Short answers, pulled from the story.
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.