Variation Of Asian Monsoon Detail And Cave Karst Process Response Recorded By Stalagmite During DO24-23

Studies on the internal structure and driving mechanisms of abrupt climatic oscillations are conducive to prediction of future climate changes under similar backgrounds.In this study,23 U/Th ages,1643 sets of isotopes(?¹⁸O and?¹³C)and trace element data from two stalagmites from Wulu cave,Guizhou Province were analyzed,and thus detailed Asian summer monsoon(ASM)variability and karstic processes were reconstructed during Marine isotope stage 5.3(MIS 5.3).The results show that millennial-scale ASM changes,evidenced by spatially-separated cave records,are consistent with climate records from high and low latitudes.However,the monsoon intensity continued to rise in mid-DO 24,which was different from temperature variability at high north latitude.Moreover,in the stadial between DO 24and DO 23,the degree of ASM depression is much lower than temperature changes at the Greenland.In detail,a precursor event before the onset of DO 23,and a ASM drop in early DO 24 are reflected in other climate records,but with a lesser degree compared with Greenlandtemperature changes.This difference indicates that the driving force of the monsoon variation on millennium to centennial scales may source from high north latitude,but the evolution of ASM is different from Greenlandtemperature changes.The westerly jet may be an important link between the low latitude monsoon and the high north latitude climates.In the overlapping period,two?¹⁸O records from Wulu cave are similar,but the?¹³Crecords are different.On centennial scale,?¹⁸O and?¹³Crecords are coupled during the warm period,but decoupled in the cold period.In weak ASM periods,the climate is relatively cooling,which reduces the effective humidity in the soil.This may increase the effect of CO₂ degassing,leading to the decoupling between oxygen and carbon isotopes.When compared with trace element records(Mg/Ca,Sr/Ca and Ba/Ca),it reveals that strong ASM corresponds to negative?¹³C values,higher growth rate,higher ratios of Mg/Ca and Ba/Ca.At this time,higher temperature promotes vegetation development,resulting in a higher p CO₂ and larger Mg/Ca.The concentration of organic acids produced by microbial activity in the soil increases,which could dissolve more Ba from the bedrock and lead to a higher Ba/Ca ratio in the stalagmite.This relationship indicates that the soil CO₂production and karstic processes can simultaneously respond to climate change outside the cave.