When the upper water layers warm in the summer months, they become separated from deep water by a transition zone known as a thermocline. In a thermocline, the temperature decreases rapidly with small increases in depth. This phenomenon linking temperature change with depth is called temperature stratification.
As we move down in the ocean, the temperature decreases. The sunlight reaches the upper surface of water and heats it.The temperature changes as the depth of the ocean increase.
The reason is sunlight does not reaches the lower part of the ocean. The density is also keeps on increasing as we move down and is maximum at 4 degree Celsius.The temperature of the water also depends on the season and climate.
