Repetitive studies of Harrison Bay, a gently sloping large shelf embayment of the Beaufort Sea, reveal an interaction of ice- and water-driven processes. Sea ice covers this environment for 9 months of the year, and varying areas of open water are present during the remaining 3 months. Fathograms and sonographs recorded yearly since 1975 indicate that an area totaling 2% of the seabed is reworked each year to depths of a meter or more by ice keels in the fast-ice zone. During fall storms in 1977, when minimal ice cover allowed development of abnormal waves and currents, the jagged ice-gouged seabed in water depths of 13 m and less was transformed into sand waves 1 to 2 m high with wavelengths of 100 m. Seaward to 15-m depth, ponding of sediment both shoreward of ice-gouge ridges and within ice gouges to depths of 60 cm suggests an offshore transport direction. Since 1977, ice has continued to gouge the wave- and current-modified seabed. On the basis of our repetitive surveys, such storms should recur at greater than 5-year intervals.

The interaction is a continuum of ice gouging, broken by major open water storms that vigorously shape the upper 1 + m of the thin (3 to 5 m) Holocene sediment. Because of the interplay of these two processes, bed forms and structures vary drastically over short distances, and rates of sediment reworking greatly exceed the regional rate of sediment accretion. On this inner shelf, sea-ice and hydraulic processes are of equal importance in forming the geologic environment. Offshore and at higher latitudes (Arctic Ocean), ice processes predominate; inshore and at lower latitudes (Chukchi and Bering Seas), hydraulic processes predominate.

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