Search

Understanding millennial‐scale East Asian summer monsoon (EASM) variability is critical for climate projection in East Asia in the context of slowing Atlantic Meridional Overturning Circulation (AMOC) caused by global warming. This study performs two groups of sensitivity experiments at 8.2 and 4.2 ka BP, both forced by the same North Atlantic freshwater hosing and corresponding orbital parameters using the Community Earth System Model, to explore the orbital effect on millennial‐scale EASM variability. Our simulations reveal that EASM variability differs significantly between these two cold events. During the 8.2 ka BP (4.2 ka BP) (0 BP = 1950 AD) cold event, North Atlantic freshwater forcing weakens the EASM, generating a meridional tripole (dipole) pattern of EASM precipitation anomalies. Furthermore, the same freshwater discharge causes a greater decline in the EASM, contrasting to a slight weaker AMOC slowdown, at 4.2 ka BP than at 8.2 ka BP. This suggests orbital parameters significantly influence the EASM response to North Atlantic cold events. The East Asian subtropical westerly jet, whose meridional position and intensity are controlled by summer insolation on an orbital timescale, plays a key role in this orbital effect. The westerly jet's meridional position determines the spatial pattern of EASM precipitation anomalies, while its intensity affects the amplitude of the EASM's response to freshwater forcing. Because of a larger EASM decline due to freshwater hosing with lower summer insolation, we anticipate a profound declining EASM precipitation in the future with low summer insolation if the AMOC continues to weaken. Key Points: Millennial‐scale East Asian summer monsoon (EASM) variability is modulated by Earth's orbital parametersThe EASM weakens more pronounced in response to North Atlantic freshwater forcing under lower summer insolationSummer insolation influences the EASM response to North Atlantic freshwater forcing via the westerly jet [ABSTRACT FROM AUTHOR]

In the East Asian monsoon region, Chinese speleothem δ18O records exhibit a maximum monsoon strength during the early Holocene. However, other proxy data from lakes or loess, interpreted as monsoon rainfall, show a mid‐Holocene monsoon optimum. This discrepancy may come from specific climate interpretation of different proxies. Here we report multiproxy records from a single loess–palaeosol sequence at Yulin in the monsoon marginal northern China, based on an independent and high‐precision chronology. Our long‐chain n‐alkane δD values, together with related biomarker proxies including the average chain length and concentration of long‐chain n‐alkanes, reveal a weakening trend in monsoon strength and less woody vegetation since ~6 ka. However, other soil formation‐related proxies, such as magnetic susceptibility, grain‐size distribution and total organic carbon, show a decreasing trend since 4–3 ka. We find that monsoon and vegetation are controlled by insolation variation, while soil formation is more related to temperature and humidity changes. Our multiple proxy comparison reveals different controlling mechanisms leading to different interpretations in monsoon, vegetation and soil formation reconstructions. This finding suggests that previous debates on Holocene monsoon changes in East Asia probably stem from the specific proxy interpretation. [ABSTRACT FROM AUTHOR]

Paleoclimatic records reveal spatially asynchronous changes of East Asian summer monsoon (EASM) precipitation during the Holocene, but the underlying mechanisms are not fully understood. This study explores the role of the zonal shift of the Asian westerly jet (AWJ) core on the spatial‐temporal variability of EASM precipitation based on Holocene climate simulations using the KCM and CESM forced by orbital variations. We analyzed the composite differences of summer precipitation and associated atmospheric circulations between the early (middle) and middle (late) Holocene. Simulations suggest a dipole pattern of summer precipitation with increasing (decreasing) precipitation in central (southern) China from the early to late Holocene, which was shaped by the eastward shift of the AWJ core. The eastward shift of the AWJ core and the accompanied eastward movement of the upper‐level convergence over the AWJ's right exit region weakened the low‐level downward motions over central China. Meanwhile, the low‐level upward motions over southern China were weakened by the concurrent eastward (westward) migration of the South Asian High (western Pacific subtropical High) during the Holocene. Consequently, summer precipitation increased (decreased) in central (southern) China from the early to late Holocene. The eastward shift of the AWJ core was primarily driven by amplified meridional insolation gradient at middle latitudes via strengthening upper‐level westerly intensity during the Holocene. In addition, land cover difference between East Asia and central Asia caused a greater enhancement of westerlies intensity in East Asia, further modulating the eastward movement of the AWJ core during the Holocene. Key Points: Our simulations reveal a dipole pattern of summer precipitation between central and southern China during the HoloceneThe dipole precipitation pattern was strongly modulated by zonal shift of the Asian westerly jet coreInsolation variation and land cover caused the eastward shift of the Asian westerly jet core during the Holocene [ABSTRACT FROM AUTHOR]

