Thee correct answer is - a deep ocean current.
The ocean's global conveyor belt is represented with the movement of the water in the deep ocean currents. These deep currents of cold water never stop, and they move constantly across the globe. They are getting their properties in close proximity to the poles, and move the cold and rich in nutrients water from the Arctic and Antarctic Circles towards the low latitudes. The conveyor belt is very important in the climate patters on the planet, but it is also crucial for the existence of the marine ecosystems.