The surface waters in Lake Ontario circulate in large swirls typically called gyres that are strongly influenced by long waves and shifts in duration and direction of strong prevailing winds. The resulting inertial motions occur at various depths and throughout the year [9]. The simple long an narrow topography of Lake Ontario, in the case of a horizontally uniform wind blowing along its axis (southeasterly in summer), favours the generation a two-gyre circulation pattern [3]. Thus, a anticyclonic vorticity (clockwise) forms to the right of the wind (northwest area of the lake), and cyclonic vorticity (counterclockwise) to the left of the wind (southeast portion of the lake).
The velocity of wind-driven currents is independent of surface wave height and only about 2% of the wind speed driving them [9]. Although storm-induced currents in the Great Lakes can be reach up to 1 m/s, the average currents are between 10 to 20 cm/s throughout most seasons of the year [3].
During the stratified period there is a tendency for colder, denser water to migrate on the left side of the current (northern shore) while the warmer less dense waters on the right side of the current (southern shore) [9]. The north shore of the lake is colder due to frequent upwellings [3] that from the combined effect of wind pushing the surface waters offshore and the Ekman spiral [5, 9].
Lake Ontario's circulation can be divided into summer circulation, which is considered thermally stratified (baroclinic) and winter circulation when the entire depth of the water column homogenous (barotropic) [3].