青藏高原东北部高山湖泊措隆喀记录的全新世气候与大气环流变化

In this research, Lake Cuolongka, located in the northeastern Qinghai-Tibetan Plateau, is chose to reconstruct the Holocene history of climatic and environmental changes and atmospheric circulation patterns. Chronological frames of the drill cores can be established through multi-dating methods of AMS C-14, Pb-210 and Cs-137. The samples of the sediments will be analyzed for biologic macrofossils, grain size, magnetic susceptibility, loss on ignition, stable isotopic compositions of authigenic carbonates and carbon isotope of organic matter. Based on a survey of aquatic plant community in Genggahai Lake at present days, the relationship between the individual living submerged plants and water depth will be quantified, which makes a semi-quantitive assessment on Holocene lake-level fluctuations using plant macrofossils. By comparing the oxygen isotope sequence and the reconstructed lake level changes, oxygen isotope compositions of anthigenic carbonate are most likely indicative of changes in vapour sources of precipitation, which will be expected to understand processes and mechanisms of oxygen isotope compositions responses to climatic and environmental changes. Importantly, it's a focus to explore changes in vapour sources of precipitation and their relationship with atmospheric circulation patterns. Furthermore, it will play a significant role in further understanding of the interplay between the Westerlies and Asian summer monsoon in the northeastern Qinghai-Tibetan Plateau and the forcing mechanism, and hence the climatic linkages between northern high- and low-latitude and the related mechanism. In addition, this research will provide some important information for studies on Holocene climatic changes in China.

项目选择青藏高原东北部措隆喀湖泊沉积为研究对象，拟重建全新世气候环境，从而揭示可能的大气环流变化。利用Pb-210、Cs-137 与AMS C-14等手段建立沉积岩芯的年代模式，分析生物大化石、粒度、磁化率、烧失量、有机质碳同位素、碳酸盐稳定同位素等代用指标。调查现代湖泊水生植物群落空间分布与水深的关系，利用植物大化石半定量重建湖泊水位变化。比较湖泊水位变化与湖泊自生碳酸盐氧同位素序列，明确碳酸盐氧同位素对气候环境变化的响应过程与机理，尤其是其对水汽来源的指示意义。重点探讨全新世水汽来源的变化及其与大气环流格局变化的联系。项目的开展不但有助于理解青藏高原东北部全新世亚洲夏季风与西风环流的相互作用过程与驱动机制，而且有助于探讨高、低纬地区间气候变化的联系与机制。此外，项目的实施可为深入理解我国全新世气候变化模式提供基础资料。

西风环流与亚洲夏季风是北半球最为重要的两个大气环流系统，对北半球的气候变化具有重要的影响。青藏高原东北部季风边缘区的措隆喀湖泊位于两个大气环流系统交汇处，是研究大气环流相互作用过程的关键区域。通过分析措隆喀湖泊沉积岩芯的粒度组成特征，结合岩性变化，揭示了21 ka以来的湖泊水文环境变化过程。在此基础上，利用多种指标重建了21 ka以来的气候变化历史。通过与邻区哈拉湖、青海湖、更尕海的气候变化记录进行对比，探讨了研究区晚冰期以来的大气环流与气候变化。21-8.0 ka期间存在21-20 ka、15 ka、12 ka、9.2 ka、8.0 ka等5次湖泊水位降低事件，气候整体偏冷干，研究区主要受西风环流的控制。早全新世增强的亚洲夏季风对该地区的影响程度不足以改变区域大的气候变化，但捕捉到的寓于全球气候变化背景下的气候干旱事件表明了区域气候变化对全球变化的响应。中全新世8.0-5.1 ka湖泊水位较低，表现出与西风区和季风区相异的气候变化特征，可能与研究区处于两种大气环流影响的边缘地区有关。5.1-4.1 ka，存在一次极端气候干旱事件，湖泊水位快速下降。晚全新世4.1ka以来流域化学风化强度的增强反映了降雨量的增加，湖泊水位升高，其间在1.6 ka左右记录了一次湖泊水位快速升高事件。晚全新世的气候变化与西风区记录的暖湿环境特征相符，尽管存在区域性差异。