Lake Vostok

Coordinates: 77°30′S 106°00′E / 77.500°S 106.000°E / -77.500; 106.000
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Lake Vostok
Coordinates77°30′S 106°00′E / 77.500°S 106.000°E / -77.500; 106.000
Typesubglacial rift lake
Basin countries- (Antarctica)
Max. length250 km (160 mi)
Max. width50 km (30 mi)
Surface area15,690 km (9,750 mi)
Average depth344 m (1,129 ft)
Max. depth~1,000 m (3,300 ft)[citation needed]
Water volume5,400 km3 (1,300 cu mi) ± 1,600 km3 (400 cu mi)
Residence time13,300 yrs
Surface elevation~ −500 m (−1,600 ft)
Islands1
SettlementsVostok Station

Lake Vostok (Russian: восток, "East") is the largest of more than 140 subglacial lakes found under the surface of Antarctica. The overlying ice provides a continuous paleoclimatic record of 400,000 years, although the lake water itself may have been isolated for 15[1][2] to 25 million years.[3] The lake is named after the Vostok, the 900-ton corvette of Russian Antarctic pioneer Fabian von Bellingshausen. No water sample has been obtained yet.

Lake Vostok is located beneath Russia's Vostok Station under the surface of the central East Antarctic Ice Sheet, which is at 3,488 metres (11,444 ft) above mean sea level. The surface of this fresh water lake is approx 4,000 m (13,100 ft) under the surface of the ice, which places it at approx 500 m (1,600 ft) below sea level. Measuring 250 km (160 mi) long by 50 km (30 mi) wide at its widest point, and covers an area of 15,690 km2 (6,060 sq mi), it's similar in area size to Lake Ontario, but with over three times the volume. The average depth is 344 m (1,129 ft). It has an estimated volume of 5,400 km3 (1,300 cu mi).[4] The lake is divided into two deep basins by a ridge. The liquid water over the ridge is about 200 m (700 ft), compared to roughly 400 m (1,300 ft) deep in the northern basin and 800 m (2,600 ft) deep in the southern.

Discovery

Location of Lake Vostok in East Antarctica

Russian scientist Peter Kropotkin first proposed the idea of fresh water under Antarctic ice sheets at the end of the 19th century. He theorized that the tremendous pressure exerted by the cumulative mass of thousands of vertical meters of ice could increase the temperature at the lowest portions of the ice sheet to the point where the ice would melt. Kropotkin's theory was further developed by Russian glaciologist I.A Zotikov, who wrote his Ph.D. thesis on this subject in 1967.

Russian scientist Andrey Kapitsa (Pyotr Kapitsa's son) used seismic soundings in the region of Vostok Station made during the Soviet Antarctic Expedition in 1959 and 1964 to measure the thickness of the ice sheet.[5] Kapitsa was the first to suggest the existence of subglacial lake in this region and named it Lake Vostok.[6]

When British scientists in Antarctica performed airborne ice-penetrating radar surveys in the early 1970s, they detected unusual radar readings at the site which suggested the presence of a liquid, freshwater lake below the ice.[7] In 1991, Jeff Ridley, a remote sensing specialist with the Mullard Space Science Laboratory at University College London, directed the ERS-1 satellite to turn its high-frequency array toward the center of the Antarctic ice cap. The data from ERS-1 confirmed the findings from the 1973 British surveys,[8] but this new data was not published in the Journal of Glaciology until 1993. Space-based radar revealed that this subglacial body of fresh water was one of the largest lakes in the world—and one of some 140 subglacial lakes in Antarctica. Russian and British scientists delineated the lake in 1996 by integrating a variety of data, including airborne ice-penetrating radar imaging observations and space-based radar altimetry. It has been confirmed that the lake contains large amounts of liquid water under the more than 3 kilometers (1.9 mi) thick ice cap, promising to be the most unspoiled lake on Earth. The lake has at least 22 cavities of liquid water, averaging 10 kilometers (6.2 mi) each.[9]

In 2005 an island was found in the central part of the lake.[10] Then, in January 2006, the discovery of two nearby smaller lakes under the ice cap was published; they are named 90 Degrees East and Sovetskaya.[11] It is suspected that these Antarctic subglacial lakes may be connected by a network of subterranean rivers. Centre for Polar Observation & Modelling glaciologists Duncan Wingham and Martin Siegert published in Nature in 2006 that many of the subglacial lakes of Antarctica are at least temporarily interconnected. Because of varying water pressure in individual lakes, large subsurface rivers may suddenly form and then force large amounts of water through the solid ice.[12]

