediment core (SL-1) was recovered from the western basin of Selin Co at a water depth of 30 m using a gravity corer. The sediments are mainly composed of alternating gray-white fine silt to very fine sand and black clay layers. Subsampling was conducted at 0.5 cm intervals throughout the core. The uppermost 25 cm of the core was dated using 210 Pb and 137 Cs methods (Fig. 2 ). The 137 Cs activity profile shows a well-defined stratigraphic pattern consistent with the global fallout history, indicating minimal post-depositional disturbance. A distinct 137 Cs peak occurs at a depth of 2.5 cm, corresponding to an age of 1987 AD, which is consistent with regional 137 Cs reference. Considering that the effective dating range of 137 Cs is approximately the past 200 years, a polynomial regression was applied to constrain the age-depth relationship for the 0-200 year interval based on the 137 Cs-derived age control points (Fig. 2 ). The resulting age-depth equation is: y = -0.0765x 4 + 1.4468x 3 − 5.4569x 2 + 13.326x + 0.9691 (R 2 = 0.9965) where y represents age (yr AD) and x represents depth (cm). According to this model, the sediment-water interface (0 cm) corresponds to an age of 1 year, which is reasonable for the coring year, while the age at 8 cm depth is estimated to be 1827 AD based on the 137 Cs-constrained model. In addition, five bulk organic carbon samples from different depths were dated by AMS 14 C analysis at the BETA Analytic Radiocarbon Dating Laboratory (USA) (Table 1 ). Comparison between the 137 Cs-derived age at 8 cm depth (185 year BP) and the age extrapolated from 14 C dates at 52.5 cm and 172.5 cm reveals a substantial age offset of approximately 1860 years. This discrepancy is interpreted as a carbon reservoir effect, which is commonly observed in Tibetan Plateau lakes due to inputs of old carbon from glacial meltwater, carbonate weathering, and catchment processes. Table 1 AMS 14 C ages from the core SL−1 (BETA Analytic Radiocarbon Dating Laboratory, USA) Sample no. Depth/cm Age/a Error Material SL2-99 52.5 2900 60 Organic carbon SL4-148 172.5 5205 5 Organic carbon SL4-208, 209 202.5 5525 65 Organic carbon SL4-259, 260 228 5960 40 Organic carbon SL4-358 277.5 7220 60 Organic carbon Accordingly, a reservoir age correction of 1860 years was applied to all AMS 14 C dates prior to calibration. The corrected 14 C ages were then calibrated relative to the standard 1950 AD reference year and incorporated into a Bayesian age-depth model constructed using the R statistical environment (Fig. 3 ). This integrated approach allows for a consistent and statistically robust chronology that reconciles short-lived radionuclide dating with radiocarbon ages. The resulting age-depth model indicates that the basal age of core SL-1 is approximately 6.20 ka, with an average sedimentation rate of 0.5216 mm/a, although sedimentation rates vary through time in response to changing hydrological and depositional conditions. Geochemical and Isotopic Analyses For carbon and oxygen isotope analyses of authigenic carbonate (δ¹³C carb and δ¹⁸O carb ), the fine-grained fraction of each sample was separated by sieving through a 40 µm mesh. The samples were reacted with phosphoric acid, and the released CO₂ was purified and analyzed using a Finnigan MAT 252 isotope ratio mass spectrometer at the Lanzhou Institute of Geology, Chinese Academy of Sciences. Calibration measurements were performed every ten samples using the international standard NBS-19 (δ¹³C = + 1.95‰, δ¹⁸O = − 2.20‰). The analytical precision was better than ± 0.2‰ for both δ¹³C carb and δ¹⁸O carb . Isotopic values are reported in conventional δ notation relative to the V-PDB (Vienna Pee Dee Belemnite) standard. Total organic carbon (TOC) content was determined using the potassium dichromate–sulfuric acid wet oxidation (antititration) method. Carbonate content was measured by treating bulk sediment samples with dilute 1 N HCl and quantifying the volume of CO₂ released during the reaction. All geochemical analyses were conducted at the National Laboratory of Western China’s Environmental Systems, Lanzhou University. Results Total organic carbon (TOC) contents of the SL-1 core range from 0.14% to 8.91%, with a mean value of 3.91%. Prior to 3.32 ka, TOC values remained relatively low with minor fluctuations. Between 3.32 and 2.21 ka, TOC exhibits pronounced variability with large-amplitude oscillations. After 2.21 ka, TOC returns to lower values with relatively small fluctuations, except for a distinct increase during the interval from 1.3 to 1.0 ka (Fig. 4 ). Carbonate contents in the SL-1 core are generally high, with an average value of 47.7%, and show relatively limited variation throughout the core. The maximum and minimum carbonate contents are 68.3% and 29.7%, respectively. A slight increase in carbonate content is observed after 2.21 ka (Fig. 4 ). The δ¹⁸O values of authigenic carbonates from Selin Co since 6.20 ka range from − 4.86‰ to 0.38‰, with a mean value of − 2.57‰. These values are broadly consistent with late Holocene authigenic carbonate δ¹⁸O records from the eastern basin of Selin Co reported by Zhu et al. (2026). Overall, δ¹⁸O values display relatively small-amplitude variations throughout the core. After 2.21 ka, fluctuations become more frequent but of lower magnitude, accompanied by a slight increase in δ¹⁸O values toward the upper part of the record (Fig. 4 ). The δ¹³C values of authigenic carbonates vary between 1.862‰ and 5.284‰, with an average value of 3.953‰. Prior to 3.32 ka, δ¹³C values are relatively low but highly variable, particularly between 4.25 and 3.88 ka, during which several large-amplitude oscillations are observed. Thereafter, δ¹³C values show a gradual increase. After 2.21 ka, it is characterized by high-frequency and low-amplitude fluctuations accompanied by a slight increase, similar to those of oxygen isotopes in the same period. (Fig. 4 ). Discussion 4.1 Evolution of atmospheric circulation in the Selin Co region during the Mid–Late Holocene The δ¹⁸O values of authigenic carbonates are primarily controlled by the temperature and isotopic composition of lake water at the time of carbonate precipitation (Leng and Marshall, 2004 ). Considering that the temperature-dependent equilibrium isotopic fractionation between carbonate and water is approximately − 0.24‰ per °C (Craig and Gordon, 1965 ), and that summer temperature variations on the Tibetan Plateau during the Holocene were likely limited to within ~ 1.5°C (Chen et al., 2020 ), the influence of temperature on carbonate δ¹⁸O values in this study can be considered relatively minor. Therefore, the variations of authigenic carbonates δ¹⁸O values are interpreted to mainly reflect fluctuations in the oxygen isotopic composition of lake water. As such, carbonate δ¹⁸O provides valuable information on past changes in regional hydrological conditions on the Tibetan Plateau (Wei and Gasse, 1999 ; Yu et al., 2009 ; Liu et al., 2018 ; Wünnemann et al., 2018 ). Former study showed that in arid to semi-arid regions, the δ¹⁸O composition of authigenic carbonate in lake sediments is highly related to the effective moisture (precipitation/evaporation (P/E) ratio) of the region (Li et al., 2017 ). Modern observations indicate that the δ¹⁸O of precipitation integrates signals from multiple atmospheric circulation systems, including the Indian summer monsoon (ISM), the East Asian summer monsoon (EASM), and the Westerlies, which together govern the climate of the Tibetan Plateau (Wu et al., 2022 ). The δ¹⁸O values of authigenic carbonates in Selin Co since 6.20 ka range from − 4.86‰ to 0.38‰. Previous oxygen isotope studies have also been conducted on lacustrine sediments from Selin Co by Morinaga et al. ( 1993 ) and Zhu et al. (2026). The core studied by Morinaga et al. ( 1993 ) was retrieved from a site approximately 1 km from the southern shore at a water depth of 27 m, whereas the core analyzed by Zhu et al. (2026) was obtained from the eastern basin near the southern shore at a water depth of 44 m. In contrast, the SL-1 core analyzed in this study was collected from the western basin, approximately 3 km offshore, at a water depth of 30 m. Differences in core locations resulted in substantial variations in sediment lithology among the studies. Morinaga et al. ( 1993 ) measured δ¹⁸O values from bulk sediments, which yielded relatively higher values. In contrast, both this study and Zhu et al. (2026) analyzed sieved fine-grained carbonate fractions, dominated by authigenic carbonates, resulting in comparable δ¹⁸O values that are slightly lower than those reported by Morinaga et al. ( 1993 ). Moreover, the temporal coverage of these studies differs substantially. Araguás-Araguás et al. ( 1998 ) demonstrated that summer monsoon precipitation originating from the western Pacific is characterized by relatively enriched δ¹⁸O values compared to that derived from the Indian Ocean, whereas precipitation associated with the westerly jet is generally more depleted in δ¹⁸O. Compared with the early–middle Holocene δ¹⁸O values reported by Zhu et al. (2026), the generally more positive δ¹⁸O values observed since 6.20 ka in Selin Co suggest a significant shift in dominant moisture sources during the mid–late Holocene. Monitoring data of precipitation δ¹⁸O on the Tibetan Plateau indicate that regions south of 30°N are mainly influenced by monsoonal systems, while the northern and northeastern Plateau are dominated by the Westerlies (Yao et al., 2013 ). However, based on precipitation amount and spatial distribution, as well as vegetation cover, the modern monsoonal domain of the Tibetan Plateau is considered to extend into the northeastern Plateau, particularly the Qinghai Lake and Qilian Mountains regions (Chen et al., 2008 ; An et al., 2012a ). During periods of strengthened Asian summer monsoon, monsoonal moisture could reach the northeastern margin of the Tibetan Plateau-especially the eastern Qaidam Basin-whereas during weakened monsoon phases, the region was predominantly controlled by the Westerlies (An et al., 2012b ; Qiang et al., 2017 ; Song et al., 2020; Wu et al., 2026). In transitional zones, the relative influence of the Westerlies and the Asian summer monsoon has shifted markedly through time. Selin Co is located in the interior of the northern Tibetan Plateau (31°32′–32°07′N), far from the western Pacific and shielded by major mountain ranges such as the Kunlun Mountains. Consequently, it is unlikely that moisture from the East Asian summer monsoon could exert