SUMMER SEA-SURFACE TEMPERATURE VARIABILITY OFF VANCOUVER-ISLAND FROM SATELLITE DATA

Satellite-sensed advanced very high resolution radiometer (AVHRR) sea surface temperature (SST) data over eight summers (1984-1991) were use d to analyze the summer SST patterns of variability off the west coast of Vancouver Island. Empirical orthogonal function (EOF) analysis of the spatial variance for 133 nearly cloud-free summer images was perfo rmed. The first EOF mode, which resembled the mean of all images, show ed a strong cool water band located at the northwest comer of Vancouve r Island, a cool tongue extending seaward from the Strait of Juan de F uca and a warm patch off Barkley Sound. The second mode revealed topog raphically controlled upwelling: cool water over the shelf region with its seaward boundary roughly following the 200-m depth contour, plus a cold eddy located just north of the Juan de Fuca Canyon. The third m ode displayed cool water extending southwestward off Brooks Peninsula, while the fourth mode showed a cool water plume extending off Cape Sc ott at the northern tip of Vancouver Island. These four modes accounte d for 33, 12, 10, and 5% of the SST variance, respectively. The tempor al amplitude of these EOF modes revealed how the SST features changed as summer progressed. From these images, we also constructed an overal l seasonal coolness index, which revealed the summers of 1986 and 1991 to have the coolest coastal water, with both summers immediately prec eding an El Nino.