Lake Vostok Research Articles

Scientists Provide Perspectives as Drilling Reaches Subglacial Antarctic Lake Vostok

Culminating decades of effort, researchers drilled to subglacial Lake Vostok on 5 February. The glacial drilling team of the 57th Russian Antarctic Expedition penetrated to the waters of the lake at a depth of 3769.3 meters through deep ice borehole 5G, according to a report sent to the Arctic and Antarctic Research Institute by the head of Vostok station and the head of the glacial drilling team. Researchers collected about 1.5 cubic meters of water while working to prevent contamination of the lake before a plug of frozen water sealed the lake again, as researchers had planned. The accomplishment culminates decades of effort to reach Lake Vostok—a freshwater lake roughly the size of Lake Ontario located near the middle of the continent—and it opens up a new era in investigating subglacial Antarctic lakes. Some scientists speculate that Lake Vostok, the largest of more than 280 known subglacial lakes on the continent, could harbor life forms in an environment that has been sealed off from light and air for possibly tens of millions of years. They also speculate that the Vostok environment could be analogous to that of some icy moons in the solar system.

A Tiny Window Opens Into Lake Vostok, While a Vast Continent Awaits

On 8 February, the Russian Arctic and Antarctic Research Institute announced that a team of its engineers and scientists had drilled through nearly 4 kilometers of Antarctic ice to Lake Vostok.

Clean access, measurement, and sampling of Ellsworth Subglacial Lake: A method for exploring deep Antarctic subglacial lake environments

Antarctic subglacial lakes are thought to be extreme habitats for microbial life and may contain important records of ice sheet history and climate change within their lake floor sediments. To find whether or not this is true, and to answer the science questions that would follow, direct measurement and sampling of these environments are required. Ever since the water depth of Vostok Subglacial Lake was shown to be >500 m, attention has been given to how these unique, ancient, and pristine environments may be entered without contamination and adverse disturbance. Several organizations have offered guidelines on the desirable cleanliness and sterility requirements for direct sampling experiments, including the U.S. National Academy of Sciences and the Scientific Committee on Antarctic Research. Here we summarize the scientific protocols and methods being developed for the exploration of Ellsworth Subglacial Lake in West Antarctica, planned for 2012–2013, which we offer as a guide to future subglacial environment research missions. The proposed exploration involves accessing the lake using a hot‐water drill and deploying a sampling probe and sediment corer to allow sample collection. We focus here on how this can be undertaken with minimal environmental impact while maximizing scientific return without compromising the environment for future experiments.

Ice-flow sensitivity to boundary processes: a coupled model study in the Vostok Subglacial Lake area, Antarctica

AbstractSeveral hundred subglacial lakes have been identified beneath Antarctica so far. Their interaction with the overlying ice sheet and their influence on ice dynamics are still subjects of investigation. While it is known that lakes reduce the ice-sheet friction towards a free-slip basal boundary condition, little is known about how basal melting and freezing at the lake/ice interface modifies the ice dynamics, thermal regime and ice rheology. In this diagnostic study we simulate the Vostok Subglacial Lake area with a coupled full Stokes 3-D ice-flow model and a 3-D lake-circulation model. The exchange of energy (heat) and mass at the lake/ice interface increases (decreases) the temperature in the ice column above the lake by up to 10% in freezing (melting) areas, resulting in a significant modification of the highly nonlinear ice viscosity. We show that basal lubrication at the bottom of the ice sheet has a significant impact not only on the ice flow above the lake itself, but also on the vicinity and far field. While the ice flow crosses Vostok Subglacial Lake, flow divergence is observed and modelled. The heterogeneous basal-mass-balance pattern at the lake/ice interface intensifies this divergence. Instead of interactive coupling between the ice-flow model and the lake-flow model, only a single iteration is required for a realistic representation of the ice/water interaction. In addition, our study indicates that simplified parameterizations of the surface temperature boundary condition might lead to a velocity error of 20% for the area of investigation.

First information about the geology of central antarctica based on study of mineral inclusions in ice cores of the Vostok station borehole

Study of mineral inclusions in the basal part of the central Antarctic ice sheet from the borehole at the Vostok station was carried out. Mineral inclusions were trapped during freezing of the subglacial Lake Vostok water on the base of the glacier, when it crossed a shallow coastal area. It is established that the mineral inclusions are aggregates consisting mainly of clay minerals and quartz up to 150 microns. Crystals of aragonite and sulfides detected in the inclusions may indicate the presence of modern hydrothermal activity beneath the ice. Small (up to 4.5 mm) fragments of siltstone and aleuropelite in some aggregates suggest that lithified clastic sediments are exposed on the western coast of Lake Vostok, where removal of debris material occurred at the expense of exaration. Detrital zircon and monazite, found in siltstones and aleuropelite, suggest the chronology of geological complexes of the provenance area, which is, as is assumed, located in the Gamburtsev mountains in the central Antarctic. The age of the provenance area is 0.8–1.2 to 1.6–2.0 billion years.

