Currents along the pacific coast of Canada

Abstract

A series of oceanographic studies along the west coast of British Columbia in 1979–1982 produced several realizations of the seasonal cycle of currents. At one site, occupied for 3–1/4 years, the monthly mean currents are stable in speed and direction indicating that a single year of data reliably describes the pattern. Based upon three sets of observations at 15‐m depth (summer only) and 17 at 50‐m depth, the flow along Vancouver Island in winter is towards the northwest, parallel to shore, with some evidence that speeds are greater 15 km from shore (30–40 cm s⁻¹) than farther offshore. In April the flow becomes more variable over the outer shelf a southeastward current develops near the shelf break in May, becoming strongest in August with speeds of 20 cm s⁻¹. This southeastward flow appears to be a response to a shift to northerly winds in summer. Near shore during summer a flow tentatively labelled the Vancouver Island Coastal Current flows towards the northwest with speeds of 10–15 cms⁻¹. By September this flow weakens and winter conditions are established by October. Only summer currents are available for Queen Charlotte Sound. These observations show less stable monthly means, which nevertheless are directed along the depth contours, with shallow water on the right (observer facing downstream). A clockwise gyre around Goose Island Bank in the centre of the Sound and a strong outflow from the Sound near Cape St James are the two dominant features observed. At depths between 150 and 330 m, the currents along Vancouver Island are generally toward the northwest at 5 to 15 cm s⁻¹, except between March and May. If this flow is the California Undercurrent, then it is wider and has greater speeds than previously expected.