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 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 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 Isotopic diffusion in polycrystalline ice

2003 ◽  
Vol 49 (166) ◽  
pp. 397-406 ◽  
Author(s):  
Alan W. Rempel ◽  
J. S. Wettlaufer
Keyword(s):  
Stable Isotopes ◽  
Stable Isotope ◽  
Vapor Phase ◽  
High Frequency ◽  
Ice Core ◽  
Accurate Analysis ◽  
Depositional Processes ◽  
Polycrystalline Ice ◽  
End Members

AbstractQuantitative ice-core paleoclimatology must account for post-depositional processes, such as vapor-phase diffusion in the firn. After pore close-off, diffusion continues to smooth the stable-isotope records δ18O and δD that are eventually recovered from the ice, leading to the loss of high-frequency information. Johnsen and others (1997) found much higher rates of diffusive smoothing in the Greenland Icecore Project (GRIP) Holocene ice than would be predicted by diffusion through solid ice alone, and Nye (1998) argued that transport through liquid veins might explain this apparent excess diffusion. However, the analysis of Johnsen and others (2000) indicates that the required vein dimensions may be unrealistically large. Here, we model the diffusion of stable isotopes in polycrystalline ice and show that the predictions of Nye (1998) and those of Johnsen and others (2000) actually represent two end-members in a range of potential behavior. Our model determines which of these asymptotic regimes more closely resembles the prevailing conditions and quantifies the role of pre-melted liquid in the smoothing of isotopic signals. The procedure thereby ties together the two approaches and provides a rostrum for accurate analysis of isotope records and paleotemperature reconstructions.

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 There and back again: A carver’s tale of losing and regaining sense of space due to a brain tumour

2021 ◽  
Vol 12 (1) ◽  
pp. 127-152
Author(s):  
Marte Sørebø Gulliksen
Keyword(s):  
Brain Tumour ◽  
Three Dimensional ◽  
Abstract Thinking ◽  
Spatial Skills ◽  
The Core ◽  
Core Ability ◽  
The Face ◽  
Core Identity ◽  
Future Education

Sense of space is a core cognitive ability necessary for imagining future three-dimensional forms, rotating them mentally, as well as for abstract thinking. It is a core ability in craft activities, enabling the maker to ideate and envision their ideas. This autoethnographic narrative inquiry presents my experience of woodworking whilst a brain tumour impeded my sense of space. The narrative describes my experience of losing and regaining this ability and the actions I took to continue carving anyway. The article’s evocative narrative exemplifies how the core identity of being a carver and the carving process itself function as coping mechanisms in the face of terminal cancer. The article’s main purpose is to generate knowledge on the role of spatial skills in carving and their elusive nature. Theoretically positioned in the field of embodied cognition, the article explains how our sense of space develops in interaction with materials and our surroundings. It also suggests how future education can be changed by purposefully incorporating targeted craft practices to better support the development of a sense of space.

scholarly journals The Morphology of Ice and Liquid Brine in the Environmental SEM: A Study of the Freezing Methods

2019 ◽  
Author(s):  
Ľubica Vetráková ◽  
Vilém Neděla ◽  
Jiří Runštuk ◽  
Dominik Heger
Keyword(s):  
Time Lapse ◽  
Solute Concentration ◽  
Environmental Scanning ◽  
Air Bubbles ◽  
Ice Recrystallization ◽  
Naturally Occurring ◽  
Polycrystalline Ice ◽  
Entrapped Air ◽  
The Impact

Abstract. The microstructure of polycrystalline ice with a threading solution of brine controls its numerous characteristics, including the ice mechanical properties, ice-atmosphere interactions, sea-ice albedo, and (photo)chemical behavior in/on the ice. Ice samples were previously prepared in laboratories to study various facets of ice-impurities interactions and (photo)reactions to model natural ice-impurities behavior. We examine the impact of the freezing conditions and solute (CsCl used as a proxy for naturally occurring salts) concentrations on the microscopic structure of ice samples via an environmental scanning electron microscope. The method allows us to observe in detail the ice surfaces, namely, the free ice, brine puddles, brine-containing grain boundary grooves, individual ice crystals, and imprints left by entrapped air bubbles at temperatures higher than −25 °C. The amount of brine on the external surface is found proportional to the solute concentration and is strongly dependent on the sample preparation method. Time-lapse images in the condition of slight sublimation reveal sub-surface association of air bubbles with brine. With rising temperature (up to −14 °C), the brine surface coverage increases to remain enhanced during the subsequent cooling and until the final crystallization below the eutectic temperature. The ice recrystallization dynamics identifies the role of surface spikes in retarding the ice boundaries propagation (Zeener pining). The findings thus quantify the amounts of brine exposed to incoming radiation, available for the gas exchange, and influencing other mechanical and optical properties of ice. The results have straightforward implications for artificially prepared and naturally occurring salty ices.

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 Where is the 1-million-year-old ice at Dome A?

