Why does a thermocline form in the ocean?

A thermocline (also known as the thermal layer or the metalimnion in lakes) is a thin but distinct layer in a large body of fluid ( e.g. water such as an ocean or lake, or air, such as an atmosphere) in which temperature changes more rapidly with depth than it does in the layers above or below.

Idon't know. the question you are trying to ask doesn't make sense.