Vertical temperature gradient
Between surface zone & deep zone, T changes rapidly with increasing depth
Region with steep T gradient = thermocline zone
- Thermoclines common in the tropics & the subtropics
- Thermoclines occur seasonally in mid-latitudes
- Thermoclines are rare at high latitudes
Thermoclines usually create a region of rapid increase in sea water density, called a pycnocline
In such cases, the ocean is stably stratified