Much larger currents are at work in our oceans, circulating water around the world. These ocean currents, which are massive currents that are influenced by a variety of different forces that act to propel the water both on the surface and in deep ocean waters. This movement has a significant effect on the earth’s weather. For example, the Gulf Stream current carries warm water toward northern Europe. Due to this, coastal countries in northern Europe have a milder winter than coastal areas in the northeast United States that are much farther south.
Ocean currents are an important abiotic factor that significantly influences food webs and the reproduction of marine organisms and the marine ecosystems that they inhabit. Many species with limited mobility are dependent on this “liquid wind” to bring food and nutrients to them and to distribute larvae and reproductive cells. Even fish and mammals living in the ocean may have their destinations and food supply affected by currents.
Knowledge of surface ocean currents is essential in reducing the costs of shipping since traveling with them reduces fuel costs. In the wind-powered sailing-ship era, knowledge of wind patterns and ocean currents was even more essential. A good example of this is the Agulhas Current (down along eastern Africa), which long prevented sailors from reaching India. In recent times, around-the-world sailing competitors make good use of surface currents to build and maintain speed. Ocean currents are also very important in the dispersal of many life forms. An example is the life-cycle of the European Eel.
- Controlling the climate – 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.
- Critical to marine life – 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. They also carry reproductive cells and ocean life to new places. The best example is sea turtles that lay eggs in the sand along the shores of the ocean. The ocean currents then carry the young hatchlings into the water.
- They are vital for ports in the Polar Regions – 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. Norway is a prime beneficiary of this drift.
- Dispersal of life forms – 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.
- Transportation by humans – Humans rely on ocean currents to move some of their sea vessels, such as boats, on water. Currents are also important as they help when docking and undocking boats, speeding up shipping lanes, and keeping the ships safe, primarily in narrow waterways. The direction of currents can also help in search and rescue missions as well as environmental disaster clean-ups.
- They are responsible for some sports – Not all sports are played on dry land. Some currents create waves that can be used for competitive sports or recreational activities such as surfing. When surfing, a surfer rides with or against the wave, helping carry the surfer to shore.
Ocean currents are important in the study of marine debris, and vice versa. These currents also affect temperatures throughout the world. For example, the ocean current that brings warm water up the north Atlantic to northwest Europe also cumulatively and slowly blocks ice from forming along the seashores, which would also block ships from entering and exiting inland waterways and seaports, hence ocean currents play a decisive role in influencing the climates of regions through which they flow. Cold ocean water currents flowing from polar and sub-polar regions bring in a lot of plankton that are crucial to the continued survival of several key sea creature species in marine ecosystems. Since plankton are the food of fish, abundant fish populations often live where these currents prevail.
Upwelling currents bring cold nutrient-rich waters from the ocean bottom to the surface, supporting many of the most important fisheries and ecosystems in the world. These currents support the growth of phytoplankton and seaweed which provide the energy base for consumers higher in the food chain, including fish, marine mammals, and humans.
Ocean currents can also be used for marine power generation, with areas off of Japan, Florida, and Hawaii being considered for test projects.