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

艾弗森-爱荷华州州立大学科恩-00- 02230耶鲁大学这是一个与爱荷华州、耶鲁大学和挪威斯瓦蒂森冰川观测站合作的项目。 据信，基底运动的影响率会影响冰体的速度，但其机制却知之甚少。 沉积物夹带在基冰中，有时将冰川与岩石分开，可能是造成基冰和岩石之间局部摩擦的重要因素，但这种摩擦的大小或控制它的因素尚不清楚。相比之下，冰碛物可以润滑床层，但其流动机理还不确定。 这种不确定性隐约可见，因为很少有现场的解释。两种类型的实验将在恩格森，一个硬层，出口冰川在挪威，在斯瓦蒂森冰川观测站提供进入床下210米的温带冰。 这些实验将是主要研究人员早期冰下工作的延伸，他们在恩格森对硬层滑动进行了研究，在其他地方对软层冰川进行了钻孔研究，并对冰碛变形进行了实验室研究。 一个包含光滑石板的面板将与床面齐平安装。 将通过测量片剂上的剪切应力、滑动速度、基底融化速率、床上的冰压力和局部基底水压来研究片剂和滑动脏冰之间的摩擦。 基础熔融速率将在宽范围内独立变化。 这些实验将提供一个控制当地碎片/河床摩擦和冰川磨损率的因素的完整特性，在第二个实验中，将在冰柱界面放置一个冰柱。 为了评估控制冰碛物中运动分布的因素，仪器将记录冰碛物剪切应变、膨胀和收缩以及孔隙水压力，而基底水压力独立变化。 在测试结束时，将通过解剖倾斜棱镜来测量传感器和应变指示器的最终位置和方向。 此外，还将研究碎屑组构的发展和对比岩性之间的混合，以制定评价河床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，更明确。

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.