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35-571: North Atlantic Deep Water ( NADW ) is a deep water mass formed in the North Atlantic Ocean . Thermohaline circulation (properly described as meridional overturning 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

70-441: A cold climate like Antarctica, the cold temperatures separate the molecular bonds of the water causing it to become less dense. However, because water increases its volume by about 9% when frozen, this makes the ice less dense than the water which is why glaciers float. This also in turn causes the salinity of the water to decrease. The salinity of the water makes water freeze at lower temperatures than freshwater. Freshwater freezes at

105-410: 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 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

140-668: A high amount of anthropogenic tracers due its exposure to the atmosphere. AIW's tritium and CFC signature is observed in DSOW at the base of the Greenland continental slope. This also showed that the DSOW flowing 450 km to the south was no older than 2 years. Both the DSOW and ISOW flow around the Irminger Basin and Labrador Sea in a deep boundary current. Leaving the Greenland Sea with 2.5 Sv , its flow increases to 10 Sv south of Greenland. It

175-473: 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 the surface from east to west over the area of the fracture zone and with

210-620: A temperature of 2-4 °C with a salinity of 34.9-35.0 psu found at a depth between 1500 and 4000m. The NADW is a complex of several water masses formed by deep convection and overflow of dense water across the Greenland-Iceland-Scotland Ridge. The upper layers are formed by deep open ocean convection during winter. Labrador Sea Water (LSW), formed in the Labrador Sea , can reach depths of 2000 m as dense water sinks downward. Classical Labrador Sea Water (CLSW) production

245-421: 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

280-615: Is cold and relatively fresh, flowing below 3500 m in the DWBC and spreading inward the deep Atlantic basins. The southward spread of NADW along the Deep Western Boundary current (DWBC) can be traced by its high oxygen content, high CFCs, and density. ULSW is the major source of upper NADW. ULSW advects southward from the Labrador Sea in small eddies that mix into the DWBC. A CFC maximum associated with ULSW has been observed along 24°N in

315-530: Is dependent on preconditioning of water in the Labrador Sea from the previous year and the strength of the North Atlantic Oscillation (NAO). During a positive NAO phase, conditions exist for strong winter storms to develop. These storms freshen the surface water, and their winds increase cyclonic flow, which allows denser waters to sink. As a result, the temperature, salinity, and density vary yearly. In some years these conditions do not exist and CLSW

350-535: Is less dense than DSOW and lays above it as it flows cyclonically in the Irminger Basin. DSOW is the coldest, densest, and freshest water mass of NADW. DSOW formed behind the ridge flows over the Denmark Strait at a depth of 600m. The most significant water mass contributing to DSOW is Arctic Intermediate Water (AIW). Winter cooling and convection allow AIW to sink and pool behind the Denmark Strait. Upper AIW has

385-469: Is not formed. CLSW has characteristic potential temperature of 3 °C, salinity of 34.88 psu, and density of 34.66. Another component of LSW is the Upper Labrador Sea Water (ULSW). ULSW forms at a density lower than CLSW and has a CFC maximum between 1200 and 1500 m in the subtropical North Atlantic. Eddies of cold less saline ULSW have similar densities of warmer saltier water and flow along

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420-749: The Norwegian Current , which splits into the Fram Strait and Barents Sea Branch. Water from the Fram Strait recirculates, reaching a density of DSOW, sinks, and flows towards the Denmark Strait. Water flowing into the Barents Sea feeds ISOW. ISOW enters the eastern North Atlantic over the Iceland-Scotland Ridge through the Faeroe Bank Channel at a depth of 850 m, with some water flowing over

455-482: 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 was proposed that the fracture zone be renamed Gibbs fracture zone, as fracture zones are generally named for research vessels. The proposal

490-595: 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

525-505: The CFCs to penetrate further downward to 2000m. These minima could be tracked, and were first observed in the subtropics in the early 1990s. ISOW and DSOW flow around the Irminger Basin and DSOW entering the DWBC. These are the two lower portions of the NADW. Another CFC maximum is seen at 3500 m in the subtropics from the DSOW contribution to NADW. Some of the NADW recirculates with the northern gyre. To

560-510: The DWBC at 1500 m. Some of the upper ULSW recirculates into the Gulf Stream, while some remains in the DWBC. High CFCs in the subtropics indicate recirculation in the subtropics. ULSW that remains in the DWBC dilutes as it moves equatorward. Deep convection in the Labrador Sea during the late 1980s and early 1990s resulted in CLSW with a lower CFC concentration due to downward mixing. Convection allowed

