Cold water currents start near the North and South Poles. Currents originating near the North Pole travel south through the Atlantic Ocean, gradually growing warmer until they reach Antarctica, where they become cold again. Near Antarctica, these currents split, with one going to the Indian Ocean and the other to the Pacific, again becoming warmer. These currents loop back to the Atlantic Ocean and head north toward the Arctic.
The currents that carry cold water toward the equator are known as eastern boundary currents and are part of what is known as the "global conveyor belt," which carries ocean water throughout the Earth. These currents tend to be shallow and are often more than 620 miles across, with badly defined boundaries. The five eastern boundary currents are the Canary Current in the North Atlantic Ocean, the Benguela Current in the South Atlantic Ocean, the California Current in the North Pacific Ocean, the Humboldt Current in the South Pacific Ocean and the West Australian Current in the Indian Ocean.
Currents affect the weather of the land masses surrounding them. For instance, the colder water of the Humboldt Current helps create the sub-tropical climate of Peru, which is cooler than the tropical climate in the surrounding area.