a strong influence on the Selin Co region (Curio et al., 2015 ). Marine air masses transported from the southwest can bypass the Himalayas to reach southern Tibet but rarely penetrate into northern Tibet (Tian et al., 2001 ). In recent decades, observational data have shown that moisture from the Indian summer monsoon has made a significant contribution to inflow into Selin Co (Tong et al., 2016 ). In addition, due to the high elevation of the Tibetan Plateau, the winter monsoon has difficulty reaching these high-altitude regions (Zhang et al., 1997 ; An et al., 2012a ). By contrast, the Westerlies, as a high-level atmospheric circulation system, are capable of transporting dust over long distances to the Tibetan Plateau. Based on the above considerations, we infer that since the mid–late Holocene, the Selin Co region in the central Tibetan Plateau has been primarily influenced by the Indian summer monsoon and the Westerlies, with only a minor contribution from the East Asian summer monsoon. The 10–70 µm fraction of grain-size is widely regarded as a sensitive indicator of wind strength in arid regions of western China (An et al., 2012c ; Wang et al., 2019 ). Therefore, variations in the 10–70 µm fraction in Selin Co sediments (Fig. 5 ) can be used to infer changes in the strength of the Westerlies. Prior to 2.21 ka, the 10–70 µm fraction exhibits relatively high values and shows an approximately in-phase relationship with carbonate δ¹⁸O values, suggesting that the Selin Co region was mainly dominated by the Westerlies during this interval. High-resolution climatology study using a High Asia Refined analysis (HAR) revealed that the mid-latitude westerlies have a higher share in summertime atmospheric water transport (AWT) over the TP than assumed so far (Curio et al., 2015 ). Enhanced westerly circulation is associated with increased dust transport and more depleted δ¹⁸O in precipitation, resulting in more negative carbonate δ¹⁸O values. Although Selin Co is also supplied by meltwater from glacier, modern hydrologic modeling study showed that glacier meltwater contributed to less than 10% of the total water input to Selin Co, while precipitation-induced runoff in nonglacierized area was responsible for about 67–75% (Tong et al., 2016 ). After 2.21 ka, both carbon and oxygen isotopes display high-frequency and low-amplitude fluctuations, a pattern characteristic of low-latitude monsoonal variability. At the same time, the 10–70 µm fraction of grain-size decreases markedly and remains at low levels with frequent fluctuations, indicating a weakening influence of the Westerlies. These observations suggest that since 2.21 ka, the Selin Co region has been predominantly influenced by the Indian summer monsoon, which also consistent with modern meteorological observations. Modern climate change research indicates that the Tibetan Plateau, particularly its central region, Atlantic Multidecadal Oscillation (AMO), Indian Ocean Basin-Wide (IOBW), and El Niño-Southern Oscillation (ENSO) jointly drive the increasing trend in the water reserve in short time scale (Ren et al., 2026). This implies that in atmospheric circulation transition zones such as Selin Co, the monsoon and the Westerlies do not operate in a strictly alternating manner but can coexist, with their relative contributions to moisture supply varying through time. We compared the variations in carbonate oxygen isotope records from Selin Co and surrounding lakes since 6.20 ka (Fig. 6 ). Nearly all records exhibit a gradual increasing trend in δ¹⁸O values, which is consistent with progressive moisture reduction, enhanced aridification, and declining lake levels following the Holocene Megathermal. Differences in lake locations and controlling factors result in slight offsets in the timing of changes and in the amplitude of fluctuations among records. Some curves, including that presented in this study, also display a pattern characterized by dominant fluctuations during the earlier stage followed by a gradual increase during the later stage. This long-term trend broadly corresponds to the decrease in summer insolation at 31°N, suggesting that changes in moisture availability in the Selin Co region have been ultimately modulated by orbital-scale insolation forcing. 4.2 Paleoclimatic and Paleohydrological Evolution and Special Climatic Events Since 6.20 ka Owing to the relatively high temporal resolution of our record, we are able to subdivide the evolutionary stages more precisely and to better characterize individual climatic events. A detailed comparison of carbonate carbon and oxygen isotope records reveals a pronounced negative correlation prior to 3.32 ka (Fig. 7 ; r = -0.759), indicating that δ¹³C and δ¹⁸O were influenced by multiple controlling factors during this interval. The early part of this period inherited the high lake levels associated with the Holocene Megathermal (Shi et al., 2017; Hou et al., 2021). Input of isotopically depleted glacial meltwater may have caused negative shifts in carbonate δ¹⁸O values (Li et al., 2021 ; Wünnemann et al., 2023 ; Yi et al., 2018 ), whereas relatively high temperatures during this interval could have promoted δ¹⁸O enrichment (Wu et al., 2015 ; Yuan et al., 2011 ). Under generally high lake-level conditions, a pronounced increase in carbonate content between 5.85 and 5.76 ka is interpreted as a significant warming event. When lake-water salinity remains relatively stable, carbonate precipitation is mainly controlled by temperature: increasing temperatures reduce carbonate solubility, thereby enhancing precipitation. Elevated temperatures also led to an increase in δ¹ 3 C values. Sedimentary δ¹ 3 C carb is governed by variations in the carbon isotopic composition of dissolved inorganic carbon (δ¹ 3 C DIC ) in lakes (Leng and Marshall, 2004 ; Li et al., 2012). In closed-basin lakes on the Tibetan Plateau, higher δ¹ 3 C DIC values are closely linked to evaporative forcing. Enhanced evaporation under warm conditions increases aqueous CO₂ partial pressure, preferentially releasing 12 C-enriched CO₂ to the atmosphere through isotopic fractionation and thus enriching 13 C in the residual DIC pool (Lei et al., 2012 ; Myrbo and Shapley, 2006 ). Ice-core comparisons across the Tibetan Plateau indicate that glacier fluctuations are more sensitive to temperature than to precipitation (Xu et al., 2014). Rapid warming would therefore have increased glacial meltwater input with depleted δ¹⁸O values, resulting in lower carbonate δ¹⁸O. The abundance of the ostracod Limnocythere inopinata shows generally low values prior to 4.18 ka (Fig. 8 ). Although L. inopinata is an euryhaline species (Song and Wang, 2014 ), it preferentially inhabits warm and saline waters and is abundant in the modern saline environment of Selin Co. During the Holocene Megathermal, high lake levels and fresh lake water likely limited the development of L. inopinata . Only during the early stage, when temperatures remained high, did favorable thermal conditions promote its temporary expansion. Notably, the abundance of L. inopinata clearly records the 4.2 ka cold–dry event. Multiple ice-core records from the Tibetan Plateau (e.g., Guliya and Dasuopu ice cores) show pronounced negative δ¹⁸O excursions around 4.2 ka, indicating significant cooling (Thompson et al., 1997 ). It is regarded as a widespread climate event in eastern, central and southern Asia (Mischke and Zhang, 2010). As shown in Fig. 8 , L. inopinata abundance declined sharply at 4.25 ka and nearly disappeared by 4.18 ka. After that, L. inopinata well developed till 3.88 ka. Meanwhile, carbonate content shows enhanced variability and rises significantly after 4.2 ka, δ¹⁸O shifts toward more positive values, and δ¹3C values exhibit large-amplitude oscillations. These proxy changes indicate that the 4.2 ka event in the Selin Co region began at 4.25 ka and was initially dominated by cold conditions, leading to near-extinction of L. inopinata under cold and relatively fresh lake conditions. Subsequently intensified aridity increased lake-water salinity, promoting the development of L. inopinata . Strong δ¹3C fluctuations during this interval suggest substantial temperature variability. Overall, the event persisted until 3.88 ka, lasting approximately 370 years, and was characterized by an initial cold phase followed by severe aridity with superimposed temperature oscillations. In comparison, a longer cold interval between ~ 4.2 and 2.8 cal ka BP has been documented in the western Tibetan Plateau at Lake Ximencuo (Mischke et al., 2010), highlighting spatial heterogeneity in event expression. After 3.32 ka, carbonate δ¹ 3 C and δ¹⁸O values exhibit a clear positive correlation (Fig. 7 ; r = 0.595), indicating that δ¹⁸O was primarily controlled by effective moisture, defined by the balance between water input and evaporation (I/E). Under these conditions, carbon and oxygen isotopes varied synchronously, consistent with modern observational studies. Modern process studies revealed that Serling Co’s water δ¹⁸O carb and volume were governed by effective moisture-the equilibrium between I/E (Ding et al., 2018 ; Guo et al., 2019 ). During 3.32–2.21 ka, δ¹ 3 C, δ¹⁸O, and TOC contents all exhibit large-amplitude fluctuations, reflecting pronounced climatic instability. Two intervals, 3.11–3.04 ka and 2.38–2.32 ka, show synchronous increases in all three proxies, particularly in δ¹⁸O, indicating relatively dry conditions and reduced effective moisture. The concurrent increase in TOC suggests warmer conditions that promoted vegetation growth and enhanced organic matter input to the lake. Warmer temperatures would also have accelerated glacial melting, increasing meltwater inflow and explaining the abrupt δ¹⁸O decreases following these warm-dry events due to the input of isotopically depleted meltwater. Notably, 3.32 ka appears to represent a major climatic transition, marked by the first appearance of the cold-preferring ostracod Limnocythere kunlunensis (Song and Zheng, 2022) and increased variability in L. inopinata , indicating a shift toward cooler and more unstable climatic conditions. This transition may represent the effective termination of Holocene Megathermal conditions in the Selin Co region. After 2.21 ka, δ¹ 3 C and δ¹⁸O values show a gradual upward trend with superimposed high-frequency, low-amplitude fluctuations, indicating progressive aridification. This pattern is consistent with the findings of Zhu et al. (2026), but the higher resolution of our record allows the