新疆赛里木湖流域过去373年降水变化的树轮记录

Tree-ring-based precipitation variability over the past 373 years in the Sayram Lake Basin,Tianshan Mountians

利用采自天山西部赛里木湖流域的树木年轮标准化宽度年表,重建了赛里木湖流域过去373年上年8月到当年7月的降水变化,重建序列的解释方差达到39.8%,多方验证表明,重建结果是稳定可靠的。分析历史降水变化特征表明,赛里木湖流域过去373年的降水经历了6干7湿的阶段变化,其中,持续最长的干旱阶段为1762—1791年,而最为干旱的阶段为1841—1865年;持续最长的湿润阶段为1794—1840年,而最为湿润的阶段为1734—1761年间;赛里木流域历史降水存在3个极端湿润年(1749,1876和1924年)和4个极端干旱年(1714,1775,1847和1917年),1910年代为最干旱的十年;降水变化存在11—12a、3.0a、2.5a、2.1a和2.0a的变化准周期;赛里木湖流域过去373年的降水的阶段变化、周期变化和极端降水年份均与天山北坡中西部和中亚天山山区降水变化具有很好的一致性,本研究的降水重建序列能较好的代表天山北坡中西部和中亚大部分区域历史降水变化。

Tianshan Mountains are an important area for water source; they are dominated by westerly winds and play an important role in global climate change research. It is vital to understand past precipitation changes and explore their mechanism for the current sustainable utilization of regional water resources. Since the Tianshan Mountains are located in an arid inland area, tree rings are sensitive to climatic moisture status and are a good proxy of past precipitation. In this study, we developed a tree-ring-width chronology of Schrenk spruce （Picea schrenkiana Fisch. et Mey） in the Sayram Lake Basin of the Tianshan Mountians. Climate-growth response results showed that the precipitation from the previous August to current July was the principal limiting factor of radial growth. We also obtained a 373 a reconstruction of August-July precipitation in the Sayram Lake Basin. The reconstruction explained 39.8% of the variance in precipitation records during the 1960-2009 calibration periods. Additionally, the precipitation over the past 373 a in the Sayram Lake Basin has experienced six drier and seven wetter periods, and the extreme drought years were 1714, 1775, 1847 and 1917; 1917 was the driest year in the past 373 year, and the driest decade was the 1910s. Meanwhile, there was large power in the 11-12 a, 3.0 a, 2.5 a, 2.1 a and 2.0 a periods. We suggest that the precipitation variability could be associated with large-scale oscillations in the climate system. The reconstruction illuminates precipitation variability and changes in a region where the climate history over the past several centuries is poorly understood.