Geological history

Main articles: Geology of Antarctica and Gondwana

Africa separated from Antarctica around 160 million years ago, followed by the Indian subcontinent, in the early Cretaceous (about 125 million years ago). About 65 million years ago, Antarctica (then connected to Australia) still had a tropical to subtropical climate, complete with marsupial fauna and an extensive temperate rainforest.[13][14][15]

The Lake Vostok basin is a small (50 km wide) tectonic feature within the overall setting of a several hundred kilometer wide continental collision zone between the Gamburtsev Mountain Range, a subglacial mountain range and the Dome C region.[16] The lake water is cradled on a bed of sediments 70 meters (230 ft) thick, offering the possibility that they contain a unique record of the climate and life in Antarctica before the ice cap formed.[8][17]

Research

Vostok Station

The lake water is believed to have been sealed off under the thick ice sheet about 15 million years ago. Initially, it was thought that the same water had made up the lake since the time of its formation, giving a residence time in the order of one million years.[12] Later research by Robin Bell and Michael Studinger from the Lamont–Doherty Earth Observatory of Columbia University suggested that the water of the lake is continually freezing and being carried away by the motion of the Antarctic ice sheet, while being replaced by water melting from other parts of the ice sheet in these high pressure conditions. This resulted in an estimate that the entire volume of the lake is frozen and removed every 13,300 years—its effective mean residence time.[18]

Drilling for sample cores was halted in 1998 at roughly 100 meters (300 ft) above the suspected boundary where the ice sheet and the liquid waters of the lake are thought to meet. In November 2010, when the team came up with new, ecologically-safe methods of probing the lake without contamination; the scientists submitted a final environmental evaluation of the project to the Antarctic Treaty System's environmental protection committee and were given the go-ahead to sample the ancient waters. In January 2011 the head of the Russian Antarctic Expedition, Valery Lukin, announced that his team had only 50 meters of ice left to drill in order to reach the water.[1] The researchers then switched to a new thermal drill head with a "clean" silicone oil fluid to drill the rest of the way.[19] Instead of drilling all the way into the water, they would stop just above it, when a sensor on the thermal drill detects free water. At that point, the drill will be stopped and extracted from the bore hole, thereby lowering the pressure beneath it and drawing water into the hole and left for quite some time to freeze, creating a plug of frozen ice in the bottom of the hole[20]. Finally, next summer, the team would drill down again to take a sample of that ice and analyze it.[1][21]

Drilling stopped on 5 February 2011 at a depth of 3,720 meters (12,200 ft) so that the research team could make it off the ice and onto the last flight before the beginning of the Antarctic winter season. The drilling team left by aircraft on February 6 and will have to wait until the next austral summer begins in December 2011 to try again.[22]

In the Antarctic summer of 2012–13, the Russian team also plans to send an underwater robot into the lake to collect water samples and sediments from the bottom. An environmental assessment of the plan will be submitted at the Antarctic Treaty's consultative meeting in May 2012.[21]

Temperature

It was at Vostok Station that the coldest temperature ever observed on Earth (−89 °C (−128 °F)) was recorded on 21 July 1983.[1] The average water temperature is calculated to be around −3 °C (27 °F); it remains liquid below the normal freezing point because of high pressure from the weight of the ice above it. Geothermal heat from the Earth's interior warms the bottom of the lake. The ice sheet itself insulates the lake from cold temperatures on the surface.

Ice core

Ice cores drilled at Vostok. Vostok Station is seen in the background.