identification of additional details. The high-frequency variability resembles the characteristic oscillations of the low-latitude Indian summer monsoon. Meanwhile, the 10–70 µm fraction of grain-size, an indicator of westerly strength, declines markedly and remains low, suggesting a weakened influence of the Westerlies and a dominant control of the Indian summer monsoon on the Selin Co region during this period. This interpretation is consistent with modern meteorological observations (Tong et al., 2016 ). During the interval from 1.15 to 0.79 ka, δ¹ 3 C, δ¹⁸O and carbonate content increase nearly synchronously, while TOC remains relatively high during the early stage, indicating warm climatic conditions corresponding to the Medieval Warm Period (MWP). Elevated temperatures during the early MWP led to the replacement of the cold-preferring Limnocythere kunlunensis by L. inopinata . During the later stage, increased glacial meltwater input likely reduced lake-water temperatures, resulting in a decline in L. inopinata abundance. L. kunlunensis reappears sporadically, indicating a transition toward colder conditions. Between 0.68 and 0.1 ka, TOC content, δ¹³C values and carbonate content remain consistently low, indicating a shift toward cold conditions. We interpret this interval as the expression of the Little Ice Age (LIA) in the Selin Co region, although at the early stage, the abundance of L. inopinata was still high. The delayed response of L. inopinata may be partly attributed to its tolerance of relatively low temperatures. After 0.39 ka, L. inopinata abundance decreases significantly, accompanied by the appearance of the cold-preferring species L. kunlunensis , indicating pronounced cooling. In summary, lake-level variations in Selin Co since 6.20 ka exhibit a pattern characterized by initially high levels (6.20–3.32 ka), followed by pronounced fluctuations period (3.32–2.21 ka), It is also from this phase that the climate in the Siling Co region began to cool. (Does this mark the true end of the Holocene Megathermal in this area?). A gradual decline during the late Holocene (since 2.21 ka). This pattern broadly follows the decreasing trend in summer insolation at 31°N throughout the Holocene (Fig. 6 ). However, lake-level fluctuations on the Tibetan Plateau cannot be attributed solely to regional precipitation changes associated with monsoon intensity. The contribution of temperature-controlled glacial meltwater must also be considered when interpreting hydrological and climatic evolution. Conclusion from 6.20 to 2.21 ka, the Selin Co region was mainly dominated by the Weserlies. However, due to the persistence of a large lake inherited from the Holocene Megathermal, lake level remained relatively high. Between 3.32 and 2.21 ka, the regional climate experienced pronounced fluctuations. After 2.21 ka, the Indian summer monsoon became the dominant controlling factor. Nevertheless, weakened solar radiation led to reduced moisture transport by the monsoon, resulting in a gradual trend toward aridification and a progressive decline in lake level. The widely recognized 4.2 ka cold-dry event began at approximately 4.25 ka in the central Tibetan Plateau and persisted for about 370 years. It was characterized by predominantly cold conditions initially, followed by pronounced aridity during the middle to late stages, with superimposed temperature fluctuations. The Medieval Warm Period (MWP) was relatively short-lived, occurring between 1.15 and 0.79 ka, and was marked by a distinct early temperature increase followed by gradual cooling. After 0.68 ka, regional temperatures declined further, with modest cooling initially and after 0.39 ka a more pronounced temperature decrease till 0.1 ka, corresponding broadly to the Little Ice Age (LIA). Declarations Funding Declaration This work was supported by the Basic Scientific Research Project of the Institute of Mineral Resources, Chinese Academy of Geological Sciences (No. KK2521) and the Tibet Autonomous Region Science and Technology Program (No. XZ202403ZY0028). Author Contribution W.H.L . collected samples and wrote the main manuscript text, Z.C.J . modified the Materials and Methods, Discussion, polished the English and prepared figure 3. S.G. prepared figure 8 and provided data on ostracod. Z.M.P. gave helpful suggestions. All authors reviewed the manuscript. Acknowledgement We would like to thank Ma Guiliang for his help in field work. References An Z, Colman SM, Zhou W, Li X, Brown ET, Jull AJT, Xu X. 2012a. 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The Input / Evaporation inferred by mineral composition and stable isotope and climatic implications in Serling Co sediment of Tibet, China since last deglacial period. Palaeogeography, Palaeoclimatology, Palaeoecology, 683: https://doi.org/10.1016/j.palaeo.2025.113484 Additional Declarations No competing interests reported. Cite Share Download PDF Status: Under Revision Version 1 posted Editorial decision: Revision requested 11 May, 2026 Reviews received at journal 30 Apr, 2026 Reviews received at journal 26 Apr, 2026 Reviewers agreed at journal 07 Apr, 2026 Reviewers agreed at journal 07 Apr, 2026 Reviewers invited by journal 07 Apr, 2026 Editor assigned by journal 25 Mar, 2026 Submission checks completed at journal 25 Mar, 2026 First submitted to journal 22 Mar, 2026 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-9194728","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":619101973,"identity":"a4bdafda-2f29-4223-a8b0-63df0aa0510f","order_by":0,"name":"Hailei Wang","email":"","orcid":"","institution":"CAGS","correspondingAuthor":false,"prefix":"","firstName":"Hailei","middleName":"","lastName":"Wang","suffix":""},{"id":619101974,"identity":"e469c157-cb3e-4f6b-9c13-4c9b90e9a694","order_by":1,"name":"Chengjun Zhang","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA1ElEQVRIie2NIQvCQBiGbwy+tHn1xlD/wg2jf2ampYFpSUXLl2Yf+CtsxhsHWxnLBoPJJhg1DPRm321N8J7w8n7wPnyEGAw/iQCVk1F7wABlBgOU72yBvRW6K2/X12kdIa04eSSS0MO2W2FCRMG+KmMkFbeyWhJ2Ed0KJ6JgLhYxWim3XZSEs1Cn5Og1WERgO9xu+ikSfBdXIcBHsfooTBTgj1EE6MAyT+vIYWeNQrPy5t1xM6VUHq/PZD6hmUb5vFEp266qo9mrN1uVG/3QYDAY/pc32zNAHAdMx5kAAAAASUVORK5CYII=","orcid":"","institution":"Lanzhou University","correspondingAuthor":true,"prefix":"","firstName":"Chengjun","middleName":"","lastName":"Zhang","suffix":""},{"id":619101975,"identity":"529792bb-bdcb-4ff3-8009-1c1a2d8e0e06","order_by":2,"name":"Gao Song","email":"","orcid":"","institution":"CAGS","correspondingAuthor":false,"prefix":"","firstName":"Gao","middleName":"","lastName":"Song","suffix":""},{"id":619101976,"identity":"be42c1b0-6496-46c3-9114-c4da4c039362","order_by":3,"name":"Mianping Zheng","email":"","orcid":"","institution":"CAGS","correspondingAuthor":false,"prefix":"","firstName":"Mianping","middleName":"","lastName":"Zheng","suffix":""}],"badges":[],"createdAt":"2026-03-23 02:39:54","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-9194728/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-9194728/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":106815537,"identity":"52541e20-faa9-4ede-a030-c7152301d5e8","added_by":"auto","created_at":"2026-04-13 17:14:55","extension":"jpeg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":1344641,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eMap showing the location of Selin Co and the direction of major atmospheric circulation\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"floatimage1.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-9194728/v1/7a6d578283f160ef92b12dd6.jpeg"},{"id":106815538,"identity":"3dcc17aa-2f51-4a6e-b21c-ed5df9f4d722","added_by":"auto","created_at":"2026-04-13 17:14:55","extension":"jpeg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":237247,"visible":true,"origin":"","legend":"\u003cp\u003e\u003csup\u003e\u003cstrong\u003e137\u003c/strong\u003e\u003c/sup\u003e\u003cstrong\u003eCs data (a) and age-depth model (b) of the uppermost of core SL-1 in Selin Co\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"floatimage2.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-9194728/v1/f5c3dd86a7402ff5818b6b21.jpeg"},{"id":106960257,"identity":"a4fbdc9c-8687-4cee-ae97-2c67330b5b8f","added_by":"auto","created_at":"2026-04-15 09:19:33","extension":"jpeg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":361116,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eAge-depth model of the core SL-1 from Selin Co. The blue symbols showed the probability density of the calibrated result for each radiocarbon date. The grey dotted lines indicate the 95 % confidence intervals. The red line indicates the best fit ages based on the weighted mean age for each depth\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"floatimage3.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-9194728/v1/78b83f68c599363963ba726d.jpeg"},{"id":106960752,"identity":"53b6f088-1e0d-4be5-a9de-5e27b5dd94e6","added_by":"auto","created_at":"2026-04-15 09:22:57","extension":"jpeg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":499936,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003evariations of TOC, Carbonate content, δ¹⁸O and δ¹³C values of authigenic carbonates from Selin Co since 6.20 ka. The dotted red lines represent the boundaries of major climatic and environmental stages. The pink shaded area represents the duration of the MWP event. The gray-green shaded area represents the duration of cold events such as the LIA and the 4.2 ka cold-dry event\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"floatimage4.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-9194728/v1/da82116d93513a5fea1d6702.jpeg"},{"id":106960633,"identity":"b5399db1-4094-41d3-8b00-1f35fa46f19f","added_by":"auto","created_at":"2026-04-15 09:22:20","extension":"jpeg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":305672,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eComparison chart of variations in the 10–70 μm fraction of grain-size and δ¹⁸O values of authigenic carbonates from Selin Co since 6.20 ka. The dotted red line divides two main stages of change: in-phase variations prior to 2.21 ka and high-frequency fluctuations after 2.21 ka. The orange dashed line marks the typical peaks and troughs of the two indicators during the in-phase variations stage\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"floatimage5.