Turbulence and internal waves in Patricia Bay, Saanich Inlet, British Columbia

Abstract

The physical environment in Patricia Bay of Saanich Inlet, British Columbia, is characterized. Turbulence and internal waves were measured over September 2010 using a moored Acoustic Doppler velocimeter and Acoustic Doppler Current Profiler, while diel vertical migration of zooplankton was recorded with an echosounder to test for possible biological generation of turbulence. The average turbulent dissipation rate 〈ϵ〉 was O(10−8Wkg−1) with the corresponding diapycnal eddy diffusivity K of ~5×10−6m2s−1. Barotropic velocities responded to forcing outside Saanich Inlet in the Strait of Georgia and Haro Strait. Subtidal baroclinic velocities were southward at the surface and northward at mid-depth during spring tides, the reverse during neaps. Mode-2 M4 frequency in cross-inlet velocity u was more energetic than any mode-1 diurnal or semidiurnal frequencies in both u and v, which may be a signature of cross-inlet seiches. Spectral energy levels of baroclinic velocities and shear were weakly correlated with ϵ. No relation was found between turbulent events and diel vertical migration.