The Holocene moisture–temperature correlation on varying spatial–temporal scales in arid Central Asia (ACA) is still controversial. It has been widely reported that ACA experienced multi-centennial alternations between warm/dry and cold/wet climates over the past two millennia. However, less attention has focused on orbital-scale moisture–temperature relationship at a regional scale across ACA. Here, we contribute a framework including a set of quantitative algorithms to acquire reliable pollen-based climatic reconstructions. We apply this methodology to a new pollen record from a wetland in northern Xinjiang (southeastern ACA) for quantitative reconstructions of moisture availability (actual/potential evapotranspiration ratio, AET/PET) and summer temperature (mean temperature of the warmest month, MTWA) over circa the last 10,300 years. We select AET/PET and MTWA because they are evaluated to be most statistically independent and ecologically significant. The effect of differing spatial extents of calibration-sets on model performance is tested to determine the optimal extent. We critically assess the reliability of all reconstructions through calculations of statistical significance, analogue quality and goodness-of-fit statistics. Our final reconstructions are statistically significant with independent features of AET/PET and MTWA, showing an increasing (declining) trend of Holocene moisture (temperature). This anti-phase pattern is consistent with other records and model simulations across southeastern ACA. The data-model consistency postulates that (i) the glacier meltwater from Tien Shan ('Water Tower of Central Asia') is crucial to support major streamflow and watersheds over ACA, and (ii) the Holocene wetting trend may be determined by the interacting effects between decreased summer temperature and increased winter precipitation. [ABSTRACT FROM AUTHOR]

Projecting how the East Asian summer monsoon (EASM) rainfall will change with global warming is essential for human sustainability. Reconstructing Holocene climate can provide critical insight into its forcing and future variability. However, quantitative reconstructions of Holocene summer precipitation are lacking for tropical and subtropical China, which is the core region of the EASM influence. Here we present high-resolution annual and summer rainfall reconstructions covering the whole Holocene based on the pollen record at Xinjie site from the lower Yangtze region. Summer rainfall was less seasonal and ~ 30% higher than modern values at ~ 10-6 cal kyr BP and gradually declined thereafter, which broadly followed the Northern Hemisphere summer insolation. Over the last two millennia, however, the summer rainfall has deviated from the downward trend of summer insolation. We argue that greenhouse gas forcing might have offset summer insolation forcing and contributed to the late Holocene rainfall anomaly, which is supported by the TraCE-21 ka transient simulation. Besides, tropical sea-surface temperatures could modulate summer rainfall by affecting evaporation of seawater. The rainfall pattern concurs with stalagmite and other proxy records from southern China but differs from mid-Holocene rainfall maximum recorded in arid/semiarid northern China. Summer rainfall in northern China was strongly suppressed by high-northern-latitude ice volume forcing during the early Holocene in spite of high summer insolation. In addition, the El Niño/Southern Oscillation might be responsible for droughts of northern China and floods of southern China during the late Holocene. Furthermore, quantitative rainfall reconstructions indicate that the Paleoclimate Modeling Intercomparison Project (PMIP) simulations underestimate the magnitude of Holocene precipitation changes. Our results highlight the spatial and temporal variability of the Holocene EASM precipitation and potential forcing mechanisms, which are very helpful for calibration of paleoclimate models and prediction of future precipitation changes in East Asia in the scenario of global warming. [ABSTRACT FROM AUTHOR]

