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An ocean current is continuous, directed movement of ocean water. Seawater is Water from a Sea or Ocean. On average seawater in the world's oceans has a Salinity of about 3 Ocean currents are rivers of hot or cold water within the ocean. The currents are generated from the forces acting upon the water like the planet rotation, the wind, the temperature and salinity (hence isopycnal) differences and the gravitation of the moon. Temperature is a physical property of a system that underlies the common notions of hot and cold something that is hotter generally has the greater temperature Salinity is the Saltiness or dissolved salt content of a body of Water. An isopycnal is a surface of constant Potential density of Water. Characteristics A tide is a repeated cycle of sea level changes in the following stages Over several hours the water rises or advances up a beach in the flood The depth contours, the shoreline and other currents influence the current's direction and strength. Bathymetry is the underwater equivalent to Hypsometry. The name comes from Greek βαθυς deep, and μετρον measure. A shore or shoreline is the fringe of land at the edge of a large body of water such as an Ocean, Sea, or Lake.
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Important currents
Ocean currents can flow for thousands of kilometers. A current, in a River or Stream, is the Flow of Water influenced by Gravity as the water moves Downhill to reduce its They are very important in determining the climates of the continents, especially those regions bordering on the ocean. Climate encompasses the temperatures humidity rainfall atmospheric particle count and numerous other meteorogical factors in a given region over long periods of A continent is one of several large Landmasses on Earth. They are generally identified by Convention rather than any strict criteria with seven regions Perhaps the most striking example is the Gulf Stream, which makes northwest Europe much more temperate than any other region at the same latitude. The Gulf Stream, together with its northern extension towards Europe the North Atlantic Drift, is a powerful warm and swift Atlantic Ocean current that Another example is the Hawaiian Islands, where the climate is cooler (sub-tropical) than the tropical latitudes in which they are located because of the California Current. The Hawaiian Islands, once known as the Sandwich Islands, form an Archipelago of 19 Islands and Atolls numerous smaller Climate encompasses the temperatures humidity rainfall atmospheric particle count and numerous other meteorogical factors in a given region over long periods of The California Current is a Pacific Ocean current that moves south along the western coast of North America, beginning off southern British Columbia
Background
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. In wind driven currents, the Ekman spiral effect results in the currents flowing at an angle to the driving winds. The Ekman spiral refers to a structure of currents or winds near a horizontal boundary in which the flow direction rotates as one moves away from the boundary The areas of surface ocean currents move somewhat with the seasons; this is most notable in equatorial currents. A season is one of the major divisions of the Year, generally based on yearly periodic changes in Weather.
Deep ocean currents are driven by density and temperature gradients. Thermohaline circulation, also known as the ocean's conveyor belt, refers to the deep ocean density-driven ocean basin currents. The term thermohaline circulation (THC refers to the part of the large-scale ocean circulation that is thought to be driven by global density gradients created by surface heat and Hydrologically an oceanic basin may be anywhere on Earth that is covered by Seawater, but geologically ocean basins are large geologic basins 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 by a fleet of underwater robots called Argo. Argo is an observation system for the Earth's oceans that provides real-time data for use in climate weather oceanographic and fisheries research Upwelling and downwelling areas in the oceans are areas where significant vertical movement of ocean water is observed. Upwelling is an oceanographic phenomenon that involves wind-driven motion of dense cooler and usually nutrient-rich water towards the ocean surface replacing the warmer Downwelling is the process of accumulation and sinking of higher density material beneath lower density material such as cold or saline Water beneath warmer or fresher water
Surface currents make up about 10% of all the water in the ocean. Surface currents are generally restricted to the upper 400 meters of the ocean. The movement of deep water in the ocean basins is by density driven forces and gravity. The density difference is a function of different temperatures and salinity. Deep waters sink into the deep ocean basins at high latitudes where the temperatures are cold enough to cause the density to increase. The main causes of currents are: solar heating, winds and gravity.
