0 1987, by the American Society of Limnology and Oceanography, Inc. The structure and dynamics of internal waves in Baldeggerseel

Analysis of long records of temperature/depth distribution determined at lo- or 20-min intervals at several stations and extending over three stratification seasons, provides a detailed picture of the characteristics, dynamics, and seasonal variation in activity of internal waves in a small lake (Baldeggersee, Switzerland). Wind stress in general was low, with occasional bursts of higher energy. The ensuing, slightly damped internal seiches govern the dynamics of the stratified lake. The vertical structure displays a dominant response of the first vertical mode. Responses in the second vertical mode, hitherto rarely recorded, are also demonstrated with the help of spectral analysis and models. The horizontal structure of the seiches motion displays dominance and persistence of the fundamental basin mode. Spectral analysis also discloses responses of the second and third basin modes. Multiplying of the spectra with the local buoyancy frequency leads to a collapse of all spectra into a narrow band, pointing toward the possibility of a universal spectrum. New light is shed on apparently common examples of waveform asymmetry and on their interpretation. It is concluded that, in this small-basin, low-energy example, internal waves provide motions at all levels, but little vertical mixing