Vostok Antarctic Research Articles

Characteristics of the Blood Protein Composition of a Healthy Human during a Year-Long Stay at the Vostok Antarctic Station

Characteristics of the Blood Protein Composition of a Healthy Human during a Year-Long Stay at the Vostok Antarctic Station

Carbon dioxide precedes temperature change during short-term pauses in multi-millennial palaeoclimate records

In Antarctica, ice-core temperature has traditionally been regarded as a leading variable to carbon dioxide, CO2 during the last 400,000 years before present (B.P.). This finding is in contrast to most reports on global mean surface temperature and atmospheric CO2 for the last 150 years. However, previous techniques for establishing leading or lagging (LL) relations between paired global warming variables have required that the time series show constant frequency (stationarity). Herein, we show that on orbital and multi-millennial time scales, the Vostok Antarctic ice core displays 9 periods of 8.7 kyr ± 5 kyr during which CO2 becomes a leading variable to temperature. Six of the 9 periods were associated with short-term pauses occurring during 4 major glaciation-deglaciation periods. We find that CO2 also leads temperature during short pauses in the major cyclic pattern of the Greenland time series. In the latter series, there are also two contrasting cycle developments. In the first contrasting cycle developments, lasting from 103.5 to 79 ka, there is an in-phase relation between CO2 and temperature, with a slope of 0.75. In the second contrasting cycle developments, lasting from 61.5 to 43.5 ka, there is an out-of-phase relation with a slope of −0.67. In addition, the latter shows a see-saw pattern between Arctic and Antarctic temperatures.

Spectrum of frequency modulation of serpentine emission as a reflection of the solar fluctuation spectrum

We study frequency modulation of serpentine emission (SE), using data from the Vostok Antarctic station. It is shown that the previously observed 5-minute modulation of the SE carrier frequency is the most prominent and stable in the emission spectrum. Frequency fluctuations of this period are present in about 70 % of the total SE observation time under moderately quiet geomagnetic conditions (Kp=0–2). We performed a per-pixel processing of SE dynamic spectra and found that the power spectrum of the signal frequency modulation contains a clearly visi-ble peak at periods close to 5 minutes. A detailed study shows the emission spectrum matching the frequency range of the solar photospheric oscilla-tions. The results of the analysis allow us to conclude that the 5-minute modulation of the SE carrier fre-quency can be viewed as a reflection of photospheric fluctuations with the same period that is typical for the solar eigenoscillations.

Спектр частотной модуляции серпентиной эмиссии как отражение спектра солнечных колебаний

We study frequency modulation of serpentine emission (SE), using data from the Vostok Antarctic station. It is shown that the previously observed 5-minute modulation of the SE carrier frequency is the most prominent and stable in the emission spectrum. Frequency fluctuations of this period are present in about 70 % of the total SE observation time under moderately quiet geomagnetic conditions (Kp=0–2). We performed a per-pixel processing of SE dynamic spectra and found that the power spectrum of the signal frequency modulation contains a clearly visi-ble peak at periods close to 5 minutes. A detailed study shows the emission spectrum matching the frequency range of the solar photospheric oscillations. The results of the analysis allow us to conclude that the 5-minute modulation of the SE carrier frequency can be viewed as a reflection of photospheric fluctuations with the same period that is typical for the solar eigenoscillations.

Relationship between the ionospheric potential and the ground-level electric field in the southern polar cap

The relationships between the average hourly values of the vertical ground-level electric field measured at the Vostok Antarctic station and the ionospheric potential above the station have been obtained. The ΔEz and Uext parts of both parameters controlled by the solar wind were considered. Convection models (Weimer, 1995; Lukianova and Christiansen, 2006) and a model based on the SuperDARN radar system were used to determine the ionospheric potential. An analysis has been performed for isolated days and the entire sample in 1998–2000 (including 170 days of “fine weather”). For an isolated day, the best correlation coefficients (R) between ΔEz and Uext obtained using the three models were 0.81, 0.80, and 0.88, respectively. The total correlation coefficient for the entire data set was R = 0.24−0.32. The R value was larger during daytime (R ≈ 0.4) and smaller at night (R ≈ 0.1) and slightly increased in the early morning hours. The specific features of daily variations in R apparently indicate that it is possible to adequately describe the structure of the ionospheric electric field equipotentials by using large-scale stationary convection models. The R value varies complexly, depending on the IMF orientation, but it generally tends to increase from IMF By 0, which is explained by the asymmetric convection patterns for opposite By signs.

