Arapid change in ocean density with change in depth is the:
1. halocline.
2. thermocline.
3. barocline.
4. isocline.
5. pycnocline.

5. pycnocline.

Explanation:

Pycnocline is the rapid change in density of ocean water with depth. With increase in depth, ocean water tends to be denser. The two major factors that determine density in ocean water are temperature and salinity(salt contents). The denser water become in the ocean the more likely it sinks easily . This is one major factor that drive Ocean currents, the process is called thermohaline circulation.

The increase in salinity of ocean water causes an increase in density . This is because the salt become tightly pack and filled the water to make it denser .  This simply means an increase in saline content of ocean water causes an increase in the density.

Another factor that affects density is temperature. Water at the surface possesses higher temperature due to direct contact with the sun. Usually, the higher the temperature the less dense ocean water becomes . This is why surface water is less dense. As water becomes warm the molecule disperse, this account for it lower density . Colder water are usually higher in density .

Generally, an increase in ocean depth causes considerable increase in density because of it colder temperature and increased salinity contents.