The global thermohaline circulation ("ocean conveyor belt") is driven by density differences created by temperature and salinity. Cold, salty water is denser and sinks at high latitudes, dragging a slow deep current around the planet while warm surface water flows in to replace it.
ρ ≈ 1000 + 0.8·(S − 35) − 0.2·(T − 4) [kg/m³, linear equation of state]
sink rate ∝ (ρ − ρ_ref)
conveyor period T_c ∝ 1 / (wind_speed · Δρ)
- Polar surface temp — colder water is denser, so lower values speed up sinking at the polar box.
- Surface salinity — higher salinity increases density and reinforces sinking; low salinity (meltwater) can shut circulation down.
- Wind-driven surface speed — scales the horizontal surface current that carries parcels toward the polar sinking zone.
- Parcel count — number of tracked water parcels shown as instanced points along the loop.
This overturning circulation redistributes heat globally — the Gulf Stream branch keeps northwest Europe far milder than other regions at the same latitude, and any weakening (from Arctic freshwater input) is a major climate-tipping-point concern.