Thermohaline circulation
Thermohaline circulation describes deep-ocean flows driven in part by seawater density differences associated with temperature and salinity. Cooling and changes in salinity can make surface water dense enough to sink, helping form deep currents; mixing and upwelling return deep water toward the surface. These flows interact with wind-driven currents and redistribute heat and other materials through the ocean. The popular global conveyor-belt image is a simplification of a complex circulation system.
Density and deep currents
Seawater density is affected by temperature and salinity: colder or saltier water is generally denser than warmer or fresher water. In some high-latitude regions, surface water loses heat to the atmosphere, and sea-ice formation can leave salt behind in surrounding seawater. If the water becomes dense enough relative to its surroundings, it sinks and contributes to deep-ocean circulation. The processes and locations involved vary; no single sinking site drives the entire ocean.
Part of a connected circulation system
Thermohaline circulation is one component of large-scale ocean circulation. Winds and Earth's rotation strongly influence surface currents, while density differences help drive deep flows. Water masses mix and exchange heat, freshwater, carbon and nutrients as they circulate. Deep waters eventually return upward through mixing and upwelling, though pathways and timescales differ across ocean basins.
Climate significance and limits of the conveyor-belt image
Ocean currents transport heat and help shape regional and global climate. A simplified global conveyor belt is useful for illustrating links between surface and deep circulation, but real currents form a complex, three-dimensional system with many interacting forces. In the Atlantic, the Atlantic Meridional Overturning Circulation (AMOC) is a related, measurable circulation system, not a synonym for every component of global thermohaline circulation. Warming and freshwater input can alter water density and influence circulation; the magnitude and consequences of changes are active areas of observation and research.
Key facts
- Name
- Thermohaline combines terms for temperature and salinity, factors that influence seawater density.
- Sinking water
- Cooling and salinity changes can increase surface-water density and promote sinking in some regions.
- Multiple drivers
- Deep density-driven flows interact with wind-driven currents, mixing and upwelling.
- Climate role
- Ocean circulation redistributes heat and other materials and influences climate.
- AMOC distinction
- The Atlantic Meridional Overturning Circulation is a specific Atlantic circulation system, not a name for all global ocean circulation.
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References
- 1.Thermohaline Circulation - Currents: NOAA's National Ocean Service Education
NOAA National Ocean Service · other · reliability: unverified · retrieved 23 October 2026
Supports: Explains the influence of temperature and salinity on density-driven deep currents, and how sea-ice formation can increase surrounding seawater salinity.
- 2.What is the global ocean conveyor belt?
NOAA National Ocean Service · other · reliability: unverified · retrieved 23 October 2026
Supports: Describes the combination of deep thermohaline currents and wind-driven surface currents in the global ocean conveyor concept.
- 3.Slowdown of the Motion of the Ocean
NASA Science · other · reliability: unverified · retrieved 23 October 2026
Supports: Explains the roles of temperature, salinity, wind and density in ocean circulation, and distinguishes the Atlantic overturning circulation in climate discussions.
References are suggested by the research engine and may be incomplete. Unverified URLs are omitted rather than guessed.
Article history
- Version 123 October 2026 · EditorCreated by Zapia