Ocean current

An ocean current is a continuous, directed movement of seawater generated by a number of forces acting upon the water, including wind, the Coriolis effect, breaking waves, cabbeling, and temperature and salinity differences.

Ocean currents flow for great distances and together they create the global conveyor belt, which plays a dominant role in determining the climate of many of Earth's regions.

They are primarily driven by winds and by seawater density, although many other factors influence them – including the shape and configuration of the ocean basin they flow through.

On their journey, the water masses transport both energy (in the form of heat) and matter (solids, dissolved substances and gases) around the globe.

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.

[15][16] Upwellings and cold ocean water currents flowing from polar and sub-polar regions bring in nutrients that support plankton growth, which are crucial prey items for several key species in marine ecosystems.

[18] The continued rise of atmospheric temperatures is anticipated to have various effects on the strength of surface ocean currents, wind-driven circulation and dispersal patterns.

[20] Over the last century, reconstructed sea surface temperature data reveal that western boundary currents are heating at double the rate of the global average.

[26][27][28] The "State of the cryosphere" report, dedicates significant space to AMOC, saying it may be en route to collapse because of ice melt and water warming.

In the same time, the Antarctic Circumpolar Current (ACC) is also slowing down and is expected to lose 20% of it power by the year 2050, "with widespread impacts on ocean circulation and climate".

[29] UNESCO mentions that the report in the first time "notes a growing scientific consensus that melting Greenland and Antarctic ice sheets, among other factors, may be slowing important ocean currents at both poles, with potentially dire consequences for a much colder northern Europe and greater sea-level rise along the U.S. East Coast.

[32] In the North Atlantic, equatorial Pacific, and Southern Ocean, increased wind speeds as well as significant wave heights have been attributed to climate change and natural processes combined.

The dispersal patterns of marine organisms depend on oceanographic conditions, which as a result, influence the biological composition of oceans.

The Gulf Stream and the Canary current keep western European countries warmer and less variable, while at the same latitude North America's weather was colder.

In recent times, around-the-world sailing competitors make good use of surface currents to build and maintain speed.

Ocean surface currents
Distinctive white lines trace the flow of surface currents around the world.
Visualization showing global ocean currents from January 1, 2010, to December 31, 2012, at sea level, then at 2,000 m (6,600 ft) below sea level
Animation of circulation around ice shelves of Antarctica
The bathymetry of the Kerguelen Plateau in the Southern Ocean governs the course of the Kerguelen deep western boundary current , part of the global network of ocean currents. [ 2 ] [ 3 ]
Coupling data collected by NASA/JPL by several different satellite-borne sensors, researchers have been able to "break through" the ocean's surface to detect "Meddies" – super-salty warm-water eddies that originate in the Mediterranean Sea and then sink more than a half-mile underwater in the Atlantic Ocean. The Meddies are shown in red in this scientific figure.
Plankton are dispersed by ocean currents.
Human-induced climate change is leading to long-term alterations in ocean and atmospheric circulation. The accumulation of greenhouse gases traps extra heat within the Earth's system, causing both the atmosphere and oceans to warm. Notably, over 90% of this trapped heat is absorbed by the oceans. There are signs that crucial circulation patterns are shifting, with growing evidence suggesting that the Atlantic Meridional Overturning Circulation may be slowing down.
Skipjack tuna fishery in Indonesia.
A 1943 map of the world's ocean currents
Device to record ocean currents
A recording current meter. It records information about currents (speed, direction, depth, temperature).