This award is for support of a program of high-resolution seismic reflection and radio-echo sounding on the surge-type Black Rapids Glacier, Alaska. Determination of changes in the structure of the glacier bed during seasonal fluctuations in velocity will be made. The measurements will be made at a location where a 100 to 400 % increase in speed is known to occur each year in the early melt season. Geophysical sensing of the basal zone will be performed before and during the speed-up. Surface motion and uplift, the discharge of water, solutes and sediment in the terminal stream, meteorological conditions, and water level in moulins will all be monitored. These measurements will allow the morphology of the glacier bed to be determined at times of differing amounts of basal motion, and thus provide valuable insight into the mechanisms of glacier and ice stream motion and the role of basal water.
