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Deserts and sandylands that are located in the semi-arid and arid regions in the middle latitudes of the Northern Hemisphere are usually regarded as environmentally sensitive change belts which respond to global climatic change. In northern China, activation or immobilization of sand dunes is mainly influenced by humid and dry variation and is related to stronger or weaker Asian monsoons. In this paper, the history of Holocene millennial-scale climatic and environmental change is reconstructed by the systematic analysis of the geochemical element contents and parameters, along with the OSL and C chronologies, from the different lithologies of the palaeosol-aeolian sand sequence in the south-eastern Mu Us Desert, northern China. Our results indicate that the region was dominated by a dry climate with intensive aeolian activity before 7.2 ka BP, and there was an optimal humid climate and fixed desert in 7.2-4.6 ka. Afterwards, the dune fields became mobile again as the effective humidity declined. Additionally, six dry events were discovered with times of ~7.2, 7.0-6.8, 6.6-5.7, 4.6-4.1, 3.7-3.5, and 3.3-2.5 ka, which were not only coincident with the intervals of millennial-scale weaker Asian summer monsoons, but also accordant with the cold events evidenced in the ice cores and deep-sea deposits of the high latitudes in the Northern Hemisphere. In general, the Holocene climatic and environmental changes had the characteristics of the 'monsoonal mode' and 'abrupt millennial-scale oscillation' in the Mu Us Desert. [ABSTRACT FROM AUTHOR]

A comprehensive and integrative view of East Asian monsoon evolution during the Holocene is still under debate, and additional high-resolution proxy records from climatically sensitive locations are requisite to solve this complex issue. In this paper, we present three well-dated mud/peat cores from a paleo-pingo depression in the Sanjiang Plain, a climatically sensitive region to monsoon variation, to reveal the paleoenvironmental history of the wetland and discuss the regional impacts from monsoon evolution. A paleolake developed in the study area before 5.5 ka BP, and a peatland initiated thereafter consequent upon the gradual shrinking of the paleolake. This transition lasted until 4.5 ka BP, when the paleolake changed entirely to a wetland. Considering the prevalent monsoon climate in the Sanjiang Plain, we suggest that the lake-to-wetland transition from 5.5 to 4.5 ka BP indicates a rapid decline of the East Asian summer monsoon in addition to autogenic basin infilling processes. Such a remarkable monsoon weakening event has been documented across northern China, and we associate this with ocean–atmosphere interactions throughout low-latitude regions. [ABSTRACT FROM AUTHOR]

The East Asian monsoon (EAM) has experienced significant changes over the past 10,000 years that influenced East Asian agricultural development. However, the magnitude and extent of the EAM precipitation fluctuations at 6 ka remain unresolved, owing to uncertainty in individual lake records and substantial variations in the expansion limits in simulations of the mid-Holocene EAM precipitation. Here we present an approach based on multiple lake-level records using the "1D lake level—2D lake area—3D catchment hydrology" model to reconstruct the precipitation patterns in northern China, and to further quantify the extent of the EAM precipitation expansion in the mid-Holocene relative to today. The precipitation reconstructions suggest an ~550–1100 km northward expansion and an ~530–840 km westward migration of the EAM at 6 ka. At that time, the EAM precipitation domain covered over 6 million square kilometers. Thus, this approach mitigates the uncertainty and arbitrariness of reconstructions of the limit of the EAM precipitation fields and provides a benchmark for future climate modeling studies. [ABSTRACT FROM AUTHOR]

Understanding the mid-Holocene dynamics of the East Asian monsoon (EAM) is integral to improving models of the Holocene development of the global climate system. Here we reconstruct the mid-Holocene EAM history from the Pearl River estuary, southern China, using bulk organic carbon isotopes (δ13C), total carbon to total nitrogen (C/N) ratios and total organic carbon (TOC) concentration. Sedimentary δ13C, C/N and TOC are potentially good indicators of changes in monsoonal precipitation strength. Sediments buried during a period of high precipitation exhibit a high proportion of terrigenous material, and have low δ13C and high C/N, and vice versa during a period of low precipitation. Results suggest a general decreasing trend in monsoonal precipitation from 6650 to 2150 cal. yr BP because of the weakening Northern Hemisphere insolation most likely related to the current precession circle. Superimposed on this trend are apparent dry–wet oscillations at centennial to millennial timescales most likely in response to solar activity. Mismatches between our δ13C record and results from the Dongge Cave in southern China at millennial timescales may indicate that the δ13C from the Pearl River estuary reveals changes in precipitation over a broader area than the δ18O from Dongge Cave. [ABSTRACT FROM AUTHOR]

