高山湖泊记录的黄土高原西部全新世温度与湿度变化研究

Due to the lack of high resolution paleoclimate records in the western Loess Plateau, Holocene climate change and variability at this region is still poorly understood. In this proposal, we plan to use sediments from 4 alpine lakes in west of Loess Plateau to reconstruct high quality records.The chronology will be determined with AMS 14C dating from terrestrial plant leafs and varve counting technique (Liupan Tianchi Lake). Based on modern process research, we will use GDGTs as temperature proxy and specific compond H isotope as moisture/precipitation proxy,together with other multiproxy proxies(grain-size, magnetic susceptibility, organic). The aims of this study are to reconstruct the high resolution Holocene temperature and moisture variations in the western Loess Plateau, to better understand the temporal variations of Holocene climatic change in the monsoon margion areas, and to descripe the spacial pattern of Holocene climate changes between monsoon region and westerly area by comparing with other high-resolution climatic records obtained in the monsoon region, and try to systematically understand the back machenisms of Holocene climate change in the western Loess Plateau.

黄土高原西部地区一直缺少全新世以来高分辨率具有明确指示意义的代用指标记录，限制了对该区域全新世气候变化历史和规律的深入认识。本项目拟以黄土高原西部4个高山湖泊为研究对象，利用连续的高山湖泊沉积记录，通过陆源植物残体AMS 14C和年纹层定年（六盘山天池具有年纹层）技术建立可靠的年代序列；在现代过程研究的基础上，明确代用指标的确切气候意义,采用湖泊沉积物GDGTs为代用指标定量重建温度变化；采用湖泊沉积物单体氢同位素来重建降水氢同位素变化，进而恢复降水量或相对湿度。在此基础上，开展与季风区和西风区其他可靠的高分辨率气候记录的对比研究，系统认识黄土高原西部全新世气候变化过程及驱动机制。

本项目通过对黄土高原西部4个高山湖泊孟达天池、冶海天池、六盘山天池和北联池湖泊沉积物为研究对象，在获取了连续高质量的湖泊沉积或进行了细致的年代重建和指标分析，最后选取六盘山天池和北联池湖泊沉积进行了详细研究，在建立可靠的年龄模式基础上进行了包括有机地球化学分析在内的多指标分析，定量重建了黄土高原西部温度和降水变化趋势。同时通过对元素和粒度的详细研究，重建了中全新世以来黄土高原西部的洪水历史。通过对比其他指标和人类活动情况，初步认识了黄土高原西部的气候驱动机制。