A high-resolution environmental change record since 19 cal ka BP in Pumoyum Co,southern Tibet |
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Authors: | XinMiao Lü LiPing Zhu Mitsugu Nishimura Yoshimune Morita Takahiro Watanabe Toshio Nakamura Yong Wang |
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Institution: | (1) Institute of Tibetan Plateau Research, Chinese Academy of Sciences, No. 18 Shuangqing Road, 100085 Beijing, People’s Republic of China;(2) Science in China Press, 100717 Beijing, People’s Republic of China;(3) School of Marine Sciences and Technology, Tokai University, Shimizu, Shizuoka 424-0902, Japan;(4) Center for Chronological Research, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan;(5) Graduate School of Science, Tohoku University, 6-3 Aramaki Aza Aoba, Aoba-ku, Sendai 980-8578, Japan; |
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Abstract: | A 380-cm-long sediment core was acquired from the deep water area of Pumoyum Co, southern Tibet. Twenty-five plant residue
samples were selected, and organic carbon stable isotopes were obtained using the AMS 14C chronological method. The 14C age and carbon reservoir effect were calibrated with surface sedimentation rate measurements using 210Pb dating. Results showed that the core sediment deposited over 19 cal ka BP. Based on a multi-proxy analysis of TOC and IC
contents, grain size and pollen assemblage data, the palaeoclimatic evolution of Pumoyum Co was reconstructed since the last
glacial. Pumoyum Co was a shallow lake prior to 16.2 cal ka BP; although the glacier around the lake began to melt due to
increasing temperatures, climate was still cold and dry. In the interval of 16.2–11.8 cal ka BP, the sedimentary environment
fluctuated drastically and frequently. Two cold-events occurred at 14.2 and 11.8 cal ka BP, and these may correspond to the
Older Dryas and the Younger Dryas events, respectively. After 11.8 cal ka BP, Pumoyun Co developed into the deep lake as it
is now. The lake water temperature was relatively lower at that time because of influx of cold water from glacial meltwater
entering the lake. As a result, the multi-proxy indicators showed no sign of warm conditions. Comparisons between the sedimentary
record of Pumoyum Co with that of other lakes of the same age in southern Tibet indicate a warmer climate following the last
deglaciation influenced the southeastern Tibetan Plateau. These results imply that the southwest Asian monsoon gradually became
stronger since the deglaciation during its expansion to the inner plateau. The glacial-supplied water of the lake responded
sensitively to cold-events. The entire southern Tibet region was dominantly influenced climatically by the southwest Asian
monsoon during the Holocene. |
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Keywords: | Tibet Pumoyum Co lake sedimentation environmental change high resolution glacial meltwater |
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