Ocean heat content describes the thermodynamic potential energy stored within seawater. Scientists define this value using the equation of state for seawater approved by the international standard TEOS-10 in 2010.
A steady upward trend in ocean heat content appeared between 1971 and 2018. Over 90% of Earth's excess energy from global warming entered the oceans during this period.
Human-caused greenhouse gas emissions reduced outgoing infrared radiation from Earth's atmosphere creating a planet-wide increase in heat. This reduction resulted in over 90% of planetary heat uptake manifesting as ocean heat content.
The subpolar North Atlantic warmed more slowly than other basins while the Southern Ocean took up a disproportionately large amount of heat. Deep-ocean warming below 2000 meters was largest in the Southern Ocean region.
Thermal expansion accounts for 30 to 40 percent of global sea-level rise from 1900 to 2020. Warming oceans accelerate melting of polar ice shelves and tidewater glaciers contributing further to rising water levels.