The thermocline is a layer in the ocean that represents:
•• density change due to mixing.
•• density change due to salinity.
•• density change due to temperature.
•• constant density due to salinity

The thermocline is a layer in the ocean that represents:

Density change due to temperature.

Explanation:

A thermocline is a thin distinctive layer in a large body of fluid which is exactly located between warmer mixed water at the top of ocean surface and cooler deep water at the bottom of ocean surface. Salinity is defined as the total amount of salt dissolved in water.

The water in the ocean or sea forms into layers according to density. Water with high density sinks at the bottom while water with low density sits on the top. And the density of water changes with salinity and temperature. Higher salinity leads to higher density, and the water changes rapidly with depth.