Sea Bottom Scouring In The Canadian Beaufort Sea

Abstract

Echo sounding, side scan sonar and seismic profile records in the canadian Beaufort Sea provide evidence of trench\;!s or "scours" on the continental shelf sea bottom. These are generally believed to be caused due to grounding of ice masses. Records obtained over a three year period by government and industry were analyzed with particular regard to frequency of scouring and scour azimuth, depth and width. Approximately 1100 n. miles of echo sounding records and 1900 n. miles of side scan sonar records obtained in 1970, 1971 and 1972 were examined in detail during-the study. These totals were made up by choosing every third or fifth mile of available records. The variations of these parameters with location are shown on maps and their relationship with water depth are presented on histograms. SpeCUlative discussion regarding causes of scouring, scour rates and sedimentation within scours is also presented. Two areas were selected where parellel side scan sonar tracks were run to prepare mozaics of the sea bottom. These areas were later resurveyed to determine the number of scours added over several years. It has been found that the preferred orientation of the scours is 105 0 -285 0 • Scouring is most common in water depths between 50 and 150 ft. where many areas are nearly saturated with scours. Maximum activity occurs at approximately 100 ft. Normally scours do not exceed 6 ft. but in places they occur up to 20 ft. in depth. Scour widths range from tens of feet to hundreds of feet. The tendency is for scours to become deeper in deeper water. The depth of scouring is particularly important in design of protection for offshore wells and future pipelines. The most important parameters in this regard are the depth of scours and the rate of new scouring.

Ice-gouging characteristics: their changing patterns from 1975-1977, Beaufort Sea, Alaska

“…The dominant gouge trend, density, maximum incision depth, and maximum disruption width were determined for 1/2 km segments of the test lines. We have tried to standardize as many of the admittedly subjective observatons (Hnatiuk and Brown, 1977) in an effort to make them comparable from one area to another and from year to year. As the reader proceeds through the various characteristics discussed below, it might be helpful to refer to the 500 m data segment depicted in Figure 4 along with a listing of the characteristics determined from this segment.…”

“…To date there has been considerable disagreement among investigators as to the age of ice gouge features and the relative intensity of contemporary gouging as related to winter ice zonations and seasonal ice patterns (Pelletier and Shearer, 1972;Kovacs and Mellor, 1974;Reimnitz and Barnes, 1974; Reimnitz and others, 1977a,b;Lewis, 1977;and Hnatiuk and Brown, 1977).…”

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

“…Beaufort Sea to document ice scours over the continental shelf (Pelletier and Shearer, 1972;Shearer and Blasco, 1975;Lewis, 1977;Hnatiuk and Brown, 1977;Shearer et al, 1986;Gilbert and Pedersen, 1987;Lewis and Blasco, 1990;Blasco et al, 1992). Most of these studies, however, were focused on ice scouring on the middle shelf, in water depths of more than 20 m, and the inner shelf has received less attention.…”

Kulluk-An Arctic Exploratory Drilling Unit

“…The physical environment of the southern Beaufort Sea has been well documented in order to define the nature of its ice cover, wind and wave regime, and sea bottom conditions (Wright et al, 1981), (Hall et al, 1983) (Hnatiuk and Wright 1983). The primary environmental constraints affecting the design and operation of floating drilling systems are the waves, and occasional sea ice intrusions, that occur during the short summer season (July through September) and the growth and decay of the sea ice cover, experienced during the remaining nine months of the year (October through June).…”