page_title: Vostok Station
section_title: Ice core drilling
hierarchical_section_title: Vostok Station / Ice core drilling
context_page_description: Vostok Station is a Russian research station in inland Princess Elizabeth Land, Antarctica. Founded by the Soviet Union in 1957, the station lies at the southern Pole of Cold, with the lowest reliably measured natural temperature on Earth of −89.2 °C. Research includes ice core drilling and magnetometry. Vostok was named after Vostok, the lead ship of the First Russian Antarctic Expedition captained by Fabian von Bellingshausen. The Bellingshausen Station was named after this captain.
context_section_description: In the 1970s the Soviet Union drilled a set of cores 500–952 metres (1,640–3,123 ft) deep. These have been used to study the oxygen isotope composition of the ice, which showed that ice of the last glacial period was present below about 400 metres' depth. Then three more holes were drilled: in 1984, Hole 3G reached a final depth of 2202 m; in 1990, Hole 4G reached a final depth of 2546 m; and in 1993 Hole 5G reached a depth of 2755 m; after a brief closure, drilling continued during the winter of 1995. In 1996 it was stopped at depth 3623 m, by the request of the Scientific Committee on Antarctic Research that expressed worries about possible contamination of Lake Vostok. This ice core, drilled collaboratively with the French, produced a record of past environmental conditions stretching back 420,000 years and covering four previous glacial periods. For a long time it was the only core to cover several glacial cycles; but in 2004 it was exceeded by the EPICA core, which, whilst shallower, covers a longer time span. In 2003 drilling was permitted to continue, but was halted at the estimated distance to the lake of only 130 m.
  The ancient lake was finally breached on 5 February 2012 when scientists stopped drilling at the depth of 3,770 metres and reached the surface of the sub-glacial lake.
  The brittle zone is approximately between 250 and 750 m and corresponds to the Last Glacial Maximum, with the end of the Holocene climatic optimum at or near the 250-metre depth.
  Although the Vostok core reached a depth of 3623 m the usable climatic information does not extend down this far. The very bottom of the core is ice refrozen from the waters of Lake Vostok and contains no climate information. The usual data sources give proxy information down to a depth of 3310 m or 414,000 years. Below this there is evidence of ice deformation.  It has been suggested that the Vostok record may be extended down to 3345 m or 436,000 years, to include more of the interesting MIS11 period, by inverting a section of the record. This then produces a record in agreement with the newer, longer EPICA record, although it provides no new information.
caption: 420,000 years of ice core data from Vostok, Antarctica, research station. Current period is at left. From bottom to top: insolation at 65°N due to Milankovitch cycles (connected to 18O); 18O isotope of oxygen; levels of methane (CH4); relative temperature; levels of carbon dioxide (CO2).
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