Related Research Articles
North Atlantic Deep Water (NADW) is a deep water mass formed in the North Atlantic Ocean. Thermohaline circulation of the world's oceans involves the flow of warm surface waters from the southern hemisphere into the North Atlantic. Water flowing northward becomes modified through evaporation and mixing with other water masses, leading to increased salinity. When this water reaches the North Atlantic it cools and sinks through convection, due to its decreased temperature and increased salinity resulting in increased density. NADW is the outflow of this thick deep layer, which can be detected by its high salinity, high oxygen content, nutrient minima, high 14C/12C, and chlorofluorocarbons (CFCs).
Salinity is the saltiness or amount of salt dissolved in a body of water, called saline water. It is usually measured in g/L or g/kg.
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. Depth contours, shoreline configurations, and interactions with other currents influence a current's direction and strength. Ocean currents are primarily horizontal water movements.
Thermohaline circulation (THC) is a part of the large-scale ocean circulation that is driven by global density gradients created by surface heat and freshwater fluxes. The adjective thermohaline derives from thermo- referring to temperature and -haline referring to salt content, factors which together determine the density of sea water. Wind-driven surface currents travel polewards from the equatorial Atlantic Ocean, cooling en route, and eventually sinking at high latitudes. This dense water then flows into the ocean basins. While the bulk of it upwells in the Southern Ocean, the oldest waters upwell in the North Pacific. Extensive mixing therefore takes place between the ocean basins, reducing differences between them and making the Earth's oceans a global system. The water in these circuits transport both energy and mass around the globe. As such, the state of the circulation has a large impact on the climate of the Earth.
The Agulhas Current is the western boundary current of the southwest Indian Ocean. It flows south along the east coast of Africa from 27°S to 40°S. It is narrow, swift and strong. It is suggested that it is the largest western boundary current in the world ocean, with an estimated net transport of 70 sverdrups, as western boundary currents at comparable latitudes transport less — Brazil Current, Gulf Stream, Kuroshio.
In oceanography, a gyre is any large system of circulating ocean surface currents, particularly those involved with large wind movements. Gyres are caused by the Coriolis effect; planetary vorticity, horizontal friction and vertical friction determine the circulatory patterns from the wind stress curl (torque).
The East Greenland Current (EGC) is a cold, low-salinity current that extends from Fram Strait (~80N) to Cape Farewell (~60N). The current is located off the eastern coast of Greenland along the Greenland continental margin. The current cuts through the Nordic Seas and through the Denmark Strait. The current is of major importance because it directly connects the Arctic to the Northern Atlantic, it is a major contributor to sea ice export out of the Arctic, and it is a major freshwater sink for the Arctic.
The Kuroshio Current, also known as the Black or Japan Current or the Black Stream, is a north-flowing, warm ocean current on the west side of the North Pacific Ocean basin. It was named for the deep blue appearance of its waters. Similar to the Gulf Stream in the North Atlantic, the Kuroshio is a powerful western boundary current that transports warm equatorial water poleward and forms the western limb of the North Pacific Subtropical Gyre. Off the East Coast of Japan, it merges with the Oyashio Current to form the North Pacific Current.
Oyashio, also known as Oya Siwo, Okhotsk or the Kurile current, is a cold subarctic ocean current that flows south and circulates counterclockwise in the western North Pacific Ocean. The waters of the Oyashio Current originate in the Arctic Ocean and flow southward via the Bering Sea, passing through the Bering Strait and transporting cold water from the Arctic Sea into the Pacific Ocean and the Sea of Okhotsk. It collides with the Kuroshio Current off the eastern shore of Japan to form the North Pacific Current . The nutrient-rich Oyashio is named for its metaphorical role as the parent that provides for and nurtures marine organisms.
The Florida Current is a thermal ocean current that flows from the Straits of Florida around the Florida Peninsula and along the southeastern coast of the United States before joining the Gulf Stream Current near Cape Hatteras. Its contributing currents are the Loop Current and the Antilles Current. The current was discovered by Spanish explorer Juan Ponce de León in 1513.
The North Pacific Current is an ocean current that flows west-to-east between 30 and 50 degrees north in the Pacific Ocean. The current forms the southern part of the North Pacific Subpolar Gyre and the northern part of the North Pacific Subtropical Gyre. The North Pacific Current is formed by the collision of the Kuroshio Current, running northward off the coast of Japan, and the Oyashio Current, which is a cold subarctic current that flows south and circulates counterclockwise along the western North Pacific Ocean. In the eastern North Pacific off southern British Columbia, it splits into the southward flowing cold water California Current and the northward flowing Alaska Current.
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 North Pacific Gyre (NPG) or North Pacific Subtropical Gyre (NPSG), located in the northern Pacific Ocean, is one of the five major oceanic gyres. This gyre covers most of the northern Pacific Ocean. It is the largest ecosystem on Earth, located between the equator and 50° N latitude, and comprising 20 million square kilometers. The gyre has a clockwise circular pattern and is formed by four prevailing ocean currents: the North Pacific Current to the north, the California Current to the east, the North Equatorial Current to the south, and the Kuroshio Current to the west. It is the site of an unusually intense collection of human-created marine debris, known as the Great Pacific Garbage Patch.
The oceanic or limnological mixed layer is a layer in which active turbulence has homogenized some range of depths. The surface mixed layer is a layer where this turbulence is generated by winds, surface heat fluxes, or processes such as evaporation or sea ice formation which result in an increase in salinity. The atmospheric mixed layer is a zone having nearly constant potential temperature and specific humidity with height. The depth of the atmospheric mixed layer is known as the mixing height. Turbulence typically plays a role in the formation of fluid mixed layers.
