Collaborative Research On the Basal Motion of Glaciers: Filed Studies of Debris/Bed Friction and Bed Deformation, Engabreen, Norway

摘要OPP-99-11559艾弗森-爱荷华州立大学OPP-00-02230科恩-耶鲁大学这是一项与爱荷华州立大学、耶鲁大学和挪威斯瓦蒂森冰川观测站合作的提案。基面运动的影响速度被认为会影响冰团的速度，但人们对其机制知之甚少。沉积物夹带在基冰中，有时将冰川和岩石分开，可能是造成基冰和岩石之间局部摩擦的一个重要因素，但这种摩擦的大小或控制它的因素尚不清楚。相反，Tell可能会润滑床层，但其流动机制也不确定。这种不确定性之所以隐约可见，是因为很少有现场解释。两种类型的实验将在挪威的坚硬冰川Engabreen进行，斯瓦蒂森冰川观测站提供进入210米温带冰层以下的冰床的通道。这些实验将是首席研究人员早期在Engabreen进行的关于硬层滑动的冰下工作、在其他地方关于软层冰川的钻孔工作以及对冰层变形的实验室研究的延伸。第一个实验将测试对比模型的碎屑[床面摩擦]。一个包含光滑石板的面板将安装在与床面齐平的位置。通过测量冰片上的剪切力、滑动速度、基础融化速率、床上的冰压力和局部基础水压力来研究冰片与滑动脏冰之间的摩擦。基本熔融速度将在很大范围内独立变化。这些实验将提供控制局部碎屑/冰床摩擦和冰川磨损率的因素的完整表征。在第二个实验中，将在冰床界面放置三棱镜。为了评价控制耕作内部运动分布的因素，仪器将记录耕作的剪切应变、伸缩和孔压，而基础水压力独立变化。传感器和应变指示器的最终位置和方向将通过在测试结束时解剖收割机棱镜来测量。此外，还将研究岩性不同的碎屑组构发育和碎屑之间的混合，以制定评估地层剪切应变的沉积学标准。这些实验将比从冰川表面进行的钻孔研究更全面，更不含糊。

AbstractOPP-99-11559Iverson - Iowa State UniversityOPP-00-02230Cohen - Yale UniversityThis is a collaborative proposal with Iowa State, Yale University, and Svartisen Glaciological Observatory in Norway. The influence rates of basal motion are believed to affect the speed of ice masses, but the mechanism is very poorly understood. The sediment, which is entrained in basal ice and sometimes separates glaciers from rock, may be an important factor by causing local friction between basal ice and rock, but the magnitude of this friction or the factors that control it are unknown. Till, in contrast, may lubricate the bed, but its mechanism of flow is also uncertain. This uncertainty looms because there have been few field interpretations.Two types of experiments will be conducted at Engabreen, a hard-bedded, outlet glacier in Norway, where the Svartisen Glaciological Observatory provides access to the bed beneath 210 m of temperate ice. These experiments will be extensions of the Principal Investigators' earlier subglacial work on hardbed sliding at Engabreen, borehole work on soft-bedded glaciers elsewhere, and laboratory studies of till deformation.The first experiment will test contrasting models of debris[bed friction. A panel that contains a smooth rock tablet will be installed flush with the bed surface. Friction between the tablet and sliding dirty ice will be studied by measuring the shear stress on the tablet, sliding speed, basal melt rate, ice pressure on the bed, and local basal water pressure. The basal melt rate will be independently varied over a wide range. These experiments will provide a complete characterization of the factors that control local debris/bed friction and rates of glacial abrasion.In the second experiment, a prism of till will be placed at the icelbed interface. To evaluate the factors that control the motion distribution in the till, instruments will record the till shear strain, dilation and contraction, and pore-water pressure, while the basal water pressure is varied independently. The final position and orientation of sensors and strain indicators will be measured by dissecting the till prism at the ends of tests. Also, clast fabric development and mixing between tills of contrasting lithology will be studied to develop sedimentological criteria for evaluating bed shear strain. These experiments will be more comprehensive and less ambiguous than borehole studies conducted from the surfaces of glaciers.