全新世早期弱夏季风事件的精确定位及机制探讨--以湖南莲花洞LHD5石笋为例

全新世早期是太阳辐射加强、全球温度上升,并伴随着冰盖消融的重要时期,而其间发生的冷事件以及亚洲季风区的弱夏季风事件的成因一直是全新世早期研究的重点。对亚洲季风-海洋-极地联系研究有着重要的意义。通过分析湖南莲花洞LHD5石笋28个U/Th年龄和535个氧同位素数据重建了全新世亚洲季风演化特征,其中全新世早期分辨率达8年。LHD5石笋记录到YD结束时间为11748±30 a B.P.,全新世开始于11684±39 a B.P.,转换时间约为64年,与格陵兰gicc05记录在误差范围内一致。LHD5石笋记录到全新世早期6次弱夏季风事件,事件年龄中心点分别为11461±34 a B.P.、10354±36 a B.P.、9957±25 a B.P.、9062±36 a B.P.、8744±23 a B.P.、8144±24 a B.P.,其δ18O值的波动幅度分别为1.08‰、0.94‰、0.66‰、0.90‰、0.55‰、1.02‰,这些弱季风事件在亚洲季风区具有普遍的区域意义。除8.2 ka事件之外,10 ka B.P.之前的弱季风事件除了受到太阳活动的影响,还受到北大西洋IRD事件的影响,而之后更多地受到太阳活动和ITCZ南移的影响。

Discussion about the Mechanism of the Weak Summer Monsoon Events during the Early Holocence: A case study of precisely dated stalagmite record from Lianhua Cave,Hunan province,China

The Early Holocene is an important period of Solar radiation strengthening, global warming and along with ice sheets melting. The cause of the colder events and the weaker summer monsoon in the Asian monsoon region during the Early Holocene has always been the focus of research. It has important significance for the study of the links among the Asian monsoon, ocean and polar regions. Based on 28 U/Th dates and 535 oxygen isotopic data of stalagmite LHD5 from Lianhua Cave, Hunan province, China, a Holocene Asian monsoon evolution record was reconstructed, and the average resolution is 8 year in the Early Holocene. From the LHD5 stalagmite record, the end of Younger Dryas was at 11748±30 a B.P., the start of the Holocene was at 11684±39 a B.P., and the conversion time is about 64 years, which is consistent with the records of the gicc05 ice core from Greenland in the error range. The central age of the six weak summer monsoon events were at 11461±34 a B.P.(1.08‰), 10354±36 a B.P.(0.94‰), 9957±25 a B.P.(0.66‰), 9062±36 a B.P.(0.90‰), 8744±23 a B.P.(0.55‰) and 8144±24 a B.P.(1.02‰) in the record of the stalagmite LHD5 during the Early Holocene, respectively. These weaker summer monsoon events in the Asian monsoon region have a common regional significance. In addition to the 8.2 ka event, the weaker summer monsoon events before 10 ka B.P. were not only affected by the summer insolation but also by the ice-rafted debris (IRD) events in the North Atlantic, but the following weak summer monsoon events were mostly influenced by solar activity and the southward migration of the mean position of the Inter-Tropical Convergence Zone.