布加岗日碑加冰前湖沉积记录的冰川变化研究  

Glacier change in the Bugyai Kangri region,southeastern Qinghai-Xizang Plateau,inferred from Beijia proglacial lake sediments

作　　者：林诗豪 徐柏青[1] 张家康 张小龙[1] LIN Shihao;XU Baiqing;ZHANG Jiakang;ZHANG Xiaolong(State Key Laboratory of Tibetan Plateau Earth System,Environment and Resources(TPESER),Institute of Tibetan Plateau Research,Chinese Academy of Sciences,Beijing,China;University of Chinese Academy of Sciences,Beijing,China)

机构地区：[1]中国科学院青藏高原研究所青藏高原地球系统与资源环境全国重点实验室,北京 [2]中国科学院大学,北京

出　　处：《北京师范大学学报（自然科学版）》2024年第4期562-573,共12页Journal of Beijing Normal University(Natural Science)

基　　金：国家自然科学基金资助项目(42371143);第二次青藏高原综合科学考察研究资助项目(2019QZKK0101);国家自然科学基金“青藏高原地球系统基础科学中心项目”(41988101)。

摘　　要：掌握过去长时间尺度的冰川变化特征是客观理解现代和准确预估未来冰川变化趋势的重要依据.冰前湖沉积物是连续反演过去冰川变化历史的良好介质;然而,因研究薄弱,青藏高原冰前湖沉积物组分变化与冰川运动的关系仍不明确,极大限制了古冰川变化研究的发展.本文利用布加岗日冰川接触型湖泊−碑加湖156 cm沉积钻孔和湖区冰川沉积物,通过粒度、元素、210Pb和137Cs分析,结合1968−2021年上游碑加冰川末端变化遥感影像解译,明确了冰川运动对沉积物组分输入的影响,在此基础上重建了1817年以来的冰川变化历史.结果表明,碑加湖钻孔样品的粒度由主峰众数粒径为9.9、31、160和520μm的4个端元(EM1、EM2、EM3、EM4)组成.其中,EM4组分主要由冰川前进对冰碛碎屑的压碎作用产生,EM3~EM1组分输入和冰川退缩、冰流加速对冰碛碎屑的磨蚀作用有关;冰舌末端距离钻孔的远近造成沉积物中EM1~EM4组分含量具有梯次变化特征.相比之下,元素主成分1(PC1,方差信息解释量为46%)对冰川变化的响应程度不及粒度端元数据.粒度端元组分含量变化揭示,碑加冰川在1817−1842年前进,之后持续退缩,体现了小冰期最后一次降温和小冰期结束后全球变暖的影响.本文结果表明,借助端元分析,冰前湖沉积物粒度组成及其含量变化是研究青藏高原冰川变化的强有力指标.Understanding the characteristics of long-term paleoglacier fluctuations is essential for objectively understanding modern and accurately predicting future glacier changes.However,due to limited research,relationship between glacier activities and changes in the components of downstream proglacial lake sediments is poorly understood,significantly hindering the development of studies on paleoglacier fluctuations.A 156 cm long sediment core,retrieved from Beijia Lake,a glacier-connected lake in the Bugyai Kangri region,along with glacial sediments in the lake catchment,were studied.Analysis of grain size,elements,210Pb and 137Cs in the lake sediments,and remote sensing images of Beijia Glacier length changes from 1968 to 2021,revealed the influence of glacier activities on proglacial lacustrine sediments and the history of Beijia Glacier changes since 1817.The grain size of Beijia lake sediments was found to consist of four end members(EM1,EM2,EM3,and EM4)with main modes at 9.9,31,160,and 520μm,respectively.The EM4 component was primarily produced by till crushing during glacier advances,while inputs of EM3 to EM1 were related to the abrasion of till along with accelerated ice flow when glacier retreats.Changes in the distance of the glacier terminus from the sediment core site caused cascading changes in the content of EM1 to EM4 components.In contrast,elemental principal component one(PC1,explaining 46%of total variance)showed relatively less sensitivity to glacier activities than grain size end members.Changes in the contents of grain size end members revealed that the Beijia Glacier advanced from 1817 to 1842 and has been retreating since then,reflecting the impact of the last cooling event of the Little Ice Age and global warming since its end.This study indicates that,with the aid of end member analysis,changes in components and their contents of the grain size in proglacial lake sediments are powerful indicators for studying glacier change on the Qinghai-Xizang Plateau.

关 键 词：冰川变化 冰前湖 湖泊沉积物 粒度 布加岗日 

分 类 号：K909[历史地理—人文地理学]