Paper No. 110-8
Presentation Time: 10:25 AM
THE SPELEOTHEM RECORDS FROM ASIAN SUMMER MONSOON MARGINAL ZONE AND THEIR CLIMATIC IMPLICATIONS
CAI, Yanjun1, AN, Zhisheng1, EDWARDS, R. Lawrence2, CHENG, Hai3, FUNG, Inez4, TAN, Liangcheng1, WANG, Xianfeng5 and ZHANG, Haiwei6, (1)State Key Lab of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an, 710075, China, (2)Department of Earth Sciences, University of Minnesota, 310 Pillsbury Dr. SE, Minneapolis, MN 55455, (3)Institute of Global Environmental Change, Xi’an Jiaotong University, Xi'an, 710075, China, (4)Earth and Planetary Science, University of California, UC Berkeley, 307 McCone Hall, Berkeley, CA 94720-4768, (5)Earth Observatory of Singapore, Nanyang Technological University, Singapore, 639798, Singapore, (6)Institute of Global Environmental Change, Xi’an Jiaotong University, Xi'an, 710075, China; State Key Lab of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an, 710075, China, yanjun_cai@ieecas.cn
The Asian continent can be subdivided into three distinct environmental regions according to the annual precipitation: 1) relatively wet and humid southeastern region with greater than 400mm annual precipitation; 2) arid northwestern inland region with less than 200 mm annual precipitation; 3) an intermediate semi-arid belt with annual precipitation of 200-400mm, which we defined as the marginal zone of Asian summer monsoon (ASM). Modern observations and model analysis have shown that the summer precipitation in the marginal zone of ASM, which amounts to more than 70% of annual precipitation, is dominated by the ASM intensity, i.e., strengthened ASM, increased precipitation in this region. Therefore, the marginal zone of ASM is ideal for studying the ASM changes.
Here, we present the speleothem records obtained from five caves (Qiongguo, Tianmen, Xiaosumang, Xiannv and Yixi caves) that are located in or very close to the marginal zone of ASM. The U-Th dates and also the δ18O records obtained from the speleothem in these caves indicate that all the stalagmites deposited during the interglacial periods, largely during the northern hemisphere high insolation intervals, suggesting that dry and/or cold climate and much less precipitation during the glacial periods on the one hand, and significantly increased precipitation and /or warm climate during the interglacial northern hemisphere high insolation intervals on the other hand. Compared with the East Asian summer monsoon changes, reflected by the δ13C of loess carbonate from the western Chinese Loess Plateau, the speleothem growth periods correlate well with the periods of enhanced East Asian summer monsoon. It suggests that the glacial-interglacial variability of Asian summer monsoon was also recorded in the speleothem and reconciles the discrepancy between speleothem and loess records from East Asia.
The discontinuous calcite δ18O records attained from these five caves show much similarities to the Hulu-Dongge-Sanbao record on precessional and millennial time scales, further confirming that the speleothem calcite δ18O can be used as a proxy index of ASM intensity on these two time-scales, and the hypothesis that ASM dominantly and directly to the northern hemisphere insolation.
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