Abstract

The meridional overturning circulation is regulated by diapycnal mixing in the abyssal ocean. This mixing is produced by the nonlinear interactions of internal waves (IWs) which are created when the barotropic tide flows over topography. Mathematically, an oscillating fluid over a stationary ridge is equivalent to a stationary fluid beneath an oscillating ridge. Motivated by this concept, we conducted a series of laboratory experiments to study the evolution of the density field by oscillating an artificial ridge in a linearly stratified tank. Using a novel Background Oriented Schlieren (BOS) software package, as well as a unique BOS setup, we can obtain the evolution of internal wave beams through visualization of the density field. This is then further analyzed to produce the resultant density and velocity fields.  We performed these experiments at both a small scale that required a few pounds of stratifying salts to create a linear regime, and at a larger scale that required over 2000 lbs of salt. The analysis of these experiments is ongoing, and I will share the background and preliminary results on both mixing efficiency measurements and the mechanisms behind a localized mixing phenomena we observed called “intrusions”.