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45-599: Charlie–Gibbs fracture zone is a system of two parallel fracture zones . It is the most prominent interruption of the Mid-Atlantic Ridge between the Azores and Iceland , with the longest faults in the North Atlantic, and is ecologically an important biosystems boundary. It can be traced over more than 2,000 kilometres (1,200 mi), from north-east of Newfoundland to south-west of Ireland . It took 90 million years for

90-439: A stratified water layer on top. The temperature of this stratified layer can get to 11 °C in the upper 100 m of the channel, with a salinity around 35.1 g/kg; between 100 and 400 m depth the temperature of the water in the stratified layer is around 8 °C, with a salinity of 35.2 g/kg. The water below 400 m, in the well-mixed layer, can be characterised as overflow water. The mixed bottom layer of

135-546: A total of 350 km to the west. The section of the Mid-Atlantic Ridge between the two fracture zones is seismically active. The flow of major North Atlantic currents is associated with this fracture zone which hosts a diverse deep water ecosystem. The Heirtzler Fracture Zone was approved by the Advisory Committee on Undersea Features in 1993. The Mendocino Fracture Zone extends for over 4,000 km off

180-415: A very diverse seafloor ecosystem. Over all Xenophyophorea are dominant, being about twice as common as sea lilies, Bathycrinidae , Bryozoa, Demosponges or sea cucumbers. The highest seafloor biodiversity have been reported at depths of 1.5–2.2 km (0.93–1.37 mi) in areas of bedrock and steeper slopes. In the past, extensive Orange roughy fisheries were in the area but over exploitation were one of

225-707: Is 125 km long and 15 km wide. Faroe-Bank Channel overflow Cold and dense water from the Nordic Seas is transported southwards as Faroe-Bank Channel overflow . This water flows from the Arctic Ocean into the North Atlantic through the Faroe-Bank Channel between the Faroe Islands and Scotland . The overflow transport is estimated to contribute to one-third (2.1±0.2  Sv , on average) of

270-423: Is 160±70 m, showing a high lateral variability, and yields a transport of ~1 Sv per branch. A transverse circulation actively dilutes the bottom branch of the plume. The shallow, intermediate branch transports warmer, less dense outflow water along the ridge slope towards the west. This branch mixes with oxygen-poor, fresh Modified East Icelandic Water . The deep (deeper than 1000 m) branch transports

315-675: Is a secondary sill with a maximum depth of 850 m. Faroe-Bank Channel overflow enters the FBC from the northeast, turns towards the west between the Faroe Islands and the Faroe Bank , and leaves the GSR in southwestern direction, west-southwest of the Faroe Islands. The water flowing over the Greenland-Scotland Ridge through the Faroe-Bank Channel consists of a very well-mixed bottom layer, with

360-430: Is an igneous province found within the otherwise nonvolcanic rifted margin in the region of transition between oceanic and continental crust. In 1963 the existence of a transform fault near latitude 53N was first postulated on the basis of earthquake epicenter data by Bruce Heezen and Maurice Ewing . A study of ocean currents also indicated that there should be a deep passage through the Mid-Atlantic Ridge. In 1966

405-496: Is important for water transport towards the deep parts of the North Atlantic, playing a significant role in Earth's climate system. The Faroe-Bank Channel (FBC) is a deeply eroded channel in the Greenland-Scotland Ridge (GSR). Its primary sill , located south of the Faroe Islands, has a width of about 15 km and a maximum depth of 840 m, with very steep walls at both sides of the channel. 100 km north-west of this sill, there

450-427: Is the average profile velocity , h 0 {\displaystyle h_{0}} is the interface height, h B {\displaystyle h_{B}} is the height of the layer below the lowest measurement station in the channel, and q B {\displaystyle q_{B}} is the volume flux per unit width of the channel. Lastly, overflow can also be defined on

495-668: Is the decrease in sea-surface height and Δ H {\textstyle \Delta H} is the decrease in interface height from upstream areas to the sill. Processes like mixing, circulation and convection contribute to these pressure gradients. The overflow velocity, then, scales as follows with the pressure gradient between the basins north and south of the ridge: v = 2 ( Δ P t r o p + Δ P c l i n ) {\displaystyle v={\sqrt {2\left(\Delta P_{trop}+\Delta P_{clin}\right)}}} This velocity can then be used to define