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-9194728/v1/be0c2aed85b71c32d40a0b6f.jpeg"},{"id":106815541,"identity":"84be28d5-bf07-4a60-9736-3d520d023e35","added_by":"auto","created_at":"2026-04-13 17:14:55","extension":"jpeg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":431063,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eSummer insolation at 31°N (A) and lacustrine δ¹⁸O records from Selin Co and surrounding lakes since 6.20 ka. (B) Selin Co (Morinaga et al., 1993); (C) Nam Co (Kasper et al., 2021); (D) Lake Bande (Li et al., 2022); (E) Chibuzhang Co (Dong et al., 2021); (F) Selin Co (this study); (G) Selin Co (Zhu et al., 2026); (H) Zigetang Co (Zhang et al., 2014); (I) Tangra Yumco (Kasper et al., 2021); (J) Linggo Co (He et al., 2016). The red line indicates the increasing trend of δ¹⁸O values\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"floatimage6.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-9194728/v1/7ac66a615f2b5e99171748d6.jpeg"},{"id":106960921,"identity":"45522ad7-5ef7-420c-9491-3045fb5cade1","added_by":"auto","created_at":"2026-04-15 09:23:37","extension":"jpeg","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":238710,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eCorrelation analysis diagram of δ¹⁸O and δ¹³C values from Selin Co since 6.20 ka. (A) Positive correlation after 3.32 ka; (B) Negative correlation before 3.32 ka\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"floatimage7.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-9194728/v1/6fca1689374364f9c14d9b04.jpeg"},{"id":106960762,"identity":"9631da5e-44db-4c7a-9f75-42e23ba64b7d","added_by":"auto","created_at":"2026-04-15 09:23:00","extension":"jpeg","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":200594,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eAbundance of the ostracod \u003c/strong\u003e\u003cem\u003e\u003cstrong\u003eLimnocythere inopinata\u003c/strong\u003e\u003c/em\u003e\u003cstrong\u003e (black) and \u003c/strong\u003e\u003cem\u003e\u003cstrong\u003eLimnocythere kunlunensis\u003c/strong\u003e\u003c/em\u003e\u003cstrong\u003e(red) in the core SL-1 from Selin Co since 6.20 ka\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"floatimage8.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-9194728/v1/8ac2956d8ea28238c83e8dc3.jpeg"},{"id":106963337,"identity":"12bdfe79-c355-47b1-81fe-fb1d9ba7831c","added_by":"auto","created_at":"2026-04-15 09:43:40","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":5034919,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9194728/v1/52a7d278-6796-49ec-a0a2-7c152a6c7540.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Paleoclimate Changes and the Evolution of Atmospheric Circulation in Selin Co on the Central Tibetan Plateau Since the Mid–Late Holocene","fulltext":[{"header":"Introduction","content":"\u003cp\u003eAs the \u0026ldquo;Third Pole of the Earth,\u0026rdquo; the Tibetan Plateau (TP) has been a major focus of international geoscientific research over recent decades. Holocene climate and environmental changes on the TP have been widely documented using various archives, including ice cores (Yao et al., \u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e1996\u003c/span\u003e; Thompson et al., \u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e1997\u003c/span\u003e), lake sediments (Mischke et al., 2010; An et al., \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2012a\u003c/span\u003e; Ahlborn et al., \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Conroy et al., \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Hou et al., \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Du et al., \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Gao et al., \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2024\u003c/span\u003e; Ma et al., \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2024a\u003c/span\u003e, \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003eb\u003c/span\u003e), as well as speleothem (Han et al., \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2017\u003c/span\u003e) and tree ring (Yang et al., \u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e2021\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eAtmospheric circulation plays a crucial role in transporting water vapor and dust, thereby exerting a strong influence on regional moisture conditions, lake-level fluctuations, and aeolian material transport. The Tibetan Plateau is located at the intersection of the East Asian summer monsoon, the Indian summer monsoon, and the Westerlies (Chen et al., \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). The southeastern and southern parts of the Plateau are primarily influenced by the Indian summer monsoon (Tian et al., \u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e2001\u003c/span\u003e; Tong et al., \u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). The East Asian summer monsoon, however, was able to extend to the northeastern margin of the Plateau, especially the eastern Qaidam Basin, during certain periods (An et al., \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2012b\u003c/span\u003e; Qiang et al., \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Song et al., 2020; Wu et al., 2026). The Westerlies, as a high-altitude airflow system, can either cover the Plateau directly or split into northern and southern branches that bypass the Plateau (Schiemann et al., \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2009\u003c/span\u003e; Molnar et al., \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2010\u003c/span\u003e; An et al., \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2012a\u003c/span\u003e; G\u0026uuml;nther et al., 2015).\u003c/p\u003e \u003cp\u003eParyal et al. (2026) recently summarized the current understanding of the East Asian summer monsoon, the Indian summer monsoon, and the Westerlies on the Tibetan Plateau since the Last Glacial Maximum based on lake sediment records. Chen et al. (\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2008\u003c/span\u003e) divided the southeastern Eurasian continent into three climatically distinct regions: humid Asia, mainly controlled by summer monsoonal circulation; arid central Asia (ACA), dominated by the Westerlies; and a transitional zone encompassing semi-arid northwestern China and the southern Mongolian Plateau.\u003c/p\u003e \u003cp\u003eSelin Co, located in the central Tibetan Plateau, lies precisely within this transitional zone. Its lacustrine sediments therefore provide valuable insights into the advance\u0026ndash;retreat history of the summer monsoon and the Westerlies. Selin Co is currently the largest lake in Tibet, with a surface area exceeding 2200 km\u0026sup2; and a maximum water depth of nearly 60 m (Zhu et al., \u003cspan citationid=\"CR68\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). These characteristics make it an ideal site for Holocene climate studies, as it preserves continuous sedimentary records without significant depositional hiatuses.\u003c/p\u003e \u003cp\u003eIn recent decades, numerous paleoclimate studies have been conducted in the Selin Co region, primarily focusing on climatic and environmental changes and lake-level fluctuations since the Last Glacial Maximum (Morinaga et al., \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e1993\u003c/span\u003e; Wang et al., 2014; Shi et al., 2017; Du et al., \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Guo et al., \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Wang et al., \u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Zhu et al., \u003cspan citationid=\"CR68\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Hou et al., 2021; Song et al., 2022; Kou et al., \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2023\u003c/span\u003e, \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2024\u003c/span\u003e; Zhu et al., 2026). Morinaga et al. (\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e1993\u003c/span\u003e) and Zhu et al. (2026) reconstructed records spanning the past 14 ka and 25.1 ka, respectively, whereas this study focuses on the period since 6.20 ka, providing higher-resolution insights. In addition, multiple proxy indicators-including total organic carbon (TOC), carbonate content, the 10\u0026ndash;70 \u0026micro;m fraction of grain-size, and ostracod assemblages-are integrated in this study, resulting in a different interpretative emphasis. This study focuses on shifts of the Asian monsoon and the Westerlies, as well as associated climatic events in the Selin Co region since 6.20 cal ka BP. By employing higher-resolution records, we aim to provide a more detailed reconstruction of the advance and retreat of major atmospheric circulation systems and the characteristics of key climatic events. Such high-resolution paleoclimate records not only improve our understanding of past climate dynamics but also offer an essential baseline for numerical climate modeling and for assessing future hydrological responses. This is particularly relevant given the rapid rise in Selin Co lake level in recent decades, which has already exerted significant impacts on local ecosystems, infrastructure, and socioeconomic activities.\u003c/p\u003e"},{"header":"Materials and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eStudy Area\u003c/h2\u003e \u003cp\u003eSelin Co is a brackish lake located in the west of Bange county in Naqu district (88\u0026deg;32\u0026acute;-89\u0026deg;22\u0026acute;E, 31\u0026deg;32\u0026acute;-32\u0026deg;07\u0026acute;N)(Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Selin Co consists of two sub-basins: an eastern basin and a western basin. The eastern basin is larger but relatively shallow, whereas the western basin is smaller, deeper, and characterized by steeper lake-floor topography. Selin Co is a terminal lake fed by several inflowing rivers, including the Zajia Zangbu (Zangbu is river in Tibetan), Zagen Zangbu, Ali Zangbu, and Boqu Zangbu, etc. Among these, the Zajia Zangbu, with a total length of approximately 409 km, is the longest inland river in Tibet. It enters the northern part of the eastern basin and serves as the primary perennial river supplying water and sediments to Selin Co. Its catchment originates from the glaciated Geladandong Mountains, providing substantial glacially derived sediment input.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe Selin Co region is located in the cold semi-arid climatic zone of the Tibetan Plateau, characterized by strong solar radiation and long sunshine duration. Mean annual precipitation ranges from 290 to 321 mm, with most rainfall occurring between June and September. In contrast, annual evaporation is extremely high, reaching approximately 2176 mm. The mean annual air temperature ranges from 0.8 to 1.0\u0026deg;C, and the number of gale days per year is between 103 and 132 (Dasang, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2011\u003c/span\u003e).