Researchers working at Vostok Station produced one of the world's longest ice cores in 1998. A joint Russian, French, and United States team drilled and analyzed the core, which is 3,623 meters (11,886 ft) long. Ice samples from cores drilled close to the top of the lake have been assessed to be as old as 420,000 years, suggesting that the lake was sealed under the ice cap 15 million years ago. Drilling of the core was deliberately halted roughly 100 meters (300 ft)[23] above the suspected boundary where the ice sheet and the liquid waters of the lake are thought to meet. This was to prevent contamination of the lake from the 60 ton column of freon and kerosene Russian scientists filled it with to prevent the borehole from collapsing and freezing over.[8]

From this core, specifically from ice that is thought to have formed from lake water freezing onto the base of the ice sheet, extremophile microbes were found, suggesting that the lake water supports life. Scientists suggested that the lake could possess a unique habitat for ancient bacteria with an isolated microbial gene pool containing characteristics developed perhaps 500,000 years ago.[24]

Oxygen

Lake Vostok is an oligotrophic extreme environment, one that is expected to be supersaturated with nitrogen and oxygen,[25][26] measuring 2.5 liters of nitrogen and oxygen per 1 kilogram (2.2 lb) of water,[27] that is 50 times higher than those typically found in ordinary freshwater lakes on Earth. The sheer weight and pressure (350 atmospheres) of the continental ice cap on top of Lake Vostok is believed to contribute to the high gas concentration.[28]

Besides dissolving in the water, oxygen and other gases are trapped in a type of structure called a clathrate. In clathrate structures, gases are enclosed in an icy cage and look like packed snow. These structures form at the high-pressure depths of Lake Vostok and would become unstable if brought to the surface.[12][27]

Tidal forces

In April 2005, German, Russian, and Japanese researchers found that the lake has tides.[29] Depending on the position of the Sun and the Moon, the surface of the lake rises about 12 millimeters.[30]

Life

The lake is under complete darkness and expected to be rich in oxygen, so there is speculation that any organisms inhabiting the lake could have evolved in a manner unique to this environment.[8][27] These adaptations to an oxygen-rich environment might include high concentrations of protective oxidative enzymes.

Living Hydrogenophilus thermoluteolus microorganisms have been found in Lake Vostok's deep ice core drillings; they are an extant surface dwelling species.[26][31] This suggests the presence of a deep biosphere utilizing a geothermal system of the bedrock encircling the subglacial lake. There is optimism that microbial life in the lake may be possible despite high pressure, constant cold, low nutrient input, potentially high oxygen concentration and an absence of sunlight.[26][32][33]

Due to the lake's similarity to Jupiter's moon Europa and Saturn's moon Enceladus, any confirmation of life living in Lake Vostok would strengthen the prospect for the possible presence of life on Europa or Enceladus.[26][34]

Controversy

The drilling project was opposed by some environmental groups and scientists who argued that hot-water drilling would do less environmental damage.[35] The Russians however complained that hot-water drilling required more power than they could generate at their remote camp.[35] Scientists of the United States National Research Council have taken the position that it should be assumed that microbial life exists in Lake Vostok and that after such a long isolation, any life forms in the lake require strict protection from contamination.[36] Sediments on its floor should give clues to its long-term climate, and isotopes in its water are expected to help geologists determine how and when subglacial lakes such as Lake Vostok form. However, meticulously documented decontamination procedures will be required to establish the credibility of the scientific data obtained.

The drilling technique employed thus far by the Russians has involved the use of freon and kerosene to lubricate the borehole and prevent it from collapsing and freezing over; 60 tons of these chemicals have been used thus far on the ice above Lake Vostok.[8] Other countries, particularly the United States and Britain, have failed to persuade the Russians not to pierce to the lake until cleaner technologies such as hot-water drilling are available.[37] Though the Russians claim to have improved their operations, they continue to use the same borehole, which has already been filled with kerosene.[38] According to the head of Russian Antarctic Expeditions, Valery Lukin, the new equipment had been developed by researchers at the St. Petersburg Nuclear Physics Institute that would ensure the lake remains uncontaminated upon intrusion.[1][39] Lukin has repeatedly reassured other signatory nations to the Antarctic Treaty System that the drilling will not affect the lake. He argues that on breakthrough, water will rush up the borehole, freeze, and seal the chemical fluids out.

