The vertical mixing is crucial for the global overturning circulation and the heat storage in the ocean, and therefore also important for the long- term response of the climate system to the emission of green-house gases. The mixing is mainly caused by breaking internal waves, and more than half of the energy input to these waves is caused by tidal flow over rough topography, creating so-called internal tides.

In order to investigate internal tides, laboratory experiments were done at a European facility in Toulouse. A large tank was filled with saline water with a linear density stratification N2. The bottom topography consisted of 10 straight ridges with rounded tops. Their height was 20 cm, and the width 10 cm. The topography rested on a false bottom that could oscillate sinusoidally. The oscillations created internal waves that propagated away from the ridge tops. The waves were diagnosed by synthetic Schlieren, an optical technique that gives the deviation of the stratification from the background value. 

The purpose of the experiment was to measure the energy flux of the internal waves, and to investigate how it scales with the parameters of the experiment. We are particularly interested in the effect of interference between the ridges. Diagnostic output from a large number of experiments have been stored, but not yet analyzed. A method for computing the energy flux from the Schlieren data has been developed in a first manuscript. In this project, that method will be used to analyze the experimental data, and compare the results to theory.