Stalagmite Records Of Climate Change In China During Different Interglacial Periods

The Asian monsoon region is densely populated,and change in the Asian summer monsoon intensity affects greatly social and economic developments.In order to understand the current marine isotope stage 1(MIS1)and the evolution process of the future Asian summer monsoon,the evolution characteristics of Asian summer monsoon in other interglacial periods need to be further compared.Based on the published records of?¹⁸O stalagmites in the interglacial period,the study will discuss the characteristics of Asian summer monsoon changes in different glacial periods,and draw the following conclusions based on the important findings of academic circles(1)The change trend of the records of?¹⁸O in China with different longitude and latitude is analyzed.It is found that the variation rhythm of them is similar,which indicates that the stalagmite?¹⁸O can indicate the effectiveness of large-scale climate change.In order to verify the influence of Indian Ocean and Pacific water vapor on the records of stalagmite?¹⁸O,13 stalagmites?¹⁸O records were selected from 12caves in Asian monsoon region.The standardized records of stalagmites?¹⁸O and were synthesized by interpolation and normalization of 30a software in sequence by past 3.0 and Origin 8.0,and the standardized records of?¹⁸O were synthesized on average.?¹⁸O_EASMand?¹⁸O_ISMwere negatively synchronous in the early stage of MIS1.It is believed that the records of stalagmites?¹⁸O in East Asia monsoon region and Indian monsoon region were in response to the changes of solar radiation and ice cover melting gradually,which supported the mainstream understanding that the records of stalagmite?¹⁸O indicate the overall intensity change of Asian summer monsoon at the sub orbital scale.In addition,the trend and period analysis of?¹⁸O records of three high-quality stalagmites in Indian and East Asian monsoon regions during the appropriate period of MIS1 climate(8-6ka BP)are analyzed.EMD(empirical mode)is used to analyze the trend and period of?¹⁸O records The results of empirical mode decomposition show that all these records have?12a,30a,60A,?110a,?200a,?530a and?1000a cycles,which are similar to the solar activity change period,suggesting the direct influence of external driving of solar activity on Asian monsoon.(2)The following similar periods exist in the records of high resolution stalagmites?¹⁸O in East Asian monsoon region during the period of MIS1,MIS5e and MIS11c:30a,?60a,?140a,?280a,?600a,?1200a and?3000a.The intrinsic module function components(IMF components)of each stalagmite?¹⁸O record representing different time scale signals are superimposed in chronological,Centennial and Millennium scales,and the characteristics of Asian summer monsoon changes in these time scales can be analyzed.The results show that the oscillation amplitude of?¹⁸O_MIS1and?¹⁸O_MIS5eis similar on the intergenerational scale,all of which are concentrated near±0.4‰,while?¹⁸O_MIS11cis recorded near±0.2‰.This shows that the Asian summer monsoon in MIS11c is more stable on the inter decadal scale;on the Centennial scale,the?¹⁸O_MIS1and?¹⁸O_MIS11crecords keep the trend of dense and dense oscillation,The significant characteristic of?¹⁸O_MIS5erecording is that the amplitude of oscillation decreases gradually;on the Millennium scale,the oscillation frequency of?¹⁸O_MIS5eis different from that of?¹⁸O_MIS1and?¹⁸O_MIS11c.The above analysis shows that there may be differences in the evolution of Asian Summer Monsoon on the Centennial Millennium scale.The results show that 17 times of positive summer monsoon events with positive amplitude of more than 0.4‰(Holocene bond event amplitude)are identified in the records of the stalagmites?¹⁸O in MIS11c,while in MIS5e,the results show that 17 times of positive amplitude are more than 0.4‰(Holocene bond event amplitude)The amplitude and frequency of oscillation recorded by?¹⁸O are different from that of MIS1 and MIS11c.It is further proved that bond like events in MIS5e have not occurred.(3)The MIS11c interglacial period is considered to be an important analogy period for studying the future climate evolution of MIS1 due to its similar orbital parameters to that of MIS1.Scholars have found that there are similar summer monsoon anomaly events in the late MIS11c and MIS1,indicating that the two phases may have similar monsoon evolution rhythms.In this paper the stalagmite record of MIS11 time cycle analysis,The results of EMD show that there are?35a,?80a,?150a,?340a,?600a,?1200a and?2800a cycles,similar to many MIS1 cycle,which indicates that the evolution history of summer monsoon in MIS11c period may provide reference for the evolution of summer monsoon in the future.It means that under natural conditions,the future Asian summer monsoon may be expected to be in the future Enter the weakening phase.