Collaborative Research: Direct Measurement of the In-situ Stress Tensor at Depth in Glacier Ice

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A technique for direct, in-situ measurement of the stress tensor in deep glacier ice will be developed by adapting methods presently in use in rock mechanics for the measurement of in-situ stress in visco-elastic/plastic materials. Direct stress and deformation measurements will be combined. This will provide two critical properties near the bed of a glacier experiencing fairly complex sliding behavior. For the first time, independent observations of the full stress tensor and the full strain rate tensor in glacier ice will be obtained. The determination of the spatial and temporal character of coupling between glacier ice and the glacier bed is necessary for understanding the dynamics of virtually all ice masses of current interest. Variations in basal and marginal tractions are critical controlling factors in polar ice streams, calving and surging glaciers. The behavior of ice sheets, as well as the stratigraphic interpretation of cores taken from ice sheets, depend on an understanding of the patterns of coupling at the bed and the velocity fields that arise in the ice as a consequence.