2.5 Ma以来柴达木盆地的气候干湿变化特征及其原因

长期以来，一直认为柴达木盆地第四纪气候在波动中向干旱方向发展。原因是青藏高原的隆升阻挡了来自印度洋、孟加拉湾的水汽。然而，来自柴达木盆地新的证据表明，柴达木盆地第四纪气候演变的总体趋势是冰期越来越干燥，间冰期干燥程度却存在减弱的趋势。并且这种变化是呈阶段性的。最明显的阶段划分应在0.8-0.6Ma前后。这种现象可以用青藏高原的隆升做出比较合理的解释：青藏高原的隆升，不仅通过增强冬季亚洲高压（西伯利亚高压）使冬季风增强，使东亚季风区冰期气候更加干燥寒冷，而且还可以通过增强夏季亚洲低压（印度低压），使夏季风增强、间冰期气候更加温暖湿润，从而使得中国季风区冰期－间冰期的气候变差增大。可是，柴达木盆地位于青藏高原北缘，我国西北内陆区受夏季风影响较弱，间冰期或者湿润期湿润程度的增大如何与高原隆升和季风系统的调整相联系，还有待于进一步的研究。

Tendency of the Quaternary Climatic Change in Qaidam Basin and Its Causal Mechanism

It has been long believed that the Quaternary climate in Qaidam Basin evolved towards dry. However, evidence from lithofacies, sporo pollen, and organic carbon content has revealed that the general evolutionary trend of Quaternary climate in Qaidam Basin, i.e., glacial climate became drier and interglacial climate became wetter at about 0.8-0.6 Ma B.P. This phenomenon can probably be attributed to the uplift of Tibetan Plateau. The uplift of Tibetan Plateau made both the Asian High (Siberia High) and the Asian Low (India Low) strengthened, which consequently intensified the winter and summer monsoons, giving rise to much drier and colder glacial climate and much wetter and warmer interglacial climate in the East Asian monsoon region. The Quaternary climatic evolution of Qaidam Basin is probably influenced by Asian monsoon circulation as well. However, how to relate the uplift of the Tibetan Plateau and the intensification of the monsoon with the increase of the amplitudes of the humidity variations in Qaidamu Basin leave unsolved.