\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eCore Sampling and Chronology\u003c/h3\u003e\n\u003cp\u003eIn 2014, a 2.78 m long sediment core (SL-1) was recovered from the western basin of Selin Co at a water depth of 30 m using a gravity corer. The sediments are mainly composed of alternating gray-white fine silt to very fine sand and black clay layers. Subsampling was conducted at 0.5 cm intervals throughout the core.\u003c/p\u003e \u003cp\u003eThe uppermost 25 cm of the core was dated using \u003csup\u003e210\u003c/sup\u003ePb and \u003csup\u003e137\u003c/sup\u003eCs methods (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). The \u003csup\u003e137\u003c/sup\u003eCs activity profile shows a well-defined stratigraphic pattern consistent with the global fallout history, indicating minimal post-depositional disturbance. A distinct \u003csup\u003e137\u003c/sup\u003eCs peak occurs at a depth of 2.5 cm, corresponding to an age of 1987 AD, which is consistent with regional \u003csup\u003e137\u003c/sup\u003eCs reference.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eConsidering that the effective dating range of \u003csup\u003e137\u003c/sup\u003eCs is approximately the past 200 years, a polynomial regression was applied to constrain the age-depth relationship for the 0-200\u0026nbsp;year interval based on the \u003csup\u003e137\u003c/sup\u003eCs-derived age control points (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). The resulting age-depth equation is:\u003c/p\u003e \u003cp\u003ey = -0.0765x\u003csup\u003e4\u003c/sup\u003e\u0026thinsp;+\u0026thinsp;1.4468x\u003csup\u003e3\u003c/sup\u003e \u0026minus;\u0026thinsp;5.4569x\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;+\u0026thinsp;13.326x\u0026thinsp;+\u0026thinsp;0.9691 (R\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;0.9965)\u003c/p\u003e \u003cp\u003ewhere y represents age (yr AD) and x represents depth (cm). According to this model, the sediment-water interface (0 cm) corresponds to an age of 1\u0026nbsp;year, which is reasonable for the coring year, while the age at 8 cm depth is estimated to be 1827 AD based on the \u003csup\u003e137\u003c/sup\u003eCs-constrained model.\u003c/p\u003e \u003cp\u003eIn addition, five bulk organic carbon samples from different depths were dated by AMS \u003csup\u003e14\u003c/sup\u003eC analysis at the BETA Analytic Radiocarbon Dating Laboratory (USA) (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Comparison between the \u003csup\u003e137\u003c/sup\u003eCs-derived age at 8 cm depth (185\u0026nbsp;year BP) and the age extrapolated from \u003csup\u003e14\u003c/sup\u003eC dates at 52.5 cm and 172.5 cm reveals a substantial age offset of approximately 1860 years. This discrepancy is interpreted as a carbon reservoir effect, which is commonly observed in Tibetan Plateau lakes due to inputs of old carbon from glacial meltwater, carbonate weathering, and catchment processes.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eAMS \u003csup\u003e14\u003c/sup\u003eC ages from the core SL\u0026minus;1 (BETA Analytic Radiocarbon Dating Laboratory, USA)\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSample no.\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eDepth/cm\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eAge/a\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eError\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eMaterial\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSL2-99\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e52.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e2900\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e60\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eOrganic carbon\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSL4-148\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e172.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e5205\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eOrganic carbon\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSL4-208, 209\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e202.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e5525\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e65\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eOrganic carbon\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSL4-259, 260\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e228\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e5960\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eOrganic carbon\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSL4-358\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e277.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e7220\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e60\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eOrganic carbon\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eAccordingly, a reservoir age correction of 1860 years was applied to all AMS \u003csup\u003e14\u003c/sup\u003eC dates prior to calibration. The corrected \u003csup\u003e14\u003c/sup\u003eC ages were then calibrated relative to the standard 1950 AD reference year and incorporated into a Bayesian age-depth model constructed using the R statistical environment (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). This integrated approach allows for a consistent and statistically robust chronology that reconciles short-lived radionuclide dating with radiocarbon ages.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe resulting age-depth model indicates that the basal age of core SL-1 is approximately 6.20 ka, with an average sedimentation rate of 0.5216 mm/a, although sedimentation rates vary through time in response to changing hydrological and depositional conditions.\u003c/p\u003e\n\u003ch3\u003eGeochemical and Isotopic Analyses\u003c/h3\u003e\n\u003cp\u003eFor carbon and oxygen isotope analyses of authigenic carbonate (δ\u0026sup1;\u0026sup3;C\u003csub\u003ecarb\u003c/sub\u003e and δ\u0026sup1;⁸O\u003csub\u003ecarb\u003c/sub\u003e), the fine-grained fraction of each sample was separated by sieving through a 40 \u0026micro;m mesh. The samples were reacted with phosphoric acid, and the released CO₂ was purified and analyzed using a Finnigan MAT 252 isotope ratio mass spectrometer at the Lanzhou Institute of Geology, Chinese Academy of Sciences. Calibration measurements were performed every ten samples using the international standard NBS-19 (δ\u0026sup1;\u0026sup3;C\u0026thinsp;=\u0026thinsp;+\u0026thinsp;1.95\u0026permil;, δ\u0026sup1;⁸O\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;2.20\u0026permil;). The analytical precision was better than \u0026plusmn;\u0026thinsp;0.2\u0026permil; for both δ\u0026sup1;\u0026sup3;C\u003csub\u003ecarb\u003c/sub\u003e and δ\u0026sup1;⁸O\u003csub\u003ecarb\u003c/sub\u003e. Isotopic values are reported in conventional δ notation relative to the V-PDB (Vienna Pee Dee Belemnite) standard.\u003c/p\u003e \u003cp\u003eTotal organic carbon (TOC) content was determined using the potassium dichromate\u0026ndash;sulfuric acid wet oxidation (antititration) method. Carbonate content was measured by treating bulk sediment samples with dilute 1 N HCl and quantifying the volume of CO₂ released during the reaction. All geochemical analyses were conducted at the National Laboratory of Western China\u0026rsquo;s Environmental Systems, Lanzhou University.\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003eTotal organic carbon (TOC) contents of the SL-1 core range from 0.14% to 8.91%, with a mean value of 3.91%. Prior to 3.32 ka, TOC values remained relatively low with minor fluctuations. Between 3.32 and 2.21 ka, TOC exhibits pronounced variability with large-amplitude oscillations. After 2.21 ka, TOC returns to lower values with relatively small fluctuations, except for a distinct increase during the interval from 1.3 to 1.0 ka (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eCarbonate contents in the SL-1 core are generally high, with an average value of 47.7%, and show relatively limited variation throughout the core. The maximum and minimum carbonate contents are 68.3% and 29.7%, respectively. A slight increase in carbonate content is observed after 2.21 ka (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe δ\u0026sup1;⁸O values of authigenic carbonates from Selin Co since 6.20 ka range from \u0026minus;\u0026thinsp;4.86\u0026permil; to 0.38\u0026permil;, with a mean value of \u0026minus;\u0026thinsp;2.57\u0026permil;. These values are broadly consistent with late Holocene authigenic carbonate δ\u0026sup1;⁸O records from the eastern basin of Selin Co reported by Zhu et al. (2026). Overall, δ\u0026sup1;⁸O values display relatively small-amplitude variations throughout the core. After 2.21 ka, fluctuations become more frequent but of lower magnitude, accompanied by a slight increase in δ\u0026sup1;⁸O values toward the upper part of the record (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe δ\u0026sup1;\u0026sup3;C values of authigenic carbonates vary between 1.862\u0026permil; and 5.284\u0026permil;, with an average value of 3.953\u0026permil;. Prior to 3.32 ka, δ\u0026sup1;\u0026sup3;C values are relatively low but highly variable, particularly between 4.25 and 3.88 ka, during which several large-amplitude oscillations are observed. Thereafter, δ\u0026sup1;\u0026sup3;C values show a gradual increase. After 2.21 ka, it is characterized by high-frequency and low-amplitude fluctuations accompanied by a slight increase, similar to those of oxygen isotopes in the same period. (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e).