The thermocline is a thermal transition zone between 50 and 300 metres depth where temperature falls rapidly (10–15 °C over a few tens of metres). It acts as a barrier limiting vertical exchange of water, nutrients, and oxygen.
Meteorological importance
Thermocline depth influences SST and, consequently, tropical cyclone intensity. A hurricane mixing cold deep water through a shallow thermocline weakens; one over a deep thermocline maintains access to warm water and can intensify. During El Niño, the equatorial Pacific thermocline deepens in the east.