The international scientific community however remains unconvinced by these arguments. The Antarctic and Southern Ocean Coalition argues that this is a profoundly misguided step, which endangers not only Lake Vostok itself, but could harm other subglacial lakes in Antarctica, which some scientists are convinced are inter-linked with Lake Vostok.[5] This coalition asserts that "it would be far preferable to join with other countries to penetrate a smaller and more isolated lake, before re-examining whether penetration of Lake Vostok is environmentally defensible. If we are wise, the Lake will be allowed to reveal its secrets in due course."[5]

See also

References

  1. ^ a b c d e Moskvitch, K (27 January 2011). "Lake Vostok drilling in Antarctic 'running out of time'". BBC News. Retrieved 2011-01-28.
  2. ^ Secrets of Antarctica's 15-Million Year-Old Lake -A Galaxy Classic (December 05, 2007)
  3. ^ Studinger, M (2008). "Subglacial Lake Vostok". Columbia University. Retrieved 2011-02-01.
  4. ^ Subglacial Lake Facts
  5. ^ a b c "Appeal to the Duma on Lake Vostok, Antarctica" (PDF). Antarctic and Southern Ocean Coalition. April 14, 2008. Retrieved 2011-02-10.
  6. ^ "Andrey Kapitsa dies in Moscow". Russian Geographical Society. 2011-08-03. Retrieved 2011-08-04.
  7. ^ Oswald, GKA (1973). "Lakes beneath the Antarctic Ice Sheet". Nature. 245 (5423): 251–4. doi:10.1038/245251a0. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  8. ^ a b c d e Morton, O. "Ice Station Vostok". Wired. Retrieved 2011-01-31.
  9. ^ Dieter Fütterer; Georg Kleinschmidt (2006). Antarctica: contributions to global Earth sciences: proceedings of the IX International Symposium of Antarctic Earth Sciences Potsdam, 2003. Birkhäuser. p. 138. ISBN 9783540306733. Retrieved 2011-05-15.
  10. ^ Whitehouse, D (25 May 2005). "Russia to resume Vostok drilling". BBC News. Retrieved 2011-01-28.
  11. ^ Robin Bell and Michael Studinger, Geophysical researchers from Columbia University, published in Geophysical Research Letters
  12. ^ a b c Siegert MJ (2000). "The identification, examination and exploration of Antarctic subglacial lakes". Sci Prog. 83 ( Pt 3): 223–42. PMID 11077478.
  13. ^ Wesibrd, S., A forest grows in Antarctica - an extensive forest may have flourished about 3 million years ago, Science News, March 1986
  14. ^ O'Hanl, L (Nov. 5, 2004). "Antarctic Forests Reveal Ancient Trees". Discovery News. Retrieved 2011-01-31. {{cite news}}: Check date values in: |date= (help)
  15. ^ "Frozen in time: Fossils from the Antarctic". British Antarctic Survey. Retrieved 2011-01-31.
  16. ^ Tectonic Control of Subglacial Lakes
  17. ^ Miles Below Antarctic Ice, a Freshwater Lake May Harbor Ancient Life.” Robert Lee Hotz, The Los Angeles Times.
  18. ^ "Columbia University Scientists Present Long Sought Opportunities to Safely Explore Life Within Earth's Most Ancient and Inaccessible Ecosystem". The Earth Institute at Columbia University. March 21, 2002. Retrieved March 31, 2010.
  19. ^ Edwards, L (10 January 2011). "Russians hope to reach Lake Vostok for the first time soon". Physorg. Retrieved 2011-01-29.
  20. ^ Vasiliev et al., 2011, Twenty years of drilling the deepest hole in ice, Scientific Drilling, 11, 41-45, doi:10.2204/iodp.sd.11.05.2011
  21. ^ a b Race against time for raiders of the lost lake (17 January 2011) Nature 469, 275 doi:10.1038/469275a
  22. ^ Israel, B (7 February 2011). "Lake Vostok Drilling Mission Iced". Our Amazing Planet. Retrieved 2011-02-07.
