末次冰消期云南程海千年尺度气候波动的湖泊沉积记录

Using well-dated and high-resolution paleoclimate records to reconstruct the Indian summer monsoon intensity and the characteristics of abrupt climate events, would help to predict the tendency of future changes in monsoonal precipitation under a global warming scenario, and to evaluate its potential effects on water resources in southwest China. However, traditional proxies still have many uncertainties because of potential influences of multiple processes, thus leading to inconsistent and sometimes even conflict conclusions. In this project, we propose a high-resolution lacustrine record from Lake Chenghai, Yunnan in the Indian summer monsoon region. Based on the spatial characteristics of stable carbon isotope of pyrogenic carbon and compound-specific carbon isotope of long-chain n-alkanes of the surface sediments, uncertainties in the climatic implications of the proxy would be evaluated. For the long time-scale cores, high-precision chronological model will be established using terrestrial plant fragments dated by AMS 14C method. Based on a systematic study, changes in monsoon intensity and effective moisture will be reconstructed during the last deglaciation by stable carbon isotope of pyrogenic carbon, compound-specific carbon isotope of long-chain n-alkanes, n-alkanes distribution, grain-size distribution, magnetic susceptibility and elemental data. By comparing the multi-proxy, abrupt climate events would be distinguished and evaluated, and then, comparing with other records at regional- and hemisphere-scale and the results of paleoclimatic models, the amplitude, periods and underlying dynamics of the millennial oscillation of Indian summer monsoon during the last deglaciation would be investigated.

利用定年可靠、分辨率较高的古气候记录研究地质时期印度夏季风的演化过程和气候突变事件，有助于理解全球暖化背景下季风变化趋势及其对我国西南地区水资源的影响。但是目前所采用的很多古气候指标，其指示意义还存在不确定性，导致了认识偏差甚至相互矛盾的结论。本申请拟以云南程海为研究对象，通过表层沉积物火成碳碳同位素和长链正构烷烃单体碳同位素的空间分布特征，研究湖泊沉积过程对其环境意义的影响；利用陆源植物残体进行AMS-14C定年并建立准确的年代序列，通过分析岩芯中火成碳碳同位素和长链正构烷烃的单体碳同位素，并结合正构烷烃组成、粒度、磁化率和元素组成，重建区域末次冰消期的环境变化序列，并与其它不同海拔的印度夏季风沉积记录、高低纬气候记录及古气候模拟结果进行对比，研究我国西南地区末次冰消期季风气候演化、千年尺度的突变事件的幅度和持续时间以及可能存在的区域差异，探讨千年尺度上印度夏季风演化的动力学机制。

利用定年可靠、分辨率较高的古气候记录研究地质时期印度夏季风的演化过程和气候突变事件，有助于理解全球暖化背景下季风变化趋势及其对我国西南地区水资源的影响。本项目以云南程海为研究对象，利用陆源植物残体进行AMS-14C定年并建立准确的年代序列，通过分析岩芯中火成碳碳同位素、碳酸盐碳氧同位素、生物标志化合物、常量元素组成、粒度分布及磁化率等多指标，重建了区域末次冰消期的环境变化序列，并与其它印度夏季风沉积记录、高低纬气候记录及古气候模拟结果进行对比，研究我国西南地区末次冰消期季风气候演化、千年尺度的突变事件的幅度和持续时间以及可能存在的区域差异，揭示了千年尺度上印度夏季风演化的动力学机制：（1）末次冰消期程海地区存在显著的H1和YD极端干旱事件，主要受北大西洋温盐环流减弱的影响；（2）在太阳辐射持续增加的影响下，YD期间降温并不显著，与热带海水表层温度变化相似；（3）在西南夏季风持续增强的作用下，区域C3植物相对丰度显著增加，而C4植物减少；（4）程海沉积过程受到洪水或地震引起的滑坡事件的影响，为重建区域长期的地质灾害发生过程提供了新的途径。