青藏高原南部枪勇错冰前湖泊沉积记录的近千年来冰川与气候变化

摘要

以钻取自青藏高原南部大枪勇错冰前湖中的1.06 m湖芯为研究对象,对沉积物样品进行了粒度、磁化率、元素含量、碳酸盐和总有机碳含量等多项指标的分析测定；在明确了沉积物来源的基础上,分析讨论了各指标变化的影响因素及其具体气候环境指示意义；结合沉积序列放射性同位素定年结果,对湖芯中各指标进行了综合对比分析,恢复了青藏高原南部枪勇错地区近千年来的冰川与气候变化.结果表明:1.06 m沉积序列年代跨度为自公元11世纪前后至今的逾千年时间；沉积物主要来源于枪勇冰川融水对冰川上部沉降粉尘颗粒的携带,而沉积物的粒度、磁化率及各组分含量与区域气候条件下枪勇冰川融化强度有密切关系；自公元11世纪至今,青藏高原南部地区环境温度总体呈现波动中逐渐升高的趋势,枪勇冰川随之逐渐融化退缩.具体来说,公元11世纪初,该地区环境温度较低,枪勇冰川融化较弱；公元11世纪中叶至13世纪初,该地区气候温暖,枪勇冰川融化较强；公元14世纪开始至18世纪中叶,该地区进入小冰期,枪勇冰川融化强度显著降低；自公元18世纪中后叶至今,该地区环境温度急剧升高,枪勇冰川呈加剧融化退缩趋势.%The 1.06 m lacustrine core, which was from the proglacial Da Qiangyong Lake, southern Tibetan Plateau, was investigated; multi indicators including grain size, magnetic susceptibility, element content, carbonate content and total organic carbon content in the sediment sample were analyzed. Based on the understanding of sediment source, the factors on these indicators and their significance on climate and environment were discussed. Associated with the radioisotope dating result, the above indicators were comprehensively compared, and the glacier and climate changes over the past millennium from Qiangyong Lake, southern Tibetan Plateau, were reconstructed. The results showed that the time scale of the 1. 06 m sediment sequence was about one millennium since the 11th century; the sediment was mainly composed of dust particles which were carried by melt water of Qiangyong glacier, and the variations of grain size, magnetic susceptibility and chemical contents of the sediment were closely related to the melting strength of Qiangyong glacier influenced by the regional climate change; the environmental temperature in southern Tibetan Plateau gradually increased with little fluctuation since the 11th century, and then Qiangyong glacier gradually melted. Particularly, the environmental temperature was lower and Qiangyong glacier weakly melted in southern Tibetan Plateau at the beginning of the llth centurys the climate was warm and the glacier strongly melted from the middle of the llth century to the beginning of the 13th century; the Little Ice Age occurred and the melting of glacier greatly weakened from the beginning of the 14th century to the middle of the 18th century; the environmental temperature increased rapidly and the melting of glacier greatly strengthened since the middle-late of the 18th century.