敦德冰芯19世纪中叶以来的环境记录

基于青藏高原祁连山敦德冰芯中近130来主要离子含量的实验测定结果，通过与高原其他冰芯的对比分析，确认冰芯中Ca^2 和CI^-可以分别作为西北干旱区和柴达木盆地干湿变化的指示器，从冰芯化学成分变化特征的角度详细讨论了我国西北干旱区近代环境演化特征。发现近代我国西北干旱区最干旱时期发生在1920－1940年，柴达木盆地蒸发作用在1890－1915年最强烈。20世纪50年代以后，西北干旱区和柴达木盆地干旱程度逐渐缓解，到80年代干旱程度达到130a来的最低水平。

Environmental record in the Dunde ice core since the Middle of the 19th Century

Ice cores of high resolution and long term span recovered from Qinghai Xizang Plateau, is very important for the study of climatic and environmental change in this region. It has been found that climatic and environmental information extracted from the Dunde ice cap, located in the Qilian mountains on the northeastern margin of the plateau, is in good agreement with the climatic change in Northern Hemisphere, which means that the Dunde ice core can offer a good opportunity to study climatic and environment change in both northwest china and Northern Hemisphere. 　　In order to reconstruct modern environmental evolution in the northwest China, ion content in the Dunde ice core is measured by ion chromatography in this study. The results show that the ion contents of the Dunde ice core are higher than that of other ice cores in the plateau, and the character of the ion content is of a typical crust resource, which mainly come from the surrounding arid areas. The especially high contents of Cl－ , Na＋ and indicate that there exists an extra input of the surrounding salt, in which Qaidam Basin s many saline lakes might probably contribute a significant large portion. The high Ca2＋ content reveals the calcareous deposits originating from the surrounding deserts. 　　The modern environmental evolution is recovered by establishing the temporal variation of the ion content covering the past 130 years. It is found that during the period of 1850～ 1900 and 1940～ 1980, the annual variation of all the ion contents are rather similar, but from 1900 to 1940, the annual variation is very different among the ion contents， which may be caused by the fluctuation of climate. 　　The evaporation of Qaidam Basin is most serious during 1890～ 1915 indicated by the high content of Cl－ . The highest Ca2＋ content during the years between 1920～ 1940 reflects both decreased precipitation and increased dry surface area in the northwest China. The reduced contents of both Ca2＋ and Cl－ in the Dunde ice core may reflect higher precipitation rates since 1950, which can be confirmed by the accumulation of the ice cap.