595-431: The DWBC, but maintain their high CFCs. The ULSW eddies erode rapidly as they mix laterally with this warmer saltier water. The lower waters mass of NADW form from overflow of the Greenland-Iceland-Scotland Ridge. They are Iceland-Scotland Overflow Water (ISOW) and Denmark Strait Overflow Water (DSOW). The overflows are a combination of dense Arctic Ocean water (18%), modified Atlantic water (32%), and intermediate water from

630-508: The Nordic seas (20%), that entrain and mix with other water masses (contributing 30%) as they flow over the Greenland-Iceland-Scotland Ridge. The formation of both of these waters involves the conversion of warm, salty, northward-flowing surface waters to cold, dense, deep waters behind the Greenland-Iceland-Scotland Ridge. Water flow from the North Atlantic current enters the Arctic Ocean through

665-542: The North Atlantic drift, in turn cooling the climate of northwestern Europe . There is concern that global warming might cause this to happen again. It is also hypothesized that during the Last Glacial Maximum , NADW was replaced with an analogous watermass that occupied a shallower depth known as Glacial North Atlantic Intermediate Water. Water mass Water masses are generally distinguished not only by their respective tracers but also by their location in

700-459: 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 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

735-413: 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 C/C, and chlorofluorocarbons (CFCs). CFCs are anthropogenic substances that enter the surface of the ocean from gas exchange with

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770-615: The Tropical Atlantic to the Mid and High Latitude Atlantic. In the conveyor belt model of thermohaline circulation of the world's oceans, the sinking of NADW pulls the waters of the North Atlantic drift northward. However, this is almost certainly an oversimplification of the actual relationship between NADW formation and the strength of the Gulf Stream /North Atlantic drift. NADW has

805-452: The Worlds' oceans. Water masses are also distinguished by their vertical position so that there are surface water masses, intermediate water masses and deep water masses. Common water masses in the world ocean are: Although there are many types of water masses, they all share characteristics. Water Masses are formed from regions of water having different temperatures. When ice is being formed in

840-551: The atmosphere. This distinct composition allows its path to be traced as it mixes with Circumpolar Deep Water (CDW), which in turn fills the deep Indian Ocean and part of the South Pacific . NADW and its formation is essential to the Atlantic Meridional Overturning Circulation (AMOC), which is responsible for transporting large amounts of water, heat, salt, carbon, nutrients and other substances from

875-477: The current density of the water is and help further classify the water mass. Charlie-Gibbs Fracture Zone 52°30′N 31°45′W  /  52.50°N 31.75°W  / 52.50; -31.75 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

910-432: 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 the area was investigated by USCGC  Spar  (WLB-403) on its return from an Arctic survey . The fault was named Charlie fracture zone after

945-786: 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

980-421: 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 is an igneous province found within the otherwise nonvolcanic rifted margin in the region of transition between oceanic and continental crust. In 1963

1015-473: The shallower Iceland-Faeroe Rise. ISOW has a low CFC concentrations and it has been estimated from these concentrations that ISOW resides behind the ridge for 45 years. As the water flows southward at the bottom of the channel, it entrains surrounding water of the eastern North Atlantic, and flows to the western North Atlantic through the Charlie-Gibbs Fracture Zone , entraining with LSW. This water

1050-586: The south of the gyre, NADW flows under the Gulf Stream, where it continues along the DWBC until it reaches another gyre in the subtropics. Lower North Atlantic Deep Water (LNADW), originating in the Greenland and Norwegian seas, brings high salinity, oxygen, and freon concentrations towards to the Romanche Trench , an equatorial fracture zone in the Mid-Atlantic Ridge (MAR). Found at depths around 3,600–4,000 m (11,800–13,100 ft), LNADW flow east through

1085-473: The standard 0 °C (32 °F), while saltwater freezes at an average of -2 °C (28.4 °F). The best method of classifying a water mass is through using a T-S diagram. In the diagram pictured at the top, it categorises a water mass by the temperature and salinity of the water and is represented by a single point. However, water masses are not constant. Throughout time climates can change, seasons can drag out, or there could be less rainfall meaning that

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1120-514: The trench over Antarctic Bottom Water —the trench is the only opening in the MAR where inter-basin exchange is possible for these two water masses. It is believed that North Atlantic Deep Water formation has been dramatically reduced at times during the past (such as during the Younger Dryas or during Heinrich events ), and that this might correlate with a decrease in the strength of the Gulf Stream and

1155-402: The water masses might change in temperature or salinity. To have a complete water mass classification, it requires the water type of the source and the standard deviations of the temperature and salinity. It can take many years to establish the standard deviations of the water mass and requires constant surveillance. Once all of the necessary measures are completed, the data will now determine what

1190-462: 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 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

1225-559: 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 the RV Akademik Nikolaj Strakhov , and the Tectonic Ocean Spreading at the Charlie–Gibbs fracture zone (TOSCA) survey by

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