近2000年来东亚夏季风石笋记录及与历史变迁的关系

基于湖北神农架犀牛洞石笋(SN)21个230Th年龄及486个δ18O数据,建立了近2 000年来平均分辨率4~5 a的δ18O时间序列。该记录显示,近两千多年来东亚夏季风强度总体呈逐步减弱趋势,并叠加数次数十年到百年尺度的振荡旋回,中世纪暖期及小冰期显示独特特征。石笋δ18O曲线与北半球(33°N)太阳辐射曲线一致,揭示了近2 000 a来亚洲季风变化主要受控于太阳辐射的变化。通过与历史气候记录对比发现,汉朝和唐朝对应δ18O偏负即相对稳定的气候阶段,而三国、两晋、南北朝、宋朝及明朝均对应于正偏且波动较大的δ18O值,存在旱涝灾害频繁交替现象,说明朝代的兴衰更替在一定程度上和气候变化存在某种联系。

A STALAGMITE-RECORD OF EAST ASIAN SUMMER MONSOON IN THE LAST 2000 YEARS AND ITS CORRELATION WITH HISTORICAL RECORDS

A 4-5 year resolution oxygen isotope record based on 21230Th dates and 486 oxygen isotope data from a 236-mm-long stalagmite, which was collected from Xi-niu Cave in Shengnongjia, Hubei Province, provides a detailed history of the East Asian Summer Monsoon (EASM) during the past 2000 years. Our δ18O sequence reveals that EASM intensity gradually weakened in the last 2000 years, superimposed by numerous decades or century-scale aridity/moisture oscillations, showing a characteristics of the typical Medieval Warming Period and Little Ice Age. The δ18O record generally correlates well with the summer insolation at 33°N, indicating that the long-term trend of the EASM is likely modulated by summer insolation. A comparison with history literatures shows that periods of constant negative δ18O values (stable moisture periods) occur during the Han and Tang Dynasties, while intervals of positive yet large oscillation in δ18O values (aridity and abrupt monsoon variability) correspond to the War Era, Song and Ming Dynasties, indicating frequent plagues of aridity/flood. This relationship suggests a clear link between climate change and the demise of these dynasties, and climate variability probably played an important role in Culture evolution.