Research Of The High Resolution Records Of Stalagmite Nsm03for Climate Change Of The Past500Years In The Three Gorges Region

The research of global climate change for past1000years, is one of the most important research content of the past global change research program(PAGES).The reconstruction of high-resolution climate records for nearly a thousand years has very important significance for understanding the evolution of the climate system,dealing with the current increasingly severe climate and environmental problems,predicting the future climate change.The LIA is an important climate change events for nearly a thousand years,which has important influence on human society and history. Research on the start-stop time and the internal structure characteristics of the climate change events, is controlled by the lack of high resolution and accurate dating of climate records, and its climatic driving factor has not yet been fully recognized. Compared with climate proxies as the loess, ice cores, tree-ring et al., stalagmite, with many advantages such as high resolution, suitable for230Th precise dating, fully storage of climatic and environmental information and so on, has become one of the most important development directions of the current research field.This paper is based on Chongqing Fengdu as the study area, which is the in the middle and upper reaches of Yangtze River and Asian monsoon significant effects there. The use of7230Th dating data and438stable oxygen and carbon isotope data of Stalagmite NSM03from shuiming Cave in Fengdu area to establishing stalagmite oxygen and carbon isotope time series of high resolution time period during AD1250-1750,combined with other stalagmite record which is belonging to the Asian monsoon region, analysis the responsible relationship between the stalagmite oxygen and carbon isotope, and with the result we analysis the beginning time of LIA, further more, we talk about the change of climate fluctuation in the inner LIA.The paper also takes use of the methods of operating ICP-MS and ICP-OES to analyze trace elements of stalagmites,by quantitative analysis and ratio analysis of7trace element come form89groups samples derived from stalagmite NSM03,the paper attempt to discuss the influencing mechanism of the trace elements and their significance for the climate.Finally, the paper use power spectrum analysis method and wavelet analysis method to analyze the data of stalagmite NSM03, by the outcome we simplely discuss the mechanism of the formation of LIA.With the work we could have the following conclusion:(1) The high resolution δ18O records of Shuiming Cave Stalagmite NSM03showing:climate change in the Three Gorges reservoir which Shuiming Cave located in, is basically the same as other areas in Asian monsoon region, the LIA begins from late thirteenth Century to early fourteenth Century in this study area;the weakening of the whole monsoon, precipitation decreases, temperature decrease within the LIA;the monsoon fluctuated frequently when in the little ice age maximum AD1400-1650, there is strengthening and weakening of the monsoon events in short time scale, such as monsoon short-term increase period in late sixteenth Century, stalagmite δ18O appears on the trend of soft, this result has been verified by tree-ring records of Bomi-Linzhi area.(2)The high resolution δ13C records of Shuiming Cave Stalagmite NSM03showing:the δ13C of Shuiming Cave Stalagmite NSM03, which record the Three Gorges Reservoir area vegetation change information over the past500years which indicated the climate and environment change indirectly, shows the beginning time of the LIA is about AD1300, and monsoon fluctuation its internal obviously, such as monsoon weakening period "the final stage of the yuan weak monsoon period" and "the final stage of the ming weak monsoon period" in mid fourteenth Century and late sixteenth Century. The changing trend of δ13C values are similar to δ18O of stalagmite NSM03, further indicated the climatic and environmental significance of stalagmite oxygen isotope.(3) The analysis of Ca, Mg, Ba, Sr, U, Ti, Mn7elements in Shuiming Cave Stalagmite NSM03shows:Sr/Ba, Mg/Ca, Ba/Ca and U/Ca showed a similar changing trend along with the variation of Asian monsoon in Stalagmite NSM03, the Asian monsoon enhanced, increased rainfall and temperature, reduced the Mg, Sr, Ba, U content in Stalagmite; and vice-versa. Changing curves of trace elements’ ratio have the same variation tendency with changing curves of the stalagmite NSM03’s stable oxygen and carbon isotope values, the compare results indicate that trace elements in stalagmite NSM03has a sensitive response for the environment and climate change of outside, they are the favorable information carrier for the research of climate change in LIA.(4) The record of power spectrum analysis and wavelet analysis results in stalagmite NSM03show that:the solar activity is the main driving mechanism of the LIA climate, the LIA is closely related to solar activity century cycle, but analysis from the shorter scale and higher frequency, couple events such as ENSO cycle, atmospheric oscillation may have an important influence to the LIA.