中亚干旱区黄土记录的末次冰期以来气候变化与驱动机制

Central Asia arid region is located between the loess areas of the Chinese Loess Plateau (CLP) and Europe, and eolian loess sediments in this region are important archive to reveal the westerly climatic changes and dust source in the Northern Hemisphere. However, in contrast to the intensive loess paleoclimate investigation in the CLP, the paleoclimate revealed by aeolian loess from central Asia arid region are still poorly understood, especially the climatic instability during the last glaciation and its driving mechanism. This proposal selects the loess deposits distributed in different region from central Asia as the main objective, employs optical stimulated luminescence (OSL) and AMS 14C to built up the high-resolution chronological frame since last glaciation. Base on sedimentological, mineralogical and geochemical analyses,Combined with other proxies e.g. palynology, to reconstruct climatic history and variability since last glaciation in central Asia arid region, and identify the climatic abrupt change events, and compare these climatic records with other records such as loess, stalagmite, ice core, marine sediment from Tibet Plateau, monsoon region, typical westerly region and polar region, to discuss the similarities and differences and possible correlation between the abrupt events recorded in proxies from region and globe respectively; to simulate the effects of north–south shifts and strength variations of westerlies circulations on aridificaion in central Asia using global climate model accompanied by existing geologic records; and to approach the possible climatic driving mechanism in this region. This work will be contributed to improve the Asia monsoon-arid environmental change theory, and provide the geological background for understanding modern climate and predicting the future climate change in central Asia arid region.

中亚干旱区地处黄土高原与欧洲两大黄土区之间，该区风成黄土的研究对揭示西风气候变化、北半球粉尘来源等具有重要意义。相对黄土高原黄土古气候的研究，中亚干旱区的研究仍较薄弱，尤其是末次冰期气候特征和驱动机制仍不清楚。项目将选择中亚不同地区黄土沉积为研究对象，利用光释光和AMS14C等方法建立末次冰期以来高精度年代序列，以沉积学、矿物学和地球化学指标为主，结合孢粉等其他指标，重建末次冰期以来研究区的气候历史与变率，捕捉气候突变事件；并将其与其它地区黄土、石笋、冰芯、海洋沉积等进行综合对比，探讨突变事件与区域和全球记录的异同和可能的联系；结合地质记录，利用全球气候模式模拟特征时期西风带位置南北移动和西风强度变化对中亚干旱区气候的影响，探讨气候变化的驱动机制，为完善亚洲季风-干旱环境变迁的理论作出贡献，为认识中亚干旱区现代气候和未来变化预测提供地质背景。

位于亚洲内陆的中亚干旱区是全球气候环境变化的敏感区，也是世界主要的黄土分布区之一。研究中亚黄土不仅对理解中亚内陆干旱化、北半球粉尘来源、古大气环流、高低纬相互作用及其与全球气候变化的关系具有重要科学意义，而且为进一步认识中亚干旱环境的发展趋势提供重要参考。本项目历时4年，基于来自中国新疆地区、哈萨克斯坦、吉尔吉斯斯坦、塔吉克斯坦的黄土沉积物，论证了光释光（OSL）和放射性碳（AMS14C）测年结果在不同时期的可靠性；对末次冰期的黄土沉积物作了定量的物源示踪研究；展示了北大西洋千年尺度气候突变事件在中亚黄土记录中的表现形式及其区域性差异，揭示了气候突变事件深入欧亚大陆的传播机制；筛选出有效指示水汽和温度变化的指标记录，明确了研究区冷湿-暖干组合的气候特点，恢复了中亚干旱区末次冰期以来的气候环境变化历史，并且结合气候敏感性试验，阐明了中亚干旱区气候环境演变的动力机制。以上研究成果给应对气候变化对中亚干旱区带来的挑战提供了重要的科学指导和现实意义，并且有助于深入认识亚洲季风-干旱环境的耦合演化过程。项目人员参加了多次国内外学术会议，实现了与中亚国家相关人员的交流互访，发表论文28篇，其中SCI检索论文17篇，实现了预期目标。