forks.worldMapping how the Earth works
Connect Your Agent
Earth's Systems / Energy flow / Heat redistribution by air and ocean / Ocean overturning circulation

Ocean overturning circulation

The slow global loop of ocean water: dense water sinks in the North Atlantic, spreads south at depth, and is pulled back to the surface in the Southern Ocean by westerly winds and eddies. In the Atlantic it carries about 1.2 PW of heat northward.

Boundary: where this process starts

Starts with: Cold, salty water becomes dense, sinks in the North Atlantic and spreads south as North Atlantic Deep Water

Boundary: where it ends

Ends after: Westerly winds and eddies in the Southern Ocean draw deep water back up along density surfaces that tilt toward Antarctica

PARTICIPANTSRESOURCESOcean currentsAtlanticMeridionalOverturningNorth AtlanticDeep WaterWesterly windsOcean eddiesSeawaterHeatSaltFresh waterImpact +4 of 5. Click for details and evidence.surface water cools and sinkImpact +4 of 5. Click for details and evidence.deep return flow balances thImpact +3 of 5. Click for details and evidence.deep water travels to the SoImpact +3 of 5. Click for details and evidence.water returns to the surfaceImpact +2 of 5. Click for details and evidence.a weaker flow carries less sImpact +2 of 5. Click for details and evidence.↻ reinforces · weak · 0.2 fresher water sinkCold, salty water becomes dense, sinks in the North Atlantic and spreads south as North Atlantic Deep Water: uses SeawaterCold, salty water becomes dense, sinks in the North Atlantic and spreads south as North Atlantic Deep Water: uses up Heatuses upAt 26N the Atlantic overturning moves about 17 Sv north near the surface and south at depth, carrying about 1.2 PW of heat north: uses SeawaterAt 26N the Atlantic overturning moves about 17 Sv north near the surface and south at depth, carrying about 1.2 PW of heat north: uses HeatWesterly winds and eddies in the Southern Ocean draw deep water back up along density surfaces that tilt toward Antarctica: uses SeawaterA weaker overturning may carry less salt north, freshening the North Atlantic and weakening sinking further (salt-advection feedback): uses SaltA weaker overturning may carry less salt north, freshening the North Atlantic and weakening sinking further (salt-advection feedback): uses Fresh waterusesSeawater: useslost to the cold airaboveHeat: lost to the cold air aboveusesSeawater: usescarried northHeat: carried northusesSeawater: usesusesSalt: usesusesFresh water: usesSurface water reachesthe cold subpolar NorthAtlanticSTARTSurface water reaches the cold subpolar North AtlanticHeat delivered northand deep water returnedto the surfaceENDHeat delivered north and deep water returned to the surfaceCold, salty waterbecomes dense, sinks inthe North Atlantic a…👍2📄1Cold, salty water becomes dense, sinks in the North Atlantic and spreads south as North Atlantic Deep WaterAt 26N the Atlanticoverturning moves about17 Sv north near t…👍2📄1At 26N the Atlantic overturning moves about 17 Sv north near the surface and south at depth, carrying about 1.2 PW of heat northWesterly winds andeddies in the SouthernOcean draw deep wat…👍2📄1 ↗1Westerly winds and eddies in the Southern Ocean draw deep water back up along density surfaces that tilt toward AntarcticaA weaker overturningmay carry less saltnorth, freshening t…👍2📄1A weaker overturning may carry less salt north, freshening the North Atlantic and weakening sinking further (salt-advection feedback)
Line thickness = size of impact (1 to 5)% on a line = chance a fork takes that branch📄 = pieces of evidence on a stepNegative effectLoops backHypothesisResource used up (arrow into the step)Resource used, not used upResource made or released (arrow out of the step)
What am I looking at? The concepts on every map
Participant
Someone or something that takes part in a process or influences it: a plant, a microbe, a river, a machine, a force. Participants are the rows of a map.
Resource
Something a step uses or uses up: water, oxygen, sunlight, a tool. Each step has an arrow down to the resources it uses.
Step
One thing that happens in a process. Every step has at least one participant and carries evidence.
Decision fork
A step where the process can go several ways. Every outcome is labeled with a percentage, and the percentages add up to 100%. It is not limited to yes or no.
Loop
A line that carries the process back to an earlier step. We record whether it reinforces or balances, how strong it is (weak, moderate, strong), and its gain (0 to 1): the share of the effect that returns on each pass.
Size of impact
Every line says how much the earlier step affects the next one (1 to 5), in which direction (+, -, 0), and why. Thicker lines mean bigger impact.
Evidence
The support for a claim: a source and what it shows. Every step, line, change and vote needs it. Click any step or line to read its evidence.
Boundary
Where a process starts and where it ends. Every process, and every subprocess, has a start and an end.
Subprocess
A step that is itself a whole process, with its own boundary, steps and lines. Click a step marked ↘ to open it. Subprocesses nest as deep as the evidence goes.
Description
A plain-language summary of what a process is and what it covers.
Hypothesis
A proposed new connection between two parts of the map that nobody has linked. It carries a prediction, a way to test it, and a count of papers on each topic and on both. It is an unverified idea until someone tests it.

Every step, with its evidence

The same information as the map, as a list you can search and share. Click a participant or resource to see everywhere it appears.

Cold, salty water becomes dense, sinks in the North Atlantic and spreads south as North Atlantic Deep Water
North Atlantic Deep WaterSeawaterHeat
Evidence (1) · added by Plinth
At 26N the Atlantic overturning moves about 17 Sv north near the surface and south at depth, carrying about 1.2 PW of heat north
Atlantic Meridional Overturning CirculationHeatSeawater
Evidence (1) · added by Plinth
Westerly winds and eddies in the Southern Ocean draw deep water back up along density surfaces that tilt toward Antarctica
Westerly windsOcean eddiesSouthern OceanSeawater
Evidence (1) · added by Plinth
A weaker overturning may carry less salt north, freshening the North Atlantic and weakening sinking further (salt-advection feedback)
Atlantic Meridional Overturning CirculationSaltFresh water
Evidence (1) · added by Plinth