2018 ◽  
Vol 12 (5) ◽  
pp. 1651-1663 ◽  
Author(s):  
Liyun Zhao ◽  
John C. Moore ◽  
Bo Sun ◽  
Xueyuan Tang ◽  
Xiaoran Guo
Keyword(s):  
Heat Flux ◽  
Depth Profile ◽  
Ice Core ◽  
Three Dimensional ◽  
Melting Rate ◽  
Dome A ◽  
Geothermal Heat ◽  
Kunlun Station ◽  
Ice Fabrics ◽  
Basal Melting

Abstract. Ice fabric influences the rheology of ice, and hence the age–depth profile at ice core drilling sites. To investigate the age–depth profile to be expected of the ongoing deep ice coring at Kunlun station, Dome A, we use the depth-varying anisotropic fabric suggested by the recent polarimetric measurements around Dome A along with prescribed fabrics ranging from isotropic through girdle to single maximum in a three-dimensional, thermo-mechanically coupled full-Stokes model of a 70 × 70 km2 domain around Kunlun station. This model allows for the simulation of the near basal ice temperature and age, and ice flow around the location of the Chinese deep ice coring site. Ice fabrics and geothermal heat flux strongly affect the vertical advection and basal temperature which consequently control the age profile. Constraining modeled age–depth profiles with dated radar isochrones to 2∕3 ice depth, the surface vertical velocity, and also the spatial variability of a radar isochrones dated to 153.3 ka BP, limits the age of the deep ice at Kunlun to between 649 and 831 ka, a much smaller range than previously inferred. The simple interpretation of the polarimetric radar fabric data that we use produces best fits with a geothermal heat flux of 55 mW m−2. A heat flux of 50 mW m−2 is too low to fit the deeper radar layers, and 60 mW m−2 leads to unrealistic surface velocities. The modeled basal temperature at Kunlun reaches the pressure melting point with a basal melting rate of 2.2–2.7 mm a−1. Using the spatial distribution of basal temperatures and the best fit fabric suggests that within 400 m of Kunlun station, 1-million-year-old ice may be found 200 m above the bed, and that there are large regions where even older ice is well above the bedrock within 5–6 km of the Kunlun station.

scholarly journals Ice-Coring At Mizuho Station, Antarctica, and Core Analyses: A Contribution from the Glaciological Research Program in East Dronning Maud Land, Antarctica

1988 ◽  
Vol 10 ◽  
pp. 213-213
Author(s):  
H. Narita ◽  
S. Mae ◽  
M. Nakawo ◽  
Y. Fujii ◽  
M. Yoshida ◽  
...  
Keyword(s):  
Research Program ◽  
Ice Core ◽  
Gas Content ◽  
List Type ◽  
Air Bubbles ◽  
The Core ◽  
Core Recovery ◽  
Burn Out ◽  
Dronning Maud Land ◽  
Antarctic Research

Between May 1983 and July 1984 glaciological parties of the 24th and 25th Japanese Antarctic Research Expeditions (JARE–24 and 25) carried out ice-core drilling using a thermal drill, down to 700.5 m depth at Mizuho Station (70°41'53"S, 44°19'54"E), as a part of the Glaciological Research Program in east Dronning Maud Land, Antarctica.The thermal drill, 3.9 m long and capable of taking a core 1.5 m long and 130 mm in diameter, is an improved version of a drill used by JARE–15 in 1975. The most important improvement was the monitoring system during drilling, for which a micro-computer was fitted in the drill. By using this system, such accidents as heater burn-out, tank overflow and failure of water suction would immediately be brought to our attention. The drilling speed was about 1.6 m/h, when the optimum output was 3.6 kW. The core recovery rate was above 99%.The core quality was good down to a depth of 80 m. Between 80 and 120 m, cracks were found at intervals of 0.15–0.5 m, and horizontal cracks were found continuously at intervals of 0.01 m or less.Immediately after the core was pulled, the stratigraphy was observed and bulk density was measured. A dust band, presumably volcanic particles, was seen at only 500.2 m depth during stratigraphic observation. The following analyses were carried out at Mizuho Station within a month of recovery: (1)Density determination by the hydrostatic method.(2)Measurement of total gas content.(3)Thin-section analyses, including observation of cracking around air bubbles and the crystalline texture, and ice-fabric studies.The 700.5 m core has been brought to Japan, and the following analyses are now under way: (1)Oxygen-isotope ratio.(2)Concentration of microparticles.(3)Electric conductivity.(4)Chemistry of soluble impurities.

scholarly journals Automatic reconstruction of polycrystalline ice microstructure from image analysis: application to the EPICA ice core at Dome Concordia, Antarctica

1999 ◽  
Vol 45 (151) ◽  
pp. 547-554 ◽  
Author(s):  
Michel Gay ◽  
Jerome Weiss
Keyword(s):  
Preliminary Analysis ◽  
Structural Parameters ◽  
Ice Core ◽  
Grain Morphology ◽  
Two Dimensional ◽  
Cross Sectional ◽  
Thin Sections ◽  
Polycrystalline Ice ◽  
Analysis Application ◽  
The Mean

AbstractA digital image-processing approach is proposed which allows the extraction of two-dimensional polycrystalline ice microstructure (grain boundaries) from thin sections observed between cross-polarisers. It is based on image segmentation of colour images. The method is applied to the preliminary analysis of the shallow ( Holocene) ice of the European Project for Ice Coring in Antarctica (EPICA) ice core at Dome Concordia. Structural parameters, such as the mean cross-sectional area, shape anisotropy and grain morphology, are obtained. The interest and limitations of this automatic procedure are discussed.

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