研究全新世典型气候突变事件的内部结构及区域特征,有助于明晰季风气候突变事件的成因机制。通过对贵州七星洞石笋14个高精度^(230)Th定年和779个氧同位素数据的分析,重建了过去6380~2700 yr B.P.时段平均分辨率达4.7年的东亚夏季风演...研究全新世典型气候突变事件的内部结构及区域特征,有助于明晰季风气候突变事件的成因机制。通过对贵州七星洞石笋14个高精度^(230)Th定年和779个氧同位素数据的分析,重建了过去6380~2700 yr B.P.时段平均分辨率达4.7年的东亚夏季风演化序列。该石笋δ^(18)O值整体上呈逐渐偏正的特征,指示中晚全新世以来东亚夏季风持续变弱的趋势。叠加在此长期季风减弱变化趋势上,最为显著的百年尺度振荡主要发生在4548~3715 yr B.P.时段,对应于4.2 kyr B.P.事件。该记录与同区域董哥洞石笋δ^(18)O记录一致,均显示在此事件内部并非持续干旱,而是具有两次显著的季风强降雨期。相似的季风强降雨期在我国北方气候记录中也有体现。在更大的空间尺度上,这种4.2 kyr B.P.事件的内部结构特征与澳洲—印度尼西亚(澳—印)季风区的石笋记录结构相对应,但呈显著的反相位耦合关系,证实了亚洲与澳—印季风间的动力学联系。此外,该事件结构与ENSO记录的耦合暗示了4.2 kyr B.P.事件的发生可能与热带太平洋密切相关。展开更多
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 uncle...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.展开更多
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)。
文摘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.
