Characteristics of the subglacially-formed debris-rich chemical deposits and related subglacial processes of Qiangyong Glacier,Tibet

Subglacially-formed debris-rich chemical deposits were found both on bedrock surface and in bedrock crevice on the edge of Qiangyong Glacier, one of the continental glaciers in Tibet. Grain size distribution, internal structures and chemical components of the chemical deposits were analyzed. It can be inferred that the temperature of some part of the ice-bedrock interface is close to the melting point and there exists pressure melting water under Qiangyong Glacier. Debris, especially those from continental aerosols, can release Ca++ in the water. At the lee-side of obstacles on glacier bed the CO2 in the melting water might escape from the water and the melting water might refreeze due to the dramatically reduced pressure, making the enrichment and precipitation of CaCO3. The existence of subglacial melting water and the process of regelation under Qiangyong Glacier indicate that sliding could contribute some proportion to the entire movement of Qiangyong Glacier and it belongs to multiplex cold-temperate glaciers.

西藏枪勇冰川冰下富碎屑化学沉淀特征与冰下过程

西藏枪勇冰川是我国现代大陆性冰川之一,在其外缘冰床背冰面的基岩表面和节理裂隙中发现了富碎屑化学沉淀,为研究冰岩界面的物理、化学过程提供了良好载体。对该区富碎屑化学沉淀理化特征的研究表明:枪勇冰川冰下存在压力融水,冰下碎屑,特别是陆源气溶胶粉尘来源的碎屑,能与融水及其中溶解的CO2发生化学反应,释放出Ca++;Ca++随融水向下游方向迁移,在冰床背冰面,由于上覆压力减小,融水中的CO2逸出并发生复冰作用,使融水中的Ca++重新富集,形成CaCO3沉淀,并将融水中的粉砂粘粒碎屑胶结,形成富碎屑化学沉淀;枪勇冰川冰下融水的存在,证明其冰下存在温度接近融点的融区,有类似于温性冰川的滑动过程。

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

以钻取自青藏高原南部大枪勇错冰前湖中的1.06m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:1.06m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。