Abstract The East Asian summer monsoon (EASM) is a complex system that brings precipitation to East Asia showing considerable spatiotemporal variations. This study explored the zonal differences of summer precipitation in Northeast Asia at orbital timescales during the Holocene by comparing proxy records with simulation results. At orbital timescales, there was generally an east–west antiphasing of summer precipitation in Northeast Asia during the Holocene. Model–proxy comparison revealed that the driest interval occurred during the late Holocene in western Northeast Asia and during the early to middle Holocene in eastern Northeast Asia. Changes of summer precipitation in western Northeast Asia were mainly influenced by precession-driven EASM circulation. On the one hand, a weaker EASM circulation during the late Holocene weakened water vapor transport from the North Pacific Ocean to Northeast Asia, and on the other hand it was associated with anomalous downward motions in western Northeast Asia. Both factors were in favor of a reduction of summer precipitation in western Northeast Asia during the late Holocene. In contrast, anomalous downward motions prevailed in eastern Northeast Asia during the early to middle Holocene, which were probably related to stronger western Pacific subtropical high and weaker westerlies. The effect of the anomalous downward motions overwhelmed the enhanced water vapor transport, leading to a dry climate in this area from the early to middle Holocene. This study suggests that special care should be taken when discussing the meridional shift of the Holocene climatic optimum in the EASM region due to the zonal precipitation contrast. Highlights • We compare proxy moisture records in Northeast Asia with the results from a transient simulation. • An east–west antiphasing of summer precipitation in Northeast Asia during the Holocene is found. • The East Asian summer monsoon circulation and mid-latitude westerlies caused the zonal precipitation contrast. [ABSTRACT FROM AUTHOR]

The precipitation changes on the northeastern Tibetan Plateau during the Holocene remain unclear due to discrepancies among different proxy records. We compared proxy records with the results from a transient simulation performed using the Kiel Climate Model forced by orbital variations, to analyse summer precipitation changes in this area during the Holocene (9.5-0 ka BP). The model results suggested increasing amounts of summer precipitation from 9.5 to ~6.2 ka BP and a persistent decline thereafter, which matched well with pollen records but was inconsistent with ostracod δ18O records. The Holocene climatic optimum lagged the Northern Hemisphere summer insolation maximum by ~3.5 ka, caused by the interplay between the East Asian summer monsoon (EASM) circulation and the mid-latitude westerlies. The ostracod δ18O values reflected the strength of the EASM circulation. A strong EASM circulation increased the transport of water vapour towards the northeastern Tibetan Plateau from the northwestern Pacific. Weakened mid-latitude westerlies increased the incursion of cold air masses into the northeastern Tibetan Plateau. During the early Holocene, relatively strong mid-latitude westerlies, resulting from an enhanced Arctic Oscillation, reduced summer precipitation on the northeastern Tibetan Plateau, in spite of a strong insolation-driven EASM circulation. The weakening EASM circulation and the strengthening westerlies together induced the decreasing trend of summer precipitation from the middle to late Holocene. In addition, summer precipitation variations were further modulated by sea-surface temperatures in the northwestern Pacific, through weakening the strength of the EASM. [ABSTRACT FROM AUTHOR]

