scholarly journals Air-hydrate crystals in deep ice-core samples from Vostok Station, Antarctica

1994 ◽  
Vol 40 (134) ◽  
pp. 79-86 ◽  
Author(s):  
T. Uchida ◽  
T. Hondoh ◽  
S. Mae ◽  
V.YA. Lipenkov ◽  
P. Duval
Keyword(s):  
Volume Concentration ◽  
Ice Core ◽  
Site Occupancy ◽  
Mean Value ◽  
Gas Content ◽  
Glacial Ice ◽  
Core Samples ◽  
Vostok Station ◽  
The Mean ◽  
Geometrical Equation

AbstractMicroscopic observation of air-hydrate crystals was carried out using 34 deep ice-core samples retrieved at Vostok Station, Antarctica. Samples were obtained from depths between 1050 and 2542 m, which correspond to Wisconsin/Sangamon/Illinoian ice. It was found that the volume and number of air-hydrate varied with the climatic changes. The volume concentration of air-hydrate in the interglacial ice was about 30% larger than that in the glacial ice. In the interglacial ice, the number concentration of air-hydrate was about a half and the mean volume of air-hydrate was nearly three times larger than that in the glacial-age ice. The air-hydrate crystals were found to grow in the ice sheet, about 6.7 × 10−12 cm3 year-1, in compensation for the disappearance of smaller ones. The volume concentration of air-hydrate was related to the total gas content by a geometrical equation with a proportional parameter α. The mean value of α below 1250 m, where no air bubbles were found, was about 0.79. This coincided with an experimentally determined value of the crystalline site occupancy of the air-hydrate in a 1500 m core obtained at Dye 3, Greenland (Hondoh and others, 1990). In the depth profile of calculated α for many samples, α in the interglacial ice was about 30% smaller than that in the glacial-age ice.

scholarly journals Air-hydrate crystals in deep ice-core samples from Vostok Station, Antarctica

1994 ◽  
Vol 40 (134) ◽  
pp. 79-86 ◽  
Author(s):  
T. Uchida ◽  
T. Hondoh ◽  
S. Mae ◽  
V.YA. Lipenkov ◽  
P. Duval
Keyword(s):  
Volume Concentration ◽  
Ice Core ◽  
Site Occupancy ◽  
Mean Value ◽  
Gas Content ◽  
Glacial Ice ◽  
Core Samples ◽  
Vostok Station ◽  
The Mean ◽  
Geometrical Equation

AbstractMicroscopic observation of air-hydrate crystals was carried out using 34 deep ice-core samples retrieved at Vostok Station, Antarctica. Samples were obtained from depths between 1050 and 2542 m, which correspond to Wisconsin/Sangamon/Illinoian ice. It was found that the volume and number of air-hydrate varied with the climatic changes. The volume concentration of air-hydrate in the interglacial ice was about 30% larger than that in the glacial ice. In the interglacial ice, the number concentration of air-hydrate was about a half and the mean volume of air-hydrate was nearly three times larger than that in the glacial-age ice. The air-hydrate crystals were found to grow in the ice sheet, about 6.7 × 10−12cm3year-1, in compensation for the disappearance of smaller ones. The volume concentration of air-hydrate was related to the total gas content by a geometrical equation with a proportional parameter α. The mean value of α below 1250 m, where no air bubbles were found, was about 0.79. This coincided with an experimentally determined value of the crystalline site occupancy of the air-hydrate in a 1500 m core obtained at Dye 3, Greenland (Hondoh and others, 1990). In the depth profile of calculated α for many samples, α in the interglacial ice was about 30% smaller than that in the glacial-age ice.

scholarly journals Crystalline Texture of the 2083 m Ice Core at Vostok Station, Antarctica

1989 ◽  
Vol 35 (121) ◽  
pp. 392-398 ◽  
Author(s):  
V.Ya. Lipenkov ◽  
N.I. Barkov ◽  
P. Duval ◽  
P. Pimienta
Keyword(s):  
Enhancement Factor ◽  
Crystal Size ◽  
Gradual Increase ◽  
Ice Core ◽  
Impurity Content ◽  
Mean Value ◽  
Axis Orientation ◽  
Vostok Station ◽  
The Mean ◽  
Convergent Flow