Radiocarbon in the Antarctic ice: The formation of the cosmic ray muon component at large depths

This study is devoted to the production of 14C by the secondary cosmic radiation in polar ice. The radiocarbon production in the reactions caused by the nuclear-active and muon components is considered. The data on 14C from the Vostok and Taylor Dome Antarctic boreholes are analyzed. The 14C concentration values at depths larger than the firn—ice boundary by a factor of 2—3 can be explained by a deep production of radiocarbon in the reactions caused by the cosmic radiation muon component.

Simulation of variations in the polar atmospheric electric field related to the magnetospheric field-aligned currents

The distribution of the electric potential, generated by the magnetospheric field-aligned currents flowing along the auroral oval and in the dayside cusp region at the upper atmospheric boundary in the polar ionosphere, is calculated. The obtained electric potential distributions are used to calculate the electric field strength near the Earth’s surface. The results of the model calculations are in good agreement with the electric field measurements at Vostok Antarctic station. It has been indicated that large-scale magnetospheric fieldaligned currents, related to IMF variations, can affect variations in the electric field strength in the polar regions via changes in the electric potential in the polar ionosphere, associated with these currents.

Evolution of the Antarctic ice sheet throughout the last deglaciation: A study with a new coupled climate—north and south hemisphere ice sheet model

The aim of this paper is to assess, through the understanding of deglaciation processes, the contribution of the Antarctic ice sheet to sea-level rise during the last deglaciation. To achieve this goal, we use an Earth System model in which the interactions between the atmosphere, the ocean, the vegetation and the northern and Antarctic ice sheets are represented. This new tool allows the simulation of the evolution of the Antarctic ice volume, which starts to decrease at around 15 ka. At the end of deglaciation, the melting of the Antarctic ice sheet contributes to an ice-equivalent sea-level rise of 9.5 m in the standard experiment and 17.5 m in a more realistic sensitivity experiment accounting for a different bathymetry in the Weddell Sea which succeeds in producing both major ice shelves (Ross and Ronne-Filchner). In both experiments, the melting of all ice sheets contributes to 121.5 m and 129.5 m, respectively, which is very consistent with data. The new coupled model provides a timing and amplitude of the Antarctic deglaciation different from those previously obtained by prescribing the temperature record from the Vostok Antarctic ice core (78°27′S 106°52′E) as a uniform temperature forcing. Sensitivity experiments have also been performed to analyse the impact of the parameters at the origin of the deglaciation process: insolation changes, atmospheric CO 2 variation, basal melting and sea-level rise. All those parameters have an influence on the timing of the deglaciation. The prescribed global sea level rise is shown to be a major forcing factor for the evolution of the Antarctic ice volume during the last deglaciation. We quantify the direct effect of the sea-level rise due to the northern hemisphere ice sheet melting on the grounding line retreat which, in turn, favours enhancement of grounded ice flow by lowering the buttressing effect of ice shelves.

Relation between the near-Earth electric field at high latitudes and intense cloud-to-ground lightning strokes initiating VLF emission bursts

Since 1998, the gradient of the near-Earth atmospheric electric field potential (|Ez|) has been continuously registered at Vostok Antarctic station within the scope of the joint Russian-Australian project. The data of the continuous 10-day period of fine weather in April 1998 have been selected for the following analysis. The field |Ez| behavior at Vostok station was compared with a number of lightning strokes obtained from data of the ground-based network of electromagnetic measurements. It has been found out that the average hourly values of |Ez| evidently negatively correlate with the number of intense lightning strokes. The causes of these relations are discussed. The obtained results are interpreted based on a theory of global electric circuit.

