全新世发生了一系列的亚洲季风突变事件,其中距今9.2 ka的弱季风事件较少受到关注,其存在与否以及成因机制仍然存在争议.本文利用通用地球系统模式(Community Earth System Model,CESM)进行全新世以来瞬变积分气候模拟试验得到的结果(Nanjing Normal University-12ka,NNU-12ka)对比重建资料和国际上已完成的过去 21 ka 以来的瞬变积分模拟试验(Transient Climate Evolution over the last 21000 years,TraCE-21ka),探究了 9.2 ka亚洲弱季风事件的时空特征及其成因.结果表明:NNU-12ka太阳活动敏感性试验模拟出了 9.6～9.4ka前后的亚洲弱季风事件,此时总太阳辐射减少了 0.38 W m-2,亚洲季风区夏季平均降水减少了 0.17 mmd-1.而基于TraCE-21ka的全强迫试验结果表明,冰川融水和冰盖变化对该时期亚洲季风变化没有显著影响.NNU-12ka太阳活动试验中亚洲热带季风区夏季降水减少尤为明显,在我国东北地区降水略有增加.热带季风减弱的原因是由于太阳辐射的骤降导致亚洲海陆热力梯度减弱,加强亚洲陆地的海平面气压,引起热带季风区的异常下沉运动,抑制水汽向亚洲季风区输送,进而通过动力作用减弱季风.
Simulation of the 9.2-ka BP Weak Asian Summer Monsoon Event
A series of abrupt Asian monsoon events occurred in the Holocene epoch.One such event,a weak monsoon event that took place approximately 9.2 ka ago,has received less attention,and its existence,as well as its underlying genetic mechanisms,remain subjects of debate.In this paper,we present the results(Nanjing Normal University-12ka;NNU-12ka)obtained from a Holocene transient integrated climate simulation test using the Community Earth System Model.We compared the reconstruction data with the Transient Climate Evolution over the last 21000 years(TraCE-21ka)to explore the spatial and temporal characteristics of the 9.2-ka Asian weak monsoon event and understand its causes.Our primary findings are the following:The solar activity sensitivity test of NNU-12ka reveals a weak Asian monsoon event around 9.6-9.4 ka.During this period,total solar radiation decreased by 0.38 W m 2,resulting in average summer precipitation in the Asian monsoon region decreasing by 0.17 mm per day.However,our comprehensive forcing test based on TraCE-21ka indicates that glacier meltwater and changes in ice cover did not significantly affect the Asian monsoon during this period.In the NNU-12ka solar activity test,summer precipitation in the Asian tropical monsoon region decreased significantly,while precipitation in Northeast China increased slightly.The weakening of the tropical monsoon is attributed to a sudden drop in solar radiation,which reduced the temperature difference between the land and sea.This led to an increase in Asia's sea-level pressure,causing abnormal subsidence in the tropical monsoon region.Consequently,the transmission of water vapor to the Asian monsoon region was suppressed,resulting in a weakened monsoon through a dynamic process.
Asian monsoonAbrupt eventEarth system modelSolar activityHolocene
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