末次间冰期东亚季风气候不稳定的神农架洞穴石笋记录

Climate Variability in Shennongjia During the Last Interglacial Inferred from a High-resolution Stalagmite Record

基于神农架永兴洞石笋(YX21)4个230Th年龄和303个δ18O测试数据,建立了东亚季风末次间冰期持续时间约2ka(127.32±1.23～124.95±1.16kaBP)的洞穴石笋高分辨率δ18O的时间序列。该洞穴末次间冰期δ18O变化曲线表现出高频振荡特征,表明东亚季风末次间冰期降水的不稳定性,并识别出该时段4个季风冷事件,这种冷事件可能与北大西洋冰漂碎屑事件有关。谱分析结果显示百年和十年际尺度的季风降水变化响应于太阳活动周期。

Speleothem studies have the potential to considerably improve our knowledge of climate changes of the past 500 000 a. Above all, this is due to the independent and reliable calendar year chronology provided by uranium-series dating techniques and to the multitude of paleoclimate proxy records preserved in speleothems. Here we present an absolute-dated and high-resolution stable oxygen record from a stalagmite （ No. YX21 ） in Yongxing Cave, Shennongjia natural reservation, central China, giving the details on climatic fluctuations during the Last Interglacial periods. Based on 4 ^230Th dates and 303 oxygen isotope data, an averaged 8 a East Asian Monsoon precipitation series was established through 127.32 to 124.95 thousand years before present （ ka BP）. This detailed record uncovered that the δ^18O have the high-frequency variability characteristic, indicating the instability of the East Asian Monsoon during the Last Interglacial. During this interval, the YX21 record has 4 Asian Monsoon weak events, possibly related to the in- terglacial ice-rafting events in the North Atlantic. Power spectral analysis of the record shows statistically significant periodicities centered on 661 a, 127 a, 118 a, 19 -22 a. These periodicities are close to significant periods of the δ^14C record, indicates that solar changes are also responsible for changes of Asian Monsoon intensity.