Punctuated equilibrium of the surface above subglacial Lake Vostok in antarctica

Progress in understanding the surface dynamics above the subglacial Lake Vostok is achieved owing to use of the ICESat satellite laser elevation measurements, which enabled us to determine surface fluctuations with precision up to 3 cm. A new idea on punctuated equilibrium of the surface above Lake Vostok is elaborated; this idea is concluded in irregular, sharp vertical displacements of the ice surface by up to 40 cm. Deformation of the surface is accompanied with a common raising or lowering, and with local vertical displacements up to 20 cm in amplitude. It has been proved experimentally that snow transport on the surface above the lake causes only redistribution of snow and forms fractal structures that do not have any effect on surface deformation. The form of the surface is not an inclined plane due to many bends that are particularly related to ice flowing on the lake water area.

Around the World

In science news around the world this week, Pfizer is cutting its R&D spending, the U.S. Congress has sworn off earmarks, one of the Channel Islands has been named the world's first "dark sky island," a Japanese volcano is gathering steam, the Great Barrier Reef escaped being battered by the recent hurricane, drillers still have not reached subglacial Lake Vostok, and European research funding is being revamped.

Searching for life in extreme environments relevant to Jovian’s Europa: Lessons from subglacial ice studies at Lake Vostok (East Antarctica)

The objective was to estimate the genuine microbial content of ice samples from refrozen water (accretion ice) from the subglacial Lake Vostok (Antarctica) buried beneath the 4-km thick East Antarctic ice sheet. The samples were extracted by heavy deep ice drilling from 3659 m below the surface. High pressure, a low carbon and chemical content, isolation, complete darkness and the probable excess of oxygen in water for millions of years characterize this extreme environment. A decontamination protocol was first applied to samples selected for the absence of cracks to remove the outer part contaminated by handling and drilling fluid. Preliminary indications showed the accretion ice samples to be almost gas free with a low impurity content. Flow cytometry showed the very low unevenly distributed biomass while repeated microscopic observations were unsuccessful. We used strategies of Ancient DNA research that include establishing contaminant databases and criteria to validate the amplification results. To date, positive results that passed the artifacts and contaminant databases have been obtained for a pair of bacterial phylotypes only in accretion ice samples featured by some bedrock sediments. The phylotypes included the chemolithoautotrophic thermophile Hydrogenophilus thermoluteolus and one unclassified phylotype. Combined with geochemical and geophysical considerations, our results suggest the presence of a deep biosphere, possibly thriving within some active faults of the bedrock encircling the subglacial lake, where the temperature is as high as 50 °C and in situ hydrogen is probably present. Our approach indicates that the search for life in the subglacial Lake Vostok is constrained by a high probability of forward-contamination. Our strategy includes strict decontamination procedures, thorough tracking of contaminants at each step of the analysis and validation of the results along with geophysical and ecological considerations for the lake setting. This may serve to establish a guideline protocol for studying extraterrestrial ice samples.

The bottom topography and subglacial Lake Vostok water body, East Antarctica

The bottom topography and subglacial Lake Vostok water body, East Antarctica

Research Spotlight: Direct access to subglacial Lake Ellsworth

Since the discovery in 1996 that Lake Vostok, a subglacial lake in Antarctica, possessed a water column of more than 500 meters, scientists have come to believe that subglacial lakes are feasible habitats for life and may contain historical records of ice sheets and past climate within the sediments on their floors. So far, however, no subglacial lakes have been directly sampled.To determine a good location for direct measurements, Woodward et al. studied subglacial Lake Ellsworth in West Antarctica. The area is ideal for access because freezing and water circulation rates are low and are not affected by inflow of sediment with base water.

Hypothesis for mega-outburst flooding from a palaeo-subglacial lake beneath the East Antarctic Ice Sheet

Subglacial outburst floods at the margins of the Antarctic and Laurentide Ice Sheets have been linked to changes in global ocean circulation and climate. The impact of palaeo-hydrological systems beneath the East Antarctic Ice Sheet (EAIS) has, however, remained elusive. By analysing bed morphology in the Wilkes Subglacial Basin, we hypothesise the occurrence of a major palaeo-subglacial lake and associated outburst floods in the interior of East Antarctica. At similar to 70 km wide and over 100 km long, the inferred area of outburst flooding is the most extensive in Antarctica, and the palaeo-subglacial lake from which the floods originated is the second largest after Lake Vostok. The scale of inferred outburst flooding is similar to mega-floods beneath the Laurentide Ice Sheet. We suggest that this major hydrological system developed during expansion of the EAIS in the middle Miocene and probably affected ice sheet stability, ocean circulation and climate evolution.

