桂林茅茅头大岩近50年来石笋δ^18O记录与局地气候／大尺度环流关系探讨

The Relationship between Local Climate/Large Scale Circulation and δ^(18)O Recorded by Stalagmite in the Past 50 Years from Maomaotou Big Cave,Guilin

石笋记录是第四纪研究的重要力量,但是近年来中国季风区石笋δ^(18)O指示意义受到一定的质疑,关键问题是尚未通过石笋记录很好的衔接古气候与现代气候。基于此认识,选择桂林茅茅头大岩一个1968年以来连续生长的石笋记录。通过解译其δ^(18)O的气候指示意义,并进行局地和区域对比,发现桂林茅茅头大岩石笋δ^(18)O能很好的指示当地的夏季降水变化,同时响应了区域一致性的信号。在年代际尺度上表现为夏季风减弱,石笋δ^(18)O变重,夏季风增强,石笋δ^(18)O变轻。而通过比较东南水汽通道和西南水汽通道水汽来源比例变化,并未发现水汽来源变化与中国季风区石笋δ^(18)O的明显相关关系。而除桂林地区外,其他记录如湖北和尚洞、福建玉华洞石笋δ^(18)O虽然一致变化,但是与当地降水并无明显相关。因此夏季风强弱变化可能导致了中国季风区石笋δ^(18)O的一致变化,但是由于局地降水影响因素更加复杂,中国季风区并不是所有石笋δ^(18)O记录均指示当地降水量的变化。

Stalagmite record is an important pillar in Quaternary research. But some query arose for the δ^18O of stalagmites stand for summer monsoon in China monsoonal area in recent years. The key point is stalagmite in monsoonal China didn＇t bridge the modern climate and paleoelimate by the index of δ^18O. In order to solve the question above, we chose a 50 years continuously growth modern stalagmite from Maomaotou big cave. After compare with the stalagmite F4 from Fengyuyan Cave in Guilin and other stalagmites from monsoonal China, δ^18O of stalagmite DY-2 from Maomaotou big Cave can stands for local summer precipitation, and regional climatic signal as well. That shows stalagmite δ^18O becomes heavier when the summer monsoon gets weak in decadal scale, vice versa. But compare with the different vapor inflow corridors, we didn＇t found obvious relationship between moisture vapor change and stalagmite δ^18O. Besides Maomaotou big cave, though stalagmite δ^18O from Yuhua Cave and Heshang Cave show synchronous variation with Maomaotou big Cave, no obvious relationship found between the local precipitation and the two caves. Although summer monsoon intensity variation make the stalagmite δ^18O show synchronous variations in monsoonal China, the stalagmite δ^18O stand for local precipitation in monsoona ocal precipitation are more complex and not all China.