The Relationship Between Oxygen Isotope Composition And Water Vapor Sources In China

Reconstruction of the paleoenvironment has achieved a lot.However,different opinions about changes of oxygen isotope composition in stalagmite into changes of paleoenvironment are still maintained.Researches have shown that oxygen isotope of stalagmites in Chinese monsoonal region follows that of precipitation,which is connected with changes of the source of the vapor closely.To explore the relation between oxygen isotope composition of precipitation and the sources of vapor,this article analyses the oxygen isotope composition and the changes of vapor source for Heshang Cave,Wanxiang Cave,Shihua cave and Penglaixian Cave in 2012 to 2013 first,then analyses and discusses the relation between them with the principles of hypothesis testing,the results of which shows that oxygen isotope composition is closely connected with vapor source of precipitation of those caves.The oxygen isotope composition of Wanxiang Cave and Penglaixian Cave are controlled by vapor source.Oxygen isotope of Shihua Cave is controlled by the amount of precipitation and that of Heshang Cave is mainly dominated by changes vapor sources but other factors also play a role in it.To explore the relation further,this paper analyses the result of fitting,and found that coefficients of independent variables are the?¹⁸O of vapor brought by the corresponding type(or types)of air masses on its arrivals.Based on this and the comparisons of those coefficients,we can classify the precipitation of Wanxiang Cave,Heshang Cave and Penglaixian Cave.The Penglaixian Cave precipitation between 2012 and 2013consists of precipitation formed by oceanic water vapor with negative?¹⁸O carried by the air masses marked by Wp,Scs,and Mh,precipitation formed by water vapor which is from the evaporation of Chinese monsoon region carried by the Pw2 and Rw air masses,and precipitation formed by inland evaporation water vapor and Arctic water vapor,both of which is carried by Pw1 air masses.The precipitation of the Heshang Cave consists of the precipitation formed by the marine water vapor carried by the Wp and Scs air masses,precipitation formed by the inland evaporative water vapor carried by the Rw,Mh,and Pw2 air masses,and the precipitation formed by the local evaporative water vapor.The Wanxiang Cave precipitation consists of the precipitation formed by the marine water vapor carried by the Scs air masses,the local evaporative water vapor carried by the air masses marked by Pw2,Rw and Wp and the precipitation formed by the water vapor which is from the Arctic Ocean,Russia and Central Asia and carried by Pw1 and Mh air masses.The classification results above contain water vapor from the ocean,the central Asian interior and the Chinese monsoon region,and there are obvious differences between the coefficients of different water vapor types.In this paper,this similarity is considered to be the basis of the cooperative variation of oxygen isotope composition of stalagmites in the Chinese monsoon region.Although the above similarities exist among the models,the coefficients of various types of precipitation are different in different models.In this paper,we believe that this phenomenon is caused by the difference of water vapor sources transported by various air masses to different caves,and the difference between fractionation during transportation.The above two differences are determined by the geographical location of each cave.