Insights into hydrological regime of Lake Vostok from differential behavior of deuterium and oxygen‐18 in accreted ice

We use isotopic data (deuterium and oxygen‐18) of the recently recovered deepest Vostok ice core section (down to 3650 m depth) to study processes leading to the formation of lake ice and the hydrological regime of subglacial Lake Vostok. The significant variability of the lake ice isotopic content implies fluctuations in physical conditions of ice formation (mainly, volume and/or growth rate of frazil ice crystals) as well as variations of the isotope composition of the freezing water. The latter implies a poor mixing of the source waters (glacier melt and hydrothermal water) with the water of the main lake body. Poor mixing within the lake may have important consequences for the lake's chemical and gas balance and, particularly, for its microbiological content. A poorly mixed lake may provide ecological niches where microbial life can hide from high oxygen concentrations likely typical for the lake. We also show that the isotopic content of the main lake's input (meltwater) significantly differs from that of the output (lake ice), which can be explained by the contribution of an additional (hydrothermal) source. This latter conclusion is supported by the observed noncovariant behavior of deuterium and oxygen‐18 isotopes in the lake ice.

A comment on the Equation of State and the freezing point equation with respect to subglacial lake modelling

The empirical Equation of State ( EoS) allows the calculation of the density of water in dependence of salinity, temperature, and pressure. Water density is an important quantity to determine the internal structure and flow regime of ocean and lakes. Hence, its exact representation in numerical models is of utmost importance for the specific simulation results. The three parameters namely salinity, temperature, and pressure have a complex interdependency on the EoS. Whether warmer water parcels sink or rise, therefore depends on the surrounding salinity and pressure. The empirical Equation of Freezing Point ( EoFP) allows to calculate the pressure- and salinity-dependent freezing point of water. Both equations are necessary to model the basal mass balance below Antarctic ice shelves or at the ice–water interface of subglacial lakes. This article aims three tasks: first we comment on the most common formulations of the EoS and the EoFP applied in numerical ocean and lake models during the past decades. Then we describe the impact of the recent and self-consistent Gibbs thermodynamic potential formulation of the EoS and the EoFP on subglacial lake modelling. Finally, we show that the circulation regime of subglacial lakes covered by at least 3000 m of ice, in principle, is independent of the particular formulation, in contrast to lakes covered by a shallower ice sheet, like e.g., Subglacial Lake Ellsworth. However, as modelled values like the freezing and melting patterns or the distribution of accreted ice at the ice–lake interface are sensitive to different EoS and EoFP, we present updated values for Subglacial Lake Vostok and Subglacial Lake Concordia.

Isolation of fungi from Lake Vostok accretion ice

Here we report the characterization of fungi from 10 accretion ice sections (3300–5100 y old) as well as two deep glacial ice sections that are close to the bottom of the glacier (1 000 000–2 000 000 y old) from the Vostok, Antarctica, 5G ice core. Fungi were characterized by fluorescence microscopy culturing and sequence analyses of ribosomal DNA internal transcribed spacers. A total of 270 fungal colonies were cultured from the accretion ice of subglacial Lake Vostok and an additional 14 from the glacial ice immediately above the accretion ice. Mean concentrations were 0–4.42 cells mL−1 ice meltwater of which 0–100% exhibited viability (as determined by fluorescence microscopy). Thirty-one unique fungal ribosomal DNA sequences (28 from accretion ice and three from glacial ice) were determined and compared to recent taxa. The results, plus tests for growth at low temperatures, indicated that Lake Vostok contains a mixture of heterotrophic psychrotolerant fungal species. This indicates that the lake is not sterile but contains a unique ecosystem.