Trace elements in Vostok Antarctic ice during the last four climatic cycles

Li, V, Cr, Mn, Co, As, Rb, Sr, Ba, Bi and U were determined by inductively coupled plasma sector field mass spectrometry (ICP-SFMS) in various sections of the 3623 m Vostok deep Antarctic ice core dated from 4600 to 410,000 years BP, which corresponds to the last four climatic cycles back to isotopic stage 11.3. Concentrations of all elements were found to be highly variable with low values during interglacial periods and warm interstadials and much higher values during the coldest periods of the last four ice ages. Crustal enrichment factors suggest various sources for the different elements. Rock and soil dust is the dominant source of V, Mn, Rb, Ba and U whatever the period, and of Li, Cr, Co, Sr and As during cold periods. Sea salt aerosol, together with aeolian dust, also contributes significantly to Sr whereas volcanic emissions could provide a significant input for As and Bi especially during warm periods.

Glacial–interglacial changes in the occurrence of Pb, Cd, Cu and Zn in Vostok Antarctic ice from 240 000 to 410 000 years BP

Lead (Pb), cadmium (Cd), copper (Cu) and zinc (Zn) have been measured by electrothermal atomic absorption spectrometry in various sections of the 3623 m deep ice core drilled at Vostok, in central East Antarctica. The sections were dated from 240 to 410 kyear BP (Marine Isotopic Stages (MIS) 7.5 to 11.3), which corresponds to the 3rd and 4th glacial-interglacial cycles before present. Concentrations are found to have varied greatly during this 170 kyear time period, with high concentration values during the coldest climatic stages such as MIS 8.4 and 10.2 and much lower concentration values during warmer periods, such as the interglacials MIS 7.5, 9.3 and 11.3. Rock and soil dust were the dominant sources for Pb, whatever the period, and for Zn and Cu and possibly Cd during cold climatic stages. The contribution from volcanic emissions was important for Cd during all periods and might have been significant for Cu and Zn during warm periods.

Past natural changes in Cu, Zn and Cd in Vostok Antarctic ice dated back to the penultimate interglacial period

Improved ice core decontamination procedures have allowed us to obtain the first reliable data on Cu, Zn and Cd in ancient Antarctic ice drilled in a fluid filled hole at Vostok Station, dated back to the beginning of the next to last ice age ∼240,000 years ago. Cu, Zn and Cd concentrations and fallout fluxes display very large natural variations by up to a factor of 35, with high values obtained during the coldest climatic stages and much lower values during warm climatic stages. Crustal dust was an important source of Cu and Zn during the coldest climatic stages, and volcanic emissions were probably an important source of Cd both during warm and cold periods.

Climate‐related variations in lead concentrations and sources in Vostok Antarctic ice from 65,000 to 240,000 years BP

Pb has been measured in various sections of the 3,623‐m Vostok deep Antarctic ice core dated from 65,000 to 240,000 years BP, i.e. back to the beginning of the penultimate ice age and the preceding interglacial (isotopic stage 7.5). Pb concentrations were highly variable during this time interval, with low values down to ∼0.5 pg/g during warm climatic stages and much higher values up to ∼20 pg/g during cold climatic stages, especially isotopic stages 4.2 and 6.2 to 6.6. Rock and soil dust accounts for virtually 100% of Pb measured in the ice during cold climatic stages, while the contribution from volcanoes might be significant during warm stages.

