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This paper reconstructs the evolutionary history of the Pearl River delta over the last 9000 years and investigates land-sea interaction in a large deltaic complex which formed under the influence of Asian monsoon climate. Specifically, this research examines the delta evolution in the context of three driving mechanisms: (1) rising sea level that influences the available accommodation space, (2) fluvial discharge as influenced by monsoon climate and (3) human activities that alter sedimentation within the deltaic system. Results reveal that the formation of deltaic sequences was initiated as a consequence of rapid sea-level rise between 9000 and 7000 cal. yr BP. The rate of sea-level rise slowed down markedly around 7000 cal. yr BP and sedimentation switched from transgressive to regressive. Initially, both the progradation of the delta plains near the apex and aggradation of delta front sedimentation in the central and lower parts of the receiving basin were fast owing to strong monsoonal-driven runoff. The progradation rate gradually slowed down between 6800 and 2000 cal. yr BP as monsoonal-driven runoff weakened. Rapid shoreline advances during the last 2000 years were the result of significantly increased human activities, a practice that trapped sediments in the encircled tidal flats along the front of delta plains. The evolutionary history of the Pearl River delta demonstrates the interplay between the three driving mechanisms. [ABSTRACT FROM AUTHOR]

The paper explores the use of Resilience Theory to provide an improved theoretical framework for the analysis of socio-ecological interactions over decadal—millennial timescales. It identifies landscape system behaviour through analysis of proxy records for land use, erosion and monsoon intensity over the past 3000 years in the Erhai lake-catchment system, Yunnan, SW China. Analysis of the records shows the possibility of alternative steady states in the landscape, as expressed by the relationship between land use and erosion. In particular, a period of agricultural expansion ~1400 cal. yr BP triggered rapid gully erosion that led to the formation of an eroded landscape state that has existed since ~800 cal. yr BP to the present day. Comparison of detrended time-series data suggests that over 3000 years erosion and land use should be considered 'slow' processes relative to the 'faster' monsoon intensity and flooding. In the past, the effects of high monsoon variance on flooding have been suppressed by paddy farming and the maintenance of terraced field systems. Mapping the Adaptive Cycle on to the millennial record of land use and erosion suggests that the modern landscape may be approaching a 'conservation' phase characterized by minimum resilience. Such 'historical profiling' of modern landscapes offers a new dimension for hypothesis testing, for the development and testing of simulation models and for the creation of appropriate management strategies. [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]

It has been suggested that late-Holocene human activities caused the increase in atmospheric methane (CH4) concentration that otherwise would have been a naturally decreasing trend. As one of the places where rice farming originated, China has been considered to play a significant role in pre-industrial changes in atmospheric CH4 concentrations. To establish the climatic context since the first rice cultivation and to evaluate the relative roles of monsoon climate and rice cultivation on late Holocene CH4 rise, we synthesized climate data from China to examine the Holocene trends in monsoon precipitation. The results show high monsoon rainfall from 10,000 to 7000 years ago, and declining precipitation in the late Holocene as shown by most reconstructions. The decreasing trend in monsoon precipitation is consistent with that in other north tropical monsoon regions, and is opposite to the trend in CH4 concentrations. After ruling out several other natural factors and estimating CH4 emissions from early rice farming, we conclude that the late-Holocene methane increase has been significantly influenced by the expansion of early rice paddy fields during the period of declining monsoon precipitation. [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]

A high-resolution record of Holocene environmental and climatic change in the Balikun area was reconstructed from a sediment core from the Lake Balikun. Multiproxy data show that the climate was extremely arid during the early Holocene (before 8.6 cal. ka BP). Moisture began to increase after 8.6 cal. ka BP and the climate was humid between 7.9 and 4.3 cal. ka BP. A significant dry event occurred around 4.3–3.8 cal. ka BP. The climate became generally wet during the late Holocene (after 3.8 cal. ka BP). The Holocene pollen and geophysical records do not indicate a wet early Holocene, making it evident that there was no early-Holocene humid period associated with peak Asian monsoon strength. Regional comparisons indicate that this region has a different pattern of Holocene environmental and climatic change from the Asian monsoonal area and south Siberia. [ABSTRACT FROM AUTHOR]

A compilation of early-Holocene terrestrial records from lacustrine sediments, ice cores, peat bog, palaeosols, stalagmites and flood sediments from China indicates that the early-Holocene climate was unstable and characterized by at least one centennial-scale (500-200 years) cooling event between 9.0 and 7.6 ka BP. The cold period recorded in different settings has been previously linked to the 8.2 ka event suggested by δ18Oice from Greenland ice cores, but the differences in time duration and regional climate conditions have been attributed to monsoon systems, inadequate age control and sampling resolution, and complex topography in China. However, our compilation indicates that it is premature to attribute the cold periods recorded at different locations in China simply to the 8.2 ka event, let alone to attribute the cause of those anomalies to a freshening of the North Atlantic Ocean circulation. Whether there was one synchronous event or not in China, where the climate is mainly affected by the monsoons and the westerlies, is open to discussion, because most of the records lack sufficient dating control to define clearly the nature of the cooling event. If a cooling event did occur, more evidence is required in multiple dimensions to characterize the time duration, magnitude and cause of the event, so much work remains to be done. [ABSTRACT FROM AUTHOR]

This study employs a multiproxy approach in the reconstruction of Holocene monsoon history from sedimentary sequences obtained from the Pearl River Estuary, southern China. A set of modern surface sediment samples were collected within and outside the estuary, and a sediment core was obtained from the mouth of the estuary. A range of modern environmental variables were recorded including water salinity (summer, winter and annual average) and water depth. The diatom results show a good relationship with water salinity, with marine diatoms dominating the more distal samples from outside the main estuary and freshwater diatoms dominating the proximal samples influenced by higher freshwater flux. This pattern is matched by the bulk organic carbon isotopes. The isotope values vary between -21.1±0.3‰ for samples from the fully marine environment, between -23.2±0.8‰ and -23.7±0.8‰ for samples from the mid to outer estuary brackish water environment and less than -24.7±1.3‰ for samples from the inner estuary close to the freshwater sources. Similarly, the C/N ratios vary from below 7±0.6 in the marine end-members to over 14.8±3.0 in the freshwater end-members. Both the diatom and carbon data from the sediment core reveal a significant increase in freshwater flux from 8500 cal. yr BP resulting from the enhanced summer monsoon regime in early Holocene. The strength of freshwater flux reached its highest between 7500 and 6000 cal. yr BP. In the last 6000 years, freshwater flux decreased towards present, reflecting a gradual weakening of the summer monsoon. [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]