Modelling flow and accreted ice in subglacial Lake Concordia, Antarctica

More than 150 subglacial lakes have been discovered in Antarctica so far. Due to obvious challenges with exploration, numerical modelling remains one of the major tools to acquire information about those hard-to-access objects. Until now only the huge Lake Vostok has been investigated in detail. This paper focuses on Lake Concordia — the second largest subglacial lake in Antarctica over which substantial geophysical data has been collected. This lake is covered by about 4000 m ice and is located near Dome C. In order to apply numerical models to the hard-to-access Antarctic subglacial lakes, decent geometries and boundary conditions are required. In this study we present the results of airborne gravity inversion, suggesting that this lake has an area of 617 km 2, a volume of 31 km 3, and a maximum water column thickness of 126 m. This bathymetry is used as geometry input for an established 3D-numerical lake-flow model to simulate the circulation and basal mass balance. Compared to our model studies of subglacial Lake Vostok, we obtain a general circulation pattern that is significantly weaker (due to the smaller size of the lake) and of reversed orientation (due to the reversed ice surface tilt). The modelled mean horizontal and vertical velocities are in the order of 0.2 mm/s and 0.5 μm/s, respectively. The larger molecular convective velocity estimations (1.35 ± 0.13 mm/s and 0.81 ± 0.08 mm/s) are similar to Lake Vostok's. The modelled average melting and freezing rates are 4.3 ± 1.1 mm/a and 1.1 ± 0.3 mm/a, respectively, and the corresponding fresh water gain is 58 ± 27 dm 3/s. Integration of the modelled freezing and melting along prescribed ice flow lines allows us to calculate the distribution and thickness of accreted ice at the ice sheet bottom. We estimate a volume of 2.6 ± 2.0 km 3 (8.3 ± 8.2% of the total lake volume) occupying the north-eastern corner of the lake covering an area of 159 ± 48 km 2 (26 ± 9% of the total lake area). With about 16,800 ± 7600 yr, the residence time of the lake's water is significantly shorter than Lake Vostok's.

Geological structure of central East Antarctica from geophysical data

Examination of the subglacial topography of central East Antarctica reveals the block structure of the Earth’s crust in this region. The intracontinental blocks of the subglacial Vostok Highlands (400 masl), Komsomol’sky Mountains (700 masl), Schmidt Basin (150 masl), and Aurora Basin (−300 masl) are distinguished. The geological nature of the Komsomol’sky Subglacial Mountains (KSM) and the Schmidt Subglacial Basin (SSB) is interpreted from gravity measurements and regional aerogeophysical routes. The basin of Vostok Subglacial Lake (VSL) is located in the conjugation zone of these blocks. The KSM are considered to be a block of the Proterozoic mobile belt disturbed by a system of normal and reverse faults. The SSB is a rigid cratonic block partly overlapped by platform cover. The localization of the VSL Graben in the zone of conjugation of heterogeneous blocks testifies to its formation in a deep fault zone characterized by intense normal and reverse dislocations.

Exploring former subglacial Hodgson Lake, Antarctica Paper I: site description, geomorphology and limnology

At retreating margins of the Antarctic Ice Sheet, there are a number of locations where former subglacial lakes are emerging from under the ice but remain perennially ice-covered. This paper presents a site description of one of these lakes, Hodgson Lake, situated on southern Alexander Island, west of the Antarctic Peninsula (72° 00.549′ S, 68° 27.708′ W). First, we describe the physical setting of the lake using topographic and geomorphological maps. Second, we determine local ice sheet deglaciation history and the emergence of the lake using cosmogenic isotope dating of glacial erratics cross-referenced to optically stimulated luminescence dating of raised lake shoreline deltas formed during ice recession. Third we describe the physical and chemical limnology including the biological and biogeochemical evidence for life. Results show that the ice mass over Hodgson Lake was at least 295m thick at 13.5ka and has progressively thinned through the Holocene with the lake ice cover reaching an altitude of c. 6.5m above the present lake ice sometime after 4.6ka. Thick perennial ice cover persists over the lake today and the waters have remained isolated from the atmosphere with a chemical composition consistent with subglacial melting of catchment ice. The lake is ultra-oligotrophic with nutrient concentrations within the ranges of those found in the accreted lake ice of subglacial Lake Vostok. Total organic carbon and dissolved organic carbon are present, but at lower concentrations than typically recorded in continental rain. No organisms and no pigments associated with photosynthetic or bacterial activity were detected in the water column using light microscopy and high performance liquid chromatography. Increases in SO4 and cation concentrations at depth and declines in O2 provide some evidence for sulphide oxidation and very minor bacterial demand upon O2 that result in small, perhaps undetectable changes in the carbon biogeochemistry. However, in general the chemical markers of life are inconclusive and abiotic processes such as the diffusion of pore waters into the lake from its benthic sediments are far more likely to be responsible for the increased concentrations of ions at depth. The next phases of this research will be to carry out a palaeolimnological study of the lake sediments to see what they can reveal about the history of the lake in its subglacial state, and a detailed molecular analysis of the lake water and benthos to determine what forms of life are present. Combined, these studies will test some of the methodologies that will be used to explore deep continental subglacial lakes.

