The oceans are an extremely important factor in climate regulation. One of the main ways that energy is redistributed around the world is through what has been nicknamed the Great Ocean Conveyor Belt, seen here in this animation. It is also known as the Thermohaline Circulation.
The Great Ocean Conveyor Belt is a very large network of eddies, currents and gyres, largely driven by differences in temperature and salinity, which form density gradients. For example, as warm, tropical water in the Atlantic Ocean travels northward towards Greenland, it cools. When this water forms sea ice, salt is left behind in the ocean, which increases salinity. Both the cooling of water and the increase in salinity serve to increase the density of the water, causing it to sink. This cool, salty, dense water then continues on a journey that distributes energy all over the globe, sometimes taking tens, hundreds, or even thousands of years to complete the cycle. This Ocean Conveyor Belt has been identified as an agent of dramatic historical climate changes, aiding in the activation and conclusion of past Ice Ages.