Identifying the relationships between moisture changes in arid central Asia and those in East Asia may help us understand the interplay between the westerlies and the Asian summer monsoon. We combined proxy moisture records with the results from a transient simulation forced by changes in orbital parameters to analyse their relationships during the Holocene (9.5–0 ka BP). The proxy records and simulation results generally agree with a relatively dry early Holocene, the wettest period in the middle Holocene, and a dry late Holocene in East Asia. These periods were not solely controlled by precession-driven East Asian summer monsoon variability, but were significantly influenced by precipitation during the other seasons and by evaporation. However, different proxy records show contrasting results for moisture changes in arid central Asia during the Holocene. To study this, we analysed the climatic signals of the competing proxy records by comparing these proxy records with simulation results. We found that speleothem δ 18 O was significantly influenced by water vapour sources and evaporation rather than by the amount of precipitation. Thus, the model data reveals a persistent wetting trend throughout the Holocene that was out-of-phase with the trend in East Asia. The wetting trend in arid central Asia was caused by precipitation that increased faster than evaporation during the Holocene. The enhanced water vapour input from South Asia and the Middle East was the main cause of the increase in precipitation in arid central Asia, which in turn gave rise to the intensification of evaporation. [ABSTRACT FROM AUTHOR]

The moisture history in arid central Asia (ACA) differs from that in the Asian monsoon region during the Holocene. Much less is known about causes of Holocene moisture changes in ACA than Asian monsoon precipitation changes, hampering our understanding of their spatiotemporal differences. In this study, orbital-scale evolution of winter rainfall in northwestern China (a part of the core zone in ACA) during the Holocene and possible driving mechanisms are investigated using results from a long-term transient simulation performed by an atmosphere–ocean–sea-ice coupled general circulation model, the Kiel Climate Model, forced by orbital variations. Our results reveal a persistent wetting trend in northwestern China in winter throughout the Holocene, which is in response to winter insolation at mid-northern latitudes. Winter insolation can influence the rainfall via three ways. First, increasing latitudinal gradient of the incoming solar insolation at mid-latitudes strengthens the westerly intensity. Second, the evaporation is enhanced because of insolation-induced winter temperature rising, resulting in an increase in the air humidity. Intensified westerly winds and the increased water vapour together are conductive to enhance moisture transport towards northwestern China and thus increase winter precipitation in this area. Third, the increasing trend of winter insolation weakens the East Asian winter monsoon, which is favourable for the formation of rainfall via crippling the Siberian High that is beneficial for atmospheric lifting motion. [ABSTRACT FROM AUTHOR]

ABSTRACT We present a pollen-based precipitation reconstruction and multi-proxy records from a 485-cm-long sequence from a sediment core from Xingyun Lake, Yunnan Plateau, south-west China, which depicts the evolution of the Indian Summer Monsoon (ISM) during the last 8500 years. Pollen and other palaeoenvironmental records document several stages of vegetation history and climate change. The warmest and wettest climate in the Xingyun Lake catchment occurred before 5500 cal a BP, and subsequently the climate became gradually drier. After 2000 cal a BP the regional environmental conditions became unstable, and a wet Medieval Warm Period is probably recorded. Our reconstruction of the ISM is similar to that portrayed by Holocene speleothem δ18O records from southern China, but is distinctly different from the East Asian Summer Monsoon (EASM) evolution, which features a mid-Holocene maximum. Our results support the hypothesis that the ISM and EASM evolved asynchronously during the Holocene, and imply that the Chinese speleothem δ18O records from southern China may principally reflect changes in moisture source from the Indian monsoon domain, and thus record the history of the ISM rather than the EASM. [ABSTRACT FROM AUTHOR]

