Thermocline
A layer in a body of water where temperature changes rapidly with depth, separating warmer surface water from colder deep water.
Stratification (water): The layering of water masses by differences in density, often caused by temperature or salinity. A thermocline is the temperature-driven layer within a stratified water column.
Density of seawater: The mass per unit volume of seawater, determined chiefly by temperature, salinity, and pressure. Temperature-dependent density helps maintain the thermocline's separation between water masses.
Ocean heat content: The thermal energy stored in the ocean, commonly assessed over a specified depth range. Thermocline position influences how much heat is stored near the surface versus at depth.
Seasonal thermocline: A thermocline that develops during warm seasons and weakens or disappears during seasonal mixing. It is the recurring form produced by surface heating in many temperate waters.
Mixed layer: The near-surface ocean layer kept relatively uniform by wind, waves, and convection. It commonly lies above the thermocline and supplies its warmer upper boundary.
Specific heat capacity: The heat required to raise a unit mass of a substance by one degree. Water's high heat capacity helps surface layers store heat above colder depths.
Upwelling: The upward movement of deeper water toward the surface, often driven by wind or currents. Upwelling can lift cold water and the thermocline toward the surface.
Permanent thermocline: A thermocline that persists year-round, especially in the open ocean at low latitudes. It distinguishes tropical ocean structure from seasonally mixed higher-latitude waters.
Halocline: A water layer where salinity changes rapidly with depth. It creates a similar density boundary, but salinity rather than temperature defines it.
Thermal conductivity: A material property describing how readily heat flows through a temperature gradient. Heat conduction gradually smooths the sharp gradient that defines a thermocline.