A tentative reconstruction of the last interglacial and glacial inception in Greenland based on new gas measurements in the Greenland Ice Core Project (GRIP) ice core

The disturbed stratigraphy of the ice in the lowest 10% of the Greenland GRIP ice core prevents direct access to climatic information older than 110 kyr. This is especially regretful since this period covers the previous interglacial corresponding to marine isotopic stage 5e (MIS 5e, 130–120 kyr B.P.). Here we present a tentative reconstruction of the disturbed GRIP chronology based on the succession of globally well mixed gas parameters. The GRIP δ18Oice chronological sequence is obtained by comparing a new set of δ18O of atmospheric O2 and CH4 measurements from the bottom section of the GRIP core with their counterpart in the Vostok Antarctic profiles. This comparison clearly identifies ice from the penultimate glacial maximum (MIS 6, 190–130 kyr B.P.) in the GRIP core. Further it allows rough reconstruction of the last interglacial period and of the last glacial inception in Greenland which appears to lay its Antarctic counterpart. Our data suggest that while Antarctica is already entering into a glaciation, Greenland is still experiencing a warm maximum during MIS 5e.

Fossil leaves: Effective bioindicators of ancient CO2 levels?

[1] Past variations in the concentration of the greenhouse gas CO2 are thought to have played a major role in controlling Earth’s climate on preQuaternary and Quaternary timescales. To identify the contribution of CO2 to past climatic change requires accurate quantification of its content in the ancient atmosphere, and a number of proxies have been developed for this purpose (for a review see Royer et al. [2001a]). For the Late Quaternary, there is the unique opportunity to measure directly the composition of fossil air samples trapped in bubbles preserved in the polar ice sheets. Results from Antarctic ice cores reveal that the glacialinterglacial changes characterizing Quaternary climate were accompanied by variations in the atmospheric concentration of CO2 [Petit et al., 1999]. Although detection of phase relations between isotope-derived temperature estimates and trace gas concentration values is hampered by the difference in age of ice and air from the same ice sample, it is believed that CO2 lags glacial-interglacial temperature change and has acted as an amplifier of orbitally forced changes in temperature [Petit et al., 1999; Shackleton, 2000; Mudelsee, 2001].

Changes in the natural lead, cadmium, zinc, and copper concentrations in the Vostok Antarctic ice over, the last two glacial-interglacial cycles (240,000 years)

We present new ice core records showing the temporal variation in the natural Pb, Cd, Zn, and Cu concentrations in the Vostok Antarctic ice over the past 240,000 years. Our data show that concentrations of these heavy metals have varied remarkably over the last two glacial-interglacial cycles. The concentrations ranged from 0.9 to 21.3, 0.04 to 0.62, 3.12 to 126, and 2.27 to 37.4 pg/g for Pb, Cd, Zn, and Cu, respectively. These profiles provide a better understanding of climate-related variation in the occurrence of these heavy metals in ancient Antarctic ice. The concentrations were much higher during cold glacial periods than during interglacials, and poked at the coldest glacial stages. The contribution of rock and soil dust is estimated to be close to the measured concentrations of Pb, Zn, and Cu, but not Cd, in the ice during cold glacial periods.

CO 2- and temperature-controlled altitudinal shifts of C 4- and C 3-dominated grasslands allow reconstruction of palaeoatmospheric pCO 2

During the Pleistocene the vegetation changes in the high Colombian Andes included changes from C 3 to C 4 plants. This is inferred from δ 13C values of the C 31 n-alkane from the Funza-2 sedimentary record taken from the high plain of Bogotá at 2550 m elevation. The environmental factors thought to be responsible for these changes were investigated using a single point simulation of the BIOME3 vegetation model, including changes in precipitation, temperature and atmospheric CO 2 concentrations. The model shows that changes are for a major part caused by these latter two factors. The isotopic signature of the n-alkanes of several extant C 3 and C 4 grasses from the area were determined to calibrate the interpretation of the isotopic record. From the geochemical record, we estimated the altitudinal distribution of C 3 and C 4 plants, using present grass distribution patterns based on floristic data as a template. This information, in combination with palaeotemperature estimates, enabled the reconstruction of atmospheric CO 2 concentrations. The reconstructed CO 2 concentrations follow the trends of the Vostok Antarctic ice core through three glacial and two interglacial stages. The lowest calculated CO 2 concentration is ca. 210 ppmV for the glacial maxima and within the range of lowest values from Vostok, our highest value (310 ppmV) is for interglacial MIS 7. This represents a new method to reconstruct palaeoatmospheric pCO 2. It is less accurate than measurements from ice cores, but has potential to be used for sediments that are much older than the ice cores.

