Ocean currents

 A current is a movement of water in one direction. Some ocean currents are small and temporary while others are permanent and circulate water all around the world. There are two main types of permanent circular circulating current wind-driven currents and thermohaline circulation. 

Currents come up wind driven currents come about when wind reaches out the ocean surface although it reaches to 100 to 200 metres but the flow of wind driven current Can reach to 1000 m. Wind driven currents move in large circular patterns called as gyres.

Thermohaline circulation reference to huge movement of water that flows down from surface to the ocean depths and then again gradually moving forward at the same time. This comes out because of differences in body temperature and salinity with heavy, cold salty water constantly falling to the bottom of the ocean and pushing warmer, less salty water to the top. Thermohaline circulation is known as 'great Ocean conveyor belt' because it moves water all around the world. In this manner it helps to keep the temperature of the earth balance when moving cold water to warmer places and warm water to coolest places for the traveling like this takes about thousand years to make one complete circuit of the planet.