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540-508: The Juan de Fuca Ridge and the Gorda Ridge . The dominating feature of the fracture zone is the 150 km long Blanco Ridge, which is a high-angle, right-lateral strike slip fault with some component of dip-slip faulting . The Charlie-Gibbs Fracture Zone consists of two fracture zones in the North Atlantic that extend for over 2000 km. These fracture zones displace the Mid-Atlantic Ridge

585-652: The RV Akademik Nikolaj Strakhov , and the Tectonic Ocean Spreading at the Charlie–Gibbs fracture zone (TOSCA) survey by a remote vehicle. The transform area contains two named seamounts : Fourteen seamounts are buried under sediments at the eastern end of fracture zone. The Charlie–Gibbs Marine Protected Area is a conservation area in the Charlie–Gibbs fracture zone in North Atlantic international waters. The North Atlantic Current flows at

630-598: The Romanche Trench , this fracture zone separates the North Atlantic and South Atlantic oceans. The trench reaches 7,758 m deep, is 300 km long, and has a width of 19 km. The fracture zone offsets the Mid-Atlantic Ridge by more than 640 km. The Sovanco Fracture Zone is a dextral-slip transform fault running between the Juan de Fuca and Explorer Ridge in the North Pacific Ocean . The fracture zone

675-449: The FBC contributes to the actual overflow. Four definitions are possible, two of which depending on the overflow velocity, one depending on the overflow flux, and one depending on the overflow water properties. The simplest definition is in terms of velocities: water with a velocity in northwestern direction is then termed Faroe-Bank Channel overflow. At the sill, velocities can grow up until 1.2 m/s, accelerating when flowing downwards

720-420: The FBC is where the actual overflow takes place, being fed by inflow of cold and fresh North Atlantic Water , Modified North Atlantic Water , Norwegian Sea Deep Water and Norwegian Sea Arctic Intermediate Water . These water masses have different temperatures (between -0.5 and 7.0 °C) and salinities (between 34.7 and 35.4 g/kg). Therefore, it may be complicated to exactly define which water entering

765-575: The FBCO. When the atmospheric circulation governing the Nordic Seas is in a cyclonic ( anticyclonic ) regime, the source of the deep water predominantly comes via a western (eastern) inflow path, and the FBCO will be weaker (stronger). The eastern inflow path is called the Faroe-Strait Channel Jet . This transition from a cyclonic to an anticyclonic regime takes place on an interannual timescale, but

810-481: The action of offset mid-ocean ridge axis segments. They are a consequence of plate tectonics . Lithospheric plates on either side of an active transform fault move in opposite directions; here, strike-slip activity occurs. Fracture zones extend past the transform faults, away from the ridge axis; are usually seismically inactive (because both plate segments are moving in the same direction), although they can display evidence of transform fault activity, primarily in

855-493: The area was investigated by USCGC  Spar  (WLB-403) on its return from an Arctic survey . The fault was named Charlie fracture zone after the USCG Ocean Weather Station Charlie at 52°45′N 35°30′W  /  52.750°N 35.500°W  / 52.750; -35.500 , athwart the fault. In July 1968 USNS  Josiah Willard Gibbs  (T-AGOR-1) conducted a more extended survey. It

900-431: The atmospheric forcing also shows a seasonal cycle. During summer the weakened cyclonic winds are associated with a higher FBCO transport. This indicates a fast barotropic response to the wind forcing. Faroe-Strait Channel Jet water is much colder than the water flowing into the Faroe-Bank Channel via its western entrance path. Within the FBC, water always flows along its eastern rather than its western boundary, regardless

945-450: The barotropic pressure gradient, however, shows an increasing trend of equal magnitude. These processes compensate each other; as a result the pressure difference at depth does not show a significant trend over time. Global inverse modelling, ocean hydrographic surveys, chlorofuorocarbon (CFC) inventories, and monitoring of the AMOC from 2004 to present have shown that the AMOC has slowed down in

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990-433: The basis of hydrographical properties: namely as water that flows through the FBC having a temperature lower than 3 °C, or having a potential density higher than 27.8 kg/m . This definition is most often used when estimating values for the magnitude of the FBCO. Temperature and salinity profiles as well as current speeds in the FBC vary strongly on a day-to-day basis. The dense water forms domes that move through

1035-456: The channel with a period of 2.5 to 6 days. At the ocean surface, this periodicity can be observed in the form of topographic Rossby waves at the sea surface, which are caused by mesoscale oscillations in the velocity field. The resulting eddies are the consequence of baroclinic instabilities within the overflow water, which then induce the observed periodicity. On a greater timescale, atmospheric forcing also causes periodic changes in

