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98-509: The salinity, nutrient, and carbon patterns in the gyre are related to seasonal ice cover and freshwater input. Antarctic toothfish , orcas , Adélie penguins , Antarctic krill , Salpidae , Slender-billed prion and many other seabirds spend part of their lives in the Ross Gyre. Climate change predictions anticipate a strengthening of the gyre's circulation which would increase shelf ice melt and slowdown deep water formation. The Ross Gyre

196-616: A 10-day duty cycle. The Argo program is a collaborative partnership of more than 30 nations from all continents (most shown on the graphic map in this article) that maintains a global array and provides a dataset anyone can use to explore the ocean environment. Argo is a component of the Global Ocean Observing System (GOOS), and is coordinated by the Argo Steering Team, an international body of scientists and technical experts that meets once per year. The Argo data stream

294-508: A broad head, an elongated body, long dorsal and anal fins , large pectoral fins , and a rudder-like caudal fin . They typically move slowly, but are capable of speed bursts that can elude predatory seals. Over the continental shelf, Antarctic toothfish feed on shrimp ( Nauticaris spp.) and small fish, principally another neutrally buoyant nototheniid, the Antarctic silverfish ( Pleuragramma antarcticum ). This loosely schooling species

392-424: A depth of 2000 metres (pressure of 2000 decibars) the temperature might be 2°C and the salinity 34.58 parts per thousand. Thus, including the effect of pressure (water is slightly compressible) the density of sea-water is about 1.0369 g/cm . The change in density divided by the deep density is 0.0109. The float has to match these densities if it is to reach 2000 metres depth and then rise to

490-568: A feature not seen in its closest relative, the Patagonian toothfish, which typically inhabits slightly warmer waters. The presence of antifreeze glycoproteins allows the Antarctic toothfish (and other notothenioids) to thrive in subzero waters of the Southern Ocean surrounding Antarctica . The Antarctic toothfish's voracious appetite also is important in coping with cold water. It is mainly caught in

588-779: A float transmits a profile it is quickly converted to a format that can be inserted on the Global Telecommunications System (GTS). The GTS is operated by the World Meteorological Organisation , or WMO, specifically for the purpose of sharing data needed for weather forecasting. Thus all nations who are members of the WMO receive all Argo profiles within a few hours of the acquisition of the profile. Data are also made available through ftp and WWW access via two Argo Global Data Centres (or GDACs), one in France and one in

686-548: A high large proportion of type-C killer whales sighted in McMurdo Sound have scars caused by cookiecutter sharks that are currently assumed to be limited to north of 50°S. At the same time as this study was occurring, Italian whale experts at Terra Nova Bay, about 360 km north of Scott Base, deployed satellite transmitters on type-C killer whales to determine the whales' movements. Their results independently verified that type-C killer whales were commuting between Scott Base and

784-501: A layer developed by the Argo Technical Coordinator. Argo is now the dominant source of information about the climatic state of the oceans and is being widely used in many publications as seen in the diagram opposite. Topics addressed include air-sea interaction, ocean currents , interannual variability, El Niño , mesoscale eddies , water mass properties and transformation. Argo is also now permitting direct computations of

882-509: A measure of both fecundity and survival to spawning age, is not known. The Antarctic toothfish has a lightweight, partially cartilaginous skeleton, lacks a swim bladder , and has fatty deposits which act as a stored energy source, particularly during spawning. This fat also makes large toothfish neutrally buoyant. Many toothfish caught over the seamounts are very depleted of fat, and this is thought perhaps to be related to spawning and spawning migration, which are energy-demanding activities. It

980-514: A more conservative reference level to allow exploitation at a level where toothfish recruitment and the ecosystem in general is not appreciably impacted. This is required by Article II of the CAMLR Convention. A common misunderstanding of the CCAMLR decision rules is an assumption that the decline in population size will follow a clear trajectory from the starting year to a point 35 years later when

1078-482: A much greater volume of the ocean to be sampled. Such measurements are important for developing a comprehensive understanding of the ocean, such as trends in heat content. The original plan advertised in the Argo prospectus called for a nearest-neighbour distance between floats, on average, of 3° latitude by 3° longitude. This allowed for higher resolution (in kilometres) at high latitudes, both north and south, and

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1176-763: A near-linear decrease in salinity of 0.170 PSU in the Ross Sea due to temperature-induced warming in the West Antarctica ice sheet. Melting of the ice sheet and freshening of the Ross Gyre is predicted to slow down deep water formation in the Southern Ocean , which threatens to slow global thermohaline circulation . Studies has explored the role of the Ross Gyre in carbon uptake by enhancing biological pump though ocean iron fertilization (OIF) experiments. Models predict this using simulated particulate organic carbon (POC) and Lagrangian particle tracking . It has been found that

1274-524: A new approach to analyzing global warming , reported in Eos in 2017. David Morrison reports that "[b]oth of these data sets show clear signatures of heat deposition in the ocean, from the temperature changes in the top 2 km of water and from the expansion of the ocean water due to heating. These two measures are less noisy than land and atmospheric temperatures." Argo and CERES data collected between 2005 and 2019 have been compared as independent measures of

1372-461: A profiling float called Navis. A typical Argo float is a cylinder just over 1 metre long and 14 cm across with a hemispherical cap. Thus it has a minimum volume of about 16,600 cubic centimetres (cm ). At Ocean Station Papa in the Gulf of Alaska the temperature and salinity at the surface might be about 6°C and 32.55 parts per thousand giving a density of sea-water of 1.0256 g/cm . At

1470-457: A result of fishing has fallen to near-zero levels in the CCAMLR convention area. No mortality of seabirds or marine mammals was recorded as a result of fishing for Antarctic toothfish in 2011–12 and only two seabirds (southern giant petrels Macronectes giganteus ) have been killed as a result of fishing in the Ross Sea since 1996/97. Compliance measures adopted by CCAMLR apply to all Antarctic toothfish fisheries. These include: In November 2010,

1568-579: A substantial reduction in accidental seabird mortalities in the CAMLR Convention Area. The 50% (target) and 20% (limit) reference points used by the CCAMLR decision rules exceed the requirements for target and limit reference points set by almost all national and international fisheries management organizations, even for species longer lived than toothfish. A wide study of many fisheries generally indicated that most reach maximum sustainable yield at 30–35% of their pre-exploitation abundances. CCAMLR uses

1666-404: A voracious predator. Furthermore, by being by far the largest midwater fish in the Southern Ocean, it is thought to fill the ecological role that sharks play in other oceans. Aiding in that role, the Antarctic toothfish is one of only five notothenioid species that, as adults, are neutrally buoyant . This buoyancy is attained at 100–120 cm in length and enables them to spend time above

1764-480: A western landmass to Southern Ocean gyre formation have been challenged, as the Ross Gyre forms without any geostrophic contours being blocked. However, modeling simulations underline the importance of the northern ridge system in strengthening subpolar gyre circulation and shaping the stratification of the region. The Ross Gyre plays an important role in exchanging polar water masses and heat in Antarctica, connecting

1862-604: Is a clockwise-rotating water mass that lies north of the Ross Sea. This gyre is bounded to the north by the Polar Front of the Antarctic Circumpolar Current (ACC) and Pacific-Antarctic Ridge bathymetry, and to the south by the Antarctic Slope Current (ASC) and the Antarctic continental shelf. The gyre is located between 160°E and 140°W with a variable eastern boundary associated with the eastern extension of

1960-467: Is a file specific to 6 November 2012 and contains all profiles in a single NetCDF file for one ocean basin. The GDACs identify three ocean basins, Atlantic, Indian and Pacific. Thus three multi-profile files will carry every Argo profile acquired on that specific day. A user who wants to explore Argo data but lacks programming skills might like to download the Argo Global Marine Atlas which

2058-576: Is also a major prey of Adélie ( Pygoscelis adeliae ) and emperor penguins ( Aptenodytes forsteri ), Weddell seals ( Leptonychotes weddellii ) and Antarctic minke whales ( Balaenoptera bonaerensis ). Therefore, competition for prey among toothfish and these other mesopredators (middle trophic level predators) could be very important. The large Antarctic toothfish are eaten by sperm whales ( Physeter macrocephalus ), killer whales ( Orcinus orca ), Weddell seals, and possibly colossal squid ( Mesonychoteuthis hamiltoni ). Toothfish that are dwelling on

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2156-417: Is an adaptation of most predatory fish , e.g., sharks, so as not to be small for very long. The maximum age recorded so far has been 48 years. Antarctic toothfish take a long time to mature (13 years for males, 17 years for females) and once mature may not spawn every year, though the actual spawning interval is unknown. Only a few Antarctic toothfish with mature eggs have ever been caught, meaning knowledge

2254-626: Is an easy-to-use utility that allows the creation of products based on Argo data such as the salinity section shown above, but also horizontal maps of ocean properties, time series at any location etc. This Atlas also carries an "update" button that allows data to be updated periodically. The Argo Global Marine Atlas is maintained at the Scripps Institution of Oceanography in La Jolla, California. Argo data can also be displayed in Google Earth with

2352-590: Is balanced by the topography of the seafloor that drives this formation. The eastern boundary is closely linked to where the ACC crosses the Pacific-Antarctic Ridge, at the Udintsev Fracture Zone , with a southward deflection to conserve vorticity. Near the shelf, the gyre circulates westward following the westward flow of the Antarctic Slope Current. Other theories attributing blocked geostrophic flows on

2450-507: Is costly and challenging due to harsh weather conditions and ice coverage during winter. Oceanographic research in these remote regions is aided by autonomous monitoring devices, such as Argo Floats , which can constantly measure the ocean's biological, physical, and chemical properties. Ice cover remains an essential challenge for data acquisition. Before 2007, 40% of Argo floats deployed in the Southern Ocean had been destroyed and lost, mainly due to ice crashes. Survival days have improved though

2548-538: Is determined by GPS or Argos system positions at the surface. The data is transmitted to shore via satellite, and is freely available to everyone, without restrictions. The Argo program is named after the Greek mythical ship Argo to emphasize the complementary relationship of Argo with the Jason satellite altimeters. Both the standard Argo floats and the 4 satellites launched so far to monitor changing sea-level all operate on

2646-565: Is estimated that the circulation of the Ross Gyre exports 20 ± 5 Sverdrup. At 500 meters deep, the surface water density in the Ross Gyre is higher than the surface water density measured at the Amundsen Seas, which is located to the east of the Ross gyre, during summer and winter because the Ross Gyre has a higher salinity at the surface than the Amundsen Seas . An explanation for these salinities

2744-436: Is forced out of the float's pressure case and expands a rubber bladder at the bottom end of the float. As the bladder expands, the float becomes less dense than seawater and rises to the surface. Upon finishing its tasks at the surface, the float withdraws the oil and descends again. A handful of companies and organizations manufacture profiling floats used in the Argo program. APEX floats, made by Teledyne Webb Research , are

2842-684: Is managed by the Argo Data Management Team. Argo is also supported by the Group on Earth Observations, and has been endorsed since its beginnings by the World Climate Research Programme's CLIVAR Project (Variability and predictability of the ocean-atmosphere system), and by the Global Ocean Data Assimilation Experiment (GODAE OceanView). A program called Argo was first proposed at OceanObs 1999 which

2940-478: Is not known what happens to these fat-depleted fish, including whether they reach, or how long it takes them to reach, breeding condition again; this ostensibly occurs upon returning to continental-slope waters. Antarctic toothfish have vision and lateral line systems well adapted to find prey in low light levels. Since ice covers the surface of the ocean where Antarctic toothfish occur even in summer, these sensory specializations likely evolved to enable survival in

3038-543: Is not the case for their second winter season. Modeled results showed that juveniles that continue to follow the ice drift by the Northern and Eastern Ross Gyre during their second winter season, instead of following the ocean currents, can result in a 70% decrease of recruitment success. Historical data from the KRILL-DATABASE project, from 1926 up to 2016, shows the presence of both Antarctic krill ( Euphausia superba ) and

Ross Gyre - Misplaced Pages Continue

3136-633: Is sparse about fecundity. They spawn sometime during winter. Large, mature, older fish have been caught among the seamounts of the Pacific-Antarctic Ridge , a location thus thought to be important for spawning. Smaller, subadult Antarctic toothfish tend to concentrate in shallower waters on the continental shelf, while a large portion of the older fish are found on in the continental slope. This sequestering by size and age could be another adaptation for small fish to avoid being eaten by large ones. The recruitment potential of Antarctic toothfish,

3234-737: Is that Argo floats now transmit much more data than was previously possible and they spend only about 20 minutes on the sea surface rather than 8–12 hours, greatly reducing problems such as grounding and bio-fouling. The average life span of Argo floats has increased greatly since the program began, first exceeding 4-year mean lifetime for floats deployed in 2005. Ongoing improvements should result in further extensions to 6 years and longer. As of June 2014, new types of floats were being tested to collect measurements much deeper than can be reached by standard Argo floats. These "Deep Argo" floats are designed to reach depths of 4000 or 6000 metres, versus 2000 metres for standard floats. This will allow

3332-485: Is the addition of more meltwater in the Amundsen sea coming from the coastal shelf than in the Ross Gyre. Salinity has been recorded to be decreasing in the 40 years in the gyre as a result of the melting of ice shelves and the addition of fresh water. The change in salinity is the same as adding 18 mm of freshwater to the surface of the gyre. The southern area of the Ross Gyre has the strongest changes in salinity recorded. As

3430-424: Is to quantify the ocean heat content (OHC). The Argo fleet consists of almost 4000 drifting "Argo floats" (as profiling floats used by the Argo program are often called) deployed worldwide. Each float weighs 20–30 kg. In most cases probes drift at a depth of 1000 metres. Experts call this the parking depth. Every 10 days, by changing their buoyancy , they dive to a depth of 2000 metres and then move to

3528-453: Is used for additional targeted data collection to better understand the lifecycle and ecosystem role of Antarctic toothfish. Research has provided evidence for long-distance migrations of type-C killer whales between the Ross Sea and New Zealand waters, indicating a much wider range that had been postulated by a number of scientists. One adult female type-C killer whale has been seen in both New Zealand waters and McMurdo Sound, Antarctica, and

3626-452: The Antarctic cod , is a large, black or brown fish found in very cold (subzero) waters of the Southern Ocean near Antarctica. It is the largest fish in the Southern Ocean, feeding on shrimp and smaller fish, and preyed on by whales, orcas , and seals. It is caught for food and marketed as Chilean sea bass together with its sister species, the more northerly Patagonian toothfish ( D. eliginoides ). Often mistakenly called "Antarctic cod",

3724-460: The Gulf Stream and Kuroshio ), extension of observations into deep water and the addition of sensors for monitoring biological and chemical changes in the oceans. In November 2012 an Indian float in the Argo array gathered the one-millionth profile (twice the number collected by research vessels during all of the 20th century) an event that was reported in several press releases. As can be seen in

3822-566: The Marine Stewardship Council (MSC) certified the Ross Sea Antarctic toothfish fishery as a sustainable and well-managed fishery. The certification is contentious, with many conservation groups protesting the certification due to the paucity of information needed to reliably manage the fishery, and that only eight of the 19 vessels in the fishery during the latest year for which data are publicly available were certified. During

3920-455: The Patagonian toothfish , D. eleginoides ) can grow to more than 1.7 m (5 ft 7 in) in length and 135 kg in weight, twice as large as the next-largest Antarctic fish. Being large, and consistent with the unstructured food webs of the ocean (i.e., big fish eat little fish regardless of identity, even eating their own offspring), the Antarctic toothfish has been characterized as

4018-741: The Ross Sea in the austral summer, but has also been recorded from Antarctic coastal waters south of the Indian Ocean sector, in the vicinity of the Antarctic Peninsula , and near the South Sandwich Islands . A fishery for Antarctic toothfish, managed by the Convention for the Conservation of Antarctic Marine Living Resources (CCAMLR), has existed since 1997. The existence of this fishery in

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4116-407: The sea-surface . As they move they measure conductivity and temperature profiles as well as pressure . Scientists calculate salinity and density from these measurements. Seawater density is important in determining large-scale motions in the ocean. Average current velocities at 1000 metres are directly measured by the distance and direction a float drifts while parked at that depth, which

4214-467: The 1999/2000 fishing season to 2013/14 in CCAMLR Subarea 88.1 when the toothfish catch first exceeded 50 tonnes and from 2.3% to 24.5% averaging 12.4% in CCAMLR Subarea 88.2 up to the latest publicly available figure from 2013/14. The bycatch of other fish species is also regulated to a maximum amount annually by CCAMLR. CCAMLR decision rules are based on determining the catch level that will ensure that

4312-590: The 2013–14 season, vessels operating under the Marine Stewardship Certification landed 51.3% of all Antarctic toothfish from the Ross Sea Region (CCAMLR Subarea 88.1) and 64.7% of Antarctic toothfish from the Amundsen Sea sector (CCAMLR Subarea 88.2). The argument that only a portion of Antarctic toothfish is certified, the high price it commands, and the remote areas where a large proportion of

4410-491: The ACC to the Antarctic shelf. The undefined eastern boundary of the gyre entrains relatively warm Circumpolar Deep Water (CDW) that is transferred to the continental shelf and the Bellingshausen and Amundsen Seas , which can effect sea ice melting rates and shelf ice extent. Eddy formation through gaps in the Pacific-Antarctic Ridge are hypothesized to facilitate this transport between the Antarctic Circumpolar Current and

4508-748: The Adélie penguin breeding season. Slender-billed prion, mottled petrels, and Adelie penguins all demonstrate a preference towards very cold waters, making the Antarctic current bordering the Ross Gyre a biogeographical boundary in the region. Distribution of bird species by latitude also indicates the presence of the following species in the Ross Gyre: cape petrel ( Daption capense ) , white-faced storm petrel ( Pelagodroma marina ) , Royal Albatross ( Diomedea epomophora ), Salvin’s Albatross ( Thalassarche salvini ) , and sooty shearwater ( Ardenna grisea ) . The Antarctic toothfish ( D. mawsoni ) plays an essential role in

4606-498: The Antarctic Slope Current (ASC), which controls Ekman Transport . La Niña plays a role in transporting heat to the ice shelf on the Amundsen Sea . The Ross Gyre SSH also varies seasonally. During autumn, coastal sea level and Ross Gyre SSH are the highest, while SSH is lowest during summer. The Southern Annular Mode (SAM) describes the north-south movement of the prevailing winds in the Southern Ocean. The positive index describes

4704-571: The Antarctic Slope, extending far beyond the Ross Sea and into the Ross Gyre. Historical data also provides insight into plankton abundance in the region. Seabirds are part of the upper trophic levels of the ocean food web. A study in 2018 showed that two main species were the most commonly observed in the Ross Gyre: the Slender-billed prion and the Mottled petrel . While both species are pelagic,

4802-416: The Antarctic toothfish belongs to the notothen family ( Nototheniidae ), a family of fish genera that are abundant near Antarctica. The common name "toothfish" refers to the two rows of teeth in the upper jaw, thought to give it a shark-like appearance. The genus name Dissostichus is from the Greek dissos (twofold) and stichus (line) and refers to the presence of two long lateral lines that enable

4900-502: The MSC. Argo (oceanography) Argo is an international programme for researching the ocean. It uses profiling floats to observe temperature , salinity and currents . Recently it has observed bio-optical properties in the Earth's oceans. It has been operating since the early 2000s. The real-time data it provides support climate and oceanographic research. A special research interest

4998-399: The McMurdo Sound area and raise questions over the previously assumed importance of assumed dominance of Antarctic silverfish ( Pleuragramma antarcticum ) in the diet of Weddell seal and Type-C killer whales. These reports highlight the importance of managing this fishery in the best interests of the ecosystem by continuing to collect information on both Antarctic toothfish life history and

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5096-687: The Pacific-Antarctic Ridge. The Ross Gyre is bounded to the west by the presence of another gyre, the Balleny Gyre, associated with the Balleny Fracture Zone . The northeast boundary of the Ross Gyre expands and contracts semiannually due to reduced sea surface height (SSH) north of the gyre following deepening of the Amundsen Sea Low (ASL) to the east. The gyre is largest in area in May and November, and lowest following winter and in summer. The center of

5194-518: The Ross Gyre cyclonic circulation will be intensified due to input from sea ice melt; causing waters from the Ross Gyre to expand into the Amundsen and Bellingshausen Seas. Predictions suggest that by the 2050s, the intensification of the Ross Gyre would also enhance the intrusion of warm Circumpolar Deep Water (CDW) towards the Antarctica west shelf, further increasing the loss of the Antarctic ice sheets. Observational records from 1957 to 2020 have shown

5292-545: The Ross Gyre is fairly remote, the biogeochemistry of this region is relatively under sampled. Recently, Argo floats , autonomous drifting and profiling platforms with various biogeochemical sensors including temperature, salinity, and nutrients, have been used to increase sampling effort. Argo floats deployed in the Ross Gyre have also measured temperatures between -1.0 - 2.5°C ± 1°C, salinity between 33.8 - 34.6 ± 0.2 PSU, and nitrate concentrations between 26 - 32 ± 1 μmol kg. The concentrations of nutrients and carbon measured in

5390-411: The Ross Gyre vary by season due to processes like seasonal primary production and ice melt. During the austral summer and the austral winter , partial pressure of carbon dioxide (pCO₂), Nitrate [NO⁻₃], and Phosphate [PO₄³⁻], total carbon dioxide (TCO₂), total alkalinity (TALK), and Silicate [SiO 3 ] vary in the concentrations measured in the gyre. During the austral summer, which refers to

5488-457: The Ross Gyre's food web, where it is a predator to other invertebrates and also part of the diet of the Weddell seal. The Antarctic toothfish has also become an important commercially harvested fish, especially around the Ross Sea. Adult individuals have been recorded as far north as 55°S and 57°S in the Ross Gyre. Juvenile toothfish dispersal has been linked to sea ice drift from the Ross Gyre, where

5586-400: The Ross Gyre. The western limb of the gyre mediates the transfer of cold meltwater and newly formed Antarctic Bottom Water (AABW) originating in the Ross Sea northward. The presence of cold surface waters and warmer intermediate waters forms a double diffusive staircase within the Ross Gyre; this feature limits vertical heat exchange, and allows the development of ice in the gyre's center. It

5684-463: The Ross Sea Antarctic toothfish fishery to a "good alternative". Following a comprehensive review in 2012, the Monterey Bay Aquarium revised its rating of Antarctic toothfish to 'good alternative'. Greenpeace International added the Antarctic toothfish to its seafood red list in 2010. This approach is at variance with the high score given the fishery when it was granted certification by

5782-481: The Ross Sea Region is estimated to be at 75% of the pre-exploitation level (95% Bayesian probability interval 71–78%), well above the 50% target reference point. An independent study was reported to have detected the disappearance of large fish at the southern periphery of its range in the McMurdo Sound and was postulated to be consistent with this apparent loss of large fish. However, more recent work has shown this

5880-422: The Ross Sea, the area where most Antarctic toothfish are caught, is very contentious - the main argument proposed for this is the lack of accurate population parameters, such as original stock size , fecundity, and recruitment. Moreover, the main fishing grounds are presumed by some researchers to cover the area through which the entire stock of Antarctic toothfish pass. Typically, the fishing season has finished in

5978-655: The US. About 90% of all profiles acquired are made available to global access within 24 hours, with the remaining profiles becoming available soon thereafter. For a researcher to use data acquired via the GTS or from the Argo Global Data Centres (GDACs) does require programming skills. The GDACs supply multi-profile files that are a native file format for Ocean DataView. For any day there are files with names like 20121106_prof.nc that are called multi-profile files. This example

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6076-412: The area by the end of February and for the remainder of the year, much of the area is covered by sea ice, providing a natural impediment to fishing. This fishery is characterised by opponents as being a challenge to manage owing to the nature of benthic longline fishing . The bycatch of other fish can also be significant, with the ratio of toothfish caught ranging from 4.5% to 17.9% and averaging 9.3% from

6174-453: The bottom without expending extra energy. Both bottom-dwelling and mid-water prey are, therefore, available to them. Most other notothenioid fish and the majority of all Antarctic fishes, including smaller toothfish, are confined to the bottom . Coloring is black to olive brown, sometimes lighter on the undersides, with a mottled pattern on body and fins. Small fish blend in very well among the benthic sponges and corals . The species has

6272-632: The bottom, particularly those caught during the summer on the continental slope , eat mainly grenadiers (Macrouridae), but also feed on other smaller fish species and skates ( Raja spp.). They also feed on the colossal squid . Antarctic toothfish have been caught to depths of 2200 m, though based on commercial fishing effort, few occur that deep. Aging data indicate Antarctic toothfish are relatively fast-growing when young, but then growth slows later in life. They reach about one-third of maximum size after 5 years, and half maximum by 10 years, after which growth slows considerably. To grow fast when small

6370-536: The calculation of these targets. Different reference points to account for the needs of dependent predators in the ecosystem are used depending on the location of the species in the food web. The ecosystem fisheries management approach by CCAMLR involves use of move-on rules to protect trophic interactions, and limit direct effects of fishing on fish bycatch, seabirds, and vulnerable marine ecosystems. Annually reviewed mitigation measures such as line weighting and streamer lines minimize seabird bycatch, which have resulted in

6468-520: The clockwise circulation of the Ross Gyre facilitates the concentration of particles within the gyre, offering high potential for carbon sequestration . Ross Gyre Sea Surface Height (SSH) is subject to interannual variability influenced by the El Niño-Southern Oscillation ( El Niño and La Niña ). During the extreme El Niño event in 2015-2016, the SSH was observed to decrease by 6 cm, weakening

6566-401: The concentration of silicate to the amount of carbon. This ratio is higher than ratios from previous years and this annual variability could be due to changes in the concentrations of nutrients and/or diatom blooms, because the cell walls of diatoms are composed of silica. The Ross Gyre hosts a wide spectrum of species and ecological interactions. Its waters contribute to the life cycle of

6664-630: The drafting of Chapter 3 (Working Group 1) of the IPCC Fifth Assessment Report (released September 2013) and an appendix was added to that chapter to emphasize the profound change that had taken place in the quality and volume of ocean data since the IPCC Fourth Assessment Report and the resulting improvement in confidence in the description of surface salinity changes and upper-ocean heat content. Argo data were used along with sea level change data from satellite altimetry in

6762-497: The economically valued Antarctic toothfish ( Dissostichus mawsoni ), commonly marketed as Chilean seabass, and at least eight species of seabirds have been recorded in the region. With the southern point of the Ross Gyre bordering the Ross Sea , it also plays an indirect role in the Adélie penguin ( Pygoscelis adeliae ) feeding grounds by controlling ice extension. Orca Type C whales have also been recorded through satellite tracking on

6860-591: The first time in 1999 in Maryland (USA) and outlined the principles of global data sharing. The Argo Steering Team made a 10-year report to OceanObs-2009 and received suggestions on how the array might be improved. These suggestions included enhancing the array at high latitudes, in marginal seas (such as the Gulf of Mexico and the Mediterranean) and along the equator, improved observation of strong boundary currents (such as

6958-497: The fish are caught have been advanced as an encouragement to illegal, unreported, and unregulated (IUU) fishing and mislabeling . A 2011 genetic study of MSC-labeled Antarctic toothfish found in markets revealed a significant proportion was not from the MSC-certified stock, and many were not toothfish at all. The MSC had conducted its own internal study, which found no evidence of mislabeling. The MSC conducts an annual audit of

7056-619: The fish to sense prey. The species name, mawsoni , honors the Australian geologist Douglas Mawson who led the 1911–1914 Australasian Antarctic Expedition that explored the Antarctic coast and obtained the species' type specimen. The Antarctic toothfish was first formally described in 1937 from the English ichthyologist John Roxborough Norman with the type locality given as off MacRobertson Land at 66°45'S, 62°03'E in Antarctica. Fully grown, these fish (and their warmer-water relative,

7154-517: The fishery which includes sampling of certified product. Due to the challenges that faced toothfish management in the 1990s and early 2000s (e.g., IUU fishing, mislabeling, and inadequate data for management), consumer seafood guides such as Seafood Watch placed toothfish of both species (Chilean seabass) on their red, or "avoid", list; however, in light of up-to-date, internationally peer-reviewed scientific information, in April 2013, Seafood Watch upgraded

7252-505: The former heavily relies on a plankton rich diet. Adélie penguins have been observed in the Antarctic and Ross Gyre regions. A study in 2019 showed Adélie penguins increased their foraging efforts by traveling beyond the Ross Sea Marine Protected Area during their sub-adult phase and non-breeding season. Slower velocities of the Ross Gyre are related to Iceberg-affected years in the Ross Sea, which can significantly impact

7350-414: The global ocean heat content . They determine that areas of the world with high surface salinity are getting saltier and areas of the world with relatively low surface salinity are getting fresher. This has been described as 'the rich get richer and the poor get poorer'. Scientifically speaking, the distributions of salt are governed by the difference between precipitation and evaporation. Areas, such as

7448-449: The gyre is located between 164°W, 68°S, and 150°W, 63°S, depending on 100/500m or 1500/3000m steric anomaly height maps, respectively. Physical formation processes for the Ross Gyre remain unclear and difficult to study, but current theories attribute wind forcing and zonal momentum conservation balanced by vorticity gradients and bottom frictional forces to its formation. Prevailing polar westerlies create an eastern flowing ACC that

7546-487: The history section, enhancements are now planned in the equatorial regions of the oceans, in boundary currents and in marginal seas. This requires that the total number of floats be increased from the original plan of 3000 floats to a 4000-float array. One consequence of the use of profiling floats to sample the ocean is that seasonal bias can be removed. The diagram opposite shows the count of all float profiles acquired each month by Argo south of 30°S (upper curve) from

7644-615: The increase in sea ice drift leads to a decrease in recruitment success. A study by the National Institute of Water and Atmospheric Research in New Zealand found that the ice drift influenced by the Ross Gyre can determine the recruitment success of healthy juveniles. Simulations based on oceanographic data indicate that juvenile toothfish initial advantage of following ice drift diminishes as they grow. At their early life stages, sea ice provides food and shelter from predators. This however,

7742-510: The interaction of that species with predators and prey. An important research programme in this regard is the annual 'Shelf' survey carried out annually since 2012, which is designed to monitor the abundance of subadult Antarctic toothfish in areas where subadult-sized fish have been regularly found (e.g., in the southern Ross Sea) has been designed provide data to better estimate recruitment variability and provide an important early-warning signal of changes in toothfish recruitment. The project also

7840-466: The median estimated spawning stock biomass (not total biomass) is greater than or equal to 50% of the average pre-exploitation spawning biomass after a further 35 years of fishing (i.e. 35 years from each year of assessment), with the additional condition that the probability is less than a 10% that the spawning biomass will decline below 20% of the pre-exploitation level at any time during this period. Current spawning stock biomass for Antarctic toothfish in

7938-403: The months of December through February, the concentrations of pCO₂ has been measured to be between the ranges of 330 - 510 μatm, NO⁻₃ between 24 – 31.5 μmol kg,  PO₄³⁻ between 1.6 – 2.3 μmol kg, TCO₂ between 2150 - 2250 μmol kg, SiO 3 between 50 - 100 μmol kg. During the austral winter, which refers to the months June through August, the concentrations of pCO₂ has been measured to be between

8036-710: The most common element of the current array. SOLO and SOLO-II floats (the latter use a reciprocating pump for buoyancy changes, unlike screw-driven pistons in other floats) were developed at Scripps Institution of Oceanography . Other types include the NINJA float, made by the Tsurumi Seiki Co. of Japan, and the ARVOR, DEEP-ARVOR & PROVOR floats developed by IFREMER in France, in industrial partnership with French Company nke instrumentation. Most floats use sensors made by Sea-Bird Scientific ( https://www.seabird.com/ ) , which also makes

8134-418: The northern North Pacific Ocean , where precipitation dominates evaporation are fresher than average. The implication of their result is that the Earth is seeing an intensification of the global hydrological cycle . Argo data are also being used to drive computer models of the climate system leading to improvements in the ability of nations to forecast seasonal climate variations. Argo data were critical in

8232-403: The ocean as they vary with depth, but an increasing number of floats also carry other sensors, such as for measuring dissolved oxygen and ultimately other variables of biological and chemical interest such as chlorophyll, nutrients and pH. An extension to the Argo project called BioArgo is being developed and, when implemented, will add a biological and chemical component to this method of sampling

8330-502: The oceans. The antenna for satellite data collection is mounted at the top of the float which extends clear of the sea surface after it completes its ascent. The ocean is saline, hence an electrical conductor, so that radio communications from under the sea surface are not possible. Early in the program Argo floats exclusively used slow mono-directional satellite communications but the majority of floats being deployed in mid-2013 use rapid bi-directional communications. The result of this

8428-420: The planktonic tunicate Salpidae along the Polar Front, which accounts for the northern boundary of the Ross Gyre. Classified as a middle trophic organism in the ecosystem’s food web, Antarctic krill serves as food for multiple seabird species, including Adélie penguins, while also commercially harvested through multiple fisheries in the Southern Ocean. Physical climate models suggest that with climate warming,

8526-486: The plot opposite, by early 2018 the Bio-Argo program is expanding rapidly. The critical capability of an Argo float is its ability to rise and descend in the ocean on a programmed schedule. The floats do this by changing their effective density. The density of any object is given by its mass divided by its volume. The Argo float keeps its mass constant, but by altering its volume, it changes its density. To do this, mineral oil

8624-503: The ranges of 525 - 560 μatm, NO⁻₃ between 30 - 32 μmol kg,  PO₄³⁻ between 2.1 – and 2.3 μmol kg, TCO₂ between 2210 – 2260 μmol kg, SiO 3 between 70 – 105 μmol kg. A cruise navigating the Ross Gyre during the austral summer found that the ratio of silicate/net community production (NCP) was 0.66 ± 0.02 at the north area of the Ross Gyre, which scientists explained is due to modified circumpolar deep water (MCDW). In this cruise, this ratio of silicate/net community productivity compares

8722-466: The reduced light levels found under ice and in the Antarctic winter, as well as at deep depths. Antarctic toothfish also have a very well developed sense of smell, which is why they are easily caught by baited hooks and also scavenge the remains of penguins killed by other predators. The Antarctic toothfish lives in subzero degree water below latitude 60°S . It is noteworthy, like most other Antarctic notothenioids, for producing antifreeze glycoproteins ,

8820-416: The start of the program to November 2012 compared with the same diagram for all other data available. The lower curve shows a strong annual bias with four times as many profiles being collected in austral summer than in austral winter. For the upper (Argo) plot, there is no bias apparent. One of the critical features of the Argo model is that of global and unrestricted access to data in near real-time. When

8918-564: The stock size will reach 50% of pre-exploitation levels and an assumption that no feedback occurs during each assessment. The catch limit, though, is recalculated based on all updated or revised data at each annual or biennial assessment. This approach is used to ensure that the 50% level will be approached slowly and enables an ongoing readjustment of catch levels as knowledge improves. CCAMLR imposes stringent environmental protection and bycatch mitigation measures to Antarctic toothfish fisheries, including: Incidental mortality of seabirds as

9016-595: The strengthening of the westerly winds, while the negative index describes the weakening. SAM is associated with ice drift and ice extent. With climate warming, positive SAM is predicted to persist over the 21st century in the Antarctic coastal currents, strengthening the upward movement of subsurface warm waters to the coast and facilitating the rapid melting of the Antarctic ice sheet. The Southern Ocean, despite its critical role in climate regulation, oceanic processes, and carbon sequestration; remains under-researched. Acquiring in-situ ship based measurements on research vessels

9114-420: The surface. Since the density of the float is its mass divided by volume, it needs to change its volume by 0.0109 × 16,600 = 181 cm to drive that excursion; a small amount of that volume change is provided by the compressibility of the float itself, and excess buoyancy is required at the surface in order to keep the antenna above water. All Argo floats carry sensors to measure the temperature and salinity of

9212-449: The use of new technology for the floats. This include temperature sensors that detect the presence of ice, allowing the instrument to communicate, avoid its ascend to the surface, store the data, and continue measurements during its descent. Other ways to make observations are using radar satellite altimetry for ice cover and SSH measurements. Antarctic toothfish The Antarctic toothfish ( Dissostichus mawsoni ), also known as

9310-585: The waters off Northland. The total catch of Antarctic toothfish in 2013–14 was 3820 tonnes; 3,320 tonnes of this were taken from the Ross Sea (FAO Statistical Divisions 88.1 and 88.2), with the remainder taken from other high seas areas within the CCAMLR convention area. The ecosystem approach to fishing is encapsulated in Article II of the CAMLR Convention. The ecosystem approach uses decision rules based on both population status targets and limit reference points, and incorporates uncertainty and ecosystem status in

9408-487: Was a conference organised by international agencies with the aim of creating a coordinated approach to ocean observations. The original Argo prospectus was created by a small group of scientists, chaired by Dean Roemmich , who described a program that would have a global array of about 3000 floats in place by sometime in 2007. The 3000-float array was achieved in November 2007 and was global. The Argo Steering Team met for

9506-539: Was considered necessary because of the decrease in the Rossby radius of deformation which governs the scale of oceanographic features, such as eddies. By 2007 this was largely achieved, but the target resolution has never yet been completely achieved in the deep southern ocean. Efforts are being made to complete the original plan in all parts of the world oceans but this is difficult in the deep Southern Ocean as deployment opportunities occur only very rarely. As mentioned in

9604-448: Was not the case in 2014. Some studies have reported that the prevalence of fish-eating killer whales has been apparently decreasing in the southern Ross Sea, foraging efficiency of Weddell seals is decreasing, and numbers of Adélie penguins (competitors for Antarctic silverfish ) have been increasing. More recent studies have confirmed visual sightings of Weddell seals and Type-C killer whales holding and consuming large toothfish in

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