摘要
The 8.2 ka B.P.event and 9.2 ka B.P.event are prominent abrupt climate events in the Early Holocene.However,the characteristics and mechanisms of the East Asian summer monsoon (EASM) during the two events remain unclear.This study provides precisely-dated and high-resolution hydroclimate reconstructions during the early Holocene from stalagmite (YQ18) multi-proxy records (δ^(18)O,δ^(13)C,Mg/Ca,and δ^(234)U) in Yuquan Cave,Central China.The observed EASM weakening and regional drought during the 8.2 ka B.P.and 9.2 ka B.P.events indicate that the dry and wet conditions in the study area are mainly controlled by changes in the EASM intensity.The YQ18 records show that the 8.2 ka B.P.weak monsoon event occurred from~8.38–8.06 ka B.P,lasting for about 320 years,with a double valley structure.The 9.2 ka B.P.event occurred in about 9.33–9.06 ka B.P.and lasted for about 270 years,characterized by a single valley structure.The monsoon declining and regional drying during the 8.2 ka B.P.event (with an amplitude of~0.88‰in δ^(18)O and ~1.42‰in δ^(13)C) are more severe than those during the 9.2 ka B.P.events (with an amplitude of ~0.44‰in δ^(18)O and~1.18‰inδ^(13)C).The comparison between the YQ18 records and the climate records in the northern high latitudes supports the view that the freshwater injections in the North Atlantic weakened the Atlantic Meridional Overturning Circulation,resulting in southward shifts in the Intertropical Convergence Zone by changing the interhemispheric temperature gradient and weakening the EASM.The two freshwater injections in the North Atlantic play an important role in the double valley structure of the 8.2 ka B.P.event.Meanwhile,the large-scale freshwater injection and volcanic eruptions likely strengthened and prolonged the 8.2 ka B.P.event.Therefore,this study highlights the sensitive response of the EASM to external forcing and internal climate variability,providing important references for understanding monsoon anomalies under contemporary anthropogenic influences.
基金
supported by the National Key Research and Development Program of China(2023YFF0804704)
the National Natural Science Foundation of China(Grant Nos.41931178 & 42071105)。
