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  • 1
    Series available for loan
    Series available for loan
    Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory
    Associated volumes
    Call number: ZSP-202-339
    In: Research report
    Description / Table of Contents: CONTENTS: Abstract. - Preface. - Introduction. - Analytical procedures. - Thick section analysis. - Measurements of inclusion pressure. - Gas volume measurements. - Density and porosity measurements. - Results and discussion. - Sizes, shapes and distributions of bubbles. - Sizes, shapes and distributions of cavities. - Inclusion abundances. - Gas pressures in bubbles and cavities. - Total gas content. - Case for lattice diffusion. - Literature cited.
    Description / Table of Contents: Cores obtained to the bottom of the Antarctic Ice Sheet at Byrd Station were used to analyze the physical properties of air bubbles trapped in the ice. These bubbles originate as pockets of air in the upper layers of snow and approximately 10 ml of air/100 cm^3 of ice; i.e., 10% by volume is retained permanently when the snow transforms into ice. Parameters measured were the sizes, shapes, abundances, spatial distributions, gas volumes and pressures of bubbles, and their variations with depth in the ice sheet. Bubbles occur abundantly in the top 800 m of ice but then gradually disappear until they can no longer be detected optically below 1100 m. This disappearance is not accompanied by any significant loss of air from the ice and all available evidence indicates that the air actually diffuses into the ice in response to increasing overburden pressure. The possibility exists that the dissolved gases are retained in the form of a gas hydrate or clathrate which, because of release of confining pressures, begins to decompose soon after ice cores are pulled to the surface. This decomposition is accompanied by the growth of gas-filled bubble-like cavities, and as much as 40% of the dissolved air has exsolved already from some cores in the space of less than three years. Bubble pressure measurements show that 1) bubbles with pressures exceeding about 16 bars begin to relax back to this value soon after in situ pressures are relieved by drilling, 2) further slow decompression occurs with time, and 3) the rate of decompression is controlled to some extent by the intrinsic structural properties of the ice and its thermal and deformational history. Only small variations were observed in the entrapped air content of the ice cores; they probably reflect variations in the temperature and/or pressure of the air at the time of its entrapment, but the data are not sufficient to draw any firm conclusions regarding past variations in ice sheet thickness. Only ice from the bottom 4.83 m was found to lack any detectable trace of air. Since this absence of air coincided precisely with the first appearance of stratified moraine in the cores, it is concluded that this ice originated from the refreezing of air-depleted water produced under pressure melting conditions at the bottom of the ice sheet.
    Type of Medium: Series available for loan
    Pages: v, 18 Seiten , Illlustrationen
    Series Statement: Research report / Cold Regions Research and Engineering Laboratory, CRREL, US Army Material Command 339
    Language: English
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  • 2
    Series available for loan
    Series available for loan
    Hanover, NH : Corps of Engineers, U.S. Army, Cold Regions Research and Engineering Laboratory
    Associated volumes
    Call number: ZSP-202-282
    In: Research report
    Description / Table of Contents: CONTENTS: Introduction. - Analytical procedures. - Measurement of crystal size. - Measurement of crystalorientation. - Results and discussion. - Byrd Station crystal structure and fabrics. - Little America V crystal structure and fabrics. - Conclusions. - Literature cited. - Abstract.
    Description / Table of Contents: Radical differences in the crystal structure and fabrics of glacier ice cores at Byrd Station and Little America V, Antarctica, are attributed to gross differences in the thermal and deformational histories of the ice at these two locations. At Byrd Station the mean size of crystals increased more than sixfold between 65 m and the bottom of the drill hole at 309 m. Crystal size was also found to increase linearly with the age of the ice, thus simulating isothermal grain growth in metals. However, this growth was not accompanied by any dimensional orientation of crystals or entrapped bubbles, or by any significant increase in the degree of preferred orientation of crystallographic c-axes. These observations imply that negligible shearing is occurring in the top 300 m of the thick grounded ice sheet at Byrd Station. By contrast very considerable deformation is indicated for the floating 258-m-thick Ross Ice Shelf at Little America. This deformation is characterized by the widespread occurrence of "strained" crystals below 65 m, the existence of elongated oriented bubbles between 95 m and 130 m and the attainment of pronounced crystal orientation (multiple-maxima fabrics) by 100-m depth. Exaggerated growth of crystals below 150 m is attributed to increasing temperatures in the ice shelf. The crystal structure of these cores clearly demonstrates that glacial ice only is present in the Ross Ice Shelf at Little America V.
    Type of Medium: Series available for loan
    Pages: iii, 21 S. : Ill.
