Lake Vostok

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Lake Vostok (Russian: восток, "east") is the largest of more than 140 subglacial lakes found under the surface of Antarctica. It is located beneath Russia's Vostok Station, 4,000 metres (13,000 ft) under the surface of the central East Antarctic ice sheet. It is 250 kilometres (160 mi) long by 50 kilometres (31 mi) wide at its widest point, thus similar in size to Lake Ontario, and is divided into two deep basins by a ridge. The water over the ridge is about 200 metres (660 ft), compared to roughly 400 metres (1,300 ft) deep in the northern basin and 800 metres (2,600 ft) deep in the southern. Lake Vostok covers an area of 15,690 square kilometres (6,060 sq mi). It has an estimated volume of 5,400 cubic kilometres (1,300 cu mi) and consists of fresh water. The average depth is 344 metres (1,129 ft). In May 2005 an island was found in the center of the lake.



Radar imaging

Airborne ice-penetrating radar data first showed lakes beneath the Antarctic ice-sheet in the late 1960s and early 1970s. The existence of Lake Vostok was first noted in 1973 by scientists of the Scott Polar Research Institute, but not named by them.[1]

Russian and British scientists delineated the lake in 1996 by integrating a variety of data, including airborne ice-penetrating radar imaging observations and spaceborne radar altimetry. It has been confirmed that the lake contains large amounts of liquid water under the more than three-kilometer thick icecap, promising to be the most unspoiled lake on Earth. The lake has at least 22 cavities of liquid water, averaging 10km each.[2]

The lake water is undoubtedly very old. 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.[3] 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.[4] In comparison, the similarly sized Lake Ontario has a residence time of six years, which is typical for a lake of that size.

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