喜马拉雅山东段雅拉香波雪山古冰川演化序列及其古气候重建研究

Modern glaciers and abundant glacial remnants are widely distributed in the Himalayas which is already become one the most important research area on Quaternary glaciations and environmental evolution. This project intends to select Yarla Shampo in the eastern Himalayas as the study area. Based on the field investigation of Quaternary glacial erosion and sedimentation landforms, with the combination of remote sensing and DEM data, Remote Sensing Images and GIS techniques, a map of the glacial geomorphology of Yarla Shampo will be presented, and dependable glacial landform and deposit sequences will be set up. The chronological framework of Quaternary glaciations in the Yarla Shampo will be established with cosmogenic 10Be technique. According to the numerical age control and well preserved moraines, the paleoglacier surface geometry will be reconstructed based on longitude section paleoglacier model. Furthermore, the Shi’s formula of the relationship between the annual atmospheric temperature and the annual precipitation at ELA(P-T model), and the degree-day model are used to reconstruct the paleoclimate based on the reconstruction of paleoglacier surface geometry. If the glacial chronology of Yarla Shampo is determined and paleoclimate is drived from the glacial record, it will be critical for understanding regional climate-glacier interactions and the forcing paleoclimatic conditions.

喜马拉雅山发育大规模现代冰川，古冰川遗迹亦十分丰富，是探讨青藏高原第四纪冰川发生、演化及驱动机制的重要区域。本项目选取位于喜马拉雅山东部的雅拉香波雪山第四纪冰川遗迹为研究对象，通过传统的野外地貌调查、采样，综合遥感、DEM、GIS 技术，绘制雅拉香波雪山冰川地貌图，并划分冰川地貌相对时代序列；应用TCN 10Be暴露年代测年技术对冰川遗迹进行综合定年，给出可靠的冰川演化绝对年代序列。再基于年代学和保存较好的冰碛地形，应用冰川纵剖线模型重建末次冰期以来古冰川表面高程，进而应用基于古冰川 ELA 的气候重建模型(ELA 处气温与降水关系模型(P-T 模型)和基于古冰川物质平衡的气候重建模型(度日模型)模拟各次冰进时的古气候特征，为深入探讨喜马拉雅山冰川发育和演化的驱动因素提供依据。

雅拉香波雪山位于青藏高原南部冈底斯——喜马拉雅造山带东北段，研究区气候主要受到以印度季风为主的季风系统控制。研究该地区第四纪冰川演化历史对于研究印度季风区气候变化以及认识季风区和季风边缘区气候演化过程都具有重要的意义。本项目采用野外地貌调查和23个冰川漂砾的10Be暴露年龄，查明了该地区4次冰川作用时代。最老的冰碛物（M5）的暴露年龄为34~25ka，对应于MIS3。分布面积最广的冰碛物（M4）暴露年龄为24~14ka,对应于末次冰盛期-冰消期。第三次冰进事件（M3，15.8ka）与Heinrich-1事件重合。第五次冰川事件（M1，0.62~0.34ka）发生在全新世小冰期。这些冰川事件与受季风影响的喜马拉雅山脉其他地区的冰川事件大致同步。自末次冰盛期以来，雅拉香波雪山地区温度似乎是驱动冰川波动的主要因素。LGM平衡线高度（ELA）比现在低~375m，第三次与第一次冰进事件（M3与M1）平衡线高度分别比现在低为~227、~55m。