Monitoring Of Atmospheric Precipitation Isotope And Modern Stalagmite Deposition In Xiaoling Tomb Of Ming Dynasty In Nanjing Area

Speleothems,which can provide long,continuous and commonly well-preserved record,can be accurately dated,and have been recognized as important archives of many climate proxies（including stable isotope,trace element,luminescent and optical banding）,especially in the East Asian Monsoon domain.However,researches focus mostly on the climate changes on the centennial to millennial timescales,leading to a scarcity on the seasonal-scale-resolution speleothem records.Among the applicable proxies,stable oxygen-isotope(δ¹⁸O)is the most widely used speleothem-based proxy,which encounters hot debates these years and urgently needs the support from modern monitering results.To improve the understanding ofδ¹⁸O signals transmitting from the atmosphere to the secondary calcite deposition,I first study the significance ofδ¹⁸O in precipitation event and monthly precipitation in Nanjing with rainfall monitering from January 2015 to December 2019,accompanied with data from GNIP during June 1987and December 1992.Then I use modern speleothem collected under Ming Castle at Xiaoling Mausoleum to examine the response of theδ¹⁸O in secondary calcite to precipitationδ¹⁸O.Speleothemδ¹⁸O in this study inherit mainly the rainfall signals.I discuss the chateractics and factors of theδ¹⁸O values in Nanjing precipitation,under control of the East Asian Summer Monsoon.The following are three main results:1)Based on the speleothem oxygen isotope theory and isotopic geochemistry theory,combined with the relationship between Asian Monsoon and moisture transport/rain-belt movement,I analyze the climatic indicator ofδ¹⁸O on seasonal timescales.It turns out that speleothemδ¹⁸O from Asian monsoon areas is mainly controlled by the changes in the moisture sources of precipitation.2)By utilizing the modern monitering on speleothem,it is confirmed that speleothemδ¹⁸O can faithfully document the isotopic signals in precipitation event.Cyclic change ofδ¹⁸O signal can be used as a chronological maker,which might be a good application of chronology to a modern speleothem.3)With the application of backward trajectory analysis,I suggest that either on the daily or the monthly scale,precipitationδ¹⁸O is able to represent the complex changes in water vapor sources.