青藏高原冰川内部富含水冰层的发现及其环境意义

doi:10.7522/j.issn.1000-0240.2013.0152

摘要/Abstract

摘要：

基于青藏高原昆仑山玉珠峰冰川Core 1冰芯钻取过程中所获得的相关资料，揭示出在该冰芯钻取点处的冰川内部34.34~34.64 m深度段存在一个富含水冰层，其未冻水(液态水)具有承压性质，水头高度至少可达到8.54 m. 该富含水冰层的存在不仅对冰川温度场带来了极大的影响，而且使该层中δ¹⁸O记录趋于均一化. 通过分析，揭示出该富含水冰层中可溶杂质离子浓度明显高于其上部冰层中的可溶杂质离子浓度，这是富含水冰层在形成初期其上部粒雪层融水下渗所引起的可溶杂质离子淋溶的结果. 同时，研究表明玉珠峰冰川粒雪中可溶杂质离子的优先淋溶顺序为NO₃^-> Mg²⁺> Na⁺> Cl^-> K⁺> SO₄^2-> Ca²⁺> NH₄⁺. 提出可利用最易淋溶离子的浓度与最不易淋溶离子的浓度之比值，来判断冰雪层中可溶杂质离子浓度峰值是否与淋溶有关. 结合青藏高原其他地点冰芯钻取过程中发现的富含水冰层状况，认为青藏高原冰川内部富含水冰层不是在整个冰川区域内呈层状分布，而是在冰川内部呈透镜状分布. 冰川内部富含水冰层的存在，表明其形成初期气候相对较暖. 最后，阐明了青藏高原冰川中富含水冰层的形成机理与演化过程，并预测了其潜在的灾害效应.

关键词: 冰川, 未冻水, 青藏高原, 冰芯记录, 冰川灾害

Abstract:

The existence, content and distribution of unfrozen water (liquid water) in glacier ice can exert an important influence on the physics and chemistry of glaciers. In this paper, we reported the discovery of the water-rich ice layers in Tibetan glaciers and its environmental significances. During the ice core drilling on the Yuzhufeng Glacier in the Kunlun Mountains in 2007, it was found that there was a water-rich ice layer at the depths from 34.34 to 34.64 m at the Core 1 site, and the water in this ice layer had a confined property and its confined water head was at least 8.54 m. The water-rich ice layer not only influences the glacier temperature field, and also makes the δ¹⁸O record homogeneous. The concentrations of ions in the water-rich ice layer were much higher than that in the ice layer above it. This was caused by the process of elution of ions in firn at the beginning of the formation of the water-rich ice layer. Through calculating, it was revealed that the sequence of preferential elution of ions in firn on the Yuzhufeng Glacier was NO₃^-> Mg²⁺> Na⁺> Cl^-> K⁺> SO₄²> Ca²⁺> NH₄⁺. Moreover, it was proposed that the ratio of the concentration of ion that was the most easily elution (NO₃^- for the Yuzhufeng Glacier) to that that was not the most easily elution (NH₄⁺ for the Yuzhufeng Glacier) might be used for recognizing whether or not a peak value of ion in ice core was related to the processes of ion elution, and the higher the ratio was, the most possibly the peak value was related to ion elution. There were very close correlations between concentrations of Ca²⁺ and SO^2-₄and electric conductivity in ice of the Yuzhufeng Glacier. Those imply that the influences of chemical composition of ice on its electric property should be considered when using electromagnetism method to estimate the water content in glacier ice. By comprehensive analysis of the water-rich ice layers appeared in other glaciers on the Tibetan Plateau, it could be concluded that the water-rich ice layers were just distributed as lentoid in glaciers, and their existences indicted that the climate was warm when they formed near surface of the accumulation zone. It was supposed that when a water-rich ice layer move down to the bed at lower part of glacier, the tongue of the glacier might break abruptly and slid downward to lower reaches owing to its large strain rate, and consequently hazards might occur.

Key words: glacier, unfrozen water, Tibetan Plateau, ice core records, glacier hazard

中图分类号:

P343.6

王宁练, 徐柏青, 蒲健辰, 张永亮. 青藏高原冰川内部富含水冰层的发现及其环境意义[J]. 冰川冻土, 2013, 35(6): 1371-1381.

WANG Ning-lian, XU Bai-qing, PU Jian-chen, ZHANG Yong-liang. Discovery of the Water-Rich Ice Layers in Glaciers on the Tibetan Plateauand Its Environmental Significances[J]. JOURNAL OF GLACIOLOGY AND GEOCRYOLOGY, 2013, 35(6): 1371-1381.

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