    Series Statement: Research report / Cold Regions Research and Engineering Laboratory, CRREL, US Army Material Command 282
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  • 3
    Call number: ZSP-201-83/6
    In: CRREL Report, 83-6
    Description / Table of Contents: During the austral summers of 1976-77 and 1978-79, several ice cores were taken from the McMurdo Ice Shelf brine zone to investigate its thermal, physical and chemical properties. This brine zone consists of a series of super-imposed brine layers (waves) that originate at the seaward edge of the ice shelf and migrate at various rates, depending upon their age and position in the ice shelf. The brine in these layers becomes increasingly concentrated as the waves migrate inland through the permeable ice shelf firn. Chemical analyses of brine samples from the youngest (uppermost) brine wave show that it contains sea salts in normal seawater proportions. Further inland, deeper and older brine layers, though highly saline (S 〉 200 ‰), are severely depleted in SO2-4 with the SO2-4/Na+ ratio being an order of magnitude less than that of normal seawater. Analyses of Na+, K+, Ca2+, Mg2+, SO2-4 and CI-, together with solubility and temperature considerations, show that the sulfate depletion is due to selective precipitation of mirabilite, Na2SO4*10H2O. The location of the inland boundary of brine penetration is closely related to the depth at which the brine en-counters the firn/ice transition. However, a small but measurable migration of brine is still occurring in otherwise impermeable ice; this is attributed to eutectic dissolution of the ice by concentrated brine as it moves into deeper and warmer parts of the McMurdo Ice Shelf.
    Type of Medium: Series available for loan
    Pages: iii, 16 Seiten , Illustrationen
    Series Statement: CRREL Report 83-6
    Language: English
    Location: AWI Archive
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  • 4
    Series available for loan
    Series available for loan
    Hanover, New Hampshire : U.S. Army Cold Regions Research and Engineering Laboratory
    Associated volumes
    Call number: ZSP-201-83/4
    In: CRREL Report, 83-4
    Description / Table of Contents: Measurements and analysis of seasonal ice growth and decay on Post Pond, New Hampshire, for the period 1973-1982 are presented. Observations included ice thickness measurements, examination of the various ice types contributing to the ice cover, and measurements of meteorological parameters for correlation with and modeling of the ice growth process. The overall nature of ice growth and decay (ice loss) on the Post Pond has been ascertained, the seasonal variability in the timing of freeze-up and ice-out and the duration of the ice cover have been determined, and the relationship of ice growth to freezing-degree-day (deg C) records evaluated on the basis of a Stefan conduction equation modified to deal with ice sheets covered with or free of snow. Ice growth occurs predominantly by the direct freezing of lake water, but snow ice may compose as much as 50% of the ice cover in winters with higher than average snowfall. Freeze-up leading to the establishment of a stable ice cover occurs during the 4-week period from the end of November to the end of December. Maximum seasonal ice thicknesses were from 45 to 67 cm and are generally attained during the first two weeks of March; ice-out, marking the final disappearance of ice from Post Pond, usually occurs by the third week of April. The overall rate of the ice loss is three to four times that of ice growth, and is dominated initially by melting from the top. As much as 50% of the ice may be lost in this way before the onset of any bottom melting. Final dissipation of the ice cover is usually expedited by candling resulting from preferential melting and disintegration of the ice at crystal boundaries.
    Type of Medium: Series available for loan
    Pages: iv, 30 Seiten , Illustrationen
    Series Statement: CRREL Report 83-4
    Language: English
    Note: CONTENTS Abstract Preface Introduction Location of study Study methods Ice thickness Ice-cover composition Surface air temperatures Freeze-up and ice-out characteristics Results and discussion Ice-growth record Freezing-degree-day records Ice-growth predictions Summary and conclusions Literature cited Appendix A: Ice-growth records Appendix B: Measured and computed ice-growth curves
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  • 5
    Call number: ZSP-201-77/29
    In: CRREL Report, 77-29
    Description / Table of Contents: Results of measurements of salinity, grain size, substructure dimensions and crystal fabrics of the undeformed 2.15-m-thick annual sea ice sheet near Narwhal Island, Alaska, are presented. A notable observation was the formation of a dominant c-axis horizontal structure in all ice below 14 cm, including transformation to a pronounced east-west alignment of the c-axes by a depth of 66 cm. This study confirms earlier reports of the occurrence of very strong horizontal c-axis alignments in arctic fast ice.
