青海湖沉积物有机碳及其同位素的气候环境信息

ENVIRONMENTAL RECORDS FROM ORGANIC CARBON AND ITS ISOTOPE OF QINGHAI LAKE SEDIMENT

通过对青海湖沉积物有机碳及其同位素的分析 ,结合碳酸盐含量的变化特征 ,探讨了青海湖沉积物有机碳及其同位素组成的环境意义 ,并且据此分析了青海湖地区近 70 0 a来的气候环境演变。青海湖沉积物的有机碳含量及其同位素较好地记录了温度的变化 ,在有机碳含量高、有机碳同位素低时 ,气温较高 ,反之则相反。小冰期的 3次冷期以及 2

Qinghai Lake is the biggest brackish lake of China. It lies in the northeast of the Tibet Plateau. That the location of the lake is influenced by the east monsoon, Siberian Mongolian monsoon and the Westerlies enables its deposits to record the climatic and environmental change sensitively. Based on the analyses on the organic carbon content and organic carbon isotope of Qinghai Lake sediments,and compared with the character of carbonate content, this paper mainly deals with the environmental significance of the organic carbon content and its isotope. Through these analyses, the climatic and environmental changes of this area during the past 700 years were reconstructed. The result shows that the organic carbon content and its isotope of Qinghai Lake well correlate with temperature changes. During the colder episodes in this area, the organic carbon content was lower, but its isotope value was higher,and vice versa. That the organic carbon content was low and its isotope was high at 1865AD,1665AD and 1565AD reflects the cold condition of these three ages, which coincides with the cold ages of Little Ice Age reconstructed by glacier and tree rings. During the last several decades, the organic carbon content decreased continually, and its isotope increased accordingly, well indicating the temperature increases since the beginning of 20th century. The organic carbon and its isotope record the environmental variations of Qinghai Lake sensitively. Three colder episodes of the Little Ice Age and rising temperature from the beginning of 20th century were clearly reflected by the Qinghai Lake sediments.