Response of the Seabed to Storm-Generated Combined Flows on a Sandy Arctic Shoreface, Canadian Beaufort Sea

Abstract

ABSTRACT 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 circulation, 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 major 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 ms-1, revealed the presence of narrow bands of large ripples (0.7-0.8 m wavelength) with crests almost parallel to shore. On the basis of theoretical calculations relating the wavelength of wave-formed ripples to w ve orbital diameter, the observed ripples were probably formed or reactivated during a storm in response to bed-orbital motion of surface gravity waves. On the sonograph, the ripple bands were separated by less reflective areas interpreted as current-parallel sand patches formed by seaward-flowing bottom currents. Cores taken on the shoreface at the end of the wave and current measurement period showed the presence of thick graded sand beds, which are thought to be the products of rapid deposition of sand from suspension during the waning phase of a recent storm. Such beds may he the modern analogues of graded sand beds in ancient wave-dominated sequences and could indicate waning storm sedimentation in shallow fetch-limited environments.