The Evolution Of Asian Summer Monsoon During MIS5c-5b From A Stalagmite Record In Wanxiang Cave,China

The main purpose of the past global climate change research is to provide reference for the prediction and simulation of future related study.East Asian monsoon system,impacts the monsoon region humanity's livelihood and the agricultural development through the interaction of ocean-land-atmosphere,is an important branch of the global climate system.Especially,most of the population and agricultural areas in our country are distributed in the monsoon region,the amount of monsoon rainfall is related to all aspects of the national economy and people's livelihood.Hence,the intensity of monsoon forecast will be very urgent and necessary.Here,we present a 334mm-long stalagmite(WX05-41A)obtained from Wanxiang Cave,China(33°1 9?N,105°00?E,elevation?1200m a.s.l.),located near the northern limit of the East Asian summer monsoon(EASM).Over 800 oxygen isotopic measureUe1ts and 6 230Th ages characterize high-resolution record of the EASM variability from 104-92ka BP,which covers marine isotope stages MIS5c?5b.The results demonstrate that the EASM shows a trend of weakening during 104?92ka B.P.and the interstadial 23(IS23)falls within MIS5c at 103.1ka BP,may be linked to the maxima in summertime insolation at 65°N which occurred about 103 kyr ago.Comparison Wanxiang ?18O record with Shanbao?Kesang record shows that they exhibit a highly similar variation tendency during the study period.Hence,it seems reasonable that the fringe of the EASM was far northwest of its current position during the MIS5c,with above-mentioned 3 caves included within the region by the EASM at the time.Besides,the Wanxiang record is dominated by 23ka cycles that are synchronous within dating errors with summer insolation at 65°N,supporting the idea that EASM responds dominantly to changes in Northern Hemisphere summer insolation on orbital timescales.The MIS5c-5b paleomonsoon record from Wanxiang Cave also agree well with the ice core record of NGRIP?EDML(Antarctica)and stalagmite BT2 record(Brazil)on millennial timescales,but they show the obvious"see-saw" patterns in Northern and Southern hemisphere,which related to the southward of Intertropical Convergence Zone(ITCZ)and the reduction in North Atlantic Meridional Circulation(AMOC).Furthermore,Wanxiang Cave stalagmites recorded 3 EASM decline events occurred at106.5?101.5?87.5ka B.P.,respectively,which are all corresponding to the North Atlantic Ice Rafted Debris events,illustrates the fact that maybe Ice Rafted Debris triggered the millennial timescale D-O events.