Final answer:
The rapid change in temperature with depth in the ocean is not called the pycnocline.
Step-by-step explanation:
The rapid change in temperature with depth in the ocean is not called the pycnocline. The pycnocline refers to the layer in the ocean where there is a rapid change in density with depth, not temperature. It is characterized by a sharp decrease in density with increasing depth. The pycnocline separates the surface layer of warm, less dense water from the colder, denser deep ocean water.