Spectra of Internal Waves: In-Situ Measurements in a Multiple-Layered Structure

Abstract

The persistence of layering between 200 and 400 m depth in the Arctic Ocean has enabled construction of accurate internal wave amplitude traces from a 30-hr series of successive temperature profiles taken at 4-min intervals. Spectral density estimates computed from this series diminish with frequency in proportion to f?2, over the frequency range 0.6 to 2.3 cycles hr?1 (cph). In the vicinity of the Väisälä frequency at 3.0 cph, the spectrum falls off as f?8. An equivalent wave amplitude signal, which would have been obtained from a sensor deployed at a fixed depth, is also constructed from the temperature profiles; the resulting spectral estimates decrease in proportion to f?2, over a frequency range from 0.7 to 7.5 cph, well beyond the Väisälä frequency. These results are consistent with recent analytical studies of internal wave spectra in the presence of fine-structure.