  23. ^ Jouzel J, Petit JR, Souchez R, Barkov NI, Lipenkov VY, Raynaud D, Stievenard M, Vassiliev NI, Verbeke V, Vimeux F (1999). "More than 200 meters of lake ice above subglacial Lake Vostok, Antarctica". Science. 286 (5447): 2138–41. doi:10.1126/science.286.5447.2138. PMID 10591641.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  24. ^ Priscu JC, Adams EE, Lyons WB, Voytek MA, Mogk DW, Brown RL, McKay CP, Takacs CD, Welch KA, Wolf CF, Kirshtein JD, Avci R (1999). "Geomicrobiology of subglacial ice above Lake Vostok, Antarctica". Science. 286 (5447): 2141–4. doi:10.1126/science.286.5447.2141. PMID 10591642.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  25. ^ Ekaykin, AA (2010). "Insights into hydrological regime of Lake Vostok from differential behavior of deuterium and oxygen-18 in accreted ice". Journal of Geophysical Research. 115 (C05003). Bibcode:2010JGRC..11505003E. doi:10.1029/2009JC005329. Retrieved 2011-01-28. {{cite journal}}: More than one of |last1= and |last= specified (help); Unknown parameter |coauthors= ignored (|author= suggested) (help)
  26. ^ a b c d Bulat, SA (2010). "Searching for life in extreme environments relevant to Jovian's Europa: Lessons from subglacial ice studies at Lake Vostok (East Antarctica)". Elsevier Ltd. doi:10.1016/j.asr.2010.11.024. Retrieved 2011-01-28. {{cite journal}}: More than one of |last1= and |last= specified (help); Unknown parameter |coauthors= ignored (|author= suggested) (help)
  27. ^ a b c Burton, K (August 11, 2003). "Researchers find antarctic lake water will fizz like a soda". NASA. Retrieved 2011-01-28.
  28. ^ Siegert, MJ (2001). "Physical, chemical and biological processes in Lake Vostok and other Antarctic subglacial lakes". Nature. 414 (6864): 603–9. doi:10.1038/414603a. PMID 11740551. Retrieved 2011-01-29. {{cite journal}}: More than one of |last1= and |last= specified (help); Unknown parameter |coauthors= ignored (|author= suggested) (help)
  29. ^ Wendt, A (2005). "The response of the subglacial Lake Vostok, Antarctica, to tidal and atmospheric pressure forcing". Geophysical Journal International. 161 (1): 41–9. doi:10.1111/j.1365-246X.2005.02575.x. Retrieved 2011-02-04. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  30. ^ Dietrich, R (2001). "Evidence for tides in the subglacial Lake Vostok, Antarctica". Geophysical Research Letters. 28 (15): 2971–4. Bibcode:2001GeoRL..28.2971D. doi:10.1029/2001GL013230. Retrieved 2011-02-04. {{cite journal}}: More than one of |last1= and |last= specified (help); Unknown parameter |coauthors= ignored (|author= suggested) (help)
  31. ^ Alan T. Bull (2004). Microbial diversity and bioprospecting. ASM Press. pp. 139–. ISBN 9781555812676. Retrieved 2011-05-15.
  32. ^ Bulat, SA (August 2004). "DNA signature of thermophilic bacteria from the aged accretion ice of Lake Vostok, Antarctica: implications for searching for life in extreme icy environments". International Journal of Astrobiology. 3: 1–12. doi:10.1017/S1473550404001879. Retrieved 2011-01-29. {{cite journal}}: More than one of |last1= and |last= specified (help); Unknown parameter |coauthors= ignored (|author= suggested) (help)
  33. ^ "...microbes found in accreted ice of Lake Vostok were relatively modern, but the probability of ancient lake-floor sediments led to a possibility of a very old biota at the base of subglacial lakes." Khare1, N (2009). "Biological and Morphological Studies Carried out in Antarctic Lakes" (PDF). International Journal of Lakes and Rivers. 2 (1): 57–102. Retrieved 2011-02-04. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)CS1 maint: numeric names: authors list (link)
  34. ^ "Mystery of Antarctica's 15-Million Year-Old Lake". The Daily Galaxy. 2007-12-04. Retrieved 2007-12-05.
  35. ^ a b Niiler, E (9 February 2011). "Antarctic Drilling Plan Raises Concerns". Discovery News. Retrieved 2011-02-10.
  36. ^ "Exploration of Antarctic Subglacial" (PDF). National Academy of Sciences. National Research Council. 2007. Retrieved 2011-02-09.
  37. ^ Darby, A (8 February 2011). "Antarctic Treaty no match for national pride". The Sydney Morning Herald. Retrieved 2011-02-09.
  38. ^ "Antarctica's Lake Vostok Controversy". Antarctic and Southern Ocean Coalition. 2010. Retrieved 2011-02-10.
  39. ^ Russians Close to Reaching Lake Vostok The St. Petersburg Times Retrieved on March 09, 2010

External links

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