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Due to sea-temperature and sea-salinity differences the density gradient driven oceanic circulation system developed called as THC system. Since all oceans are interconnected, THC loop of each ocean join together to form global conveyor belt.
Ideal THC loop consist of 4 parts :-
1) surface warm, saline waters moves from lower latitude to higher latitude. It is a fast process.
2) overturning or oceanic mixing or downwelling, happens at 3 locations for example in north Atlantic ocean b/w Greenland and Iceland, in North Pacific ocean at North Japan, in circum-Antartic region,
At overturning regions, warm and cold oceanic water meets and mixed up, leading to transfer of surplus heat and salt to the bottom of the sea.
3) colder, deep, salty, denser water moves from higher latitude to lower latitude. It is a slow process.
4) Upwelling of cold deeper waters to the surface in tropical areas especially at 15-30degree latitude in western margin of continent. It happens at 5 locations on the earth as given below.
1) California current on North American coast.
2) Peru current/Humboldt current on South American coast.
3) Benguela current on south Africa to Angola.
4) Canary current on coast of Azore islands to cape Verde in Africa.
5) west Australian current on Indian ocean coast of Australia.
Role of THC system :--
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--Equilibrium maintenance by circulating surplus heat and salts.
--warm surface currents
-- climates and weather patterns
-- icesheet covers
-- fishing at mixing zone and upwelling
-- stratification of sea/ocean by thermocline zones, halocline zones, pycnocline zone.
-- distribution of marine organism
-- maintenance of properties of sea waters.
--- THC shutdown is last stage of climate change. Which establish new climatic order of the world.
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