SEA-ICE SCOURING ON THE INNER SHELF OF THE SOUTHEASTERN CANADIAN-BEAUFORT-SEA

About 2200 ice scours were observed and analyzed over a distance of ap proximately 500 km on the inner shelf of the southeastern Canadian Bea ufort Sea. Ice scours were divided into two types based on their morph ology: multiple scours consisting of a series of parallel scours and r idges, and single scours. Single scours are the dominant type represen ting more than 85% of the total observations. The mean scour depth and width are 0.3 m and 11 m respectively, but scour depths of more than 2 m and a scour width up to 345 m were documented. The magnitude of ic e scouring processes increases with water depth. In water depths less than 10 m, less than 25% of the seafloor surface is reworked by ice sc ours. This percentage increases significantly seaward of the 10 m isob ath, being more than 75% in water depths in excess of 12 m. A break in the seabed slope at about 10 to 12 m water depth marks a boundary bet ween a nearshore zone moderately influenced by ice processes and an ou ter zone affected by intense ice scouring. This morphological boundary could be due to intense erosion by the keels of pressure ice ridges a t the inner edge of a zone of grounded ice ridges. Most of the observe d ice scours appear to be reworked, especially in water depths of less than 10 m, and represent small-scale sediment sinks. Inshore of the 1 0 m isobath, scour reworking is believed to be mainly due to frequent bottom disturbance by wave orbital currents and mean near-bottom flows during the open water season. Scour orientations show that the domina nt motion of ice during scouring events is east or west, which is subp arallel to the bathymetric contours and coastline. Scour terminal push mounds, however, suggest a dominant east to southeast movement that m ay contribute to onshore sediment transport during ice push events.