树轮碳氧同位素记录的南疆500年来干湿变化及其机制研究

The study on the characteristic of regional dry/wet changes from inter-annual to centennial scale is crucial to the understanding of the mechanisms of aridification under global warming, as well as the prediction for drought in the future. The southern Xinjiang in China is the important part of Silk Road, which is located at the arid northwestern China. The dry/wet changes have influenced the rise and decline of Silk Road, and is also one of the important factor restricting the development of this region at present. However, the short instrumental records and the scarcity of paleoproxy with high-resolution have limited the understanding of the variations, as well as mechanisms of the dry and wet climatic changes at annual to centennial scale. This project plans to use tree ring carbon and oxygen isotopes in 3 sites from the southern Xinjiang, to reconstruct the history of regional dry/wet changes over the past 500 years, to analyze the temporal and spatial characteristic at inter-annual to centennial scale. The intra-annual variation of tree ring oxygen will also be measured to analyze the moisture source and atmospheric circulation system in this area. Moreover, we will analyze co-variation patterns between the reconstructed series and various external climatic and internal forcings. Using fully coupled Ocean-Land-Atmosphere climate model we will simulate the climate in past 500 years, and design a series of sensitive experiments to understand the possible potential mechanisms for the detected climate variability recorded in tree ring archives. This proposed project is expected to enrich the paleo-proxy data in the region for better understanding the past climate change, in order to provide the reference for future climate projection.

年际至百年尺度的干湿变化特征的研究，对深入了解全球变化背景下干旱化机制及未来预测有重要意义。南疆位于我国西北干旱区，是丝绸之路的重要节点。干湿变化影响了南疆丝绸之路的兴衰，也是制约当前区域经济社会发展的重要因素之一。但是，器测数据较短及年际分辨率代用指标的缺乏，限制了对该区域年际—百年尺度干湿变化机制的理解。本项目拟在南疆的帕米尔高原至天山地区，开展3个样点的树轮碳氧同位素工作，通过建立南疆地区500年来的树轮碳氧同位素年序列，重建区域干湿变化历史，分析年际—百年尺度区域干湿变化的特征及规律；测量器测记录以来的树轮氧同位素年内变化，尝试分析区域水汽来源和大气环流；揭示南疆干湿变化与外部强迫及气候系统内部驱动的关系，结合海陆气耦合模式对南疆500年来气候的模拟，通过设计合理的敏感性试验进行验证，探讨500年来南疆干湿变化可能的动力学机制，为预测全球变暖背景下区域干湿状况提供基础数据和参考。

南疆地区是丝绸之路的重要节点，干湿变化是制约区域经济社会发展的重要因素之一。但是，器测数据较短及年际分辨率代用指标的缺乏，限制了对该区域年际—百年尺度干湿变化机制的理解。本项目以南疆地区（帕米尔高原-天山南部一线3个采样点）具有年轮的针叶树为对象，对每个样点进行交叉定年确定了每个年轮形成的年代，每个样点分析6-10棵树的纤维素氧同位素，在帕米尔高原和天山南部地区建立了长达500年的树轮宽度年表3条，树轮氧同位素年表2条，通过对比发现树轮宽度和氧同位素是区域年降水量和春季干湿变化的良好指标，利用树轮宽度和树轮氧同位素定量重建了南疆地区的干湿变化历史。结果显示南疆地区小冰期相对干旱，而1850年以来呈变湿趋势。西风带南移，和全球增温导致蒸发增强、局地水汽再循环增强，是引起南疆地区变湿的主要原因。未来全球增暖背景下，南疆地区极端洪涝事件的发生频率可能增加。