Analysis of Continuous Vertical Current Profiles in Lake Erie

As part of an extensive survey of the temperature and currents of Lake Erie, a vertical automatic profiling system (EVAPS) was deployed for three days in August 1980. This system consisted of acoustic current meters, temperature sensors and a pressure gauge. The buoyant sensor package was winched from the bottom up and down through the water column. The system collected essentially continuous vertical temperature and velocity profiles. From these profiles, the barotropic component of the flow was extracted; it shows the presence of longitudinal seiche and lunar tidal motions and demonstrates favourable agreement with a numerical model. An experimental momentum balance allows the identification of the important terms (Coriolis force, pressure gradient and local acceleration) and the crude estimation of the numerical value of the wind drag coefficient. The baroclinic part of the flow was decomposed into the three lowest order empirically-computed internal wave modes. The first and second modes could account for most of the variation of the profiles. The temporal variation of the second mode was characteristic of pure inertial waves while that of the first mode was characteristic of inertial-gravitational waves.