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
The rainfall changes in East Asian summer monsoon(EASM)regions on the orbital timescale remain controversial due to the lack of reliable rainfall records.Here,we present new multiproxy records(δ^(18)O,δ^(13)C,Sr/Ca ...The rainfall changes in East Asian summer monsoon(EASM)regions on the orbital timescale remain controversial due to the lack of reliable rainfall records.Here,we present new multiproxy records(δ^(18)O,δ^(13)C,Sr/Ca and Mg/Ca)of a230Thdated stalagmite from Hulu Cave in central eastern China.Multiproxy records reconstruct a regional hydroclimate history from 340 to 261 kyr BP(thousand years before present),approximately covering the antepenultimate glacial period.Theδ^(18)O record is dominated by the precessional cycles,suggesting that EASM responds to changes in Northern Hemisphere summer insolation(NHSI)on the orbital timescale.Significant correlations amongst theδ^(13)C,Sr/Ca and Mg/Ca suggest that a common factor,i.e.,the local hydrological cycle,controlled their variability,and their leading principal component can be used as a proxy linked to regional rainfall.This composite record bears a good similarity to those from the Chinese Loess Plateau,showing a gradually decreasing rainfall during the antepenultimate glacial period,consistent with changes in global ice volume.Superimposed on the long-term trend,three relative wetter intervals were responding to the higher NHSI periods,suggesting that EASM rainfall variability was induced by integrated effects of global ice volume and NHSI.The increased ice sheets and lower NHSI resulted in an increased meridional temperature gradient and southward shift of the westerlies,which shortened the duration of Meiyu and midsummer rainfall.The differences between the rainfall record and the stalagmiteδ^(18)O record indicate that the latter represents the overall EASM intensity linked to monsoon circulation,but does not directly reflect the rainfall changes at the cave sites.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.
基金supported by the National Nature Science Fundation of China(Grant Nos.42002200&42071105)the Open Fund for the State Key Laboratory of Loess and Quaternary Geology(Grant No.SKLLQG1922)+1 种基金the Science and Technology Research Program of Chongqing Municipal Education Commission(Grant No.KJQN201900536)the Chongqing Nature Science Fund(Grant No.cstc2020jcyj-msxm X0598)。
文摘The rainfall changes in East Asian summer monsoon(EASM)regions on the orbital timescale remain controversial due to the lack of reliable rainfall records.Here,we present new multiproxy records(δ^(18)O,δ^(13)C,Sr/Ca and Mg/Ca)of a230Thdated stalagmite from Hulu Cave in central eastern China.Multiproxy records reconstruct a regional hydroclimate history from 340 to 261 kyr BP(thousand years before present),approximately covering the antepenultimate glacial period.Theδ^(18)O record is dominated by the precessional cycles,suggesting that EASM responds to changes in Northern Hemisphere summer insolation(NHSI)on the orbital timescale.Significant correlations amongst theδ^(13)C,Sr/Ca and Mg/Ca suggest that a common factor,i.e.,the local hydrological cycle,controlled their variability,and their leading principal component can be used as a proxy linked to regional rainfall.This composite record bears a good similarity to those from the Chinese Loess Plateau,showing a gradually decreasing rainfall during the antepenultimate glacial period,consistent with changes in global ice volume.Superimposed on the long-term trend,three relative wetter intervals were responding to the higher NHSI periods,suggesting that EASM rainfall variability was induced by integrated effects of global ice volume and NHSI.The increased ice sheets and lower NHSI resulted in an increased meridional temperature gradient and southward shift of the westerlies,which shortened the duration of Meiyu and midsummer rainfall.The differences between the rainfall record and the stalagmiteδ^(18)O record indicate that the latter represents the overall EASM intensity linked to monsoon circulation,but does not directly reflect the rainfall changes at the cave sites.
