the Global Conveyor Belt

It also has a higher concentration of salt,because the ice crystals that form trap water while leaving salt behind.This cold, salty water is more dense,so it sinks,and warmer surface water takes its place,setting up a vertical current called thermohaline circulation.Thermohaline circulation of deep water and wind-driven surface currents combine to form a winding loop called the Global Conveyor Belt.As water moves from the depths of the ocean to the surface,it carries nutrients that nourish the microorganisms which form the base of many ocean food chains.