Oceanography Students Investigate Water Densities

Students in Brad Turner’s Oceanography class recently visited the MBS Environmental Systems Lab where they investigated water densities based on temperature and salinity in some brightly colored experiments.

The students used a red and blue colored model to represent different water densities based on temperature — warm and cold water.  The warm water is less dense so it is more buoyant.  The students then attached an air mattress pump to one end of the tank to simulate wind blowing off the continent onto the ocean to produce upwelling. “The waters moved offshore by the wind are replaced by waters from the depths below,” said Mr. Turner. “To replace the water moving offshore, waters are brought to the surface from the ocean bottom. These waters are normally very cold and rich in nutrients. Areas of coastal up-welling are typically areas of high productivity and important for fisheries.”

The students also experimented with a yellow/green model designed to represent saltwater and freshwater. The freshwater is less dense than the saltwater so it is more buoyant.  “I isolated a small portion of the water and stirred it with red coloring so that it has a salinity value in between fresh and salt — brackish,” said Mr. Turner. “That was the red water that flowed down the middle of the yellow and green.” 

Mr. Turner also highlighted internal waves in the demonstrations. “Students are familiar with surface waves, but they can happen along any boundary such as the themoclines and haloclines that we produced in the lab,” he said.