AERIAL PHOTOGRAPHIC SURVEYS ANALYZED TO DEDUCE OIL SPILL MOVEMENT DURING THE DECAY AND BREAK-UP OF FAST ICE, PRUDHOE BAY, ALASKA

Abstract

During the summers of 1979 and 1980 aerial photographs of the land fast ice north of Prudhoe Bay, Alaska, were taken. These photographs, covering two-week periods, highlight the decay and break-up of the land fast ice sheet. During the period of photography, wind speed, wind direction, barometric pressure, and tidal height measurements were recorded continuously. Several larger ice floes were 'tagged' with colored plywood markers during 1979. Both these marked flows and other distinctively shaped floes were tracked on the photographic surveys to determine the effect the wind had on their movement. Within the barrier islands, average ice floe velocities as a percentage of wind speed exceeded the 3.5% figure 'normally' found in the literature. North of these islands average ice floe velocities as a percentage of wind speed were less than the 3.5% value. In addition to the flow drift calculations the photographs provide information on melt pool formation and a comparison of the decay and breakup processes between the 1979 and 1980 seasons. The decay and breakup process appears to be triggered by strong wind events in early July.