\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003e \u003cb\u003e4.1 Evolution of atmospheric circulation in the Selin Co region during the Mid\u0026ndash;Late Holocene\u003c/b\u003e \u003c/p\u003e \u003cp\u003eThe δ\u0026sup1;⁸O values of authigenic carbonates are primarily controlled by the temperature and isotopic composition of lake water at the time of carbonate precipitation (Leng and Marshall, \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2004\u003c/span\u003e). Considering that the temperature-dependent equilibrium isotopic fractionation between carbonate and water is approximately\u0026thinsp;\u0026minus;\u0026thinsp;0.24\u0026permil; per \u0026deg;C (Craig and Gordon, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e1965\u003c/span\u003e), and that summer temperature variations on the Tibetan Plateau during the Holocene were likely limited to within ~\u0026thinsp;1.5\u0026deg;C (Chen et al., \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2020\u003c/span\u003e), the influence of temperature on carbonate δ\u0026sup1;⁸O values in this study can be considered relatively minor. Therefore, the variations of authigenic carbonates δ\u0026sup1;⁸O values are interpreted to mainly reflect fluctuations in the oxygen isotopic composition of lake water. As such, carbonate δ\u0026sup1;⁸O provides valuable information on past changes in regional hydrological conditions on the Tibetan Plateau (Wei and Gasse, \u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e1999\u003c/span\u003e; Yu et al., \u003cspan citationid=\"CR64\" class=\"CitationRef\"\u003e2009\u003c/span\u003e; Liu et al., \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; W\u0026uuml;nnemann et al., \u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). Former study showed that in arid to semi-arid regions, the δ\u0026sup1;⁸O composition of authigenic carbonate in lake sediments is highly related to the effective moisture (precipitation/evaporation (P/E) ratio) of the region (Li et al., \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2017\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eModern observations indicate that the δ\u0026sup1;⁸O of precipitation integrates signals from multiple atmospheric circulation systems, including the Indian summer monsoon (ISM), the East Asian summer monsoon (EASM), and the Westerlies, which together govern the climate of the Tibetan Plateau (Wu et al., \u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e2022\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe δ\u0026sup1;⁸O values of authigenic carbonates in Selin Co since 6.20 ka range from \u0026minus;\u0026thinsp;4.86\u0026permil; to 0.38\u0026permil;. Previous oxygen isotope studies have also been conducted on lacustrine sediments from Selin Co by Morinaga et al. (\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e1993\u003c/span\u003e) and Zhu et al. (2026). The core studied by Morinaga et al. (\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e1993\u003c/span\u003e) was retrieved from a site approximately 1 km from the southern shore at a water depth of 27 m, whereas the core analyzed by Zhu et al. (2026) was obtained from the eastern basin near the southern shore at a water depth of 44 m. In contrast, the SL-1 core analyzed in this study was collected from the western basin, approximately 3 km offshore, at a water depth of 30 m. Differences in core locations resulted in substantial variations in sediment lithology among the studies.\u003c/p\u003e \u003cp\u003eMorinaga et al. (\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e1993\u003c/span\u003e) measured δ\u0026sup1;⁸O values from bulk sediments, which yielded relatively higher values. In contrast, both this study and Zhu et al. (2026) analyzed sieved fine-grained carbonate fractions, dominated by authigenic carbonates, resulting in comparable δ\u0026sup1;⁸O values that are slightly lower than those reported by Morinaga et al. (\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e1993\u003c/span\u003e). Moreover, the temporal coverage of these studies differs substantially.\u003c/p\u003e \u003cp\u003eAragu\u0026aacute;s-Aragu\u0026aacute;s et al. (\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e1998\u003c/span\u003e) demonstrated that summer monsoon precipitation originating from the western Pacific is characterized by relatively enriched δ\u0026sup1;⁸O values compared to that derived from the Indian Ocean, whereas precipitation associated with the westerly jet is generally more depleted in δ\u0026sup1;⁸O. Compared with the early\u0026ndash;middle Holocene δ\u0026sup1;⁸O values reported by Zhu et al. (2026), the generally more positive δ\u0026sup1;⁸O values observed since 6.20 ka in Selin Co suggest a significant shift in dominant moisture sources during the mid\u0026ndash;late Holocene.\u003c/p\u003e \u003cp\u003eMonitoring data of precipitation δ\u0026sup1;⁸O on the Tibetan Plateau indicate that regions south of 30\u0026deg;N are mainly influenced by monsoonal systems, while the northern and northeastern Plateau are dominated by the Westerlies (Yao et al., \u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e2013\u003c/span\u003e). However, based on precipitation amount and spatial distribution, as well as vegetation cover, the modern monsoonal domain of the Tibetan Plateau is considered to extend into the northeastern Plateau, particularly the Qinghai Lake and Qilian Mountains regions (Chen et al., \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2008\u003c/span\u003e; An et al., \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2012a\u003c/span\u003e). During periods of strengthened Asian summer monsoon, monsoonal moisture could reach the northeastern margin of the Tibetan Plateau-especially the eastern Qaidam Basin-whereas during weakened monsoon phases, the region was predominantly controlled by the Westerlies (An et al., \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2012b\u003c/span\u003e; Qiang et al., \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Song et al., 2020; Wu et al., 2026). In transitional zones, the relative influence of the Westerlies and the Asian summer monsoon has shifted markedly through time. Selin Co is located in the interior of the northern Tibetan Plateau (31\u0026deg;32\u0026prime;\u0026ndash;32\u0026deg;07\u0026prime;N), far from the western Pacific and shielded by major mountain ranges such as the Kunlun Mountains. Consequently, it is unlikely that moisture from the East Asian summer monsoon could exert a strong influence on the Selin Co region (Curio et al., \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). Marine air masses transported from the southwest can bypass the Himalayas to reach southern Tibet but rarely penetrate into northern Tibet (Tian et al., \u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e2001\u003c/span\u003e). In recent decades, observational data have shown that moisture from the Indian summer monsoon has made a significant contribution to inflow into Selin Co (Tong et al., \u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). In addition, due to the high elevation of the Tibetan Plateau, the winter monsoon has difficulty reaching these high-altitude regions (Zhang et al., \u003cspan citationid=\"CR66\" class=\"CitationRef\"\u003e1997\u003c/span\u003e; An et al., \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2012a\u003c/span\u003e). By contrast, the Westerlies, as a high-level atmospheric circulation system, are capable of transporting dust over long distances to the Tibetan Plateau.\u003c/p\u003e \u003cp\u003eBased on the above considerations, we infer that since the mid\u0026ndash;late Holocene, the Selin Co region in the central Tibetan Plateau has been primarily influenced by the Indian summer monsoon and the Westerlies, with only a minor contribution from the East Asian summer monsoon. The 10\u0026ndash;70 \u0026micro;m fraction of grain-size is widely regarded as a sensitive indicator of wind strength in arid regions of western China (An et al., \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2012c\u003c/span\u003e; Wang et al., \u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). Therefore, variations in the 10\u0026ndash;70 \u0026micro;m fraction in Selin Co sediments (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e) can be used to infer changes in the strength of the Westerlies.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003ePrior to 2.21 ka, the 10\u0026ndash;70 \u0026micro;m fraction exhibits relatively high values and shows an approximately in-phase relationship with carbonate δ\u0026sup1;⁸O values, suggesting that the Selin Co region was mainly dominated by the Westerlies during this interval. High-resolution climatology study using a High Asia Refined analysis (HAR) revealed that the mid-latitude westerlies have a higher share in summertime atmospheric water transport (AWT) over the TP than assumed so far (Curio et al., \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). Enhanced westerly circulation is associated with increased dust transport and more depleted δ\u0026sup1;⁸O in precipitation, resulting in more negative carbonate δ\u0026sup1;⁸O values. Although Selin Co is also supplied by meltwater from glacier, modern hydrologic modeling study showed that glacier meltwater contributed to less than 10% of the total water input to Selin Co, while precipitation-induced runoff in nonglacierized area was responsible for about 67\u0026ndash;75% (Tong et al., \u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). After 2.21 ka, both carbon and oxygen isotopes display high-frequency and low-amplitude fluctuations, a pattern characteristic of low-latitude monsoonal variability. At the same time, the 10\u0026ndash;70 \u0026micro;m fraction of grain-size decreases markedly and remains at low levels with frequent fluctuations, indicating a weakening influence of the Westerlies. These observations suggest that since 2.21 ka, the Selin Co region has been predominantly influenced by the Indian summer monsoon, which also consistent with modern meteorological observations. Modern climate change research indicates that the Tibetan Plateau, particularly its central region, Atlantic Multidecadal Oscillation (AMO), Indian Ocean Basin-Wide (IOBW), and El Ni\u0026ntilde;o-Southern Oscillation (ENSO) jointly drive the increasing trend in the water reserve in short time scale (Ren et al., 2026). This implies that in atmospheric circulation transition zones such as Selin Co, the monsoon and the Westerlies do not operate in a strictly alternating manner but can coexist, with their relative contributions to moisture supply varying through time.