Monsoonal water vapour transport is an active component of the hydrological cycle, which has a profound influence on regional climate changes. This study explored how far can the East Asian summer monsoon (EASM) transport water vapour to the west during the Holocene using published speleothem oxygen isotope (δ18O) records inferred from modern analogues of precipitation δ18O in the summer monsoon season (May to September) at mid-latitudes. Modern climate analyses suggest that there are two water vapour transport pathways to arid central Asia in the summer monsoon season: westerly transport and monsoonal easterly transport. Westerly transport from the North Atlantic and Arctic Oceans is associated with 18O-depleted water vapour, while monsoonal easterly transport from the tropical Indian Ocean, South China Sea, and East Asia is associated with 18O-enriched water vapour. The mixture of these water vapour dominates precipitation δ18O in arid central Asia from May to September. The difference of δ18O between precipitation in arid central Asia and the southern Urals reflects the penetration of monsoonal water vapour into arid central Asia. Speleothem δ18O records from Kesang Cave in the central Tianshan Mountains and Kinderlinskaya Cave in the southern Urals were therefore selected to indicate monsoonal water vapour transport into arid central Asia during the Holocene. Their differences suggest prominent monsoonal water vapour were transported to arid central Asia during the early Holocene, 8.2 ka BP event and late Holocene when the EASM was very weak. The results indicate that monsoonal water vapour could be transported at least as far west as the central Tianshan Mountains (∼81.75° E) in arid central Asia during the Holocene under weak EASM conditions rather than as previously supposed under strong EASM conditions. Although the amount of monsoonal water vapour is relatively less compared with that of westerly water vapour, it cannot be neglected because this source plays an important role in changes of precipitation and its δ18O in arid central Asia during the summer monsoon season. • Monsoonal water vapour can be transported as far west as the central Tianshan Mountains in arid central Asia. • A weak East Asian summer monsoon promotes the westward penetration of monsoonal water vapour into arid central Asia. • Speleothem (precipitation) oxygen isotope in arid central Asia is controlled by water vapour sources. • Speleothem (precipitation) oxygen isotope reveals a new mode of interaction between the westerlies and EASM. [ABSTRACT FROM AUTHOR]

Abstract: The interpretation of the stalagmite δ18O record from southern China as an indicator of East Asian summer monsoon (EASM) rainfall amount or intensity is strongly debated. Soil development in the Chinese Loess Plateau (CLP), situated in the modern summer monsoon domain, has long been treated as a direct and reliable EASM proxy. In this study, we compiled 81 loess and 229 palaeosol dates from 77 profiles across the CLP and synthesized the data statistically in order to investigate the EASM history during the Holocene. The resulting history of Holocene loess deposition and palaeosol development demonstrates that: (1) loess deposition decreased and palaeosol formation increased across the CLP after 11.5 ka (1 ka = 1000 cal yr BP), revealing a gradually intensified EASM during the early Holocene; (2) numerous palaeosols developed in the CLP between 8.8 ka and 3.4 ka, indicating a generally strong EASM during the mid-Holocene; (3) the number of palaeosol dates decreased rapidly at around 3 ka, suggesting a sudden retreat of the EASM in the late Holocene. These trends of EASM evolution are broadly consistent with variations in aeolian sand activity in the four main sandlands (the Mu Us, Otindag, Horqin and Hulun Buir sandlands) along the modern monsoon fringe in northern China, and are supported by a wide range of independent evidence. In addition we also found that high loess deposition and stronger aeolian activity occurred at ∼5 ka, representing a weak EASM event within the context of an overall strong mid-Holocene EASM. The strong mid-Holocene EASM, revealed by palaeosol development in the CLP and aeolian sand activity in the sandlands in northern China, contrasts with the early Holocene EASM maximum suggested by stalagmite δ18O data from southern China. Our results are compatible with the proposal that the stalagmite δ18O variations in China do not result from changes in EASM rainfall amount or intensity, but instead reflect changes in moisture source driven by variations in atmospheric-oceanic circulation. [Copyright &y& Elsevier]