    Type of Medium: Series available for loan
    Pages: iii, 8 Seiten , Illustrationen
    Series Statement: CRREL Report 77-29
    Language: English
    Note: CONTENTS Abstract Preface Introduction Sampling and analytical procedures Results Discussion Conclusions Literature cited
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  • 6
    Series available for loan
    Series available for loan
    Hanover, NH : Corps of Engineers, U.S. Army Cold Regions Research and Engineering Laboratory
    Associated volumes
    Call number: ZSP-202-318
    In: Research report
    Description / Table of Contents: CONTENTS: Introduction. - Drilling and field observations. - Interpretation. - Implications for the feasibility study. - Conclusions. - Literature cited. - Abstract.
    Description / Table of Contents: Two holes were drilled through the Greenland ice sheet during 1973 and temperature measurements were made in one hole drilled during 1972. These measurements show that the area of liquid water beneath the ice cap extends to ice depths as shallow as 100 m. The consequences of removing the frozen margin of glacial ice could be serious and more temperature measurements are needed to exactly locate the subglacial water. Petrographic studies of a few ice cores revealed a strongly oriented crystal fabric and an appreciable surface accumulation of superimposed ice.
    Type of Medium: Series available for loan
    Pages: iii, 15 Seiten , Illustrationen, Karten
    Series Statement: Research report / Cold Regions Research and Engineering Laboratory, CRREL, US Army Material Command 318
    Language: English
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  • 7
    Series available for loan
    Series available for loan
    Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory
    Associated volumes
    Call number: ZSP-202-336
    In: Research report
    Description / Table of Contents: CONTENTS: Abstract. - Preface. - Nomenclature. - Introduction. - Description of study. - Sample preparation. - Test equipment and procedure. - Discussion of results. - Stress-density relationship. - Effect of rate of deformation. - Effect of temperature. - Effect of initial snow density. - Stress-deformation relationship. - Summary and conclusions. - Microstructural analysis. - Introduction. - Analytical methods. - Results and discussion. - Conclusion. - Literature cited. - Anpendix: Test data.
    Description / Table of Contents: The effects of snow temperature, rate of deformation, and initial density on the stress vs density and stress vs deformation relationships were investigated in the pressure range of 0.1 to 75 bars. The rate of deformation in the range of 0.027 to 27 cm sec^-1 does not have a significant effect. A decrease in temperature in the range of 0° to -40°C increases the resistance to stress and deformation, the temperature effect increasing with applied pressure and initial density. The effect of initial density is significant. For any stress, an increase in the initial density results in an increase in the resulting density, particularly at low stress levels and at temperatures near 0°C. The texture of artificially compacted snow is significantly different from that of naturally compacted snow of the same density because of the very short recrystallization time period.
    Type of Medium: Series available for loan
    Pages: iv, 57 Seiten , Illustrations
    Series Statement: Research report / Cold Regions Research and Engineering Laboratory, CRREL, US Army Material Command 336
    Language: English
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  • 8
    Series available for loan
    Series available for loan
    Hanover, NH : Corps of Engineers, U.S. Army Cold Regions Research and Engineering Laboratory
    Associated volumes
    Call number: ZSP-202-300
    In: Research report
    Description / Table of Contents: CONTENTS: Introduction. - Sampling. - Byrd Station. - Plateau Station. - Camp Century. - lnge Lehmann. - Grain-crystal relations. - Analytical techniques. - Thin sections. - Crystal size measurements. - Results and discussion. - Literature cited. - Appendix A: Crystal size as a function of depth and age in the Antarctic and Greenland ice sheets. - Abstract.
    Description / Table of Contents: The growth of ice crystals as a function of depth and time in polar firn and glacier ice has been investigated at a number of locations in Antarctica and Greenland. Thin sections of snow and ice were used to measure crystal size variations which showed, in all cases, that crystal size increases essentially linearly with the age of samples. Crystal growth rates are strongly temperature dependent. At Camp Century, Greenland, where the firn temperature is -24°C, crystals grow approximately 23 times faster than at Plateau Station, Antarctica, where the in situ temperature is -57°C. Extrapolation of the existing data indicates that crystal growth rates in polar firn and ice could be expected to vary by about two orders of magnitude over the temperature range -60°C to -15°C. Examination of the changes in the pore-crystal structure relationships to a dpeth of 100 m at Camp Century shows that these changes closely resemble those occuring in the full-scale isothermal sintering of powder compacts.