\u003c/p\u003e \u003cp\u003eWe compared the variations in carbonate oxygen isotope records from Selin Co and surrounding lakes since 6.20 ka (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e). Nearly all records exhibit a gradual increasing trend in δ\u0026sup1;⁸O values, which is consistent with progressive moisture reduction, enhanced aridification, and declining lake levels following the Holocene Megathermal. Differences in lake locations and controlling factors result in slight offsets in the timing of changes and in the amplitude of fluctuations among records. Some curves, including that presented in this study, also display a pattern characterized by dominant fluctuations during the earlier stage followed by a gradual increase during the later stage. This long-term trend broadly corresponds to the decrease in summer insolation at 31\u0026deg;N, suggesting that changes in moisture availability in the Selin Co region have been ultimately modulated by orbital-scale insolation forcing.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cb\u003e4.2 Paleoclimatic and Paleohydrological Evolution and Special Climatic Events Since 6.20 ka\u003c/b\u003e \u003c/p\u003e \u003cp\u003eOwing to the relatively high temporal resolution of our record, we are able to subdivide the evolutionary stages more precisely and to better characterize individual climatic events. A detailed comparison of carbonate carbon and oxygen isotope records reveals a pronounced negative correlation prior to 3.32 ka (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e; r = -0.759), indicating that δ\u0026sup1;\u0026sup3;C and δ\u0026sup1;⁸O were influenced by multiple controlling factors during this interval. The early part of this period inherited the high lake levels associated with the Holocene Megathermal (Shi et al., 2017; Hou et al., 2021). Input of isotopically depleted glacial meltwater may have caused negative shifts in carbonate δ\u0026sup1;⁸O values (Li et al., \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; W\u0026uuml;nnemann et al., \u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e2023\u003c/span\u003e; Yi et al., \u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e2018\u003c/span\u003e), whereas relatively high temperatures during this interval could have promoted δ\u0026sup1;⁸O enrichment (Wu et al., \u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e2015\u003c/span\u003e; Yuan et al., \u003cspan citationid=\"CR65\" class=\"CitationRef\"\u003e2011\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eUnder generally high lake-level conditions, a pronounced increase in carbonate content between 5.85 and 5.76 ka is interpreted as a significant warming event. When lake-water salinity remains relatively stable, carbonate precipitation is mainly controlled by temperature: increasing temperatures reduce carbonate solubility, thereby enhancing precipitation. Elevated temperatures also led to an increase in δ\u0026sup1;\u003csup\u003e3\u003c/sup\u003eC values. Sedimentary δ\u0026sup1;\u003csup\u003e3\u003c/sup\u003eC\u003csub\u003ecarb\u003c/sub\u003e is governed by variations in the carbon isotopic composition of dissolved inorganic carbon (δ\u0026sup1;\u003csup\u003e3\u003c/sup\u003eC\u003csub\u003eDIC\u003c/sub\u003e) in lakes (Leng and Marshall, \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2004\u003c/span\u003e; Li et al., 2012). In closed-basin lakes on the Tibetan Plateau, higher δ\u0026sup1;\u003csup\u003e3\u003c/sup\u003eC\u003csub\u003eDIC\u003c/sub\u003e values are closely linked to evaporative forcing. Enhanced evaporation under warm conditions increases aqueous CO₂ partial pressure, preferentially releasing \u003csup\u003e12\u003c/sup\u003eC-enriched CO₂ to the atmosphere through isotopic fractionation and thus enriching \u003csup\u003e13\u003c/sup\u003eC in the residual DIC pool (Lei et al., \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Myrbo and Shapley, \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e2006\u003c/span\u003e). Ice-core comparisons across the Tibetan Plateau indicate that glacier fluctuations are more sensitive to temperature than to precipitation (Xu et al., 2014). Rapid warming would therefore have increased glacial meltwater input with depleted δ\u0026sup1;⁸O values, resulting in lower carbonate δ\u0026sup1;⁸O.\u003c/p\u003e \u003cp\u003eThe abundance of the ostracod \u003cem\u003eLimnocythere inopinata\u003c/em\u003e shows generally low values prior to 4.18 ka (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e). Although \u003cem\u003eL. inopinata\u003c/em\u003e is an euryhaline species (Song and Wang, \u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e2014\u003c/span\u003e), it preferentially inhabits warm and saline waters and is abundant in the modern saline environment of Selin Co. During the Holocene Megathermal, high lake levels and fresh lake water likely limited the development of \u003cem\u003eL. inopinata\u003c/em\u003e. Only during the early stage, when temperatures remained high, did favorable thermal conditions promote its temporary expansion. Notably, the abundance of \u003cem\u003eL. inopinata\u003c/em\u003e clearly records the 4.2 ka cold\u0026ndash;dry event. Multiple ice-core records from the Tibetan Plateau (e.g., Guliya and Dasuopu ice cores) show pronounced negative δ\u0026sup1;⁸O excursions around 4.2 ka, indicating significant cooling (Thompson et al., \u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e1997\u003c/span\u003e). It is regarded as a widespread climate event in eastern, central and southern Asia (Mischke and Zhang, 2010).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAs shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e, L. \u003cem\u003einopinata\u003c/em\u003e abundance declined sharply at 4.25 ka and nearly disappeared by 4.18 ka. After that, \u003cem\u003eL. inopinata\u003c/em\u003e well developed till 3.88 ka. Meanwhile, carbonate content shows enhanced variability and rises significantly after 4.2 ka, δ\u0026sup1;⁸O shifts toward more positive values, and δ\u0026sup1;3C values exhibit large-amplitude oscillations. These proxy changes indicate that the 4.2 ka event in the Selin Co region began at 4.25 ka and was initially dominated by cold conditions, leading to near-extinction of \u003cem\u003eL. inopinata\u003c/em\u003e under cold and relatively fresh lake conditions. Subsequently intensified aridity increased lake-water salinity, promoting the development of \u003cem\u003eL. inopinata\u003c/em\u003e. Strong δ\u0026sup1;3C fluctuations during this interval suggest substantial temperature variability. Overall, the event persisted until 3.88 ka, lasting approximately 370 years, and was characterized by an initial cold phase followed by severe aridity with superimposed temperature oscillations. In comparison, a longer cold interval between ~\u0026thinsp;4.2 and 2.8 cal ka BP has been documented in the western Tibetan Plateau at Lake Ximencuo (Mischke et al., 2010), highlighting spatial heterogeneity in event expression.\u003c/p\u003e \u003cp\u003eAfter 3.32 ka, carbonate δ\u0026sup1;\u003csup\u003e3\u003c/sup\u003eC and δ\u0026sup1;⁸O values exhibit a clear positive correlation (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e; r\u0026thinsp;=\u0026thinsp;0.595), indicating that δ\u0026sup1;⁸O was primarily controlled by effective moisture, defined by the balance between water input and evaporation (I/E). Under these conditions, carbon and oxygen isotopes varied synchronously, consistent with modern observational studies. Modern process studies revealed that Serling Co\u0026rsquo;s water δ\u0026sup1;⁸O\u003csub\u003ecarb\u003c/sub\u003e and volume were governed by effective moisture-the equilibrium between I/E (Ding et al., \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; Guo et al., \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). During 3.32\u0026ndash;2.21 ka, δ\u0026sup1;\u003csup\u003e3\u003c/sup\u003eC, δ\u0026sup1;⁸O, and TOC contents all exhibit large-amplitude fluctuations, reflecting pronounced climatic instability. Two intervals, 3.11\u0026ndash;3.04 ka and 2.38\u0026ndash;2.32 ka, show synchronous increases in all three proxies, particularly in δ\u0026sup1;⁸O, indicating relatively dry conditions and reduced effective moisture. The concurrent increase in TOC suggests warmer conditions that promoted vegetation growth and enhanced organic matter input to the lake. Warmer temperatures would also have accelerated glacial melting, increasing meltwater inflow and explaining the abrupt δ\u0026sup1;⁸O decreases following these warm-dry events due to the input of isotopically depleted meltwater. Notably, 3.32 ka appears to represent a major climatic transition, marked by the first appearance of the cold-preferring ostracod \u003cem\u003eLimnocythere kunlunensis\u003c/em\u003e (Song and Zheng, 2022) and increased variability in \u003cem\u003eL. inopinata\u003c/em\u003e, indicating a shift toward cooler and more unstable climatic conditions. This transition may represent the effective termination of Holocene Megathermal conditions in the Selin Co region.\u003c/p\u003e \u003cp\u003eAfter 2.21 ka, δ\u0026sup1;\u003csup\u003e3\u003c/sup\u003eC and δ\u0026sup1;⁸O values show a gradual upward trend with superimposed high-frequency, low-amplitude fluctuations, indicating progressive aridification. This pattern is consistent with the findings of Zhu et al. (2026), but the higher resolution of our record allows the identification of additional details. The high-frequency variability resembles the characteristic oscillations of the low-latitude Indian summer monsoon. Meanwhile, the 10\u0026ndash;70 \u0026micro;m fraction of grain-size, an indicator of westerly strength, declines markedly and remains low, suggesting a weakened influence of the Westerlies and a dominant control of the Indian summer monsoon on the Selin Co region during this period. This interpretation is consistent with modern meteorological observations (Tong et al., \u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e2016\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eDuring the interval from 1.15 to 0.79 ka, δ\u0026sup1;\u003csup\u003e3\u003c/sup\u003eC, δ\u0026sup1;⁸O and carbonate content increase nearly synchronously, while TOC remains relatively high during the early stage, indicating warm climatic conditions corresponding to the Medieval Warm Period (MWP). Elevated temperatures during the early MWP led to the replacement of the cold-preferring \u003cem\u003eLimnocythere kunlunensis\u003c/em\u003e by \u003cem\u003eL. inopinata\u003c/em\u003e. During the later stage, increased glacial meltwater input likely reduced lake-water temperatures, resulting in a decline in \u003cem\u003eL. inopinata\u003c/em\u003e abundance. \u003cem\u003eL. kunlunensis\u003c/em\u003e reappears sporadically, indicating a transition toward colder conditions.