1. Global Ocean Conveyor Belt
The term thermohaline circulation (THC) refers to a part of the large-scale ocean circulation that is driven by global density gradients created by surface heat and freshwater fluxes.

2. This dense water then flows into the ocean basins.
The adjective thermohaline derives from thermo- referring to temperature and -haline referring to salt content, factors which together determine the density of sea water.
Wind-driven surface currents (such as the Gulf Stream) travel polewards from the equatorial Atlantic Ocean, cooling enroute, and eventually sinking at high latitudes (forming North Atlantic Deep Water).
This dense water then flows into the ocean basins.

3. The dense water masses that sink into the deep basins are formed in quite specific areas of the North Atlantic and the Southern Ocean. In these polar regions, seawater at the surface of the ocean is intensely cooled by the wind.
Wind moving over the water also produces a great deal of evaporation, leading to a decrease in temperature, called evaporative cooling. Evaporation removes only water molecules, resulting in an increase in the salinity of the seawater left behind, and thus an increase in the density of the water mass