Which ocean currents are the slowest?

The slowest currents are found deep in the world's oceans. These "sluggish," cold waters take up to about 1,000 years to circulate around the entire globe.

What is the average temperature of the world's oceans?

The average temperature of the oceans and seas is about 40°F (4.4°C).

What are the major surface and subsurface currents in the oceans?

The major warm ocean surface currents are the North Equatorial, Kuro Siwo, Gulf Stream, and South Equatorial Currents, plus the Equatorial Countercur

In this 1968 image, infrared cameras show the warmth of the Gulf Stream flowing off the U.S. East Coast. (NOAA)

In this 1968 image, infrared cameras show the warmth of the Gulf Stream flowing off the U.S. East Coast. (NOAA)

rent and North Atlantic Drift. The major cold ocean surface currents are the Oyashio, California, Labrador, Peru (Humboldt), Benguela, Canaries, and Antarctic Circumpolar Currents. The major subsurface currents—all of them cold—are the Cromwell Current, Weddell Sea Bottom Water, Deep Western Boundary Current (the largest deep-ocean current), and the North Atlantic Deep Water.

What causes deep ocean currents to flow around the world?

The deep ocean currents are driven by thermohaline circulation, which is movement caused by differences in the temperature and salinity content of the water. Because cold, salt-laden water is heavier than warm water, it sinks to the bottom of oceans. To replace it, warmer water fills in, and as it subsequently cools, the rotation is repeated. This constant movement of water has often been referred to as a giant global conveyor belt or pump that slowly circulates water all over the world's oceans.

For example, the warm Gulf Stream current is heated by the Sun, "starting" in the Caribbean. It then flows north along the east coast of North America (mostly along the United States coastline) until it reaches sub-polar waters in the North Atlantic. Between Greenland and Norway, the cold Arctic winds cool the salt-laden water almost to the freezing point. Huge amounts of the now-cold, heavy salt water sink at this point to depths of around 3 to 4 miles (5 to 6.5 kilometers) and begin the next phase of the journey, traveling southwards through the Western Atlantic Basin to the Antarctic Circumpolar Current, and then into the Indian and Pacific Oceans. This trip takes many years. Off the coasts of Peru and California, for instance, upwelling's often consist of ocean waters that sank to the depths centuries before.

How does the Gulf Stream affect the weather of the British Isles and Scandinavia?

The Gulf Stream currents move warm water in the Atlantic Ocean from the Caribbean Sea northeast to northern Europe and the British Isles. The current flows in this manner because currents heading west from the south Atlantic run into Central America. If North and South America were not connected by this relatively thin strip of land, the current would continue to flow westward and none of the warmer waters would reach Europe. Scotland, Ireland, England, Wales, and the Scandinavian countries would have climates more closely resembling Greenland's. When you look at a world map, you will notice that England, for instance, is at a latitude north of Newfoundland. Logically, it should be a lot colder there than it is, but thanks to the Gulf Stream, England has a climate more like that of New York City than northern Canada. Indeed, mainland Europe is warmer than North America because the Gulf Stream brings warmer weather with it.

What is El Niño?

El Niño refers to the phenomenon that occurs when warming waters in the tropical Pacific build up around Christmastime. It is a fairly regular occurrence (every two to seven years, but usually every three to four years, and with powerful ones

What is the story behind the man who lent his name to the Humboldt Current?

Next to Napoleon Bonaparte, Alexander von Humboldt (full name, Friedrich Wilhelm Heinrich Alexander Freiherr von Humboldt, 17691859) was largely regarded as the most famous man in Europe in his day. Educated in everything from finance and languages to astronomy, geology, and anatomy, Humboldt had a passion for science and travel. Most notable was his voyage to South America (1799-1804), during which he explored the natural landscape, making observations about the animal and plant life, as well as geological and astronomical observations. From this experience, he originated the idea that species vary depending on the climate, which varies with temperature and elevation. He also correctly surmised volcanoes probably align themselves along geological fissures in the Earth's crust. Humboldt connected the dots between geology and weather, noting how climate changes with elevation; he also was the first to observe how the Earth's magnetic field varies with latitude, and made observations that would later contribute to theories on how weather systems are generated with the planet's middle latitudes. When Humboldt's expedition reached the Pacific, he discovered the Peru Current, which is now also known as the Humboldt Current. For all his explorations and discoveries, Humboldt became a hero when he arrived back in Europe. He wrote about his journeys in the epic 30-volume work The Voyage of Humboldt and Bonpland (1805-1834) and was even more lauded for his two-volume Cosmos (1845, 1847), in which he attempted to unify many scientific disciplines to describe the complexity of nature as a whole system.

every 10 to 15 years), and because it happens around Christmas, Spanish-speaking people called it El Niño after the Christ child. Meteorologists often refer to it as the ENSO, which is short for El Niño Southern Oscillation. The term Southern Oscillation was coined by Sir Gilbert Thomas Walker (1868-1958), a British statistician and physicist who was studying the pattern of Indian monsoon seasons. The El Niño effect influences weather not only along the Pacific coasts of the Americas, but also worldwide. The consequences range from colder-than-normal temperatures in the central and eastern United States to strong storms in Africa, Australia, and the coast of California, flooding in Europe, and declines in fish populations in South America. Climatologists increasingly believe that strong El Niños increase droughts in Africa and may be accelerating desertification there. A moderate El Niño effect was in action during the years 2006 through 2008.

How does El Niño occur?

The El Niño weather phenomenon happens because of the unstable interaction of ocean surface temperatures with the lower atmosphere of the tropical Pacific Ocean in processes that are so complicated even modern science does not fully understand it. The process has to do with worldwide dynamics of the ocean and atmosphere, including oceanic waves crossing the entire planet, currents, and global circulation of the atmospheric. About the only thing that scientists have concluded with much certainty is that neither sunspots nor volcanic eruptions seem to influence El Niño.

What is La Niña?

It's pretty easy to guess that La Niña would be the opposite of El Niño. Instead of warm waters in the tropical Pacific, the surface waters are inordinately cool. In 2009, predictions were for a La Niña to dominate Pacific waters.

A February 2007 image taken by the U.S.-French satellite Jason shows ocean temperatures (red for warmer, blue for cooler) as El Niño transitions to La Niña. (NASA)

A February 2007 image taken by the U.S.-French satellite Jason shows ocean temperatures (red for warmer, blue for cooler) as El Niño transitions to La Niña. (NASA)

What years have been El Niño years versus La Niña years since 1950?

El Niño years since 1950 are: 1951, 1957-58, 1963, 1965, 1969, 1972, 1976-77, 1982-83, 1986-87, 1991-92, 1994-95, 1997-98 (the strongest in the past 50 years), 2002-03, 2004, 2006.

La Niña years include: 1950, 1954-56, 1962, 1964, 1968, 1970-71, 1973-76, 1984-85, 1988-89, 1995-96, 1998-2000, 2007-2009.

What is an ENSO-neutral year?

An ENSO-neutral year is a year during which neither El Niño nor La Niña conditions are present.

What are atmospheric teleconnections?

Atmospheric teleconnections refers to the way that conditions in the oceans, including such phenomena as El Niño, La Niña, and ocean currents, interact with and affect the weather.

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