Seasonal evolution of the basin-scale internal wave field in a large stratified lake

The response of the water column to varying conditions of stratification an d wind forcing was investigated in Lake Kinneret (Israel) using data collec ted from thermistor chains and acoustic Doppler current profilers during 19 97 and 1998. The strong daily sea breeze was found to generate a vertical m ode 1 internal Kelvin wave and basin-scale internal Poincare waves of verti cal modes 1, 2, and 3. The Kelvin wave, the dominant component of the inter nal wave field, was responsible for alongshore velocities in the nearshore regions. In the upwind nearshore regions, velocities were dominated by the forced response to the wind and were cross shore in nature. In the lake int erior, the Kelvin wave effect on the horizontal velocity field was minor co mpared to the higher vertical mode Poincare waves. The Kelvin wave is shown to exist in resonant and nonforced states with the wind, whereas the verti cal mode 1 Poincare wave energy remained relatively constant, despite large variability in the forcing conditions. The energy in the higher mode Poinc are waves varied greatly, both on daily and seasonal timescales. The result s demonstrate that the wind energy forces multiple basin-scale internal wav e modes and that prior motion in the water column must be considered when d etermining the subsequent internal wave response in periodically forced sys tems.