Subglacial observations from øksfjordjøkelen, North Norway
Subglacial observations from øksfjordjøkelen, North Norway
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挪威北部 øksfjordjøkelen 的冰下观测
DOI：
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发表时间：
1994
期刊：
影响因子：
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通讯作者：
W. B. Whalley
中科院分区：
文献类型：
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作者：
B. Rea;W. B. Whalley
挪威北部Oksfjordjokelen的一个小型出口冰川的鼻端处的阶梯状基岩地形产生了一个广泛的冰下洞穴系统，该系统延伸约70 m，向上冰川延伸100 m，在厚度≤50 m的冰下提供通道。在洞内，已观察到降水冰、干净的冰川冰和变形的基底冰。采集了样品，发现冰川底部的基本碎片浓度按体积计在0.005%至15.38%之间。基冰速度已被确定使用一个线性可变差分Transformer连接到一个模拟记录仪，也通过测量的冰船和碎屑嵌入在基冰的位移。发现速度在空间和时间上都不同，最大值为2.55 mm h-1，最小值为0.3 mm h-1。测量和观察，这已经与目前的理论，显示如何空间平均值的一些变量可能会导致不准确的预测侵蚀值，当然在当地的规模。在暴露的前陆，联合控制背风面提供了证据，广泛的冰下采摘（这里采取的意思是去除预松动床材料和/或床故障造成的材料）。事实上，在洞穴中，已经观察到了冰变形沿着接缝移动接缝控制块体的早期阶段。在前陆上形成的大条纹（可达500 cm × 16 cm × 2 cm）显示了富含碎屑的基底冰的重要性。
Stepped bedrock topography at the snout of a small outlet glacier from Oksfjordjokelen, North Norway, produces an extensive subglacial cavity system which stretches some 70m across and 100m up-glacier, giving access beneath ice ≤50 m thick. Inside the cavity, regelation ice, clean glacier ice and deforming basal ice have been observed. Samples were taken and basal debris concentrations at the glacier sole were found to vary between 0.005 and 15.38 per cent by volume. The basal ice velocity has been determined using a linear variable differential transformer attached to an analogue recorder, and also by means of measured displacements of ice crews and clasts embedded in the basal ice. Velocities were found to differ both spatially and temporally from a maximum of 2.55 mm h1 to a minimum of 0.3 mm h−1. The measurements and observations, which have been related to present theory, show how spatially averaged values for a number of variables could lead to inaccuracies in predicted erosion values, certainly at a local scale. On the exposed foreland, jointcontrolled lee-side faces provide evidence for extensive subglacial plucking (here taken to mean the removal of preloosened bed material and/or material resulting from bed failure). Indeed, in the cavity the early stages of removal of joint-controlled blocks by ice deformation along joints have been observed. The importance of debris-rich basal ice is shown in the formation of large striations (up to 500cm × 16cm × 2cm) present on the foreland.