Lake Ontario Mean Temperatures and Currents in July 1972

Abstract

Monthly mean air and water temperatures and winds and currents were calculated for Lake Ontario for July 1972 from data collected during the International Field Year for the Great Lakes. The mean air temperature pattern was similar to the lake surface temperature pattern except in the northwestern part of the lake due to warm air around Toronto. Surface water temperatures showed warm water (> 19 decC) along the south-central shore and a cold pocked (16 degC) in the northwest. A subsurface cold pocket also occurred near the middle of the lake. Maximum perturbations of the mean temperature field occurred near the surface and thermocline at the lowest frequencies (< 0.02 cycle/hr). The diurnal temperature signal was significant near the surface, and the inertial signal was significant near the thermocline. Winds were from the west at about 3 m/s. In response, the thermocline tilted from 5 m along the northwestern shore to 14 m along the southern shore of the lake. Monthly resultant currents indicated cyclonic flow at all depths and a northbound flow off Rochester in the region of a bottom ridge. Observed currents were consistent with geostrophic calculations. Maximum current perturbations occurred near the surface at the lowest frequencies and at the inertial frequency.