Whole-Field Measurement of Ice Displacement and Strain Rates

The flow of glacier ice is mapped using high-resolution photography and noncoherent light speckle interferometry. Time-lapse, double-exposures of a straining surface yield Young’s fringes when the resulting image is interrogated by a narrow beam of coherent light. Such fringe patterns, when corrected for camera motion, are indicative of the surface displacement occurring between exposures. Results of glacier field experiments are consistent with those garnered by conventional methods at the Nisqually Glacier, Washington. The interferometric method seems amenable to other geophysical applications, such as mapping sea ice flow, using terrestrial or space-based camera platforms.