1080-448: The coast of California and separates the Pacific plate and Gorda plate . The bathymetric depths on the north side of the fracture zone are 800 to 1,200 m shallower than to the south, suggesting the seafloor north of the ridge to be younger. Geologic evidence backs this up, as rocks were found to be 23 to 27 million years younger north of the ridge than to the south. Also known as

1125-426: The coldest part of the FBCO warmed in that same period with 0.1±0.06 °C (which made density decrease), causing increasing transport of heat into the AMOC. This warming, however, is accompanied by an observed salinity (and therefore density) increase, which results in no net change in density. Climate models have shown an overall decreasing trend in the baroclinic component of the overflow between 1948 and 2005;

1170-509: The deepening bathymetry . In this respect, high velocities are associated with strong mixing and highly turbulent flows. In the stratified layer at the top of the channel, velocities become negative (i.e., in southeastern direction), which makes these water no part of the overflow. Another option is to take into account the barotropic (i.e., horizontal sea-surface height gradients determine currents) and baroclinic (i.e., horizontal density gradients determine currents) pressure gradients at

1215-464: The different ages of the crust on opposite sides of the zone. In actual usage, many transform faults aligned with fracture zones are often loosely referred to as "fracture zones" although technically, they are not. They can be associated with other tectonic features and may be subducted or distorted by later tectonic activity. They are usually defined with bathymetric , gravity and magnetic studies. Mid-ocean ridges are divergent plate boundaries. As

1260-410: The different inflow pathways from the Nordic Seas. Moreover, at times the eastern inflow path is dominant, overflow waters are denser and higher in volume. After passing the primary Faroe-Bank Channel sill, the overflow bifurcates into two different branches that both flow with a maximum velocity of 1.35 m/s on top of each other. The average thickness of the total outflow plume along its descent

1305-422: The factors that resulted in the establishment of a protected area. During 2018 studies at Hecate Seamount, Orange roughy was observed. This very long lived species (over 250 years) can take considerable time to recover from overfishing as it does not reproduce every year. Fracture zone A fracture zone is a linear feature on the ocean floor—often hundreds, even thousands of kilometers long—resulting from

1350-408: The fault to grow to this length. The transform fault of the southern fracture zone displaces the Mid-Atlantic Ridge, coming from the Azores triple junction , to the west over a distance of 120 km (75 mi). At longitude 31.75W a south to north seismically active rift valley with a length of 40 km (25 mi) connects the western end of the southern transform to the eastern end of

1395-415: The fracture zone are higher than those in the south, as part of a geological transition in the North Atlantic sea floor which is higher to the north of the fracture zone. Both transform faults continue eastward and westward as inactive fracture zones. The Charlie–Gibbs fracture zone has large amounts of mid-ocean ridge igneous and metamorphic rocks. At the eastern termination off shore of Newfoundland there

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1440-778: The fracture zone the water mass originates from the Iceland–Scotland Ridge in the form of the Faroe-Bank Channel overflow with a fair load of organic material and is driven west through the fracture zone by the boundary current. The seafloor contains many corals including reef forming stony corals such as Madrepora oculata and octocorals . Coral species separate from reefs including Desmophyllum , Solenosmilia variabilis and Madrepora oculata have been described. Also found are Demosponge and Hexactinellid sponges, sea lilies , and sea cucumbers In all at least 309 species have been characterised to date making for

1485-463: The globe. The strength of the Faroe-Bank Channel overflow is an important indicator for the stability of the AMOC, since the overflow produces dense waters that contribute for a large extent to the total overturning in the North Atlantic. Parameters that can effect the AMOC are kinematic overflow (i.e., the magnitude of the overflow transport) and overflow density (as the AMOC being a density-driven circulation). In this respect, density characteristics of

1530-421: The most dense, cold water towards the deep parts of the North Atlantic. This branch entrains warmer and more saline water, mixes, and consequently obtains higher temperatures and salinity. Both branches ultimately contribute to the formation of North Atlantic Deep Water . The Atlantic meridional overturning circulation (AMOC) is important for Earth's climate because of its distribution of heat and salinity over