AbstractCrystalline texture andc-axis orientation of the 2083 m ice core at Vostok Station, covering more than 150kyear, reveal the existence of strong anisotropics. Changes in crystal size with depth are compatible with the growth of grains driven by the free energy of grain boundaries. A smaller growth rate appears to be associated with cold periods. A gradual increase in the horizontal elongation of grains was observed between 350 and 680 m. But, the mean value of the coefficient of the linear dimensional orientation of grains does not change below 700 m.Thec-axis orientation of ice grains tends to orientate perpendicular to the direction of the elongation of grains, forming a vertical girdle pattern. This characteristic fabric has been interpreted as resulting from the gradual rotation of grains by basal glide under uniaxial longitudinal tension. The rotation of grains was calculated with respect to the total strain, simulating the formation of the girdle fabric pattern. The fabric-enhancement factor was calculated at various depths. It appears that Vostok ice hardens gradually with depth when considering the transverse convergent flow. No significant variation of the enhancement factor was observed with changes in climate and impurity content.

scholarly journals Crystalline Texture of the 2083 m Ice Core at Vostok Station, Antarctica

1989 ◽  
Vol 35 (121) ◽  
pp. 392-398 ◽  
Author(s):  
V.Ya. Lipenkov ◽  
N.I. Barkov ◽  
P. Duval ◽  
P. Pimienta
Keyword(s):  
Enhancement Factor ◽  
Crystal Size ◽  
Gradual Increase ◽  
Ice Core ◽  
Impurity Content ◽  
Mean Value ◽  
Axis Orientation ◽  
Vostok Station ◽  
The Mean ◽  
Convergent Flow

AbstractCrystalline texture and c-axis orientation of the 2083 m ice core at Vostok Station, covering more than 150kyear, reveal the existence of strong anisotropics. Changes in crystal size with depth are compatible with the growth of grains driven by the free energy of grain boundaries. A smaller growth rate appears to be associated with cold periods. A gradual increase in the horizontal elongation of grains was observed between 350 and 680 m. But, the mean value of the coefficient of the linear dimensional orientation of grains does not change below 700 m.The c-axis orientation of ice grains tends to orientate perpendicular to the direction of the elongation of grains, forming a vertical girdle pattern. This characteristic fabric has been interpreted as resulting from the gradual rotation of grains by basal glide under uniaxial longitudinal tension. The rotation of grains was calculated with respect to the total strain, simulating the formation of the girdle fabric pattern. The fabric-enhancement factor was calculated at various depths. It appears that Vostok ice hardens gradually with depth when considering the transverse convergent flow. No significant variation of the enhancement factor was observed with changes in climate and impurity content.

scholarly journals Spatial and temporal variability in isotope composition of recent snow in the vicinity of Vostok station, Antarctica: implications for ice-core record interpretation

2002 ◽  
Vol 35 ◽  
pp. 181-186 ◽  
Author(s):  
Alexey A. Ekaykin ◽  
Vladimir Ya. Lipenkov ◽  
Narcisse I. Barkov ◽  
Jean Robert Petit ◽  
Valerie Masson-Delmotte
Keyword(s):  
Isotope Composition ◽  
Ice Core ◽  
Snow Accumulation ◽  
Spatial And Temporal Variability ◽  
Weak Correlation ◽  
Ice Core Record ◽  
Vostok Station ◽  
The Mean ◽  
Mean Annual Air Temperature ◽  
Snow Samples

AbstractContinuous, detailed isotope (δD and δ18O) profiles were obtained from eight snow pits dug in the vicinity of Vostok station, Antarctica, during the period 1984– 2000. In addition, snow samples taken along the 1km long accumulation-stake profile were measured to determine spatial variability in isotope composition of recent snow. the stacked δD time series spanning the last 55 years shows only weak correlation with the mean annual air temperature recorded at Vostok station. Significant oscillations of both snow accumulation and snow isotope composition with the periods 2.5, 5, 20 and, possibly, ~102 years observed at single points are interpreted in terms of drift of snow-accumulation waves of various scales on the surface of the ice sheet.

scholarly journals Life in Solid Ice on Earth and Other Planetary Bodies

2004 ◽  
Vol 213 ◽  
pp. 363-366 ◽  
Author(s):  
P. Buford Price
Keyword(s):  
Fluorescence Microscopy ◽  
Direct Observation ◽  
Ice Core ◽  
Analytical Techniques ◽  
Bacterial Spores ◽  
Glacial Ice ◽  
Core Samples ◽  
Planetary Bodies ◽  
Micro Organisms

