亚洲中部干旱区全新世气候变化的西风模式* ——以新疆博斯腾湖记录为例

位于受西风环流显著影响区的我国最大内陆淡水湖——新疆博斯腾湖提供了全新世亚洲中部干旱区气候变化的可靠记录。对该湖钻探岩芯、沉积年代以及孢粉、碳酸盐含量、粒度等代用指标分析结果表明,末次冰消期到全新世早期湖泊干涸,风砂沉积盛行,气候干旱;约8cal.kaB.P.以来现代湖泊形成,气候相对湿润,其中,约6.0~1.5cal.kaB.P.期间代用指标A/C值指示的流域湿度增加,盘星藻指示的湖泊深度最大,全新世最湿润时段发生在中晚全新世。博斯腾湖记录的早全新世干旱和中晚全新世湿润的气候框架得到中亚其他较高分辨率湖泊记录的支持,具有普遍性。亚洲中部西风影响区这一全新世气候变化框架与亚洲季风区早中全新世夏季风强盛、中晚全新世季风衰落的变化模式显著不同,具有近似反相位(out of phase)变化特征。广大中亚内陆干旱区中晚全新世湿润气候不大可能是东亚季风深入内陆造成的,更可能是通过西风环流与高纬度北大西洋相联系,其驱动机制需要更深入研究。

WESTERLY DOMINATED HOLOCENE CLIMATE MODEL IN ARID CENTRAL ASIA——CASE STUDY ON BOSTEN LAKE, XINJIANG, CHINA

The Asian monsoon evolution history has been well documented by various reliable records which generally showed the same model and process.However,the climatic system in Western China,the westerly dominated area,has been poorly understood due to the lack of reliable climatic records.The Bosten Lake,the largest inland freshwater lake in China,can provide good Holocene regional climate records within westerly dominated area.Based on investigations of stratigraphy and chronology of several piston cores from the Bosten Lake and analyses of some proxies including pollen analysis,carbonate content and grain size,the climate evolution history has been revealed.The result suggests that the regional climate was dry during the Late Glacial to Early Holocene,and became humid abruptly since around 8cal.kaB.P.,while the most humid period is approximately between 6.0cal.kaB.P.to 1.5cal.kaB.P.This climate evolution model is supported by some other lake records in Central Asia.In Holocene,the climatic model and process in westerly dominated Central Asia generally differs from those of monsoon area.The humid Mid-Late Holocene climate in Central Asia was not caused by penetration of Asian monsoon,but more likely connected with the westerly circulation and North Atlantic climate system.