过去3000年季风降水变化与突变事件的洞穴石笋记录对比

基于辽宁省暖和洞2支石笋6个230Th年龄与190个δ18O数据,建立了晚全新世3500～200a B.P.东亚季风降水序列。3个百年尺度的弱季风事件已被证实:2800-2600、1500-1200和400-200a B.P.,其与北大西洋冰漂碎屑事件在发生时间上具有较好的一致性。与内陆高精度、高分辨率石笋δ18O记录对比结果显示:1)轨道-千年尺度季风降水长期趋势变化相一致;2)百年-数十年尺度上季风降水具有明显的区域性,如距今1200-500 a B.P.,东北地区降水逐渐增加,西部干旱-半干旱地区降水逐渐减少,长江中下游以及南方地区降水变化趋势不明显。太阳活动与北大西洋气候波动可能对百年尺度东亚夏季风的强弱变化施加了重要影响。

Summer monsoon precipitation variations and abrupt climate events during the 3000 years:records from stalagmites in China

We developed a composite oxygen isotopic record of cave calcite for the last 3500 years based on two stalagmites from the Nuanhe Cave in eastern Liaoning province,northeastern China. Replication of the stalagmite δ18O from several caves in all contemporaneous growth intervals shows the kinetic fractionation was negligible and the δ18O shifts were primarily caused by regional climate change.We interpreted our record in terms of meteoric precipitation changes,hence the variability of East Asian Monsoon intensity.Three internals of low precipitation were inferred in 2800-2600 y B.P.,1500-1200y B.P.and 400-200 y B.P.,which correlated well with North Atlantic drift ice events.A comparison with other high-resolution and high-precise speleothem records from different climate regions indicates:(1) On orbital-millennial scale it indeed displayed similar long-trend change of monsoon precipitation.(2) However,regional differences in monsoon precipitation occurred along the latitudinal transect from 25°N to 41°N on centennial-to decadal-scale.For example,summer monsoon precipitation in the northeastern and northern China increased gradually during the 9-16th centuries,and oppose trends were found in arid and semi-arid western China,and no obvious trends were found in mid-Yangtze River valley and southern China.Our study suggests that both solar activity and North Atlantic thermohaline circulation may have had important influence on Asian monsoon precipitation in China over the past 3500 years.