Theory and direct observation indicate that micro-organisms exist in liquid veins in ice and permafrost, provided the temperature is above the eutectic for H2O and soluble impurities present. Microbes can exist and metabolize in glacial ice and permafrost on Earth, Mars, and Europa. One can search directly (with fluorescence microscopy at liquid veins in Vostok ice core samples) or with a biologging instrument (for microbial fluorescence in a borehole in terrestrial or martian permafrost or ice). The viability lifetime against DNA destruction of bacterial spores can be measured with analytical techniques that identify calcium dipicolinate, which is unique to spores.

scholarly journals Ice Structure and Crystal Fabrics of the 2200 M Ice Core at Vostok Station, Antarctica

1988 ◽  
Vol 10 ◽  
pp. 223-223
Author(s):  
N.I. Barkov ◽  
V.Ya. Lipenkov ◽  
V.N. Petrov
Keyword(s):  
Ice Core ◽  
Three Dimensional ◽  
Air Bubbles ◽  
The Core ◽  
Polycrystalline Ice ◽  
Vostok Station ◽  
Dimensional Parameters ◽  
The Mean ◽  
Ice Fabrics

Both the ice structure and the ice fabric along the 2200 m ice core at Vostok Station were investigated during the 25th, 29th and 30th Soviet Antarctic Expeditions.Several kinds of three-dimensional parameters of polycrystalline ice were measured, e.g. the mean diameter and size distribution of ice crystals and air bubbles, and specific volumeThe variation in most of these parameters along the core reflects not only the process of metamorphism in ice but also changes in the environmental conditions at the surface. The causes of these variations are discussed, in order to estimate the possibility of a paleoclimatic interpretation.The evolution of c-axis fabrics with depth is discussed in relation to the ice-deformation conditions.A comparison of ice fabrics at Vostok, Byrd Station and Camp Century shows that similar mechanisms cause the reorientation of crystals. The role of temperature in fabric development is discussed.

scholarly journals Gas Diffusion and Fractionation in Clathrated Ice-Core Samples (Abstract)

1988 ◽  
Vol 10 ◽  
pp. 214-214
Author(s):  
J. Ocampo
Keyword(s):  
Ice Core ◽  
Diffusion Constant ◽  
Greenland Ice Sheet ◽  
Ice Cores ◽  
Gas Diffusion ◽  
Gas Content ◽  
Diffusion Control ◽  
Mechanical Relaxation ◽  
Recrystallization Process ◽  
Core Samples

The evolution of gas content from clathrated ice is very sensitive to pressure and to storage temperature. As such substances are likely to be found in deep Antarctic ice and the Greenland ice sheet (Miller 1969, Shoji and Langway 1982), the influence of clathrate formation and incomplete back-diffusion on the measured air composition was investigated.We have undertaken laboratory studies on the kinetics of formation and decomposition of clathrate hydrates of air and carbon dioxide. The kinetics were found to be controlled mainly by the self-diffusion of water molecules. The clathrate structure being of type II (Davidson and others 1984), the diffusion of guest molecules and the role of auxiliary gases was studied.A bubble-relaxation model is presented for air-hydrate inclusions in fresh ice cores. It takes into account the diffusion constant for desorption of clathrates and the mechanical relaxation of the bulk ice. The increasing pressure and the initially low bubble surface are factors which limit the rate of decomposition. The rate of decomposition was compared with the natural bubble relaxation measured in deep ice cores (Gow and Williamson 1975).Fractionation was also observed through the formation and decomposition of mixed hydrates. The diffusion control of the recrystallization process affects this fractionation.On the basis of this study we make some recommendations for the analysis of deep ice-core samples.

scholarly journals Gas Diffusion and Fractionation in Clathrated Ice-Core Samples (Abstract)

1988 ◽  
Vol 10 ◽  
pp. 214
Author(s):  
J. Ocampo
Keyword(s):  
Ice Core ◽  
Diffusion Constant ◽  
Greenland Ice Sheet ◽  
Ice Cores ◽  
Gas Diffusion ◽  
Gas Content ◽  
Diffusion Control ◽  
Mechanical Relaxation ◽  
Recrystallization Process ◽  
Core Samples

