A Stalagmite Record Of The Evolution Of The Holocene Asian Summer Monsoon In Luoshuidong, Hubei

The millennial-scale oscillations of the Holocene have been focused by climatologists.However,records of the Holocene climate events have different characteristics.Based on 27 precise 230Th dates and 1086 oxygen and carbon isotope datas from a stalagmite from Luoshui cave,Hubei province of China,we reconstructed changes of the Asian monsoon in the Holocene.LS21 ?18O values range from-6.8‰ to-9.5‰,with a mean of-8.3‰.The temporal resolution is 11 yr.An agreement between the Asian monsoon and the Northern Hemisphere 65°N summer insolation indicates that Holocene Asian monsoon broadly follows Northern Hemisphere summer insolation on orbital scale.Between 9800 and 9200 yr BP,the weak monsoon event surrounding "9200 yr BP" was clearly recorded in the LS21 ?18O,with an amplitude of about 1.29‰.Between 9800 and 9600 yr BP,the Asian monsoon strength weakened slowly.Between 9300 and 9200 yr BP,the monsoon strengthened rapidly.The entire event shows an asymmetric structure,with a "W" in the 5180 profile.Comparatively,this event has a longer onset but a shorter end.At the same time,we find that the "9200 yr BP" weak monsoon event is a global phenomenon,based on the combination of the ice core,abyssal deposit,lacustrine records.This is likely due to changes of the solar activity and Atlantic Meridional Overturning Circulation(AMOC).Solar activity influenced the hydrologic cycle in the low latitudes directly.At the same time,the input of the fresh water resulted the southward migration of the Intertropical Convergence Zone(ITCZ)indirectly.Several Bond events of the Holocene,e.g.8200 yr BP event,7200 yr BP event,4200 yr BP event and 2800 yr BP event,in LS21 record have the depositional hiatuses.The climate of the mid-late Holocene changed from humid to cold and dry.When compared with Sanbao cave records in the interglacial periods,we find that abrupt climate change occurred in other geologic time,such as MIS5.When compared with other records,we find that atmospheric circulation recombination could be associated with ocean-atmosphere coupling,i.e.,the ENSO and AMOC.In the late Holocene,LS21 ?18O sequence and solar proxies show a common cycle of 200 yr,indicating that solar activity plays an important role in Asian monsoon changes.The weak Asian monsoon between 2100 and 2550 yr BP is consistent with the tumultuous Spring and Autumn period.This suggests a relationship between climate changes and the development of the society.