天山中段地区树轮气候重建与冰川波动响应分析

TREE-RING CLIMATE RECONSTRUCTION AND ITS IMPACTS ON GLACIER FLUCTUATIONS IN MIDDLE TIANSHAN MOUNTAINS

利用天山中段地区4个不同海拔高度雪岭云杉树轮宽度数据,建立了该地区4个树轮宽度标准化年表与2个高低海拔合成年表。2个合成年表与邻近气象站气温和降水的相关和响应分析结果表明,高海拔树轮宽度合成年表与夏季平均气温变化呈显著正相关,低海拔树轮宽度合成年表与上一年夏季平均气温变化呈显著负相关。基于上述树轮气候响应关系,建立了合成年表与夏季平均气温的二元线性转换方程,重建方程通过了稳定性与可靠性检验。重建结果表明,夏季平均气温在1840s之前呈现整体波动下降趋势,1840s~1920s呈现缓慢振荡上升趋势,1920s~1960s呈现显著下降趋势,1970s以后呈现快速升温趋势。整个11年滑动平均后的分析时段(1739~2014年)的偏暖阶段包括1744~1746年、1751~1762年、2000~2014年(极暖阶段2005~2014年),偏冷阶段包括1835~1837年、1885~1887年、1891~1893年、1949~1969年。频谱分析表明研究区气候变化可能受到多种气候驱动机制的影响,空间相关分析结果表明,重建序列对天山中段地区夏季平均气温的变化特征有较好的空间代表性。利用重建的夏季平均气温和已有的现代小冰期以来重建的降水结果,并结合现有的冰川物质平衡度日模型结论对乌鲁木齐河源1号冰川进行分析,结果显示1734~1805年的小冰期第二次冰进可能受降水量显著增加的影响;1806~1865年的冰川退缩可能受降水量下降的影响较大;1866~1961年的小冰期第三次冰进则可能由温度降低和降水量增加共同影响所致;1962~1978年的冰川后退一定程度上受到降水量显著减少的影响;1980s以后降水量的增加不足以弥补因快速升温而引起的冰川消融,导致冰川在近几十年来急剧消融。

Based on the Schrenk’s spruce tree-ring data at four different elevation sites in the middle Tianshan Mountain region,the standardized chronology of four tree-ring width records and the synthetic chronology of two regions were established.The calculated results of correlation and response functions between the synthesized chronology of the two regions and the temperature and precipitation of the adjacent meteorological stations show that the synthesized chronology of the tree-ring width records at high altitude is positively correlated with the change of average summer temperature,while the synthesized chronology of the tree-ring width records at low altitude is negatively correlated with the change of previous summer average temperature.Based on the above tree-ring and climate relationship,the bivariate linear transformation equation of the regional synthesis chronology and summer average temperature was established,and the reconstruction equation has passed the stability and reliability test.The reconstruction results showed that the average temperature in summer indicated an overall fluctuating downward trend before 1840 s,a slow fluctuating trend from 1840 s to 1920 s,a significant downward trend from 1920 s~1960 s,and a rapid warming trend after 1970 s.The warm stage during the entire 11-year moving average period included 1744~17461751~1762 and 2000~2014(including extremely warm stage 2005~2014),and the cold stage included 1835~18371885~18871891~1893 and 1949~1969.Result of spectrum analysis shows that the climate change in the study area can be affected by a variety of driving mechanisms of climate.Result of spatial correlation analysis shows that the reconstructed sequence can be better represent the spatial characteristics of the average summer temperature in Tianshan region.Based on the reconstructed average summer temperature,the results of the existing glacier mass balance degree-day model and the reconstructed precipitation records since the Little Ice Age,it can be seen that the second glacier advance during the Little Ice Age from 1734 to 1805 might be caused by the increase in precipitation.The glacial retreat during 1806~1865 may be attributed to a decline in rainfall;The third glacier advance of the Little Ice Age from 1866 to 1961 was caused by both the decrease in temperature and the increase in precipitation.The glacial retreat during 1962~1978 can be partly affected by the reduce in rainfall.The increase in precipitation after 1980 s was not enough to compensate for the rapid warming of glaciers,which resulted to the rapid melting of glaciers in recent decades.