Turbulent exchange characteristics in the hypolimnion layer of Lake Ontario

Flow regime and turbulence characteristics in a hypolimnion of Lake Ontario are determined using time series current measurements from a vertical stri ng of moored current meters and a bottom mounted Acoustic Doppler Current P rofiler (ADCP). The diffusion and turbulent structures of the water column are parameterised in terms of horizontal exchange coefficients for momentum (K-x and K-y) during these deployments. The analysis suggests that the str ucture of the turbulent fluctuations is isotropic. The kinetic energy and h orizontal exchange coefficients decrease with depth. The mean flow at all m oorings appears to be strongly correlated with the zonal surface wind stres s. Fifteen to twenty metres above the bottom, the flow is marked by an incr ease in kinetic energy, turbulence intensities, and eddy viscosity coeffici ents. Strong episodic wind impulse decreases horizontal exchange coefficien ts through the water column but probably enhances the vertical mixing due t o increase in current shear. It is suggested that the associated current-in duced sediment resuspension may contribute to the establishment and mainten ance of a Nepheloid layer in Lake Ontario.