Understanding the factors behind past vegetation changes is instructive to anticipate how vegetation will react to future climate change and human activities. The factors that contribute to the changes in vegetation during the Holocene in the topographically diverse southeast China are still not well understood. This study presents a recently acquired subalpine pollen record and combines it with pollen records from low-lying areas and mountains in southeast China. We utilized a Rate of Change (RoC) analysis on the pollen sequences to detect shifts in vegetation composition. Our findings indicate a significant increase in vegetation rate of change in southeast China over the past 3000 years, comparable to or exceeding maximum levels seen during the early Holocene, a period characterized by greater climate variability. By analyzing available paleorecords of climate, fire, and human activity, it becomes clear that vegetation in southeast China was significantly affected by climate before c. 3 ka BP. However, after this time, human impacts began to play a prominent role, first in the lowlands and later in the mountains, in addition to the influence of climate variations. Our study emphasizes the significance of taking into account the rate of vegetation compositional change when examining the factors that influence long-term vegetation changes. • A new subalpine pollen and charcoal record from southeast China. • Rate of change analysis in synthesized pollen records reveals vegetation turnover. • Climate is the main factor driving regional vegetation changes before 3 ka BP. • Humans played a prominent role, first in the lowlands and later in the mountains. [ABSTRACT FROM AUTHOR]

There are significant differences in the interpretation of the moisture (precipitation) history of arid central Asia (ACA) during the Holocene, as inferred on one hand from speleothem oxygen isotope records, and on the other from lake sediments. Here we present the results of measurements of climatically-sensitive magnetic properties and soil color from four well-dated loess-paleosol sequences from the northern slopes of the Tienshan Mountains and the Yili River valley, Xinjiang, China, in the core area of ACA. Our results demonstrate that the characteristic Holocene paleosol, indicating relatively moist conditions, generally formed after ∼6 ka (1 ka = 1000 cal yr BP) in the study region, and that the accumulation of unweathered loess prevailed during the early Holocene, indicating a dry climate at that time. The magnetic proxies further reveal a trend of generally increasing moisture since the Last Glacial Maximum, with the wettest climate occurring during the late Holocene. This trend of increasing moisture during the Holocene is representative of the Xinjiang region and possibly of the whole of the core area of ACA, and is in marked contrast both to the mid-Holocene moisture maximum observed in the East Asian summer monsoon region and to the general decrease in the strength of the Indian summer monsoon since the early Holocene. Our findings are supported by the results of a climate simulation which indicate a trend of increasing summer and winter precipitation during the Holocene in the core area of ACA, caused mainly by an increase in the strength of the westerlies effected by an increasing latitudinal insolation gradient and by a negative trend of the Arctic Oscillation (AO) or North Atlantic Oscillation (NAO). [ABSTRACT FROM AUTHOR]

Abstract: Paleoclimate proxy records of precipitation/effective moisture show spatial–temporal inhomogeneous over Asian monsoon and monsoon marginal regions during the Holocene. To investigate the spatial differences and diverging temporal evolution over monsoonal Asia and monsoon marginal regions, we conduct a series of numerical experiments with an atmosphere–ocean–sea ice coupled climate model, the Kiel Climate Model (KCM), for the period of Holocene from 9.5 ka BP to present (0 ka BP). The simulations include two time-slice equilibrium experiments for early Holocene (9.5 ka BP) and present-day (0 ka BP), respectively and one transient simulation (HT) using a scheme for model acceleration regarding to the Earth's orbitally driven insolation forcing for the whole period of Holocene (from 9.5 to 0 ka BP). The simulated summer precipitation in the equilibrium experiments shows a tripole pattern over monsoonal Asia as depicted by the first modes of empirical orthogonal function (EOF1) of H0K and H9K. The transient simulation HT exhibits a wave train pattern in the summer precipitation across the Asian monsoon region associated with a gradually decreased trend in the strength of Asian summer monsoon, as a result of the response of Asian summer monsoon system to the Holocene orbitally-forced insolation change. Both the synthesis of multi-proxy records and model experiments confirm the regional dissimilarity of the Holocene optimum precipitation/effective moisture over the East Asian summer monsoon region, monsoon marginal region, and the westerly-dominated areas, suggesting the complex response of the regional climate systems to Holocene insolation change in association with the internal feedbacks within climate system, such as the air-sea interactions associated with the El Nino/Southern Oscillation (ENSO) and shift of the Intertropical Convergence Zone (ITCZ) in the evolution of Asian summer monsoon during the Holocene. [Copyright &y& Elsevier]