Ocean currents are measured in Sverdrup with the symbol Sv, where 1 Sv is equivalent to a volume flow rate of 106 cubic meters per second. The sverdrup, named in honour of the pioneering oceanographer Harald Sverdrup, is a Unit of measure of Volume transport
Significance to people and sea life
Knowledge of surface ocean currents is essential in reducing costs of shipping, since they reduce fuel costs. In the sail-ship era knowledge was even more essential. A good example of this is the Agulhas current, which long prevented Portuguese sailors from reaching India. Even today, the round-the-world sailing competitors employ surface currents to their benefit.
Ocean currents are also very important in the dispersal of many life forms. A dramatic example is the life-cycle of the eel. The Eel is a long thin bony fish of the order Anguilliformes.
Important currents
See also
- Gyre
- Hydrothermal circulation
- Thermohaline circulation
- Marine current power
- Water mass
- Rogue wave (oceanography)
External links
- NOAA Ocean Surface Current Analyses - Realtime (OSCAR) Near-realtime Pacific Ocean Surface Currents derived from satellite altimeter and scatterometer data. The Arctic Ocean, located in the Northern Hemisphere and mostly in the Arctic north polar region is the smallest and shallowest of the world's five major The East Greenland Current originates in the Arctic Ocean and brings cold low Salinity, southbound water along the East Coast of Greenland The Norwegian Current (also known as the Norwegian Coastal Current) is a water current that flows north-easterly along the Atlantic coast of Norway at depths of between Angola current is a temporary ocean surface Current. It is an extension of the Guinea Current, flowing near western Africa's coast The Antilles Current is a warm water current that flows northwesterly past the island chain that separates the Caribbean Sea and the Atlantic Ocean. Baffin Island Current (or Baffin Current) is an Ocean current running south down the western side of Baffin Bay in the Arctic Ocean, along The frigid waters of the north-flowing Benguela current move from the western coast of South Africa, Namibia and Angola towards north and northwest The Brazil Current is a warm water current that flows south along the Brazilian south coast to the mouth of the Río de la Plata. The Canary Current is an Ocean current which branches south from the North Atlantic Current and flows toward the south-west about as far as Senegal where The Cape Horn Current is a cold water current that flows west-to-east around Cape Horn. The Caribbean Current is a warm water current that flows into the Caribbean Sea from the east along the coast of South America. The East Greenland Current originates in the Arctic Ocean and brings cold low Salinity, southbound water along the East Coast of Greenland The Falkland Current is a cold water current that flows northward along the Atlantic coast of Patagonia as far north as the mouth of the Río de la Plata. The Gulf Stream, together with its northern extension towards Europe the North Atlantic Drift, is a powerful warm and swift Atlantic Ocean current that The Guinea Current is a slow warm water current that flows easterly along the Guinea coast of West Africa. The Labrador Current is a cold current in the north Atlantic Ocean which flows from the Arctic Ocean south along the coast of Labrador and passes around The Lomonosov current (also called Lomonosov Under Current or Equatorial Under-Current) is a deep current in the Atlantic Ocean. The North Atlantic Current ( North Atlantic Drift and the North Atlantic Sea Movement) is a powerful warm Ocean current that continues the Gulf Stream North Brazil Currents is a term of the complexion of Atlantic Southern equatorial current and the Atlantic equatorial counter current Guinea current. The Norwegian Current (also known as the Norwegian Coastal Current) is a water current that flows north-easterly along the Atlantic coast of Norway at depths of between The Portugal Current is a weak warm water current that flows south-easterly towards the coast of Portugal. South Atlantic Current is an eastward Ocean current, fed by the Brazil Current. Spitsbergen current is the northernmost part of the North Atlantic Current. The West Greenland Current is a weak cold water current that flows to the north along the west coast of Greenland. The Antarctic Circumpolar Current ( ACC) is an Ocean current that flows from west to east around Antarctica. The Pacific Ocean is the largest of the Earth 's Oceanic divisions The Alaska Current is a northward warm-water current along the coast of British Columbia and the Alaska Panhandle. Aleutian