West Coast of Vancouver Island - Environment

The west coast of Vancouver Island, Canada, includes a relatively wide continental shelf (about 100 km) along the west coast of North America south of the Aleutian Islands. Offshore of Vancouver Island, the Subarctic Current splits into the northward flowing Alaska Current and the southward flowing California Current (McFarlane et al. 1997). The WCVI is at the northern extent of the California upwelling zone (Ware and McFarlane 1989, McFarlane and Beamish 1992, Beamish and Bouillon 1993) and experiences seasonal (spring-summer) upwelling. The mid and outer parts of the continental shelf undergo reversals in the major surface current direction (northward flowing in winter; southward in summer), whereas there is a year-round northward flow at mid-depths (California Undercurrent). The inner (near-coastal) part of this region consists of a persistent northward flowing current (Vancouver Island coastal current) driven by freshwater runoff (Thomson et al. 1989). The transition periods between the upwelling and downwelling seasons occur in February-April and October-November (Ware and McFarlane 1995). There are strong between-year modulations of the timing of the spring and fall transitions, which may produce varying degrees of match or mismatch between biological processes and environmental conditions (Mackas et al. 2001).