%0 Journal Article %T Holocene Asian monsoon evolution revealed by a pollen record from an alpine lake on the southeastern margin of the Qinghai¨CTibetan Plateau, China %A Shen %A Ji %A Sun %A Weiwei %A Wang %A Yongbo %A Zhang %A Enlou %J - %D 2016 %R https://doi.org/10.5194/cp-12-415-2016 %X

Abstract. We present the results of pollen analyses from a 1105£¿cm long sediment core from Wuxu Lake in southwestern China, which depict the variations of the East Asian winter monsoon (EAWM) and the Indian summer monsoon (ISM) during the last 12.3£¿ka. During the period of 12.3 to 11.3£¿cal£¿ka£¿BP, the dominance of Betula forest and open alpine shrub and meadow around Wuxu Lake indicates a climate with relatively cold winters and dry summers, corresponding to the Younger Dryas event. Between 11.3 and 10.4£¿cal£¿ka£¿BP, further expansion of Betula forest and the retreat of alpine shrubs and meadows reflect a greater seasonality with cold winters and gradually increasing summer precipitation. From 10.4 to 4.9£¿cal£¿ka£¿BP, the dense forest understory, together with the gradual decrease in Betula forest and increase in Tsuga forest, suggest that the winters became warmer and summer precipitation was at a maximum, corresponding to the Holocene climatic optimum. Between 4.9 and 2.6£¿cal£¿ka£¿BP, Tsuga forest and alpine shrubs and meadows expanded significantly, reflecting relatively warm winters and decreased summer precipitation. Since 2.6£¿cal£¿ka£¿BP, reforestation around Wuxu Lake indicates a renewed humid period in the late Holocene; however, the vegetation in the catchment may also have been affected by grazing activity during this period. The results of our study are generally consistent with previous findings; however, the timing and duration of the Holocene climatic optimum from different records are inconsistent, reflecting real contrast in local rainfall response to the ISM. Overall, the EAWM is broadly in-phase with the ISM on the orbital timescale, and both monsoons exhibit a trend of decreasing strength from the early to late Holocene, reflecting the interplay of solar insolation receipt between the winter and summer seasons and El Ni£¿o¨CSouthern Oscillation strength in the tropical Pacific.