摘要
据湖北省神农架天鹅洞一支石笋11个230Th年龄和254个δ18O数据,建立了28.5～22.0kaB.P.同位素分辨率平均约30a的东亚季风气候变化序列。该石笋δ18O曲线与南京葫芦洞石笋记录在重叠时段基本一致,说明本区石笋δ18O反映了区域性东亚季风经向环流特征。在24.3kaB.P.左右,石笋δ18O明显正偏,持续时间近1ka,指示一次显著的弱夏季风事件,与北大西洋倒数第二次冰漂碎屑事件(Heinrich2)同步发生,可视为东亚季风气候对H2事件的响应。高分辨率的δ18O序列揭示了H2事件的内部结构特征:(1)事件发生的突变性,石笋δ18O记录指示事件发生时在100a内δ18O从-8.59‰迅速正偏为-6.75‰,振幅达1.84‰;(2)事件结束的渐变性,δ18O正偏到-6.75‰后便以阶梯状缓慢负偏到-8.86‰至事件结束,持续时间近900a。这一过程与末次盛冰期东亚季风气候H1事件表现的季风强弱转换方式基本一致,说明末次盛冰期东亚季风气候H型事件具有共同的内部结构特征。研究表明,末次盛冰期东亚季风气候H事件的突变可能受北大西洋驱动并经青藏高原冰川变化放大。
One stalagmite （SW4） was collected from Swan Cave situated at 1 600 m above sea level in Shennongjia area. Eleven sub-samples were dated by Finnigan MAT 262-RPQ type meter at the Isotope Laboratory of Geology and Geophysics Department, Minnesota University, USA, and 254 δ^18O data were conducted with MAT 253 mass spectrometer linked with automatic equipment at Isotope Lab, Nanjing Normal University. These results provide a 30-year-resolution paleoclimate record of East Asian monsoon during a time interval from 28.5 to 22. 0 ka B P of the Last Glacial Maximum. In order to check the reliability of stalagmite SW4 δ^18O record, it was compared with stalagmite MSD from Hulu Cave in Nanjing between 28.5 and 22.0 ka B P. The general replication of δ^18O values in this interval suggests that variations of the stalagmite δ^18O record from Swan Cave reflect large spatial changes in circulation strength of East Asian monsoon. There was a remarkable weak summer monsoon event at ～ 24.3 ka B P in our stalagmite δ^18O record, which, lasting about 1 ka, shows a conspicuous positive shift of 1.84‰ in δ^18O. It is believed that this event is the response of East Asian monsoon climates to ice-rafted events in the northern Atlantic. The comparability between stalagmite δ^18O record and the northern Atlantic deep-sea record indicates that there is a strong climatic tele-connection on millennial-century time scale between the East Asian monsoon and the North Atlantic atmospheric circulations. Our high resolution δ^18O record reveals a striking internal structure of Heinrich event 1, which shows an abrupt rise by - 8.59‰ to - 6. 75‰ within 100 years at initiation and a progressive drop by - 6. 75‰ to - 8.86‰ with 900 years at termination. Such a pattern is similar to Heinrich event 1 （H1） in term of the internal structure, which suggests a similar characteristic for Heinrich events during the Last Glacial Maximum. In this time interval, about half of the Qinghai-Xizang Plateau might be covered by snow and glaciers. Such a large glaciers may play a positive feedback in lowering temperature over the East Asian monsoon area. It is suggested that the pattern of Heinrich Events in East Asian monsoon during the Last Glacial Maximum might be driven by the North Atlantic circulation and amplified by the snow on the Qinghai-Xizang Plateau.
出处
《地球化学》
CAS
CSCD
北大核心
2006年第6期586-592,共7页
Geochimica
基金
国家杰出青年科学基金(40225007)
江苏省研究生创新计划项目
作者简介
陈仕涛（1974-），男，博士研究生、讲师，第四纪地质专业，主要从事全球变化与区域响应研究。通讯作者（Corrcsponding author）：CHEN Shi-tao，E-mail：chenshitao@njn．edu．cn，Tel：＋86-25-83598125
