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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]

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]

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]