Millennial-scale climate variability has not been well documented in arid northwest China due to the scarcity of high-resolution, well-dated paleoclimate records. Here we present multi-proxy records from sediment cores taken in freshwater Hurleg Lake on the northeastern Tibetan Plateau, which reveal millennial-scale lake-level and climate variations over the past 8,000 years. This high-elevation region is very sensitive to large-scale climate change, thus allowing us to better understand Holocene climate variations in East Asia. The lake-level record, derived from lithology, magnetic mineralogy, carbonate isotopes, ostracode shell isotopes and trace elements, X-ray fluorescence (XRF), and gray scale data, indicates a highly variable and generally dry climate from 7.8 to 1 ka (1 ka = 1,000 cal year BP), and a relatively stable and wet climate after 1 ka. Superimposed on this general trend, six dry intervals at 7.6-7.2 ka, 6.2-5.9 ka, 5.3-4.9 ka, 4.4-3.8 ka, 2.7-2.4 ka, and 1.7-1.1 ka were detected from the high-resolution carbonate content and XRF data. The generally dry climate between 7.8 and 1 ka was almost synchronous with the decrease of East Asian and Indian monsoon intensities shortly after 8 ka. The six dry intervals can be correlated with weak monsoon events recorded in the East Asia and Indian monsoon regions, as well as the North Atlantic cold events. Our data suggest that millennial-scale monsoon variations could cause highly variable climate conditions in arid northwest China during the Holocene. These millennial-scale climate variations may reflect changes in solar variation and/or changes in oceanic and atmospheric circulation. [ABSTRACT FROM AUTHOR]

A high-resolution oxygen-isotope record from a thorium-uranium-dated stalagmite from Shanbao Cave at Shennongjia reflects variations in the amount of monsoon precipitation for the period from 11.5 to 2.1 ka (1 ka = 1000 cal aBP). Between 11.5 and 9.3 ka, a sharp decrease in δ18O indicates a rapid increase in monsoon precipitation. An interval of generally high monsoon precipitation is observed between 9.3 and 4.4 ka. An arid period has prevailed between 4.4 and 2.1 ka. The long-term trend of Shanbao record appears to follow summer insolation at 33°N latitude. An abrupt decrease in monsoon precipitation around 4.3 ka is synchronous with the collapse of Neolithic culture in central China. This abrupt change could have resulted from the amplification of the gradually decreased summer insolation by the positive vegetation-atmosphere-aerosol feedback. The weakened Asian monsoon events were in concert with decreased Greenland temperature during the early Holocene, centered at 8.2, 8.6, 9.3, 10.2 and 11.0 ka. This correlation suggests that changes in low-latitude monsoon are connected with climate change in high-latitude polar region. [ABSTRACT FROM AUTHOR]

Middle- to late-Holocene palaeoclimate change has been reconstructed at high resolution by the analysis of the carbon and oxygen isotopes from a thermal ionization mass spectrometric (TIMS) U / Th dated stalagmite from Xiangshui Cave, near Guilin, Guangxi Province, China. The carbon and oxygen isotopic records from the stalagmite suggest that changes in the Asian monsoon since the middle Holocene (6000 BP) can be divided into two periods: (1) an interval from 6000 to 3800 BP when a strong East Asian summer monsoon gradually weakened and climate was relatively warm and humid; (2) a cool period from 3800 to 373 BP when the East Asian summer monsoon was relatively weak and the winter monsoon was probably relatively strong. This cooler interval was interspersed with a number of short warm periods. This interpretation is largely based upon the general increase in δ18O values of the stalagmite between 6000 and 3800 BP and shifts in δ18O about a relatively heavy mean value between 3800 and 373 BP. The 6000 to 3800 BP trend is probably associated with decrease in precipitation and temperature subsequent to the mid-Holocene climatic optimum. [ABSTRACT FROM AUTHOR]