1575-485: The northern transform, sometimes called an intra-transform spreading centre. The northern transform fault displaces the spreading ridge over another 230 km (140 mi) to the west before it connects to the northern part of the Mid-Atlantic Ridge going to Iceland. Thus these, the longest faults under the Atlantic Ocean have a total offset of the system of over 340 km (210 mi). The northern rift mountains of

1620-406: The offset in the magnetic striping, one can then determine the rate of past plate motions. In a similar method, one can use the relative ages of the seafloor on either side of a fracture zone to determine the rate of past plate motions. By comparing how offset similarly aged seafloor is, one can determine how quickly the plate has moved. The Blanco Fracture Zone is a fracture zone running between

1665-424: The overflow could vary even if the kinematic overflow does not. From 1995 onwards, FBCO has been monitored by a continuous Acoustic Doppler current profiler (ADCP) mooring, measuring volume transport, hydrographic properties and the density of the overflow. The kinematic overflow, derived from the velocity field, showed a non-significant positive linear trend of 0.01±0.013 Sv/yr between 1995 and 2015, whereas

1710-511: The overflow depth between both sides of the GSR: Δ P t r o p = g Δ h {\displaystyle \Delta P_{trop}=g\Delta h} Δ P c l i n = g Δ H Δ ρ ρ {\displaystyle \Delta P_{clin}=g\Delta H{\frac {\Delta \rho }{\rho }}} where Δ h {\textstyle \Delta h}

1755-409: The plates on either side of an offset mid-ocean ridge move, a transform fault forms at the offset between the two ridges. Fracture zones and the transform faults that form them are separate but related features. Transform faults are plate boundaries, meaning that on either side of the fault is a different plate. In contrast, outside of the ridge-ridge transform fault, the crust on both sides belongs to

1800-408: The same plate, and there is no relative motion along the junction. The fracture zone is thus the junction between oceanic crustal regions of different ages. Because younger crust is generally higher due to increased thermal buoyancy , the fracture zone is characterized by an offset in elevation with an intervening canyon that may be topographically distinct for hundreds or thousands of kilometers on

1845-422: The sea floor. As many areas of the ocean floor, particularly the Atlantic Ocean, are currently inactive, it can be difficult to find past plate motion. However, by observing the fracture zones, one can determine both the direction and rate of past plate motion. This is found by observing the patterns of magnetic striping on the ocean floor (a result of the reversals of Earth's magnetic field over time). By measuring

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1890-604: The surface from east to west over the area of the fracture zone and with the route of the Atlantic Deep Western Boundary Current along the fracture zone and through the barrier of the Mid-Atlantic Ridge, this results in two different water masses to the north and south of the zone. The subarctic intermediate water is brought in by the higher eastward flow, resulting in the freshest, high nutrient Labrador Sea Water occurring between 1–1.5 km (0.62–0.93 mi) depth. Deeper than 2 km (1.2 mi) along

1935-959: The total overflow flux in the FBC. A third definition is so-called kinematic overflow : the water flux from the bottom of the channel up to the interface height, being the level where the velocity in northwestern direction measures one half of the maximum velocity in the profile. The overflow flux is then calculated through Q k ( t ) = ∫ x 1 x 2 v 0 ( x , t ) ( h 0 ( x , t ) − h B ) d x + ∫ x 1 x 2 q B ( x , t ) d x {\displaystyle Q_{k}(t)=\int _{x_{1}}^{x_{2}}v_{0}(x,t)\left(h_{0}(x,t)-h_{B}\right)\operatorname {d} \!x+\int _{x_{1}}^{x_{2}}q_{B}\left(x,t\right)\operatorname {d} \!x} where v 0 {\displaystyle v_{0}}

1980-627: The total overflow over the Greenland-Scotland Ridge . The remaining two-third of overflow water passes through Denmark Strait (being the strongest overflow branch with an estimated transport of 3.5 Sv ), the Wyville Thomson Ridge (0.3 Sv), and the Iceland-Faroe Ridge (1.1 Sv). Faroe-Bank Channel overflow (FBCO) contributes to a large extent to the formation of North Atlantic Deep Water . Therefore, FBCO

2025-438: Was proposed that the fracture zone be renamed Gibbs fracture zone, as fracture zones are generally named for research vessels. The proposal was accepted only in part, and currently the official name is Charlie–Gibbs fracture zone. Note that the double name refers to the two parallel fracture zones together. The individual fracture zones have to be referred to as Charlie–Gibbs North and South. Recent studies have been carried out by

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