The Atlantic meridional overturning circulation (AMOC) is part of a global thermohaline circulation in the oceans and is the zonally integrated component of surface and deep currents in the Atlantic Ocean. It is characterized by a northward flow of warm, salty water in the upper layers of the Atlantic, and a southward flow of colder, deep waters. These "limbs" are linked by regions of overturning in the Nordic and Labrador Seas and the Southern Ocean, although the extent of overturning in the Labrador Sea is disputed. The AMOC is an important component of the Earth's climate system, and is a result of both atmospheric and thermohaline drivers.
The Mindanao Current (MC) is a southward current in the western Pacific Ocean that transports mass and freshwater between ocean basins. It is a low-latitude western boundary current that follows the eastern coast of the Philippine island group and its namesake, Mindanao. The MC forms from the North Equatorial Current (NEC) that flows from east to west between 10-20°N. As it travels west, the NEC reaches its western limit: the coast of the Philippines. Once it encounters shallower waters near land, it “splits” into two branches: one moves northward and becomes the Kuroshio current and one moves southward and becomes the Mindanao Current. The process of splitting is called a bifurcation.
Brine rejection is a process that occurs when salty water freezes. The salts do not fit in the crystal structure of water ice, so the salt is expelled.
Mode water is defined as a particular type of water mass, which is nearly vertically homogeneous. Its vertical homogeneity is caused by the deep vertical convection in winter. The first term to describe this phenomenon is 18° water, which was used by Valentine Worthington to describe the isothermal layer in the northern Sargasso Sea cool to a temperature of about 18 °C each winter. Then Masuzawa introduced the subtropical mode water concept to describe the thick layer of temperature 16–18 °C in the northwestern North Pacific subtropical gyre, on the southern side of the Kuroshio Extension. The terminology mode water was extended to the thick near-surface layer north of the Subantarctic Front by McCartney, who identified and mapped the properties of the Subantarctic mode water (SAMW). After that, McCartney and Talley then applied the term subpolar mode water (SPMW) to the thick near-surface mixed layers in the North Atlantic’s subpolar gyre.
Labrador Sea Water is an intermediate water mass characterized by cold water, relatively low salinity compared to other intermediate water masses, and high concentrations of both oxygen and anthropogenic tracers. It is formed by convective processes in the Labrador Sea located between Greenland and the northeast coast of the Labrador Peninsula. Deep convection in the Labrador Sea allows colder water to sink forming this water mass, which is a contributor to the upper layer of North Atlantic Deep Water. North Atlantic Deep Water flowing southward is integral to the Atlantic Meridional Overturning Circulation. The Labrador Sea experiences a net heat loss to the atmosphere annually.
Thermohaline staircases are patterns that form in oceans and other bodies of salt water, characterised by step-like structures observed in vertical temperature and salinity profiles; the patterns are formed and maintained by double diffusion of heat and salt. The ocean phenomenon consists of well-mixed layers of ocean water stacked on top of each other. The well-mixed layers are separated by high-gradient interfaces, which can be several meters thick. The total thickness of staircases ranges typically from tens to hundreds of meters.
References
- ↑ Talley, Lynne D. (1993-03-01). "Distribution and Formation of North Pacific Intermediate Water". Journal of Physical Oceanography. 23 (3): 517–537. Bibcode:1993JPO....23..517T. doi: 10.1175/1520-0485(1993)023<0517:DAFONP>2.0.CO;2 . ISSN 0022-3670.
- ↑ Talley, Lynne D.; Nagata, Yukata; Fujimura, Masahiko; Iwao, Takanori; Kono, Tokihiro; Inagake, Denzou; Hirai, Mitsuyuki; Okuda, Kuniaki (1995-04-01). "North Pacific Intermediate Water in the Kuroshio/Oyashio Mixed Water Region". Journal of Physical Oceanography. 25 (4): 475–501. Bibcode:1995JPO....25..475T. doi: 10.1175/1520-0485(1995)025<0475:NPIWIT>2.0.CO;2 . ISSN 0022-3670.
- ↑ Yasuda, Ichiro (1997). "The origin of the North Pacific Intermediate Water". Journal of Geophysical Research: Oceans. 102 (C1): 893–909. Bibcode:1997JGR...102..893Y. doi: 10.1029/96JC02938 . ISSN 2156-2202.
- ↑ You, Yuzhu; Suginohara, Nobuo; Fukasawa, Masao; Yasuda, Ichiro; Kaneko, Ikuo; Yoritaka, Hiroyuki; Kawamiya, Michio (2000). "Roles of the Okhotsk Sea and Gulf of Alaska in forming the North Pacific Intermediate Water". Journal of Geophysical Research: Oceans. 105 (C2): 3253–3280. Bibcode:2000JGR...105.3253Y. doi: 10.1029/1999JC900304 . ISSN 2156-2202.
- Shimizu, Y., T. Iwao, I. Yasuda, S. Ito, T. Watanabe, K. Uehara, N. Shikama, and T. Nakano, 2004: Formation process of North Pacific intermediate water revealed by profiling floats set to drift on 26.7 σθ isopycnal surface. J. Oceanogr., 60, 453–462.
- Talley, L., Y. Nagata, M. Fujimura, T. Kono, D. Inagake, M. Hirai, and K. Okuda, 1995: North Pacific intermediate water in the Kuroshio/Oyashio mixed water region. J. Phys. Oceanogr.,25, 475–501.