current - also called subarctic current An eastward flowing ocean current which lies north of the North Pacific Current; it is the northern branch of the Kuroshio The California Current is a Pacific Ocean current that moves south along the western coast of North America, beginning off southern British Columbia The Cromwell current (also called Pacific Equatorial Undercurrent or just Equatorial Undercurrent) is a Submarine river: A particular kind of Ocean The East Australian Current is an Ocean current that moves warm water in a counter clock-wise fashion down the east coast of Australia. The Equatorial Counter Current is a significant Ocean current in the Pacific and Indian Oceans that flows west-to-east at approximately five degrees north The Humboldt Current is a cold low- Salinity Ocean current that flows north-westward along the west coast of South America from the southern tip of Chile The Kamchatka Current is a cold-water current flowing south-westward from the Bering Strait, along the Siberian Pacific coast and the Kamchatka Peninsula The North Equatorial Current is a significant Pacific and Atlantic Ocean current that flows east-to-west between about 10° north and 20° north The North Pacific Current (sometimes referred to as the North Pacific Drift is a slow warm water current that flows west-to-east between 40 and 50 degrees north in the Pacific The Oyashio Current (also named 'Oya Siwo' the Kurile current Japanese 親潮 is a cold subarctic Ocean current that flows south and circulates counterclockwise The South Equatorial Current is a significant Pacific, Atlantic, and Indian Ocean current that flows east-to-west between the equator and about 20 degrees The Antarctic Circumpolar Current ( ACC) is an Ocean current that flows from west to east around Antarctica. The Indian Ocean is the third largest of the world's Oceanic divisions covering about 20% of the water on the Earth 's surface The Agulhas Current is the Western Boundary Current of the South-West Indian Ocean and is part of the westward flowing South Equatorial Current The East Madagascar Current is an oceanic flow feature near Madagascar. The Equatorial Counter Current is a significant Ocean current in the Pacific and Indian Oceans that flows west-to-east at approximately five degrees north Indonesian Throughflow is an Ocean current that transports water between the Pacific Ocean and the Indian Ocean through the Indonesian Archipelago Leeuwin Current is a warm Ocean current which flows southwards near the western coast of Australia. The Madagascar Current is an ocean current that flows northwards near the western coast of Madagascar, and it is the only current which sailors can employ on trips from The Mozambique Current is an Ocean current in the Indian Ocean, usually defined as warm surface waters flowing south between the African east coast in the vicinity The South Equatorial Current is a significant Pacific, Atlantic, and Indian Ocean current that flows east-to-west between the equator and about 20 degrees The Antarctic Circumpolar Current ( ACC) is an Ocean current that flows from west to east around Antarctica. The Southern Ocean, also known as the Great Southern Ocean, the Antarctic Ocean and the South Polar Ocean, comprises the southernmost waters of The Antarctic Circumpolar Current ( ACC) is an Ocean current that flows from west to east around Antarctica. Two anti-clockwise Antarctic gyres swirl within the Southern ocean. The Tasman Outflow is the most recently discovered of the World Ocean 's major Ocean currents The existence of the outflow was published by scientists of the Australian A gyre is any manner of swirling Vortex. It is often used to describe large-scale Wind or Ocean currents. Hydrothermal circulation in its most general sense is the circulation of hot water 'hydros' in the Greek meaning water and 'thermos' meaning heat The term thermohaline circulation (THC refers to the part of the large-scale ocean circulation that is thought to be driven by global density gradients created by surface heat and Tidal power, sometimes called tidal energy, is a form of Hydropower that converts the energy of Tides into electricity or other useful forms of power An oceanographic water mass is an identifiable body of Water which has physical properties distinct from surrounding water Rogue waves, also known as freak waves, monster waves or extreme waves, are relatively large and spontaneous Ocean surface waves that are a threat
- RSMAS Ocean Surface Currents
- Coastal Ocean Current Monitoring Program
- Ocean Motion and Surface Currents
- Data Visualizer from OceanMotion.org
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