从古里雅冰芯与祁连山树轮记录看过去2000年气候变化

通过藏南沉错湖芯的210Pb和137Cs的测试,获得湖芯的平均沉积速率为0.16cm/a.根据湖芯长度和分样间距,获得平均分辨率为6～7年,长达1 350年的连续湖芯环境序列.对湖芯样品磁学指标的低频磁化率(Xlf)、等温剩磁(IRM)、饱和等温剩磁(SIRM)、非滞后剩磁(ARM)等指标及其比值的测试,划分了650 A D.以来沉错湖区的冷暖变化阶段和相对强度.结果表明,690～860A D.和1 120～1 320 A.D.分别出现两个相对集中的暖期,每个暖期中间又具有相对寒冷时段.1 520～1 650A.D.出现寒冷时段之后,1 820A D.左右直至现在环境又逐渐进入转暖时期.在3个暖期中,以1 220A.D.前后的温暖程度最强,而冷期中以1 610～1 650A.D.达到最盛.沉错湖区冷暖环境的演变得到了其他资料的很好验证.

COMPARATIVE STUDY OF THE CLIMATE CHANGES IN THE PAST 2 000 YEARS BY USING ICE CORE AND TREE RING RECORDS

In this paper, the features of the climate changes since 2 000a B.P. were examined by comparing the high-resolution records of the Guliya ice core and the Dulan tree ring. The results show the temperature has been increasing with fluctuations since 2 000a B.P.. This is especially true since the beginning of the 20 th century. There were 3 cold periods in the Little Ice Age, which are recorded by the Guliya ice core and the Dulan tree ring. The ice core and the tree ring show that the LIA is not the coldest period in the past 2 000 years. They demonstrated the early century was colder than the LIA. The temperature (δ 18O) and precipitation (net accumulation) recorded in the Guliya ice core show that the temperature fluctuations is positively correlated to the precipitation on a long time scale. However, the temperature and precipitation fluctuations are not synchronous on a relatively short time scale. On a long time scale the temperature fluctuations is more than that of precipitation. This means that the number of the cold/warm period of temperature is more than that of precipitation. But the lasting time of the cold/warm period is shorter than that of precipitation. Although temperature and precipitation are positively correlated on a century scale, precipitation lagged temperature about 50～100a. This is more evident during the temperature decreasing period.