In this talk, I will discuss about the variability of internal turbulent mixing in temperature stratified waters, observed from field work conducted in the water-column of Lake Simcoe in August – September, 2011. I will specifically show how these episodic mixing events exhibited strong correlation with the environmental variability in air temperatures and wind forcing. The observations are made from high-frequency water column thermal stratification measurements by a chain of thermistors, along-beam velocity measurements by an Acoustic Doppler Current Profiler (ADCP), and air temperature and wind speed records in the observation period from Environment Canada.

We estimated the internal turbulence products (Reynolds stress, turbulence production and dissipation, eddy viscosity and diffusivity) by processing ADCP data using two methods - variance and structure function methods , and thermistors data using Thorp-scale analysis . Our characterization of the variability of theses estimated turbulence products based on wind speed, Lake number (a number that estimates the strength of the stratification to the wind forcing), and gradient Richardson number (estimate the strength of the stratification in relation to the velocity shear) will be discussed.