To estimate basal water storage beneath the Antarctic ice sheet, it is essential to have data on the three-dimensional characteristics of subglacial lakes. We present a method to estimate the water depth and surface area of Antarctic subglacial lakes from the inversion of hydraulic potential method. Lake Vostok is chosen as a case study because of the diverse and comprehensive measurements that have been obtained over and around the lake. The average depth of Lake Vostok is around 345±4 m. We estimated the surface area of Lake Vostok beneath the ice sheet to be about 13300±594 km^2. The lake consists of two sub-basins separated by a ridge at water depths of about 200–300 m. The surface area of the northern sub-basin is estimated to be about half of that of the southern basin. The maximum depths of the northern and southern sub-basins are estimated to be about 450 and 850 m, respectively. Total water volume is estimated to be about 4658±204 km^3. These estimates are compared with previous estimates obtained from seismic data and inversion of aerogravity data. In general, our estimates are closer to those obtained from the inversion of aerogravity data than those from seismic data, indicating the applicability of our method to the estimation of water depths of other subglacial lakes.
Thermobaric conditions of subglacial Antarctic environment remain poorly understood, despite recent advances in radar and seismic surveying. The direct accessing to the largest subglacial lake, Lake Vostok, was carried out twice by Russian scientists in February 2012 and January 2015, opening new opportunities for assessing the thermobaric conditions at ice-water interface. According to the assumption that ice sheet is “floating” on the lake, it was predicted that the water would rise 30 - 40 m in the bottom part of the borehole, but in fact the water rose from the lake to a height of more than 500 m. To explain this phenomenon we assume that the pressure in Lake Vostok results from the external pressure of the entire mass of ice above it and the pressure of the water column that is overlaid above the point being considered. Extrapolation of temperature measurements from the deep bore-holes drilled at Vostok Station also confirmed that the bed of the ice sheet is at pressure melting point. As a result of accessing Lake Vostok, the pressure in the lake is reduced that would lead to the formation of a new additional layer of accretion ice on the lower ice sheet surface.
This study presents the results of forward numerical models of a series of sections of the Aurora Trench (East Antarctica) derived from radio echo-sounding data that allowed to reconstruct the 3D shape of the Aurora Fault, a crustal listric normal fault characterized by a length exceeding 100 km. A similar extensional fault setting allows to replicate the asymmetric buried morphology of the magnetic basement at the Lake Vostok depression derived by the available gravity and magnetic profiles. Both the Aurora and Vostok listric fault reach their basal decollment at 34 km depth, possibly the base of the crust in this intracratonic environment. Integration of these results with the existing geologic interpretations of the tectonic origin of the Concordia Trench by normal faulting allowed to frame the Concordia, Aurora and Vostok normal faults within an intraplate transtensional corridor with a left-lateral movement component. The westward projection of the proposed strike-slip deformation belt may develop in correspondence of an older tectonic lineament stretching from the Eastern flanks of the Gamburtsev Subglacial Mts to the Lambert rift and characterized by a poly-phased complex tectonic history. The possible Cenozoic reactivation of these structures is discussed in the paper.
Opening a new scientific frontier lying under the Antarctic ice, Russian researchers have drilled down and finally reached the surface of the gigantic freshwater lake, Lake Vostok. The mission chief likened the achievement to placing a man on the moon. Drilling in the area of the lake began 22 years ago in 1990, but progressed slowly as a result of funding shortages, equipment breakdowns, difficulties of drilling in the "warm" ice, and environmental concerns. In 1996, six years after drilling was started, a group of Russian and British scientists discovered the lake believed to be one of the largest fresh water reservoirs on the planet. This lake is among the last unexplored places on Earth. Sealed from the Earth's atmosphere for millions of years, it may provide vital information about microbial evolution, the past climate of the Earth, and the formation of the Antarctic ice sheet. Russian experts waited several years for international approval of their drilling technology before proceeding. As anticipated, lake water under pressure rushed up the borehole, pushing the drilling fluid up and away, then froze, forming a protective plug that prevented contamination of the lake. In December of the next Antarctic season, 2012--2013, researchers plan to re-drill the frozen sample of subglacial water for analysis.
The detailed electrical conductivity measure- ment (ECM), trace chemical compositions and microparti- cles concentration analysis are performed for BH8 ice core from the depth of 126.0m to 130.0m at Vostok Station. At depth 128.7m, a volcanic signal 4726 a B.P. is detected. The volcanic sulphate flux is 95.8 kg·km?2, sulphate peak concen- tration 1352.8 ng·g?1, duration time about 10.1 years, com- parable with some well-known volcanic events. The results indicate that it seems to be a relatively large scale, long last- ing volcanic signal with farther volcanic origin.
LIU LeibaoKANG JianchengJean R. PetitJefferson C. SimoesMartine De Angelis