\u003c/p\u003e \u003cp\u003eBetween 0.68 and 0.1 ka, TOC content, δ\u0026sup1;\u0026sup3;C values and carbonate content remain consistently low, indicating a shift toward cold conditions. We interpret this interval as the expression of the Little Ice Age (LIA) in the Selin Co region, although at the early stage, the abundance of \u003cem\u003eL. inopinata\u003c/em\u003e was still high. The delayed response of \u003cem\u003eL. inopinata\u003c/em\u003e may be partly attributed to its tolerance of relatively low temperatures. After 0.39 ka, \u003cem\u003eL. inopinata\u003c/em\u003e abundance decreases significantly, accompanied by the appearance of the cold-preferring species \u003cem\u003eL. kunlunensis\u003c/em\u003e, indicating pronounced cooling.\u003c/p\u003e \u003cp\u003eIn summary, lake-level variations in Selin Co since 6.20 ka exhibit a pattern characterized by initially high levels (6.20\u0026ndash;3.32 ka), followed by pronounced fluctuations period (3.32\u0026ndash;2.21 ka), It is also from this phase that the climate in the Siling Co region began to cool. (Does this mark the true end of the Holocene Megathermal in this area?). A gradual decline during the late Holocene (since 2.21 ka). This pattern broadly follows the decreasing trend in summer insolation at 31\u0026deg;N throughout the Holocene (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e). However, lake-level fluctuations on the Tibetan Plateau cannot be attributed solely to regional precipitation changes associated with monsoon intensity. The contribution of temperature-controlled glacial meltwater must also be considered when interpreting hydrological and climatic evolution.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003efrom 6.20 to 2.21 ka, the Selin Co region was mainly dominated by the Weserlies. However, due to the persistence of a large lake inherited from the Holocene Megathermal, lake level remained relatively high. Between 3.32 and 2.21 ka, the regional climate experienced pronounced fluctuations. After 2.21 ka, the Indian summer monsoon became the dominant controlling factor. Nevertheless, weakened solar radiation led to reduced moisture transport by the monsoon, resulting in a gradual trend toward aridification and a progressive decline in lake level.\u003c/p\u003e \u003cp\u003eThe widely recognized 4.2 ka cold-dry event began at approximately 4.25 ka in the central Tibetan Plateau and persisted for about 370 years. It was characterized by predominantly cold conditions initially, followed by pronounced aridity during the middle to late stages, with superimposed temperature fluctuations. The Medieval Warm Period (MWP) was relatively short-lived, occurring between 1.15 and 0.79 ka, and was marked by a distinct early temperature increase followed by gradual cooling. After 0.68 ka, regional temperatures declined further, with modest cooling initially and after 0.39 ka a more pronounced temperature decrease till 0.1 ka, corresponding broadly to the Little Ice Age (LIA).\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eFunding Declaration\u003c/h2\u003e \u003cp\u003e \u003cb\u003e\u003c/b\u003e This work was supported by the Basic Scientific Research Project of the Institute of Mineral Resources, Chinese Academy of Geological Sciences (No. KK2521) and the Tibet Autonomous Region Science and Technology Program (No. XZ202403ZY0028).\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eW.H.L . collected samples and wrote the main manuscript text, Z.C.J . modified the Materials and Methods, Discussion, polished the English and prepared figure 3. S.G. prepared figure 8 and provided data on ostracod. Z.M.P. gave helpful suggestions. All authors reviewed the manuscript.\u003c/p\u003e\u003ch2\u003eAcknowledgement\u003c/h2\u003e\u003cp\u003eWe would like to thank Ma Guiliang for his help in field work.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003e\u003cspan\u003eAn Z, Colman SM, Zhou W, Li X, Brown ET, Jull AJT, Xu X. 2012a. Interplay between the Westerlies and Asian monsoon recorded in Lake Qinghai sediments since 32 ka. Sci Rep 2(1): 619. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1038/srep00619\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\n \u003cli\u003e\u003cspan\u003eAn, Z.S., Colman, S.M., Zhou, W.J., Li, X.Q., Brown, E.T., Jull, A.J.T., Cai, Y.J., Huang, Y.S., Lu, X.F., Chang, H., Song, Y.G., Sun, Y.B., Xu, H., Liu, W.G., Jin, Z.D., Liu, X.D.,Cheng, P., Liu, Y., Ai, L., Li, X.Z., Liu, X.J., Yan, L.B., Shi, Z.G., Wang, X.L., Wu, F.,Qiang, X.K., Dong, J.B., Lu, F.Y., Xu, X.W., 2012b. 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Res. 32 (3), 373\u0026ndash;379. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.16089/j.cnki.1008-2786.2014.03.002\u003c/span\u003e\u003c/span\u003e (in Chinese with English abstract).\u003c/span\u003e\u003c/li\u003e\n \u003cli\u003e\u003cspan\u003eZhu, L., Wang, J., Ju, J., Ma, N., Zhang, Y., Liu, C., Han, B., Liu, L., Wang, M., Ma, Q. 2019. Climatic and lake environmental changes in the Serling Co region of Tibet over a variety of timescales. Sci. Bull. 64, 422\u0026ndash;424. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.scib.2019.02.016\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\n \u003cli\u003e\u003cspan\u003eZhu Xinghuan, Zhu Liping, Wang Junbo, Ju Jianting, Li Minghui, Kou Qiangqiang, Ma Qingfeng. 2026. The Input / Evaporation inferred by mineral composition and stable isotope and climatic implications in Serling Co sediment of Tibet, China since last deglacial period. Palaeogeography, Palaeoclimatology, Palaeoecology, 683: \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.palaeo.2025.113484\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"journal-of-paleolimnology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"jopl","sideBox":"Learn more about [Journal of Paleolimnology](http://link.springer.com/journal/10933)","snPcode":"10933","submissionUrl":"https://submission.nature.com/new-submission/10933/3","title":"Journal of Paleolimnology","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Selin Co, mid–late Holocene, organic and inorganic carbon contents, carbon and oxygen isotopes, atmospheric circulation shifts, climate evolution","lastPublishedDoi":"10.21203/rs.3.rs-9194728/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-9194728/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eSelin Co, the largest lake on the Central Tibetan Plateau, is located at the junction of the Asian summer monsoon and the Westerlies, making it an ideal site for investigating the evolution of atmospheric circulation. In this study, variations in total organic carbon (TOC) and total carbonate contents, carbon and oxygen isotopic compositions of authigenic carbonates, together with grain-size parameters and changes in ostracod assemblages from lake sediments, are used to reconstruct the advance and retreat of the Asian summer monsoon and the Westerlies circulation since 6.20 ka. The regional climate evolution and the characteristics of specific climatic events in the Selin Co area are also discussed.\u003c/p\u003e \u003cp\u003eThe results indicate that from 6.20 to 2.21 ka, the Selin Co region was mainly dominated by the Westerlies. Lake level remained relatively high as it inherited from the highstand during the Holocene Megathermal, the supply of glacial meltwater also contributed. Between 3.32 and 2.21 ka, the regional climate experienced pronounced fluctuations. After 2.21 ka, the Indian summer monsoon became the dominant controlling factor. Nevertheless, weakened solar radiation led to reduced moisture transport by the monsoon, resulting in a gradual trend toward aridification and a progressive decline in lake level.\u003c/p\u003e \u003cp\u003eThe widely recognized 4.2 ka cold-dry event began at approximately 4.25 ka in the central Tibetan Plateau and persisted for about 370 years. It was characterized by predominantly cold conditions during its initial phase, followed by pronounced aridity during the middle to late stages, with superimposed temperature fluctuations. The Medieval Warm Period (MWP) was relatively short-lived, occurring between 1.15 and 0.79 ka, and was marked by a distinct early temperature increase followed by gradual cooling. After 0.68 ka, regional temperatures declined further, with modest cooling initially and a more pronounced temperature decrease after 0.39 ka, corresponding broadly to the Little Ice Age (LIA).\u003c/p\u003e","manuscriptTitle":"Paleoclimate Changes and the Evolution of Atmospheric Circulation in Selin Co on the Central Tibetan Plateau Since the Mid–Late Holocene","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-04-13 17:14:47","doi":"10.21203/rs.3.rs-9194728/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2026-05-11T09:54:23+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-04-30T17:42:02+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-04-27T03:16:25+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"135360108882229332487565663785553474665","date":"2026-04-07T15:07:39+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"211991518700456304541881407602620363049","date":"2026-04-07T08:14:46+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-04-07T07:29:10+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-03-25T10:58:43+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2026-03-25T10:57:46+00:00","index":"","fulltext":""},{"type":"submitted","content":"Journal of Paleolimnology","date":"2026-03-23T02:34:21+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"journal-of-paleolimnology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"jopl","sideBox":"Learn more about [Journal of Paleolimnology](http://link.springer.com/journal/10933)","snPcode":"10933","submissionUrl":"https://submission.nature.com/new-submission/10933/3","title":"Journal of Paleolimnology","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"c980732f-ffd2-477a-9bcd-559679395a5b","owner":[],"postedDate":"April 13th, 2026","published":true,"recentEditorialEvents":[{"type":"decision","content":"Revision requested","date":"2026-05-11T09:54:23+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-04-30T17:42:02+00:00","index":14,"fulltext":""}],"rejectedJournal":[],"revision":"","amendment":"","status":"in-revision","subjectAreas":[],"tags":[],"updatedAt":"2026-05-11T10:13:09+00:00","versionOfRecord":[],"versionCreatedAt":"2026-04-13 17:14:47","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-9194728","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-9194728","identity":"rs-9194728","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}