Antarctic Circumpolar Current: Facts, Discussion Forum, and Encyclopedia Article

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Antarctic Circumpolar Current

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	Antarctic Circumpolar Current
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	Topics Antarctic Circumpolar Current Topic Home The Antarctic Circumpolar Current (ACC) is an ocean currentFacts About Ocean current An ocean current is any more or less permanent or continuous, directed movement of ocean water that flows in one of the Eart... that flows from west to east around AntarcticaAntarctica Antarctica is the southernmost continent and encompasses the South Pole.... . An alternate name for the ACC is the West Wind Drift. The ACC is the dominant circulation feature of the Southern OceanSouthern Ocean The Southern Ocean, also known as the South Polar Ocean , is the body of water encircling the continent of Antarctica.... . It keeps warm ocean waters away from Antarctica, enabling that continent to maintain its huge ice sheetIce sheet An Ice sheet is a mass of glacier ice that covers surrounding terrain and is greater than 50,000 km.... . The ACC has been known to sailors for many years; Jack LondonJack London Jack London, probably born John Griffith Chaney was an American author who wrote The Call of the Wild and over fi... 's story "Make Westing" poignantly illustrated the difficulty it caused for mariners seeking to round Cape HornCape Horn Cape Horn is the southernmost headland of the Tierra del Fuego archipelago of southern Chile.... on the clipper ship route between New York and California. The current creates two Antarctic gyres. Structure The ACC connects the AtlanticAtlantic Ocean The Atlantic Ocean is the second-largest ocean, covering approximately one-fifth of the Earth's surface.... , PacificPacific Ocean The Pacific Ocean is the world's largest body of water. ... and Indian OceanIndian Ocean The Indian Ocean is the third largest body of water in the world, covering about 20% of the Earth's water surface.... basins, and as such serves as a principal pathway of exchange between these basins. The current is strongly constrained by landformLandform Summary A landform comprises a geomorphological unit.... and bathymetric features. Starting at South AmericaSouth America South America is a continent situated in the western hemisphere and, mostly, the southern hemisphere, bordered on the west b... , it flows through the Drake PassageDrake Passage The Drake Passage is the body of water between the southern tip of South America at Cape Horn and the South Shetland Islands... between South America and the Antarctic PeninsulaAntarctic Peninsula The Antarctic Peninsula is the northernmost part of the mainland of Antarctica, and almost the only part of that continent t... and then is split by the Scotia ArcScotia Arc Scotia Arc is the island arc system forming the north, east and south border of Scotia Sea.... to the east, with a shallow warm branch flowing to the north in the Falkland CurrentFalkland Current The Falkland Current is a cold water current that flows northward along the Atlantic coast of Patagonia as far north as the ... and a deeper branch passing through the Arc more to the east before also turning to the north. Passing through the Indian Ocean, the current is split by the Kerguelen PlateauKerguelen Plateau The Kerguelen Plateau is an underwater volcanic large igneous province in the Indian Ocean.... in the Indian Ocean, with most of the transport passing to the north. South of New ZealandNew Zealand New Zealand is a country in the south-western Pacific Ocean consisting of two large islands and many much smaller islands, m... , it follows the contours of the Campbell PlateauCampbell Plateau Summary The Campbell Plateau is a large submarine plateau to the south of New Zealand.... , first deflecting far to the south and then moving northward again. Deflection is also seen as it passes over the mid-ocean ridgeMid-ocean ridge A mid-ocean ridge or mid-oceanic ridge is an underwater mountain range, formed by plate tectonics.... in the Southeast Pacific. The current consists of a number of frontFront Front may refer to:* Front for a blacklisted artist... s. The northern boundary of the ACC is defined by the Subtropical FrontSubtropical Front Subtropical Front is a term used in Oceanography to describe a boundary between water systems based on temperature and salin... . This marks the boundary between warm, salty subtropical waters (generally with a salinitySalinity Salinity is the saltiness or dissolved salt content of a body of water.... of greater than 34.9 parts per thousand) and fresher, cooler subpolar waters. Moving southward we find the Subantarctic Front, along which much of the ACC transport is carried, which is defined as the latitude at which a subsurface salinity minimum or a thick layer of unstratified Subantarctic Mode WaterSubantarctic Mode Water Subantarctic mode water is an important water mass in the earth's oceans.... first appears. Still further south lies the Polar Front, which is marked by a transition to very cold, relatively fresh, Antarctic Surface Water at the surface. Further south still is the Southern Boundary front, which is determined as the point where very dense abyssal watersAbyssal zone The abyssal zone is the pelagic zone that contains the very deep benthic communities near the bottom of oceans.... upwell