Echo sounding, side scan sonar and seismic profile records in the Canadian Beaufort Sea provide evidence of trenches 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 parallel side scan sonar tracks were run to prepare mosaics 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 1050 -2850. 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.
The continental shelf of the Beaufort Sea has long been considered to have the potential for major oil and gas accumulations. During the period 1963 to 1969, offshore permits to explore for oil and gas were issued for the majority of the shelf which extends some 75 to 100 miles from shore to water depths of approximately 600 feet. Interest intensified following the discovery of Prudhoe Bay in 1968.
Offshore drilling activity to date in the Canadian Beaufort Sea has consisted of fifteen wells drilled from fourteen artificial islands over the past four years and two wells drilled from drill ships in 1976. The blowout preventions for one of the latter wells was protected from possible ice damage by placing it in a pre-dredged depression 40 feet deep. Three drill ships are currently in the area to resume drilling activity this summer. Oil and gas has been indicated in several offshore wells.
In 1970 Canadian Government agencies undertook a comprehensive study of the Beaufort Sea which included bathymetry, shallow seismic, side scan sonar, piston cores, grab samples and other oceanographic surveys.