The Tibetan Plateau (TP) is one of the most sensitive areas to global climate changes. Quantitative paleotemperature reconstructions on the TP since the Last Deglaciation provide a prominent opportunity not only for assessing the position, but also for better understanding the mechanism of recent warming. In this study, we first present a well-dated, high-resolution (~70 years), ice-free-season temperature (from March to October, T M-O) record over the past 19 ka from a small alpine lake on the southeastern TP based on brGDGT proxy. Our reconstructed T M-O record displays a long-term ~4 °C warming trend during the past 19 ka with a deglacial increase of ~3 °C and Holocene increase of ~1 °C. To better understand the pattern and mechanism of postglacial temperature changes on the TP, we review 16 published paleotemperature records since the Last Deglaciation. The results show a general warming pattern during the Last Deglaciation but divergent trends of seasonal temperatures during the Holocene with a gradual cooling pattern in summer temperature, an overall warming pattern in winter temperature, annual temperature, and T M-O as well as a warming-cooling-warming pattern in T MJJAS (temperature from May to September). Data-model comparison indicates that the long-term warming trend in deglacial temperatures are primarily driven by rising atmospheric greenhouse gases (GHGs) on the TP. In contrast, Holocene temperature changes are mainly controlled by local seasonal insolation and additional radiative forcing of GHGs on the TP, thereby resulting in divergent patterns of seasonal temperature changes. Our study highlights the necessity of taking into account the seasonal bias when reconstructing temperatures, especially in high latitudes and high altitudes where the freezing occurs. • A brGDGT-based high-resolution quantitative temperature record shows a warming of ~4 ºC on the TP over the past 19 ka. • The compiled records reveal a deglacial warming pattern and divergent trends for Holocene seasonal temperature. • Data-model comparison indicates insolation and GHGs reconcile divergent trends of Holocene seasonal temperature on the TP. • Seasonal biases of proxy reconstructions should be considered. [ABSTRACT FROM AUTHOR]

• A 15,000-year moisture/rainfall record for the western Chinese Loess Plateau. • Two independent dating methods were used. • Holocene east-west asymmetry in precipitation in the Chinese Loess Plateau. • Westward extension of the western Pacific subtropical high affected precipitation. As the cradle of Chinese civilization the Chinese Loess Plateau (CLP) and its climatic and environmental history have attracted much research attention; however, the spatial characteristics of Holocene climatic conditions across the CLP remains unclear. We investigated five loess sections from the Ganjia Basin in the western CLP, and used paleoclimatic indexes from one well-dated loess-paleosol sequence to reconstruct precipitation variation during the past ~15,000 years. The chronology of the loess section is well established, based on 12 AMS 14C dates from bulk organic matter. Loess deposited before 8 ka (1 ka = 1000 years before 1950 CE) indicates that precipitation was low from ~15 to 8 ka. Subsequently, a paleosol, characterized by higher magnetic susceptibility and more negative organic carbon isotopic values, developed under the moist conditions of the middle to late Holocene. Comparison with paleoclimatic records from the CLP revealed that precipitation across the CLP was low during the early Holocene and reached its highest level during 8–3 ka, against the background of an enhanced East Asian summer monsoon (EASM). In the eastern CLP (the region east of the Liupan Mountains), the climate became dry after 3 ka because of a weakening of the EASM; however, precipitation in the western CLP was relatively high at this time. This observation of an east–west asymmetry in precipitation in the CLP during the Holocene based on geological data is supported by numerical modeling results from PMIP3, which indicate that it could have been caused by the westward extension of the western Pacific subtropical high. Our findings provide an analog for the study of interglacials on a longer time-scale and they demonstrate that the pattern of moisture conditions between the eastern and western CLP may differ on sub-orbital timescales. [ABSTRACT FROM AUTHOR]