TRACKING ICE FLOW VELOCITY AT DEPTH BY MONITORING METALLIC TARGETS USING GROUND PENETRATING RADAR

The dynamics of glaciers are important for everything from mountain belt evolution to climate change. A critical variable in understanding glacier dynamics is ice flow velocity; however, this variable may be difficult to measure using conventional techniques (such as tilt meters) especially if the ice velocity over longer periods of time is desired. An alternative method for measuring ice flow velocity is to track a metallic target through time using ground-penetrating radar (GPR). Two boreholes were melted near the terminus of Matanuska Glacier in July 2002 and several metallic targets were lowered to known depths from the surface and allowed to freeze in place. The locations of the boreholes and the positions of the targets were surveyed. In July 2003 a grid of GPR profiles were collected at each of the boreholes and diffraction hyperbolae generated from the targets were identified. Allowing for both vertical and horizontal resolution, a measurable change in the position of the targets over the one-year period was determined. As a result, the ice flow velocity at the locations of the boreholes could be calculated. This technique provides a straightforward alternative to traditional techniques, and also offers many additional benefits such as the ability to track particle velocities within a glacier over a longer period of time than is possible using existing methods.