3D model shows how sea waves move materials over long distances.

Mathematicians have developed a new 3-D model that reveals how invisible internal sea waves move over long distances microscopic organisms, contaminants and nutrients necessary to support aquatic life.

The simulation developed by researchers at the University of Waterloo showcases behaviour of underwater bulges called mode-2 internal waves.

In the model, fluids of different densities are layered like the layers of a cake, creating an environment similar to that found in large aquatic bodies such as oceans and lakes.

A middle layer of fluid, known as a pycnocline, over which the layers are closely packed together is created, and it is in this layer that materials tend to be caught, according to the study presented recently in the journal Physics of Fluids.

"When the fluid behind the gate is mixed and then the gate is removed, the mixed fluid collapses into the stratification because it is both heavier than the top layer and lighter than the bottom one," said David Deepwell, who created the 3-D model along with Marek Stastna of Waterloo.

"Adding dye to the mixed fluid while the gate is in place simulates the material we want the mode-2 waves -- the bulges in the pycnocline formed once the gate is taken away -- to transport. We can then measure the size of the wave, how much dye remains trapped within it, and how well the wave carries its captured material," he added.

The researchers found that the larger the bulge within the pycnocline, the larger the amount of material carried by the mode-2 wave.

The study can help researchers understand how this type of wave interacts with underwater topography like sea mounts.