Ocean currents are the movements of ocean water due to gravity, the rotating earth (Coriolis effect), water density, the sun, and wind. The various forces determine the size, speed direction, and shape of ocean currents. The water can either move horizontally – known as currents, or vertically – known as downwellings or upwellings. Ocean currents are responsible for the transfer of heat, variations in biodiversity, and the climate of the planet.
What causes currents
Solar heating causes water to expand. The water around the equator is roughly 8cm high than in middle latitudes. It causes a slight slope in the water and it flows down the slopes. Warm water flows towards the cold Polar Regions and cold water flows towards the warmer equatorial regions.
Wind is responsible for ocean currents as it blows the water on the surface, causing the currents. The wind is responsible for surface currents where ocean water is redistributed based on its density and temperature.
Gravity tends to pull items towards the surface of the earth. When the wind blows ocean water, the water piles up in the direction of the wind. Gravity, therefore, pulls the water down the ‘hill’ against the pressure gradient.
Effects of currents
Warm currents lead to evaporation, which turns into the rain for the coastal areas. For instance, North Atlantic Drift brings rainfall to Western parts of Europe that results in rains throughout the year.
Some currents might be too strong and end up destroying planktons. For instance, El Nino currently destroys planktons along the Peruvian coasts. It also brings with it several diseases that kill fish.
In Antarctica, strong upwelling currents pump nitrogen and phosphates up from the deep sea to blooms of algae and other plants. The planktons are eaten by crustaceans called krill. The krill in turn feed penguins, seabirds, seals, etc.
Ocean currents are responsible for moving the heat from the equator and towards the poles. As such, they maintain the natural order and balance of the climate.
Marine wildlife is heavily dependent on the balance created by the ocean and is maintained by the ocean currents. The currents carry nutrients and food organisms, feeding the plants and animals that depend on them.
Warm ocean currents are responsible for keeping the ports in polar regions operational. It is because they keep the ports ice-free. The North Atlantic Drift, for instance, keeps most of the European ports ice-free and operational.
Ocean currents are also important as they disperse many life forms. For instance, the lifecycle of the European eel is highly sustained and influenced by ocean currents.
Humans rely on ocean currents to move some of their sea vessels, such as boats, on water. They help when docking and undocking boats, speeding up shipping lanes, and keeping the ships safe, primarily in narrow waterways.