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

iverson -爱荷华州立大学opp -00-02230 cohen -耶鲁大学这是一项与爱荷华州立大学、耶鲁大学和挪威Svartisen冰川学观测站的合作提案。据信，基底运动的影响率会影响冰块的速度，但对其机制了解甚少。基底冰中携带的沉积物有时使冰川与岩石分离，可能是造成基底冰与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这种摩擦的因素尚不清楚。相反，它可以润滑床层，但其流动机制也不确定。这种不确定性的出现是因为很少有现场解释。两种类型的实验将在Engabreen进行，这是挪威的一个硬层冰川出口，在那里，Svartisen冰河学观测站提供了通往210米以下温带冰床的通道。这些实验将是首席调查员早期在恩格布雷恩进行的冰下硬层滑动研究、在其他地方进行的软层冰川钻孔研究以及对土壤变形的实验室研究的延伸。第一个实验将测试碎屑[床]摩擦的对比模型。装有光滑石碑的面板将与床面齐平安装。通过测量片剂上的剪切应力、滑动速度、基底融化速率、床上冰压力和局部基底水压力，研究片剂与滑动脏冰之间的摩擦。基础熔化速率将在一个很宽的范围内独立变化。这些实验将提供控制局部碎屑/床摩擦和冰川磨损速率的因素的完整特征。在第二个实验中，在冰床界面处放置一个斜棱镜。为了评估控制犁铧内运动分布的因素，仪器将记录犁铧的剪切应变、扩张收缩和孔隙水压力，而基础水压力是独立变化的。传感器和应变指示器的最终位置和方向将在测试结束时通过解剖前棱镜来测量。此外，还将研究碎屑组构的发育和对比岩性层间的混合，以建立评价床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.