EAST ASIAN MONSOON CLIMATE DURING THE LATE PENULTIMATE GLACIATION BASED ON STALAGMITE RECORDS
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摘要: 基于南京洞穴2支石笋的11个230Th年龄、658个氧碳同位素分析数据,建立了倒数第二次冰期晚期(155~128 kaBP)东亚季风高分辨率的气候演化序列。在岁差尺度上,石笋δ18O记录与65°N夏季太阳辐射量曲线变化基本一致,说明北纬夏季太阳辐射对该地区气候演变起宏观调控作用。石笋δ18O变化曲线千年尺度上显示了8个明显的峰谷变化,δ18O值平均变幅约为1.5‰,平均频率在2 ka左右,十分类似于末次冰期东亚季风Dansgaard-Oeschger旋回,说明东亚季风气候在末次冰期的千年级不稳定波动也可能存在于更久远的冰期过程中,冰期气候的不稳定性很可能是第四纪冰盖、大尺度海洋/大气环流共同作用的结果。Abstract: Two stalagmites are from Hulu cave, which is 1 600 m above sea level (ASL) in Nanjing. 11 sub-samples are dated by Finnigan MAT 262-RPQ at the Isotope Laboratory of Geology and Geophysics Department, Minnesota University, USA, and all 230Th ages are in stratigraphic order. The results provided a high-resolution paleoclimate record for East Asian monsoon area during a time interval from 155 to 128 kaBP of the penultimate glaciation.In order to check reliability of the stalagmite δ18O record, we compared δ18O records of these two stalagmites, for both grew contemporaneously during a time interval from 154.5 to 133 kaBP. The general replication of δ18O values of contemporaneous growth for 21.5 ka suggests fidelity of δ18O values as a proxy of paleoclimates.There were eight remarkable apexes in our stalagmite δ18O record, which show a mean shift of 1.5‰ in δ18O, lasting about 2ka, and a mean frequency of 2 ka. It bears a striking resemblance to D/O events during last glacial period in terms of structure and transition well expressed in the Hulu δ18O records. It is therefore likely that the dramatic climate fluctuation during the last glaciation may have occurred pervasively in the early glaciation time in Asian monsoon climates. Climate instability of glacial period may be also related to changes in the ice-sheets and tropical oceanic/atmospheric circulation.
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Key words:
- East Asian monsoon /
- stalagmite /
- the late penultimate glaciation /
- Nanjing
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