The slow, density-driven part of the global ocean circulation, set in motion where cold, salty surface water grows dense enough to sink, notably in the North Atlantic and around Antarctica, and balanced by upwelling and surface return flows elsewhere. Because it moves heat between hemispheres and stores carbon in the deep ocean, its stability is a central question of modern climate science. This description is adapted from Wikipedia contributors under CC BY-SA 4.0; changes were made. https://creativecommons.org/licenses/by-sa/4.0/
Facts
TimescaleA single circuit of the global overturning takes on the order of a thousand years 1 Driving ForceDifferences in seawater density created by variations in temperature and salinity, principally the cooling and sinking of dense, salty water at high latitudes. 1 Resulting FeatureA deep, slow global circulation, popularly called the ocean conveyor belt, that moves heat between ocean basins over centuries. 1 SignificanceThermohaline circulation, particularly the Atlantic branch known as the AMOC, redistributes enough heat to moderate the climate of western Europe; whether it is weakening as polar ice melt freshens the surface ocean is an active scientific question. 1 Driving Force
Driving Force (category) Timescale
Timescale (category) Connections
Associated With
Together with ocean circulation it redistributes thermal energy across Earth's surface.
Source Atmospheric Circulation (Wikipedia)
Wind driving and the global overturning circulation both feed the Gulf Stream; its northern extension carries part of the overturning's warm upper limb.
Source Gulf Stream (Wikipedia)
The overturning circulation is balanced by upwelling and surface return flows.
Source Thermohaline Circulation (Wikipedia)
Causes
Read from this phenomenon's own Wikipedia article (Atlantic meridional overturning circulation); earth5 pass cause judgment: Thermohaline Circulation.
Source Wikidata: Atlantic meridional overturning circulation
Read from this phenomenon's own Wikipedia article (Brine rejection); earth5 pass cause judgment: Thermohaline Circulation.
Source Brine rejection (Wikipedia)
Read from this phenomenon's own Wikipedia article (Gulf Stream); earth5 pass cause judgment: Thermohaline Circulation.
Source Wikidata: Gulf Stream
Read from this phenomenon's own Wikipedia article (El Nino Southern Oscillation); earth5 pass cause judgment: Thermohaline Circulation.
Source El Nino Southern Oscillation (Wikipedia)
Read from this phenomenon's own Wikipedia article (Younger Dryas); earth5 pass cause judgment: Thermohaline Circulation.
Source Younger Dryas (Wikipedia)
In Discipline
Source Thermohaline Circulation (Wikipedia)
Open Questions
Source Thermohaline Circulation (Wikipedia)
Sources
1. Thermohaline Circulation (Wikipedia)
Wikimedia FoundationIntroduction, opening sentenceQuote, Introduction, opening sentence
Thermohaline circulation (THC) is a part of the large-scale ocean circulation driven by global density gradients formed by surface heat and freshwater fluxes.
Open Questions (1 open question)
Is the Atlantic Meridional Overturning Circulation Approaching a Tipping Point?
Direct measurement since the mid-2000s and proxy reconstructions suggest the Atlantic branch of the thermohaline circulation, the AMOC, has weakened, but as of the mid-2020s there is no scientific consensus on whether a consistent slowing has actually occurred, how much of any weakening reflects climate change versus natural multi-decadal variability, or whether an abrupt collapse could arrive within this century rather than the more gradual decline most comprehensive climate models project.
What would resolve this A longer continuous observational record of the overturning circulation's strength, and climate models whose treatment of Atlantic freshwater transport can be tested against that record rather than relying on simulations some researchers argue understate collapse risk.
Oceanography and ClimatologyThermohaline Circulation (Wikipedia)
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