Sea ice scouring on the inner shelf of the southeastern Canadian Beaufort Sea

Abstract

About 2200 ice scours were observed and analyzed over a distance of approximately 500 km on the inner shelf of the southeastern Canadian Beaufort Sea. Ice scours were divided into two types based on their morphology: multiple scours consisting of a series of parallel scours and ridges, and single scours. Single scours are the dominant type representing 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 ice scouring processes increases with water depth. In water depths less than 10 m, less than 25% of the seafloor surface is reworked by ice scours. This percentage increases significantly seaward of the 10 m isobath, 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 between a nearshore zone moderately influenced by ice processes and an outer zone affected by intense ice scouring. This morphological boundary could be due to intense erosion by the keels of pressure ice ridges at the inner edge of a zone of grounded ice ridges. Most of the observed ice scours appear to be reworked, especially in water depths of less than 10 m, and represent small-scale sediment sinks. Inshore of the 10 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 dominant motion of ice during scouring events is east or west, which is subparallel to the bathymetric contours and coastline. Scour terminal push mounds, however, suggest a dominant east to southeast movement that may contribute to onshore sediment transport during ice push events.