NOAA Ocean Currents
- Ocean currents are the vertical or horizontal movement of both surface and deep water throughout the world's oceans.
- Oceanic currents are driven by tides, winds, and differences in water density.Currents are essential for maintaining the existing balance of life on Earth, but they can be deadly as well.
- Tides create a current in the oceans, near the shore, and in bays and estuaries along the coast.These are called "tidal currents."
- Surface ocean currents are generally wind-driven and develop their typical clockwise spirals in the northern hemisphere and counter-clockwise rotation in the southern hemisphere because of the imposed wind stresses.
- The areas of surface ocean currents move somewhat with the seasons ; this is most notable in equatorial currents.
- These currents, which flow under the surface of the ocean and are thus hidden from immediate detection, are called submarine rivers.
- These are currently being researched using a fleet of underwater robots called Argo . Upwelling and downwelling areas in the oceans are areas where significant vertical movement of ocean water is observed.
- Winds drive currents that are at or near the ocean's surface.The primary force responsible for surface currents is wind.
- Gyres in balance between the pressure gradient and the Coriolis effect are called geostrophic gyres, and their currents are called geostrophic currents.
- There are six great current circuits in the world ocean: two in the Northern Hemisphere and four in the Southern Hemisphere. Five are geostrophic gyres: the North Atlantic gyre, the South Atlantic gyre, the North Pacific gyre, the South Pacific gyre, and the Indian Ocean gyre.
- Knowledge of surface ocean currents is essential in reducing costs of shipping, since traveling with them reduces fuel costs.