A thermocline indicates a layer in the ocean where temperature differences are pronounced. What does this layer separate?

A thermocline is a distinct layer in the ocean that marks a significant transition in water temperature. This phenomenon often occurs with depth, where the temperature decreases sharply, delineating the warm shallow waters above from the colder, deeper waters below. In essence, the thermocline serves as a barrier that separates these two layers—warm, sunlit water that is typically well-mixed and influenced by solar heating from the deep cold water that remains relatively stable and isolated from atmospheric conditions.

Understanding this separation is crucial for divers, as it impacts marine life distribution, visibility, and thermoregulation. For instance, many marine species tend to inhabit regions above the thermocline where temperatures support higher biological activity. Knowing about thermoclines can also help divers avoid rapid temperature shifts that could lead to thermal shock.