【摘要】 基于四川省黑竹沟洞一支石笋（编号:EB1）高精度²³⁰Th年龄和氧同位素数据,建立小冰期时期（1375¹810A.D.）气候变化时间序列。该序列δ¹⁸O值变化范围为-10.37%^-8.58%,敏感响应于区域气候变化过程。高分辨率δ¹⁸O变化序列能清晰地捕捉到10年际尺度振荡旋回。该石笋记录根据δ¹⁸O值变化可分为4个阶段:1375¹540A.D.和1680¹780A.D.时段,δ¹⁸O值整体偏负,指示季风增强时期;1540¹680A.D.和1780¹810A.D.时段,δ¹⁸O值整体偏正,处于弱季风阶段。与贵州董哥洞、甘肃万象洞和印度Jhumar洞石笋记录对比发现在小冰期时期δ¹⁸O变化特征具有一定的相似性,表明上述区域降水可能共同受控于印度季风水汽输送影响,反映了区域性夏季风经向环流及其降水变化特征。通过EB1石笋记录与北半球温度曲线的对比发现,两者在百年尺度上同相位变化,可能指示北高纬气候的控制作用。而该石笋与秘鲁东北部Cascayunga洞石笋记录的进一步对比结果显示亚洲季风与南半球季风记录呈反相位关系,证实了ITCZ位置的南北移动在半球间能量传递和交换过程中的重要作用。功率谱分析结果显示小冰期季风波动具有显著的25a和9a周期旋回,接近太阳黑子22a和11a周期频率,表明太阳活动变化可能是小冰期十年际尺度亚洲季风波动的重要驱动因素。更多还原

【Abstract】 The Heizhugou Cave（28°56’02"N,103°05’47"E;1400m a.s.l.） is located at Leshan,Sichuan Province,Southwest China.This study region lies in the eastern part of the Tibetan Plateau,southwest of Sichuan Basin.It is dominantly influenced by the Asian Summer Monsoon（ASM） whose mean annual rainfall ranges from 700 to1200 mm.The mean annual temperature in the cave is approximately 16 t with relative humidity close to 100%.A stalagmite（EB1） was collected in the chamber with a total length of about 160 mm.This sample is divided into two sections of 0 110 mm and 110 160 mm but there is no evidence of growth hiatus at the depth of 110 mm according to lithology.Besides,the growth rate is stable throughout the entire stalagmite,as is supported by the Th dating results.We present a continuous high-resolution（ca.3a） record of ASM evolution from 1375 A.D.to 1810 A.D.,roughly corresponding to the period of Little Ice Age（1300 1900 A.D.,LIA）.This paleoclimate time sequence was established by 9 precise ²³⁰Th dates and 160 stable oxygen isotope ratios(δ¹⁸O).The dating measurements were conducted by multi-collector inductively coupled plasma spectrometer（MC-ICP-MS） at Institute of Global Environmental Change,Xi’an Jiaotong University,China with error of ±2σ and δ¹⁸O data were run at the Isotope Laboratory of Nanjing Normal University with Finnigan MAT-253 mass spectrometer fitted with a Kiel Carbonate Device accompanied by a standard deviation error of 0.06%o.The δ¹⁸O values of the stalagmite（EB1） vary from-10.37‰ to-8.58% o and its maximum amplitude is close to 2% o,illustrating sensitive response to regional climate change.The average δ¹⁸O values during the periods of 1540 1680 A.D.and 1780-1810 A.D.is negative,implying relatively stronger ASM.And the average δ¹⁸O values during the periods of 1375 1540 A.D.and 1680 1780 A.D.is positive,implying relatively weaker ASM.The general trend of δ¹⁸O record from stalagmite EB1 is temporally consistent with the stalagmite records from the Dongge Cave in Guizhou,the Wanxiang Cave in Gansu and the Jhumar Cave in central India within dating errors.This phenomenon shows that the precipitation in these areas is possibly controlled by the same moisture source.Five strong monsoon oscillations during 1600 1800 A.D.（Fig.6 W1^W5） are distinctly registered by the stalagmite δ¹⁸O record from Dongge and Heizhugou caves.The δ¹⁸O record of EB1 also indicates a weak monsoon event in the late 16th and early 17th centuries,which is mirrored in the stalagmite records from Wanxiang,Dongge,and Jhumar caves as well as tree-ring records and historical documents.The δ¹⁸O profile of the stalagmite EB1 is positively correlated with Northern Hemisphere temperature while it has an inverse association with the record of Southern Hemisphere summer monsoon.These results indicate that northern high latitude climatic signals possibly couple with the Intertropical Convergence Zone（ITCZ） by the Atlantic Meridional Overturning Circulation（AMOC） over the centennial timescale,and thus influence the global monsoon.Significant 25 a and 9a cycles in the EB1 δ¹⁸O sequence is respectively shown by spectral analysis（above the 90% confidence level）,equivalent to the 11 a and 22 a sunspot cycles,suggesting that solar activities are likely responsible for ASM strength changes on the decadal scale during LIA.更多还原