The evolution of gas content from clathrated ice is very sensitive to pressure and to storage temperature. As such substances are likely to be found in deep Antarctic ice and the Greenland ice sheet (Miller 1969, Shoji and Langway 1982), the influence of clathrate formation and incomplete back-diffusion on the measured air composition was investigated. We have undertaken laboratory studies on the kinetics of formation and decomposition of clathrate hydrates of air and carbon dioxide. The kinetics were found to be controlled mainly by the self-diffusion of water molecules. The clathrate structure being of type II (Davidson and others 1984), the diffusion of guest molecules and the role of auxiliary gases was studied. A bubble-relaxation model is presented for air-hydrate inclusions in fresh ice cores. It takes into account the diffusion constant for desorption of clathrates and the mechanical relaxation of the bulk ice. The increasing pressure and the initially low bubble surface are factors which limit the rate of decomposition. The rate of decomposition was compared with the natural bubble relaxation measured in deep ice cores (Gow and Williamson 1975). Fractionation was also observed through the formation and decomposition of mixed hydrates. The diffusion control of the recrystallization process affects this fractionation. On the basis of this study we make some recommendations for the analysis of deep ice-core samples.

scholarly journals Ice Structure and Crystal Fabrics of the 2200 M Ice Core at Vostok Station, Antarctica

1988 ◽  
Vol 10 ◽  
pp. 223 ◽  
Author(s):  
N.I. Barkov ◽  
V.Ya. Lipenkov ◽  
V.N. Petrov
Keyword(s):  
Ice Core ◽  
Three Dimensional ◽  
Air Bubbles ◽  
The Core ◽  
Polycrystalline Ice ◽  
Vostok Station ◽  
Dimensional Parameters ◽  
The Mean ◽  
Ice Fabrics

Both the ice structure and the ice fabric along the 2200 m ice core at Vostok Station were investigated during the 25th, 29th and 30th Soviet Antarctic Expeditions. Several kinds of three-dimensional parameters of polycrystalline ice were measured, e.g. the mean diameter and size distribution of ice crystals and air bubbles, and specific volume The variation in most of these parameters along the core reflects not only the process of metamorphism in ice but also changes in the environmental conditions at the surface. The causes of these variations are discussed, in order to estimate the possibility of a paleoclimatic interpretation. The evolution of c-axis fabrics with depth is discussed in relation to the ice-deformation conditions. A comparison of ice fabrics at Vostok, Byrd Station and Camp Century shows that similar mechanisms cause the reorientation of crystals. The role of temperature in fabric development is discussed.

scholarly journals Hot Groundwater Systems in Iceland Traced by Deuterium

1977 ◽  
Vol 8 (2) ◽  
pp. 93-102 ◽  
Author(s):  
Bragi Arnason
Keyword(s):  
Thermal Water ◽  
Hot Springs ◽  
Ice Core ◽  
Mean Value ◽  
Hydrothermal Systems ◽  
Deuterium Content ◽  
Groundwater Systems ◽  
The Mean ◽  
Underground Flow ◽  
Drill Holes

This paper summarizes the result obtained for hydrothermal systems in Iceland, by using deuterium and oxygen-18 as natural tracers. The deuterium content of a single sample of a local cold spring or river, except those rivers fed by considerable amount of glacier melt water, can be used to estimate the mean deuterium concentration of precipitation in the corresponding locality. Furthermore the deuterium content of the last winter layer, collected on Icelandic glaciers in spring before the melting season, is practically identical to the mean value of the corresponding annual precipitation. These facts have been used to draw a detailed map showing the amount of deuterium in precipitation over the whole country. Deep ice core studies show that the deuterium content of precipitation in each place has remained more or less unchanged during the last 8000 years. Measurements of both deuterium and oxygen-18 in the groundwater have confirmed that all groundwater in Iceland is originally meteoric and that the deuterium content of the thermal water does not change on its way through the bed-rock. The deuterium content of water discharging from hot springs or drill holes is often very different from the deuterium content of local precipitation. On the other hand, by comparing results obtained with the deuterium map, it is often possible to find where this water has fallen as rain and to trace its underground flow path. Deuterium measurements have been made on water from nearly all geothermal areas in the country. The results are drawn up together in one picture, which shows the origin and flow paths of most of the hot groundwater systems in Iceland. Finally it has been possible to give som idea of the age of the thermal groundwater, i.e. the time past since precipitation. The thermal water is obviously of varying ages. The »youngest« water seems only to be a few decades old, whereas the »oldest« appears to be from the last glaciations.

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