Details Of The Asian Monsoon Abrupt Change Recorded By Stalagmites In MIS 5/4

Millennial-scale abrupt climate oscillations during the last interglacial caused a series of changes in the Earth's environments.Detection of internal structures of these climate events has important theoretical significance and is of potentially practical value.Here we present a composite and thus a continuous summer monsoon record during last interglacial period to last glacial period from Wulu Cave,southern China,constrained by 27 U/Th dates and 1905 isotopic subsamples.The duplication between Wulu and other cave records can reflect changes in the Asian summer monsoon(ASM)intensity over broad regions.Moreover,these millennial-scale ASM variations correspond to changes in Greenland temperature,indicating that the ASM is closely related to northern high-latitude climates.At the end of of CIS(Chinese Interstadial,CIS)21 and CIS 20,?18O values decrease abruptly following a centennial weak monsoon interval(WMI),referred to a rebound-type event.These events are also observed in NGRIP ?18O and low-latitude marine sediment record from Cariaco Basin and Arabian Sea,illustrating a tight link between high-and low-latitude climates and a persistently northerly positioned of intertropical convergence zone(ITCZ)and strong Indian summer monsoon.Additionally,a linear link can be found between the duration of the WMI and the amplitude of rebound event.This structure of ASM variability is consistent with Greenland temperature changes.The longer WMI at the end of CIS 21 and a higher amplitude of the subsequent rebound event further indicates that ice sheet expansion may become an amplifier for climate abrupt events.Therefore,the occurrence of monsoon enhancement at the end of CIS(rebound event)is the result of the interaction of tropical hydrothermal conditions with sea ice.Additionally,our high-resolution ?18O records show that three centennial-scale minor ASM oscillations are evident during the CS 20.These weaker ASM intensification events are similar to,regarding the amplitude and duration,the rebound events.Furthermore,three peaks of volcanic-associated trace elements significantly precede or postdate CS 20.It implicates that the weak ASM during 72 kyr BP is probably uninfluenced by the Toba eruption.Other climatically-related indicators of trace element ratio,combined with the ?S13C record,provide strong evidence for a persistent wetting condition between 78.5 and 72.0 kyr BP.Surrounding 72 kyr BP,climate background conditions,including a decline of northern summer insolation and global sea level,an increase of ice-sheet and sea-ice,might favor the ASM weakening.At the same time,a southern warming can be observed,and the sea surface temperature within the mid to low latitudes did not significantly decrease.Therefore,these observations suggest that summer insolation changes and internal feedbacks within the climate system,i.e.,ITCZ shifts,are probably a forcing factor for weak ASM during 72 kyr BP,so the Toba eruption is not a direct reason.The increase in monsoon intensity within the CS 20 is most likely due to the interaction of air-sea interaction under the strong hydrothermal activity of tropical and subtropical oceans.