Englacial water distribution in a temperate glacier from surface and borehole radar velocity analysis
Englacial water distribution in a temperate glacier from surface and borehole radar velocity analysis
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根据表面和钻孔雷达速度分析温带冰川中的恩冰川水分布
DOI：
10.3189/172756500781833188
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发表时间：
2000
影响因子：
3.4
通讯作者：
M. D. Crabtree
中科院分区：
文献类型：
--
作者：
T. Murray;G. Stuart;M. Fry;Nicola H. Gamble;M. D. Crabtree
摘要我们已经获得了共同的偏移，共同中点（CMP）和钻孔垂直（VRP）探地雷达剖面接近Falljökull，一个小的，陡峭的温带山谷冰川位于冰岛东南部的边缘。CMP和VRP测量的速度分析提供了四层速度模型。通过对比钻孔视频中所见的冰内反射体和水道的深度以及钻孔至河床的深度，验证了该模型。在冰川冰内没有沉积物的情况下，雷达速度与含水量成反比。使用Paren和Looyenga开发的混合物模型，根据雷达速度剖面确定含水量随深度的变化。在冰川表面，计算出的含水量为0.23-0.34%（速度0.166 m ns−1），在28 m深度（解释为测压表面的水平）急剧上升至3.0-4.1%（速度0.149 m ns−1）。在测压管表面以下，含水量缓慢下降至2.4-3.3%（速度0.152 m ns−1），直到102 m深度，其福尔斯下降至0.09-0.14%（速度0.167 m ns−1）。冰的含水量保持在约112米的冰川床低。这些结果表明冰川冰中储存了大量的水，这对冰川水文学、冰流变学以及雷达和地震调查的解释具有重要影响。
Abstract We have obtained common offset, common midpoint (CMP) and borehole vertical (VRP) ground-penetrating radar profiles close to the margin of Falljökull, a small, steep temperate valley glacier situated in southeast Iceland. Velocity analysis of CMP and VRP surveys provided a four-layered velocity model. This model was verified by comparison between the depths of englacial reflectors and water channels seen in borehole video, and from the depths of boreholes drilled to the bed. In the absence of sediment within the glacier ice, radar velocity is inversely proportional to water content. Using mixture models developed by Paren and Looyenga, the variation of water content with depth was determined from the radar velocity profile. At the glacier surface the calculated water content is 0.23–0.34% (velocity 0.166 m ns−1), which rises sharply to 3.0–4.1% (velocity 0.149 m ns−1) at 28 m depth, interpreted to be the level of the piezometric surface. Below the piezometric surface the water content drops slowly to 2.4–3.3% (velocity 0.152 m ns−1) until ∼102 m depth where it falls to 0.09–0.14% (velocity 0.167 m ns−1). The water content of the ice then remains low to the glacier bed at about 112 m. These results suggest storage of a substantial volume of water within the glacier ice, which has significant implications for glacier hydrology, ice rheology and interpretations of both radar and seismic surveys.