Thermoclines

A thermocline is the transition layer between warmer mixed water at the surface and cooler water below. Bodies of water are made up of layers, determined by temperature. The top surface layer is called the epipelagic zone, and is sometimes referred to as the "ocean skin" or "sunlight zone." This layer interacts with the wind and waves, which mixes the water and distributes the warmth. At the base of this layer is the thermocline. A thermocline is the transition layer between the warmer mixed water at the surface and the cooler deep water below. It is relatively easy to tell when reaching the thermocline in a body of water because there is a sudden change in temperature. In the thermocline, the temperature decreases rapidly from the mixed layer temperature to the much colder deep water temperature. The depth and strength of the thermocline vary from season to season and year to year. It is semi-permanent in the tropics, variable in temperate regions (often deepest during the summer), and shallow to nonexistent in the polar regions, where the water column is cold from the surface to the bottom.

Here are some examples of what a thermocline looks like on the STRIKER Vivid series: