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76-475: Lake CECs is a subglacial lake in Antarctica at approximately latitude 80°S. It has an estimated area of 18 km. The territory where the lake is located, some 160 km from Union Glacier , is claimed only by Chile . The lake is located in a buffer zone of three major West Antarctic glaciers. The movement of the ice is almost nonexistent and the area is in a situation of low disturbance. This allows

152-498: A code of conduct for ice drilling expeditions and in situ (on-site) measurements and sampling of subglacial lakes. This code of conduct was ratified at the Antarctic Treaty Consultative Meeting (ATCM) of 2011. By the end of 2011, three separate subglacial lake drilling exploration missions were scheduled to take place. In February 2012, Russian ice-core drilling at Lake Vostok accessed the subglacial lake for

228-420: A flat surface around the northern border of Lake Vostok, and the data collected from ERS-1 further built the geographical distribution of Antarctic subglacial lakes. In 2005, Laurence Gray and a team of glaciologists began to interpret surface ice slumping and raising from RADARSAT data, which indicated there could be hydrologically “active” subglacial lakes subject to water movement. Between 2003 and 2009,

304-402: A former subglacial lake. The water in a subglacial lake can have a floating level much above the level of the ground threshold. In fact, theoretically a subglacial lake can even exist on the top of a hill, provided that the ice over it is thin enough to form the required hydrostatic seal . The floating level can be thought of as the water level in a hole drilled through the ice into the lake. It

380-459: A mobile research station team journeyed through the central plateau of West Antarctica. Measurements showed unusual subglacial radar returns, indicating the presence of a waterbody at some 2.6 km depth under the ice. An initial mapping with an ice-penetrating radar confirmed the finding. The research team returned in summer of 2015 and the mapping was completed. The findings were published in a Geophysical Research Letters report by four members of

456-452: A prominent scientist studying polar lakes, has called Antarctica's subglacial ecosystems "our planet's largest wetland .” Microorganisms and weathering processes drive a diverse set of chemical reactions that can drive a unique food-web and thus cycle nutrients and energy through subglacial lake ecosystems. No photosynthesis can occur in the darkness of subglacial lakes, so their food webs are instead driven by chemosynthesis and

532-760: A redesigned seal face; new face control grooves were added to help stabilize the seals while under extreme conditions. Prior to the face control grooves, the seal faces were not balanced and would begin to move under high pressure conditions. Due to the movement, the seal faces would become misaligned when the seals moved, and that caused the seal faces to deteriorate, resulting in an unusable seal. - attempt to fix warping caused by system error - added face control grooves to prevent any erosion of seal faces - resolved any areas where fluid remains stagnant and cause blockage Hydrostatic seals should last multiple years without any deterioration to its components due to its overall structure. There should not be any contact between

608-465: A researcher at the Lewis Research Center , conducted an experiment to test what happens to a hydrostatic seal when its faces are misaligned. Etsion discovered that high pressures directed towards the outer face of the seal would cause static instability, while high pressure on the inner face of the seal would cause the seal to become more stable. In addition, axial misalignment would also cause

684-602: A survey of long-track measurements of ice-surface elevation using the ICESat satellite as a part of NASA's Earth Observing System produced the first continental-scale map of the active subglacial lakes in Antarctica. In 2009, it was revealed that Lake Cook is the most hydrologically active subglacial lake on the Antarctic continent. Other satellite imagery has been used to monitor and investigate this lake, including ICESat , CryoSat-2 ,

760-685: Is Lake Vostok with other lakes notable for their size being Lake Concordia and Aurora Lake. An increasing number of lakes are also being identified near ice streams. An altimeter survey by the ERS-2 satellite orbiting the East Antarctic Ice Sheet from 1995 to 2003 indicated clustered anomalies in ice sheet elevation indicating that the East Antarctic lakes are fed by a subglacial system that transports basal meltwater through subglacial streams . The largest Antarctic subglacial lakes are clustered in

836-461: Is an excess of pressure between the face plates, the two faces move apart and the seal begins to open. On the contrary, if the pressure is dropped and there is not enough pressure within the seal, the two seal faces come together and the hydrostatic seal begins to form. The flow rate of the system can also be controlled with great accuracy by limiting the amount of pressure within the seal. Pressure zones can be changed to create an equilibrium within

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912-858: Is based on a small number of samples, mostly from Antarctica. Inferences about solute concentrations, chemical processes, and biological diversity of unsampled subglacial lakes have also been drawn from analyses of accretion ice (re-frozen lake water) at the base of the overlying glaciers. These inferences are based on the assumption that accretion ice will have similar chemical signatures as the lake water that formed it. Scientists have thus far discovered diverse chemical conditions in subglacial lakes, ranging from upper lake layers supersaturated in oxygen to bottom layers that are anoxic and sulfur-rich. Despite their typically oligotrophic conditions, subglacial lakes and sediments are thought to contain regionally and globally significant amounts of nutrients, particularly carbon. Air clathrates trapped in glacial ice are

988-455: Is continuously repeated while the seal is in operation. Hydrostatic seals were first developed in the early 1960s to control the sealing of compressor air in the aircraft industry. Recently hydrostatic seals have only been used in the compressor industry because hydrodynamic seals have much greater application. The hydrostatic seal also has great potential in the chemical industry since it can be used to transport and seal chemicals . However,

1064-455: Is created when the ice is so much higher around the lake that the equipotential surface dips down into impermeable ground. Water from underneath this ice rim is then pressed back into the lake by the hydrostatic seal. The ice rim in Lake Vostok has been estimated to a mere 7 meters, while the floating level is about 3 kilometers above the lake ceiling. If the hydrostatic seal is penetrated when

1140-402: Is equivalent to the level at which a piece of ice over it would float if it were a normal ice shelf . The ceiling can therefore be conceived as an ice shelf that is grounded along its entire perimeter, which explains why it has been called a captured ice shelf . As it moves over the lake, it enters the lake at the floating line, and it leaves the lake at the grounding line. A hydrostatic seal

1216-464: Is known in downstream areas where ice streams are known to migrate, accelerate or stagnate on centennial time scales and highlights that subglacial water may be discharged over the ice sheet grounding line. Russian revolutionary and scientist Peter A. Kropotkin first proposed the idea of liquid freshwater under the Antarctic Ice Sheet at the end of the 19th century. He suggested that due to

1292-755: Is mainly carried out by chemolithoautotrophic microbes. Like plants, chemolithoautotrophs fix carbon dioxide (CO 2 ) into new organic carbon, making them the primary producers at the base of subglacial lake food webs. Rather than using sunlight as an energy source, chemolithoautotrophs get energy from chemical reactions in which inorganic elements from the lithosphere are oxidized or reduced . Common elements used by chemolithoautotrophs in subglacial ecosystems include sulfide , iron , and carbonates weathered from sediments. In addition to mobilizing elements from sediments, chemolithoautotrophs create enough new organic matter to support heterotrophic bacteria in subglacial ecosystems. Heterotrophic bacteria consume

1368-436: Is of particular interest to scientists studying astrobiology , as well as the history and limits of life on Earth. In most surface ecosystems, photosynthetic plants and microbes are the main primary producers that form the base of the lake food web . Photosynthesis is impossible in the permanent darkness of subglacial lakes, so these food webs are instead driven by chemosynthesis . In subglacial ecosystems, chemosynthesis

1444-880: Is only one order of magnitude smaller than the amount of organic carbon in all surface freshwaters (5.10 x 10 petagrams). This relatively smaller, but potentially more reactive, reservoir of subglacial organic carbon may represent another gap in scientists’ understanding of the global carbon cycle . Subglacial lakes were originally assumed to be sterile , but over the last thirty years, active microbial life and signs of higher life have been discovered in subglacial lake waters, sediments, and accreted ice. Subglacial waters are now known to contain thousands of microbial species, including bacteria , archaea , and potentially some eukaryotes . These extremophilic organisms are adapted to below-freezing temperatures, high pressure, low nutrients, and unusual chemical conditions. Researching microbial diversity and adaptations in subglacial lakes

1520-624: Is perhaps the best known subglacial lake beneath the Vatnajökull ice cap. Other lakes beneath the ice cap lie within the Skatfá, Pálsfjall and Kverkfjöll cauldrons. Notably, subglacial lake Grímsvötn's hydraulic seal remained intact until 1996, when significant meltwater production from the Gjálp eruption resulted in uplift of Grímsvötn's ice dam. The Mýrdalsjökull ice cap, another key subglacial lake location, sits on top of an active volcano- caldera system in

1596-432: Is slow. Oxic or slightly suboxic waters often reside near the glacier-lake interface, while anoxia dominates in the lake interior and sediments due to respiration by microbes. In some subglacial lakes, microbial respiration may consume all of the oxygen in the lake, creating an entirely anoxic environment until new oxygen-rich water flows in from connected subglacial environments. The addition of oxygen from ice melt and

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1672-467: Is suspected that there is a possibility of more. Subglacial lakes have also been discovered in Greenland, Iceland, and northern Canada. Scientific advances in Antarctica can be attributed to several major periods of collaboration and cooperation, such as the four International Polar Years (IPY) in 1882-1883, 1932-1933, 1957-1958, and 2007-2008. The success of the 1957-1958 IPY led to the establishment of

1748-536: Is unclear. Certainly on the Greenland Ice Sheet subglacial water acts to enhance basal ice motion in a complex manner. The "Recovery Lakes" beneath Antarctica's Recovery Glacier lie at the head of a major ice stream and may influence the dynamics of the region. A modest (10%) speed up of Byrd Glacier in East Antarctica may have been influenced by a subglacial drainage event. The flow of subglacial water

1824-483: The Advanced Spaceborne Thermal Emission and Reflection Radiometer , and SPOT5 . Gray et al. (2005) interpreted ice surface slumping and raising from RADARSAT data as evidence for subglacial lakes filling and emptying - termed "active" lakes. Wingham et al. (2006) used radar altimeter (ERS-1) data to show coincident uplift and subsidence, implying drainage between lakes. NASA's ICESat satellite

1900-549: The American Geophysical Union Chapman Conference in Baltimore. The conference allowed engineers and scientists to discuss the equipment and strategies used in ice drilling projects, such as the design of hot-water drills, equipment for water measurement and sampling and sediment recovery, and protocols for experimental cleanliness and environmental stewardship . Following this meeting, SCAR drafted

1976-469: The Antarctic Ice Sheet have accumulated an estimated ~21,000 petagrams of organic carbon, most of which comes from ancient marine sediments. This is more than 10 times the amount of organic carbon contained in Arctic permafrost and may rival the amount of reactive carbon in modern ocean sediments, potentially making subglacial sediments an important but understudied component of the global carbon cycle . In

2052-579: The Scientific Committee on Antarctic Research (SCAR) and the Antarctic Treaty System , paving the way to formulate a better methodology and process to observe subglacial lakes. In 1959 and 1964, during two of his four Soviet Antarctic Expeditions , Russian geographer and explorer Andrey P. Kapitsa used seismic sounding to prepare a profile of the layers of the geology below Vostok Station in Antarctica. The original intent of this work

2128-565: The Subglacial Antarctic Lakes Scientific Access (SALSA) team announced they had reached Lake Mercer after melting their way through 1,067 m (3,501 ft) of ice with a high-pressure hot-water drill. The team collected water samples and bottom sediment samples down to 6 meters deep. The majority of the nearly 400 Antarctic subglacial lakes are located in the vicinity of ice divides , where large subglacial drainage basins are overlain by ice sheets. The largest

2204-506: The body of water to be extremely stable, with minimal mass exchanges with its environment. This favors the hypothesis that the lake could support endemic life, which would have developed in extreme isolation. Lake CECs was discovered by the Chilean research center Centro de Estudios Científicos (CECs). The first signs of the lake were detected during Antarctic summer in January 2014, when

2280-473: The geothermal heating at the bottom of the ice sheets, the temperature beneath the ice could reach the ice melt temperature, which would be below zero. The notion of freshwater beneath ice sheets was further advanced by Russian glaciologist Igor A. Zotikov , who demonstrated via theoretical analysis the possibility of a decrease in Antarctic ice because of melting of ice at a lower surface. As of 2019, there are over 400 subglacial lakes in Antarctica , and it

2356-594: The limiting nutrient that constrains growth in the ecosystem, although co-limitation by both nitrogen and phosphorus supply seems most common. However, evidence from subglacial Lake Whillans suggests that nitrogen is the limiting nutrient in some subglacial waters, based on measurements showing that the ratio of nitrogen to phosphorus is very low compared to the Redfield ratio . An experiment showed that bacteria from Lake Whillans grew slightly faster when supplied with phosphorus as well as nitrogen, potentially contradicting

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2432-599: The Antarctic Ice Sheet took place again between 1971–1979. During this time, a US-UK-Danish collaboration was able to survey about 40% of East Antarctica and 80% of West Antarctica – further defining the subglacial landscape and the behavior of ice flow over the lakes. In the early 1990s, radar altimeter data from the European Remote-Sensing Satellite (ERS-1) provided detailed mapping of Antarctica through 82 degrees south. This imaging revealed

2508-1002: The CECs Glaciology Laboratory. Subglacial lake Since the first discoveries of subglacial lakes under the Antarctic Ice Sheet , more than 400 subglacial lakes have been discovered in Antarctica , beneath the Greenland Ice Sheet , and under Iceland 's Vatnajökull ice cap. Subglacial lakes contain a substantial proportion of Earth's liquid freshwater , with the volume of Antarctic subglacial lakes alone estimated to be about 10,000 km , or about 15% of all liquid freshwater on Earth. As ecosystems isolated from Earth's atmosphere , subglacial lakes are influenced by interactions between ice , water , sediments , and organisms . They contain active biological communities of extremophilic microbes that are adapted to cold, low- nutrient conditions and facilitate biogeochemical cycles independent of energy inputs from

2584-729: The Dome C-Vostok area of East Antarctica, possibly due to the thick insulating ice and rugged, tectonically influenced subglacial topography . In West Antarctica , subglacial Lake Ellsworth is situated within the Ellsworth Mountains and is relatively small and shallow. The Siple Coast Ice Streams, also in West Antarctica, overlie numerous small subglacial lakes, including Lakes Whillans , Engelhardt , Mercer , Conway , accompanied by their lower neighbours called Lower Conway (LSLC) and Lower Mercer (LSLM). Glacial retreat at

2660-455: The available methane. There is also evidence for active methane production and consumption beneath the Greenland Ice Sheet . Antarctic subglacial waters are also thought to contain substantial amounts of organic carbon in the form of dissolved organic carbon and bacterial biomass. At an estimated 1.03 x 10 petagrams, the amount of organic carbon in subglacial lake waters is far smaller than that contained in Antarctic subglacial sediments, but

2736-450: The base of the ice sheet through the storage of supraglacial meltwater, is thought to influence the rate of ice flow and overall behavior of the Greenland Ice Sheet. Much of Iceland is volcanically active, resulting in significant meltwater production beneath its two ice caps . This meltwater also accumulates in basins and ice cauldrons, forming subglacial lakes. These lakes act as a transport mechanism for heat from geothermal vents to

2812-644: The bottom of the ice caps, which often results in melting of basal ice that replenishes any water lost from drainage. The majority of Icelandic subglacial lakes are located beneath the Vatnajökull and Mýrdalsjökull ice caps, where melting from hydrothermal activity creates permanent depressions that fill with meltwater. Catastrophic drainage from subglacial lakes is a known hazard in Iceland, as volcanic activity can create enough meltwater to overwhelm ice dams and lake seals and cause glacial outburst flooding . Grímsvötn

2888-402: The chemical industry has set very strict regulations and the seal cannot be used for certain chemicals because of the constant seal leakage. The first hydrostatic seal was developed to replace current hydrodynamic seals ; previous hydrodynamic seals were costly to manufacture and were tedious to assemble. First generation hydrostatic seals used a two pressure system to establish equilibrium at

2964-936: The cold temperatures in subglacial lakes, which slow down microbial metabolism and reaction rates. The variable redox conditions and diverse elements available from sediments provide opportunities for many other metabolic strategies in subglacial lakes. Other metabolisms used by subglacial lake microbes include methanogenesis , methanotrophy , and chemolithoheterotrophy , in which bacteria consume organic matter while oxidizing inorganic elements. Some limited evidence for microbial eukaryotes and multicellular animals in subglacial lakes could expand current ideas of subglacial food webs. If present, these organisms could survive by consuming bacteria and other microbes. Subglacial lake waters are considered to be ultra- oligotrophic and contain low concentrations of nutrients , particularly nitrogen and phosphorus . In surface lake ecosystems, phosphorus has traditionally been thought of as

3040-400: The consumption of ancient organic carbon deposited before glaciation. Nutrients can enter subglacial lakes through the glacier ice-lake water interface, from hydrologic connections, and from the physical, chemical, and biological weathering of subglacial sediments . Since few subglacial lakes have been directly sampled, much of the existing knowledge about subglacial lake biogeochemistry

3116-460: The consumption of oxygen by microbes may create redox gradients in the subglacial lake water column, with aerobic microbial mediated processes like nitrification occurring in the upper waters and anaerobic processes occurring in the anoxic bottom waters. Concentrations of solutes in subglacial lakes, including major ions and nutrients like sodium , sulfate , and carbonates , are low compared to typical surface lakes. These solutes enter

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3192-501: The event of ice sheet collapse , subglacial organic carbon could be more readily respired and thus released to the atmosphere and create a positive feedback on climate change . The microbial inhabitants of subglacial lakes likely play an important role in determining the form and fate of sediment organic carbon. In the anoxic sediments of subglacial lake ecosystems, organic carbon can be used by archaea for methanogenesis , potentially creating large pools of methane clathrate in

3268-401: The famous SPRI-NSF-TUD surveys undertaken until the mid-seventies. Since this original compilation several smaller surveys has discovered many more subglacial lakes throughout Antarctica, notably by Carter et al. (2007), who identified a spectrum of subglacial lake types based on their properties in (RES) datasets. In March 2010, the sixth international conference on subglacial lakes was held at

3344-791: The first time. Lake water flooded the borehole and froze during the winter season, and the sample of re-frozen lake water (accretion ice) was recovered in the following summer season of 2013. In December 2012, scientists from the UK attempted to access Lake Ellsworth with a clean access hot-water drill; however, the mission was called off because of equipment failure. In January 2013, the US-led Whillans Ice Stream Subglacial Access Research Drilling (WISSARD) expedition measured and sampled Lake Whillans in West Antarctica for microbial life. On 28 December 2018,

3420-598: The floating level is high, the water will start flowing out in a jökulhlaup . Due to melting of the channel the discharge increases exponentially, unless other processes allow the discharge to increase even faster. Due to the high hydraulic head that can be achieved in some subglacial lakes, jökulhlaups may reach very high rates of discharge. Catastrophic drainage from subglacial lakes is a known hazard in Iceland, as volcanic activity can create enough meltwater to overwhelm ice dams and lake seals and cause glacial outburst flooding . The role of subglacial lakes on ice dynamics

3496-430: The horizontal shaft to shift in the vertical direction; this misalignment would result in a faulty seal if the restoring force is not great enough to correct the shift in components. The structure of the seal brings up the problem of leakage within the system. Since there is always a minuscule gap between two parts, there is always the problem of leakage, however the system’s structure allows leakage to be controlled to

3572-402: The ice surface at around x10 of the surface slope angle, as this is required for hydrostatic stability. In the late 1960s, they were able to mount RES instruments on aircraft and acquire data for the Antarctic Ice Sheet. Between 1971 and 1979, the Antarctic Ice Sheet was profiled extensively using RES equipment. The technique of using RES is as follows: 50-meter deep holes are drilled to increase

3648-492: The ice-sheet base, stronger than adjacent ice- bedrock reflections; 2) echoes of constant strength occurring along the track, which indicate that the surface is very smooth; and 3) a very flat and horizontal character with slopes less than 1%. Using this approach, 17 subglacial lakes were documented by Kapista and his team. RES also led to the discovery of the first subglacial lake in Greenland and revealed that these lakes are interconnected. Systematic profiling, using RES, of

3724-410: The idea that growth in these ecosystems is limited by nitrogen alone. Hydrostatic seal A hydrostatic seal is a non-contacting mechanical seal that operates under an equilibrium of forces . Unlike traditional hydrodynamic seals , hydrostatic seals have two different pressure zones that are used to establish a balanced pressure zone between two seal faces. The two-pressure system makes

3800-629: The last glacial period had been identified in Canada. These paleo-subglacial lakes likely occupied valleys created before the advance of the Laurentide Ice Sheet during the Last Glacial Maximum . However, two subglacial lakes were identified via RES in bedrock troughs under the Devon Ice Cap of Nunavut, Canada. These lakes are thought to be hypersaline as a result of interaction with

3876-419: The layer of glacial ice above the subglacial lake also supplies underlying waters with iron , nitrogen , and phosphorus -containing minerals , in addition to some dissolved organic carbon and bacterial cells. Because air clathrates from melting glacial ice are the primary source of oxygen to subglacial lake waters, the concentration of oxygen generally decreases with depth in the water column if turnover

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3952-557: The level where the pressure melting point of water intersects with the temperature gradient. In Lake Vostok , the largest Antarctic subglacial lake, the ice over the lake is thus much thicker than the ice sheet around it. Hypersaline subglacial lakes remain liquid due to their salt content. Not all lakes with permanent ice cover can be called subglacial, as some are covered by regular lake ice. Some examples of perennially ice-covered lakes include Lake Bonney and Lake Hoare in Antarctica's McMurdo Dry Valleys as well as Lake Hodgson ,

4028-486: The main source of oxygen entering otherwise enclosed subglacial lake systems. As the bottom layer of ice over the lake melts, clathrates are freed from the ice's crystalline structure and gases such as oxygen are made available to microbes for processes like aerobic respiration . In some subglacial lakes, freeze-melt cycles at the lake-ice interface may enrich the upper lake water with oxygen concentrations that are 50 times higher than in typical surface waters. Melting of

4104-523: The margins of the Antarctic Ice Sheet has revealed several former subglacial lakes, including Progress Lake in East Antarctica and Hodgson Lake on southern Alexander Island near the Antarctic Peninsula . The existence of subglacial lakes beneath the Greenland Ice Sheet has only become evident within the last decade. Radio-echo sounding measurements have revealed two subglacial lakes in

4180-435: The northwest section of the ice sheet. These lakes are likely recharged with water from the drainage of nearby supraglacial lakes rather than from melting of basal ice. Another potential subglacial lake has been identified near the southwestern margin of the ice sheet, where a circular depression beneath the ice sheet evidences recent drainage of the lake caused by climate warming. Such drainage, coupled with heat transfer to

4256-412: The organic material produced by chemolithoautotrophs, as well as consuming organic matter from sediments or from melting glacial ice. Despite the resources available to subglacial lake heterotrophs, these bacteria appear to be exceptionally slow-growing, potentially indicating that they dedicate most of their energy to survival rather than growth. Slow heterotrophic growth rates could also be explained by

4332-787: The overlying glacier, after which these sulfides are oxidized to sulfate by aerobic or anaerobic bacteria, which can use iron for respiration when oxygen is unavailable. The products of sulfide oxidation can enhance the chemical weathering of carbonate and silicate minerals in subglacial sediments, particularly in lakes with long residence times. Weathering of carbonate and silicate minerals from lake sediments also releases other ions including potassium (K ), magnesium (Mg ), sodium (Na ), and calcium (Ca ) to lake waters. Other biogeochemical processes in anoxic subglacial sediments include denitrification , iron reduction , sulfate reduction , and methanogenesis (see Reservoirs of organic carbon below). Subglacial sedimentary basins under

4408-417: The potential to change their hydrology and circulation patterns. Areas with the thickest overlying ice experience greater rates of melting. The opposite occurs in areas where the ice sheet is thinnest, which allows re-freezing of lake water to occur. These spatial variations in melting and freezing rates lead to internal convection of water and circulation of solutes, heat, and microbial communities throughout

4484-478: The seal face. The seal face was developed to work under high pressure conditions, however the seal face began to warp and deteriorate during stress tests . Once ammonia ( the liquid used in the first hydrostatic seal ) was added, the two seal faces would make contact with each other and begin the erosion process. Cold water was then tested as the incompressible fluid, it has double the viscosity as ammonia, which showed favorable results. Since cold water had double

4560-420: The seal unique because typical mechanical seals have one pressure zone that created causes a buildup of pressure that will eventually cause the seal to malfunction. After pressure has come to an equilibrium at the seal face, an incompressible fluid is then released between the two seal faces. The fluid creates a film around the seal face that acts as a lubricant and as a medium for the substance flowing through

4636-443: The seal will begin to occur. The rear face plate consists of a small opening that houses the injection system, which feeds the incompressible fluids through the system. Once the fluid is inside the seal, it forms a thin film around the entire inner system. After creating the film, the fluids then flow out of the seal and on to the rear face plate, which cools the system and prevents any excess heat from building up. This fluid cycle

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4712-410: The seal. Hydrostatic seals have been used in the aircraft industry; however they have seen very little commercial use because there is minimal research about the seals. Once pressure is applied and the seal comes together, a viscous liquid is released between the two seal faces and a thin film is formed to help create an airtight seal. If the amount of pressure inside of the seal is increased and there

4788-531: The sediments that could be released during ice sheet collapse or when lake waters drain to ice sheet margins. Methane has been detected in subglacial Lake Whillans, and experiments have shown that methanogenic archaea can be active in sediments beneath both Antarctic and Arctic glaciers. Most of the methane that escapes storage in subglacial lake sediments appears to be consumed by methanotrophic bacteria in oxygenated upper waters. In subglacial Lake Whillans, scientists found that bacterial oxidation consumed 99% of

4864-428: The signal-to-noise ratio in the ice. A small explosion sets off a sound wave , which travels through the ice. This sound wave is reflected and then recorded by the instrument. The time it takes for the wave to travel down and back is noted and converted to a distance using the known speed of sound in ice. RES records can identify subglacial lakes via three specific characteristics: 1) an especially strong reflection from

4940-608: The southernmost part of the Katla volcanic system . Hydrothermal activity beneath the Mýrdalsjökull ice cap is thought to have created at least 12 small depressions within an area constrained by three major subglacial drainage basins . Many of these depressions are known to contain subglacial lakes that are subject to massive, catastrophic drainage events from volcanic eruptions, creating a significant hazard for nearby human populations. Until very recently, only former subglacial lakes from

5016-524: The subglacial lake reservoir. Longer residence times, such as those found beneath the interior Antarctic Ice Sheet, would lead to greater contact time between the water and solute sources, allowing for greater accumulation of solutes than in lakes with shorter residence times. Estimated residence times of currently studied subglacial lakes range from about 13,000 years in Lake Vostok to just decades in Lake Whillans. The morphology of subglacial lakes has

5092-403: The subglacial lake, which will vary among subglacial lakes of different regions. Subglacial sediments are primarily composed of glacial till that formed during physical weathering of subglacial bedrock . Anoxic conditions prevail in these sediments due to oxygen consumption by microbes, particularly during sulfide oxidation . Sulfide minerals are generated by weathering of bedrock by

5168-412: The sun. Subglacial lakes and their inhabitants are of particular interest in the field of astrobiology and the search for extraterrestrial life . The water in subglacial lakes remains liquid since geothermal heating balances the heat loss at the ice surface. The pressure from the overlying glacier causes the melting point of water to be below 0 °C. The ceiling of the subglacial lake will be at

5244-442: The system that would allow less leakage in the overall system. The seals dual pressure zone helps maintain a constant pressure zone within the system. The constant pressure stabilizes the seal and does not allow the two seal faces to come in contact. There are face control grooves on both of seal faces that stabilize each face in the axial direction. The slightest axial movement will cause the two seal faces to touch and erosion of

5320-401: The two seal faces or else the condition of the seal will begin to deteriorate. Current Hydrodynamic seals begin to deteriorate over time because the two faces are always in contact with each other. In addition, any misalignment of the seal faces will cause them to rub which will begin to morph the seal faces and eventually cause the entire seal to become structurally unstable. Izchak Etsion,

5396-611: The underlying salt-bearing bedrock, and are much more isolated than the few identified saline subglacial lakes in Antarctica. Unlike surface lakes, subglacial lakes are isolated from Earth's atmosphere and receive no sunlight. Their waters are thought to be ultra- oligotrophic , meaning they contain very low concentrations of the nutrients necessary for life. Despite the cold temperatures, low nutrients, high pressure, and total darkness in subglacial lakes, these ecosystems have been found to harbor thousands of different microbial species and some signs of higher life. Professor John Priscu ,

5472-514: The viscosity of ammonia, the water prevented the seals from making contact with each other, thus causing the system to run properly. - High pressure conditions - recycles fluid in a continuous cycle, may have stagnant fluids which cause blockage - Seal faces began to erode under certain circumstances The second hydrostatic seal was an attempt to resolve first generation hydrostatic seal problems: erosion of seals, high pressure build up, and stagnant fluids. Second generation hydrostatic seals had

5548-479: The water column from glacial ice melting and from sediment weathering. Despite their low solute concentrations, the large volume of subglacial waters make them important contributors of solutes, particularly iron, to their surrounding oceans. Subglacial outflow from the Antarctic Ice Sheet , including outflow from subglacial lakes, is estimated to add a similar amount of solutes to the Southern Ocean as some of

5624-481: The world's largest rivers. The subglacial water column is influenced by the exchange of water between lakes and streams under ice sheets through the subglacial drainage system; this behavior likely plays an important role in biogeochemical processes, leading to changes in microbial habitat, particularly regarding oxygen and nutrient concentrations. Hydrologic connectivity of subglacial lakes also alters water residence times , or amount of time that water stays within

5700-496: Was key in developing this concept further and subsequent work demonstrated the pervasiveness of this phenomenon. ICESat ceased measurements in 2007 and the detected "active" lakes were compiled by Smith et al. (2009) who identified 124 such lakes. The realisation that lakes were interconnected created new contamination concerns for plans to drill into lakes ( see the Sampling expeditions section below ). Several lakes were delineated by

5776-472: Was to conduct a broad survey of the Antarctic Ice Sheet. The data collected on these surveys, however, was used 30 years later and led to the discovery of Lake Vostok as a subglacial lake. Beginning in the late 1950s, English physicists Stan Evans and Gordon Robin began using the radioglaciology technique of radio-echo sounding (RES) to chart ice thickness. Subglacial lakes are identified by (RES) data as continuous and specular reflectors which dip against

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