to within a few hundred meters of the surface. The bulk of the transport is carried in the middle two fronts. The total transport of the ACC at Drake Passage is estimated to be around 135 SverdrupSverdrup The sverdrup, named in honour of the pioneering oceanographer Harald Sverdrup, is a unit of measure of volume transport.... s (135,000,000 m³/s), or about 135 times the transport of all the world's rivers combined. There is a relatively small addition of flow in the Indian Ocean, with the transport south of TasmaniaTasmania The island of Tasmania, is located 200 km south of the eastern side of the continent Australia, being separated from it by B... reaching around 147 Sv, at which point the current is probably the largest on the planet. Dynamics There is general agreement that the large transport of the Circumpolar Current is linked to the strong westerly windWind Wind is the roughly horizontal movement of air caused by uneven heating of the Earth's surface.... s which are found in the Southern Ocean and that these winds blow over a band of open latitudeLatitude Latitude, usually denoted symbolically by the Greek letter f , gives the location of a place on Earth north or south of the ... s. In latitudes where there are continents, winds blowing on light surface water can simply pile up light water against these continents. But in the Southern Ocean, the momentum imparted to the surface waters cannot be balanced in this way. Different theories of the Circumpolar Current balance the momentum imparted by the winds in different ways. The increasing eastward momentum imparted by the winds causes water parcels to drift outwards from the axis of the earth's rotation (in other words, northward) as a result of the Coriolis force. This northward transport is balanced by a southward, pressure-driven flow below the depths of the major ridge systems. Some theories connect these flows directly, implying that there is significant upwelling of dense deep waters within the Southern Ocean, transformation of these waters into light surface waters, and a transformation of waters in the opposite direction to the north. Such theories link the magnitude of the Circumpolar Current with the global thermohaline circulationThermohaline circulation The thermohaline circulation is a term for the global density-driven circulation of the oceans.... , particularly the properties of the North Atlantic. Alternatively, ocean eddies, the oceanic equivalent of atmospheric storms, or the large scale meanders of the Circumpolar Current may directly transport momentum downwards in the water column. This is because such flows can produce a net southward flow in the troughs and a net northward flow over the ridges without requiring any transformation of density. In practice both the thermohaline and the eddy/meander mechanisms are likely to be important. The current flows at a rate of about four km per hour. Recent studies have indicated that the Antarctic Circumpolar Current varies with time. Evidence of this is the Antarctic Circumpolar WaveAntarctic Circumpolar Wave Overview The Antarctic Circumpolar Wave is a coupled ocean/atmosphere wave that circles the Southern Ocean in approximately eight yea... , a periodic oscillationOscillation Oscillation is the periodic variation, typically in time, of some measure as seen, for example, in a swinging pendulum.... that affects the climate of much of the southern hemisphere. There is also the Antarctic oscillationAntarctic oscillation The Antarctic oscillation is a mode of atmospheric variability of the southern hemisphere.... , which involves changes in the location and strength of Antarctic winds. Trends in the Antarctic Oscillation have been hypothesized to account for an increase in the transport of the Circumpolar Current over the past two decades. Formation The Antarctic Circumpolar Current formed during the MioceneMiocene Overview The Miocene epoch is a period of time that extends from about 23 to 5.3 million years before the present.... epoch, when the pieces of the former supercontinent GondwanaGondwana The southern supercontinent Gondwana included most of the landmasses in today's southern hemisphere, including Antarctica, ... which would become AntarcticaAntarctica Antarctica is the southernmost continent and encompasses the South Pole.... and South AmericaSouth America South America is a continent situated in the western hemisphere and, mostly, the southern hemisphere, bordered on the west b... finally separated enough for the Drake PassageDrake Passage The Drake Passage is the body of water between the southern tip of South America at Cape Horn and the South Shetland Islands... to form about 23 million years ago. As Antarctica was isolated from warmer waters it became progressively cooler, and glaciers began to form on the formerly forested continent. Studies An expedition in May 2008 by 19 scientists studied the geology and biology of eight Manquarie Ridge sea mounts, as well as the Antarctic Circumpolar Current to investigate the effects of climate change of the southern Ocean. The circumpolar current merges the waters of the Atlantic, Indian, and Pacific Oceans and carries up to 150 times the volume of water flowing in all of the world's rivers. After studying the circumpolar current it is clear that it strongly influences regional and global climate as well as underwater biodiversity. External links Good graphics later in article.