Ocean heat content
Ocean heat content is the thermal energy stored in seawater, commonly calculated over a specified depth and relative to a reference temperature.
Seawater temperature: A measure of the thermal state of seawater, varying with depth, location, and time. Temperature profiles are the observations used to calculate heat stored through the water column.
Earth's energy imbalance: The difference between the solar energy Earth absorbs and the energy it releases to space. The ocean absorbs most of the excess energy associated with the present imbalance.
Ocean temperature measurement: The observation of ocean temperature using instruments deployed from ships, floats, and other platforms. Changing measurement methods shaped which depths and regions could contribute to heat estimates.
Sea surface temperature: The temperature of the ocean's uppermost layer, measured by ships, buoys, and satellites. Surface temperature samples a thin layer, whereas heat content accounts for energy accumulated through depth.
Specific heat capacity: The heat required to raise the temperature of a unit mass of a substance by one degree. It determines how much energy a given ocean temperature change represents.
Global warming: The long-term rise in Earth's average surface temperature, driven mainly by human-caused greenhouse-gas emissions. Ocean heat uptake is a major part of the broader warming of the climate system.
Mechanical bathythermograph: A shipboard instrument that records ocean temperature against depth using a moving stylus and smoked glass slide. It supplied many historical upper-ocean temperature profiles before modern digital systems.
Ocean temperature anomaly: The difference between an observed ocean temperature and a chosen reference average. An anomaly describes departure from a baseline; heat content combines temperature departures with water mass and depth.
Ocean stratification: The layering of ocean water by density, which limits mixing between layers. Stratification controls how heat is distributed vertically and how readily it reaches deeper water.
Tropical cyclone: A rotating storm system that forms over warm tropical or subtropical waters. Heat stored beneath the surface can sustain a cyclone when winds mix cooler water upward.