摘要
通过湖北省神农架永兴洞石笋(编号:YX92)230Th年龄和纹层计数年代学研究,建立了1788AD-1956AD时段年际分辨率石笋氧同位素序列。该序列δ18O值变化范围为-9.70‰^-7.87‰,最大振幅约达1.83‰,呈现显著的年代际尺度振荡旋回特征。功率谱分析结果揭示存在显著的60~70年准周期信号。该记录与同区域和尚洞石笋δ18O曲线具有很好的重现性,说明其可能受控于共同的气候因子,指示了东亚夏季风大尺度环流特征。将石笋重建的东亚夏季风指标与全印度夏季降水量指示的印度夏季风指数对比,结果显示两者在年代际旋回特征上具有很好的相似性,但是呈反相位关系。进一步与ENSO指数对比,发现东亚夏季风年代际尺度变化与ENSO存在密切联系,表现为东亚夏季风增强,对应于ENSO暖期,反之亦然。因此,东亚季风与印度季风在年代际尺度上的反相位关系可能源于两者对ENSO机制的不同响应。
An annually-laminated and230Th-dated stalagmite oxygen isotope(δ18O) record from Yongxing Cave, central China, provides an average annual resolution East Asian summer monsoon(EASM) history covering from 1788-1956. The δ18O values of stalagmite show variations ranging from-9.70‰ to-7.87‰(VPDB), with an amplitude as large as ~1.83‰. The δ18O profile exhibits clear inter-decadal oscillations over the past ~200 years. A comparison of δ18O records from Yongxing Cave and Heshang Cave, both located in the mid-low Yangtze River Valley, shows a close similarity during their contemporaneous growth periods. The two duplicated stalagmite δ18O records suggest that oxygen isotopic variations are primarily caused by climate change, possibly related to the EASM changes. Power spectral analysis of the δ18O data indicates that the EASM varies at a periodicity of ~60-70 years(above the 95% confidence level).The changes in EASM are comparable to Indian summer monsoon(ISM) changes derived from all Indian summer rainfall(JJAS) over the past ~200 years. The comparison result shows a broad similarity on inter-decadal timescale between the EASM and ISM, but in an opposite sense, with a correlation coefficient of 0.47(n=141, p<0.001). Furthermore, the EASM and ISM records are compared to a unified ENSO proxy(UEP), which is revealed by Principal Component Analysis of 10 commonly used ENSO proxies. On inter-decadal timescale, weak/strong EASM and strong/weak ISM intervals are linked to cool/warm ENSO phases. This observation might suggest a strengthening influence of ENSO on decadal Asian monsoon variability.
出处
《地理研究》
CSSCI
CSCD
北大核心
2015年第1期74-84,共11页
Geographical Research
基金
国家自然科学基金项目(41202123
41072126)
江苏高校优势学科建设工程资助项目
关键词
石笋
氧同位素
东亚季风
ENSO
永兴洞
oxygen isotope(δ18O)
stalagmite
East Asian monsoon
ENSO
Yongxing Cave