Ultra-low rare earth element content in accreted ice from sub-glacial Lake Vostok, Antarctica

This paper reports the first rare earth element (REE) concentrations in accreted ice refrozen from sub-glacial Lake Vostok (East Antarctica). REE were determined in various sections of the Vostok ice core in order to geochemically characterize its impurities. Samples were obtained from accreted ice and, for comparison, from the upper glacier ice of atmospheric origin (undisturbed, disturbed and glacial flour ice). REE concentrations ranged between 0.8–56 pg g −1 for Ce and 0.0035–0.24 pg g −1 for Lu in glacier ice, and between <0.1–24 pg g −1 for Ce and <0.0004–0.02 pg g −1 for Lu in accreted ice. Interestingly, the REE concentrations in the upper accreted ice (AC 1; characterized by visible aggregates containing a mixture of very fine terrigenous particles) and in the deeper accreted ice (AC 2; characterized by transparent ice) are lower than those in fresh water and seawater, respectively. We suggest that such ultra-low concentrations are unlikely to be representative of the real REE content in Lake Vostok, but instead may reflect phase exclusion processes occurring at the ice/water interface during refreezing. In particular, the uneven spatial distribution (on the order of a few cm) and the large range of REE concentrations observed in AC 1 are consistent with the occurrence/absence of the aggregates in adjacent ice, and point to the presence of solid-phase concentration/exclusion processes occurring within separate pockets of frazil ice during AC 1 formation. Interestingly, if the LREE enrichment found in AC 1 was not produced by chemical fractionation occurring in Lake Vostok water, this may reflect a contribution of bedrock material, possibly in combination with aeolian dust released into the lake by melting of the glacier ice. Collectively, this valuable information provides new insight into the accreted ice formation processes, the bedrock geology of East Antarctica as well as the water chemistry and circulation of Lake Vostok.

Deep structure of the Vostok Basin, East Antarctica as deduced from seismological observations

Seismological observations using the earthquake converted-wave method were carried out from December 7, 2002 to January 23, 2003 (season 48 of the Russian Antarctic Expedition) in the southern part of Vostok Subglacial Lake for the purpose of studying the structure of the Earth’s crust. Three observation points were placed. One of them was located at the Vostok Station and the other two were located at distances of 8.7 and 12.02 km to the east and to the west of the station, respectively. The performed investigation showed that the thickness of the Earth’s crust in the studied area is 34–36 km. The crust is subdivided into three blocks of different ranks. The low-velocity block is situated immediately beneath the Vostok Basin. Seven interfaces of mode conversion were detected. The results obtained allow us to suggest an increase in heat flow in the Vostok Basin and to the east of this basin. The seismic layering of the ice cover is correlated with the results of radioecho sounding and the structure of the glacier documented in cores of 5G-1 Borehole. The interfaces within the glacier near the Vostok Station are located at depths of 700 ± 100 m, 1600 ± 100 m, and 2200 ± 100 m.

Radar detection of accreted ice over Lake Vostok, Antarctica

Airborne radar data collected over Lake Vostok, East Antarctica, show a reflection close to the Vostok ice core below the depth of the meteoric-accreted ice boundary (MAIB) and near the boundary between impurity-rich (1) and impurity-poor (2) accreted ice (A12B). The spatial pattern of detection of this reflection is aligned with ice flow over the southern half of the lake. Ice-core data from the accreted ice show large variations in the number density of inclusions, soluble chloride-ion concentration ([Cl −]), charge-balance-derived acidity ([H +] cb) and crystal-orientation fabric. Here we investigate the existing hypothesis that this reflection is due to the MAIB and seek possible reflection causes that explain the radar-derived reflectivity (− 51 ± 8 dB). The likely maximum reflectivity due to an insoluble mineral-inclusion contrast is − 125 dB. If none of the Cl − or H + ions are trapped within inclusions, then ice-conductivity models predict a reflectivity of − 50 dB near the MAIB and − 58 dB near the A12B, both primarily due to large [H +] cb changes. If some of those ions are trapped within inclusions, then those values are smaller. Fabric contrasts at either boundary can produce significant reflectivities (− 62 dB). These results indicate that the mineral-inclusion contrast near the MAIB does not cause the observed reflection. Because of uncertainty in the in situ location of the soluble impurities, and because impurity-rich accreted ice 1 is believed to only originate in the small bay in the southwestern corner of the lake yet the reflection is observed over a much wider area, we argue that a fabric contrast at the A12B is the probable reflection cause. Both predicted spatial variations in accretion rates near the upstream shoreline, or lower ice temperatures along flowbands that originate at bedrock ridges near the upstream shoreline, may explain why the reflection is not detected everywhere that accretion is predicted.