Laboratory experiments on internal wave reflection and absorption at a simulated oceanic pycnocline

Laboratory experiments have been performed to investigate the reflection of an internal wave beam with a ``pycnocline'' layer situated below an unstratified layer in order to simulate observed oceanic processes. An oscillating cylinder was used to generate wave beams in the well-known ``St. Andrew's Cross'' pattern that interacted with the pycnocline. The internal waves were observed and the incident and reflected amplitudes measured using the synthetic schlieren technique. In virtually all instances, near-perfect reflection or near-complete absorption at the pycnocline was observed, depending on the value of the pycnocline density gradient. The data indicate the existence of a transition from reflection to absorption that is a function of the ratio of the maximum BV frequency in the pycnocline to the BV frequency of the stratified layer.