Oceanographic Features, Currents, and Transport in Cabot Strait

Abstract

Seventy oceanographic sections across Cabot Strait, taken at various times of the year between 1950 and 1974, were utilized to describe the average oceanographic featues, currents, and volume transport patterns as well as their variations with depth and time. The water mass structure in Cabot Strait is a two-layered structure; the water in the upper 50–100 m is typically moving seaward, while below that depth it is commonly found to be moving into the Gulf. The character of the upper layer which is normally not of uniform thickness across the Strait, but is distinctly wedge-shaped, is subject to considerable seasonal variation, whereas that of the lower is quite uniform the year round. Seasonal and long-term variations of the physical properties in Cabot Strait are described.Outflow through Cabot Strait is shown to be concentrated in the upper layer off Cape Breton and is balanced by inflow at intermediate depths on the Newfoundland side and in the deep portions of the section. The maximum and minimum transports, both inflow and outflow, occur in August and June, respectively. The net outward volume transport through the Strait increases from 9 × 103m3/s in April to 25 × 103m3/s in August and decreases to about 0.1 × 103m3/s in February. The weighted mean value, 13 × 103m3/s agrees well with the value obtained from an estimate of net freshwater input rate (run-off plus precipitation minus evaporation) above the section. The maximum transport occurs at times of surface minimum salinity. Horizontal advective transport of salt is found to be more important than horizontal diffusive transport. Recommendations for future transport studies in Cabot Strait are presented.