    Type of Medium: Series available for loan
    Pages: iii, 19 Seiten , Illustrationen
    Series Statement: Research report / Cold Regions Research and Engineering Laboratory, CRREL, US Army Material Command 300
    Language: English
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  • 9
    Series available for loan
    Series available for loan
    Hanover, NH : U.S. Army Materiel Command, Terrestrial Sciences Center, Cold Regions Research & Engineering Laboratory
    Associated volumes
    Call number: ZSP-202-249
    In: Research report
    Description / Table of Contents: CONTENTS: Preface. - Abstract. - Introduction. - Analytical procedures. - Results and discussion. - Bubbles in ice. - Conclusions. - Literature cited.
    Description / Table of Contents: Application of the gas law to fourth-place density measurements of ice samples from two deep drill holes at Byrd Station and Little America V, Antarctica, shows that virtually all density increase beyond the pore close-off density (0.830 g/cm^3) can be attributed to compression of the entrapped bubbles of air. Data from Byrd Station also indicate that the lag between overburden pressure and bubble pressure, initially 4-5 kg/cm^2 at pore close-off, diminishes to less than 1.0 kg/cm^2 at about 200-m depth. By substituting the overburden pressure for the bubble pressure in the pressure-density relationship based on the gas law, ice densities below 200 m can be calculated more accurately than they can be measured per se on cores because of the relaxation that occurs in samples recovered from high confining pressures. This relaxation, resulting in a progressive increase in the bulk volume of the ice with time, is generally attributed to decompression of the entrapped air bubbles following removal of the ice from high confining pressures. However, calculations of the stress in ice due to bubble pressure, together with measurements of bubble sizes in cores from various depths at Byrd Station, both tend to indicate that there has'been negligible decompression of the inclosed bubbles. It is suggested that most of this relaxation may be due to the formation of microcracks in the ice. Anomalous bubble pressure-density relations at Little America V tend to confirm abundant stratigraphic evidence of the existence of considerable deformation in the upper part of the Ross Ice Shelf. Studies of crystal-bubble relations at Byrd Station revealed that the concentration of bubbles in ice remains remarkably constant at approximately 220 bubbles per cm^3. Bubbles and crystals were found to be present in approximately equal numbers at pore close-off at 64-m depth, at which level the average bubble diameter was 0.95 mm, decreasing to 0.49 mm at 116 m and to 0.33 mm at 279 m. Despite a tenfold increase in the size of crystals between 64 and 279 m, the bubbles showed no tendency to migrate to grain boundaries during recrystallization of the ice. The observation that most of the bubbles had assumed substantially spherical shapes by 120-m depth points to essentially hydrostatic conditions in the upper layers of the ice sheet at Byrd Station.
    Type of Medium: Series available for loan
    Pages: iv, 16 S. : Ill.
    Series Statement: Research report / Cold Regions Research and Engineering Laboratory, CRREL, US Army Material Command 249
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  • 10
    Series available for loan
    Series available for loan
    Hanover, NH : U.S. Army Materiel Command, Terrestrial Sciences Center, Cold Regions Research & Engineering Laboratory
    Associated volumes
    Call number: ZSP-202-248
    In: Research report
    Description / Table of Contents: CONTENTS: Preface. - Abstract. - Introduction. - Analytical procedures. - Results and discussion. - Literature cited.
    Description / Table of Contents: Conductivity measurements have been made on snow and ice samples from pits and deep drillholes at a number of localities in Antarctica and Greenland. Conductivities of the order 1-2 [My]mho/cm only were recorded at the inland sites. Data from deep cores representing more than 1900 years of continuous snow accumulation at Byrd Station, Antarctica, and more than 400 years deposition at Inge Lehmann, Greenland, showed no significant variations of conductivity with time. Measurements of freshly precipitated snow from a single coastal location in McMurdo Sound, Antarctica, also yielded relatively low conductivities of the order 3-4 [My]mho/cm. The substantial increase observed in the conductivity of core samples from near the surface of the Ross Ice Shelf at Little America V can be attributed most probably to windborne salts of marine origin that had accumulated on the surface after the snow was deposited. A peak conductivity of 49 [My]mho/cm was recorded in snow estimated to have been deposited within 20 km of the seaward edge of the Ross Ice Shelf and the maritime effect could still be detected in samples deposited more than 40 km from the ice front. For samples deposited at distances of greater than 200 km from the edge of the Ross Ice Shelf conductivities never exceeded 2 [My]mho/cm. The very low conductivities observed in ice cores from near the bottom of the Ross Ice Shelf confirm earlier conclusions based on detailed petrographic studies oi the cores that the 258-m-thick ice shelf at Little America V is composed entirely of glacial ice.
    Type of Medium: Series available for loan
    Pages: iv, 8 S. : Ill.
    Series Statement: Research report / Cold Regions Research and Engineering Laboratory, CRREL, US Army Material Command 248
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