The "Cline Curves" - changes in temperature, salinity, and density with depth
- Thermocline - a steep temperature gradient in a body of water marked by a layer above and below which the water is at different temperatures.
- Halocline - a vertical zone in the oceanic water column in which salinity changes rapidly with depth.
- Pycnocline - a layer in an ocean or other body of water in which water density increases rapidly with depth.
NOAA Animation: Annual changes of pychnocline depth
Mixing (Surface) Zone
Uppermost water where mixing from currents make temperature, salinity, and density mostly constant.
Vertical changes in temperature with latitude:
• Polar regions have almost no thermocline.
• Temperate regions have weak thermoclines (moderate in summer, less in winter).
• Tropical regions have a strong thermocline.