Spatial distribution of air molecules within individual clathrate hydrates in polar ice sheets

AbstractWe measured the N2/O2 ratios in clathrate hydrate crystals from Vostok Antarctic ice cores using Raman spectroscopy in order to investigate the spatial distribution of air molecules within a crystal. The results showed that the pattern of the spatial distribution of air molecules in clathrate hydrate depends on the crystal. Some clathrate hydrates have inhomogeneous distributions of the N2/O2 ratio within the crystals, while others are practically homogeneous. The spatial distribution of air molecules within an individual clathrate hydrate changes with time due to three processes: (1) the initial selective enclathration caused by the difference between the dissociation pressures of pure N2- and O2–clathrate hydrates, (2) the diffusive mass transfer of air molecules from surrounding air bubbles through the ice matrix, and (3) diffusion of air molecules in the clathrate hydrate crystal. The dissociation pressures and the diffusion rates of air molecules in ice and clathrate hydrate strongly depend on temperature. Therefore, it is concluded that the pattern of the spatial distribution of air molecules in clathrate hydrate is mainly determined by the depth at which they formed and the temperature in the ice sheet.

Extreme fractionation of gases caused by formation of clathrate hydrates in Vostok Antarctic Ice

Atmospheric gases are trapped in ice sheets. These gases stored in air‐bubbles at shallower depth are gradually transformed into clathrate hydrates below the depth where the hydrostatic pressure exceeds the dissociation pressure of the clathrate hydrates. We measured Raman spectra of air‐bubbles and clathrate hydrates in Vostok Antarctic ice cores in order to determine the fractionation effects on the concentrations of gases during their transition process. The results showed variations of the N2/O2 ratios with depth. The average N2/O2 ratio in the air‐bubbles increases from the atmospheric value at the beginning of the transition to 11.7 at the end. The average N2/O2 ratio for the clathrate hydrates is 2.0 at the beginning, and asymptotically approaches the atmospheric value. This fractionation is attributed to faster diffusion of O2 than N2 through the ice lattice.

Palaeoclimatic information from ice cores: the Vostok records

ABSTRACTIce deposits from Greenland and Antarctic ice sheets have stored over long periods of time information about the climate and environment of our planet. Attention will be focused on the 2083 m Vostok Antarctic ice core which represents a unusually long record (160 000 ka) due to the low accumulation rate (∼2 g cm−2a−1) and the rather uniform conditions of ice flow. This ice core provides a unique opportunity to obtain several palaeo-data such as temperature, accumulation (precipitation), aerosol loading, CO2 and trace gases over a full glacial-interglacial climatic cycle.The Vostok temperature, deduced from the interpretation of the deuterium content, and the CO2 records show a large 100 ka signal with a change of the order of 10°C and 70 ppmv respectively. The two records are closely correlated and both display shorter periodicities characteristic of the earth orbital parameters. CH4 concentrations also show variations from about 0·35 to about 0·65 ppmv linked with the glacial-interglacial warming. These features suggest a fundamental link between the climatic system and the carbon cycle and stress the role of radiatively active gases in climatic changes.The accumulation (precipitation) record appears to be governed by temperature with values during the coldest stages reduced by a factor of 2 with respect to the present rate. Ice deposited during these coldest stage is also characterised by high concentration of marine and terrestrial aerosols; these peaks probably reflect strengthened sources and meridional transport during full glacial conditions, linked to higher wind speed, more extensive arid areas on surrounding continent and a greater exposure of continental shelves.