RESPONSE OF THE SEABED TO STORM-GENERATED COMBINED FLOWS ON A SANDY ARCTIC SHOREFACE, CANADIAN-BEAUFORT SEA

Wave and current measurements in 3.4 and 5.0 m water depths on a sandy shoreface of the Canadian Beaufort Sea showed that a down-welling cir culation, accompanied by strong offshore-flowing near-bottom currents, develops during storm surges induced by northwesterly winds. Because fine to medium sand prevails on the shoreface, a significant sediment load is probably moved down the shoreface by such currents during majo r storms. A sidescan sonar profile recorded in 4.4 m water depth, the day after a storm with seaward-directed currents with mean velocity up to 0.49 m s(-1), revealed the presence of narrow bands of large rippl es (0.7-0.8 m wavelength) with crests almost parallel to shore. On the basis of theoretical calculations relating the wavelength of wave-for med ripples to wave orbital diameter, the observed ripples were probab ly formed or reactivated during a storm in response to bed-orbital mot ion of surface gravity waves. On the sonograph, the ripple bands were separated by less reflective areas interpreted as current-parallel san d patches formed by seaward-flowing bottom currents. Cores taken on th e shoreface at the end of the wave and current measurement period show ed the presence of thick graded sand beds, which are thought to be the products of rapid deposition of sand from suspension during the wanin g phase of a recent storm. Such beds may be the modern analogues of gr aded sand beds in ancient wave-dominated sequences and could indicate waning storm sedimentation in shallow fetch-limited environments.