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  • 1
    Book
    Book
    Bering Strait sea ice and the Fairway Rock icefoot (1982)
    Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory
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    UID:
    kobvindex_GFZ20190417101919
    Format: 44 Seiten , Illustrationen
    Series Statement: CRREL Report 82-31
    Content: Information on sea ice conditions in the Bering Strait and the icefoot formation around Fairway Rock, located in the strait, is presented. Cross-sectional profiles of Fairway Rock and the relief of the icefoot are given along with theoretical analyses of the possible forces active during icefoot formation. It is shown that the ice cover most likely fails in flexure as opposed to crushing or buckling, as the former requires less force. Field observations reveal that the Fairway Rock icefoot is massive, with ridges up to 15 m high, a seaward face only 20 degrees from vertical, and interior ridge slopes averaging 33 degrees. The icefoot is believed to be grounded and its width ranges from less than 10 to over 100 m.
    Note: CONTENTS Abstract Preface Introduction Bering Strait Field reconnaissance Estimation of ice forces on Fairway Rock 1. Creep deformation 2. Crushing failure 3. Flexural failure 4. Forces required to form floating or grounded pressure ridges along therock or to pile ice on the beaches 5. Buckling failure Driving forces Angle of internal friction of sea ice Summary Literature cited Appendix A: April 1982 field observations at Fairway Rock
    In: CRREL Report, 82-31
    Language: English
    Keywords: Forschungsbericht
    URL: https://apps.dtic.mil/docs/citations/ADA122477
    URL: https://hdl.handle.net/11681/9317
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  • 2
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    Book
    Evaluation of a portable electromagnetic induction instrument for measuring sea ice thickness (1991)
    Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory
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    UID:
    kobvindex_GFZ20190731153737
    Format: iv, 23 Seiten , Illustrationen
    Series Statement: CRREL Report 91-12
    Content: Field trials using a man-portable Geonics, Ltd., EM31 electromagnetic induction sounding instrument, with a plug-in data processing module, for the remote measurement of sea ice thickness, are discussed. The processing module was made by Flow Research Inc., to directly measure sea ice thickness and show the result in a numerical display. The EM31-processing module system was capable of estimating ice thickness within 10% of the true value for ice from about 0.7 to 3.5 m thick, the oldest undeformed ice in the study area. However, since seawater under the Arctic pack ice has a relatively uniform conductivity (2.5 + or - 0.05 S/m), a simplified method, which can be used for estimating sea ice thickness using jet an EM31 instrument, is discussed. It uses only the EM31's conductivity measurement, is easy to put into use and does not rely on theoretically derived look-up tables or phasor diagrams, which may not be accurate for the conditions of the area.
    Note: CONTENTS Preface Introduction EM 31 Sounding concepts Previous EMI studies Beaufort Sea field trials EM 31 Conductivity reading versus sea ice thickness General comments Literature cited Abstract
    In: CRREL Report, 91-12
    Language: English
    Keywords: Forschungsbericht
    URL: https://apps.dtic.mil/dtic/tr/fulltext/u2/a240974.pdf
    URL: https://hdl.handle.net/11681/9126
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  • 3
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    Book
    The effects of conductivity on high-resolution impulse radar sounding, Ross Ice Shelf, Antarctica (1982)
    Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory
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    UID:
    kobvindex_GFZ20190423134848
    Format: iv, 19 Seiten , Illustrationen
    Series Statement: CRREL Report 82-42
    Content: A high-resolution impulse radar profiling system was evaluated for 1) detecting the existence of sea ice which coring has revealed to exist on the bottom of the Ross Ice Shelf at Site J-9, 2) detecting the preferred horizontal c-axis azi-muthal direction of the sea ice crystals, using the voltage amplitude of the radar reflection from the sea ice bottom, and 3) determining the direction of the currents under an Antarctic ice shelf. A field program was conducted consisting of a surface radar survey on the Ross Ice Shelf at Site J-9 and surface and airborne radar profiling on the McMurdo Ice Shelf. The CRREL impulse radar system, operating at a center frequency of either 80 MHz or 20 MHz, was unable to detect the shelf bottom at Site J-9, which drilling revealed to be 416 m below the snow surface. The radar system was used to profile the McMurdo Ice Shelf both from the snow surface and from the air; a shelf thickness of about 275 m was easily detected. Theoretical considerations indicate that the bulk conductivity of the ice shelf at Site J1-9 was higher than originally anticipated, and this limited the radar sounding depth to about 405 m when operating at a frequency of 20 MHz.
    Note: CONTENTS Abstract Introduction Profiling system Theoretical considerations Field program Discussion Literature cited
    In: CRREL Report, 82-42
    Language: English
    Keywords: Forschungsbericht
    URL: https://apps.dtic.mil/dtic/tr/fulltext/u2/a124456.pdf
    URL: https://hdl.handle.net/11681/9323
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  • 4
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    Book
    Variation of some mechanical properties of polar snow, Camp Century, Greenland (1969)
    Hanover, NH : U.S. Army Corps of Engineers, Cold Regions Research and Engineering Laboratory
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    UID:
    kobvindex_GFZ123540
    Format: 35 Seiten , Illustrationen, graphische Darstellungen
    Series Statement: Research report / Cold Regions Research and Engineering Laboratory, CRREL, US Army Material Command 276
    Content: CONTENTS: Introduction. - Test site. - Test procedures. - Equipment. - Unconfined compression tests. - Ring tensile tests. - Test results. - Unconfined compression tests. - Ring tensile tests. - Discussion. - Literature cited. - Appendix A. Calculation of the effect of nonaxial loading of unconfined compression specimens. - Appendix B. Camp Century unconfined compressive strength data at -25C. - Appendix C. Camp Century ring-tensile strength data at -25C. - Appendix D. Unconfined compressive strength of Camp Century vertical snow samples 8.25 in. length, 3.0 in. diam at -25C. - Abstract.
    Content: The unconfined compressive strengths [Sigma]c and the ring-tensile strengths [Sigma]T of snow and ice specimens from the Inclined Drift at Camp Century, Greenland, were determined. The specimen densities varied over essentially the complete natural density range of polar snow and ice (0.340 to 0.890 g/cm^3). The specimens were loaded rapidly to failure with times varying between 0.2 and 1.4 sec. During loading, head speeds varied between 5.1 and 23.6 cm/min, although during individual tests they were constant. Even the low density specimens failed in the brittle mode. Although a plot of [Sigma]T vs [Gamma] is linear, [Sigma]c vs [Gamma] is clearly nonlinear. This nonlinearity may result from either changes in the level of the internal stress concentrations associated with the voids in the snow or from changes in the ratio (bulk porosity/effective porosity of the failure surface) with density. Both tangent and secant moduli are linear functions of [Gamma]. There is no pronounced change in [Sigma]c with changes in strain rate. A significant increase in [Sigma]T, [Sigma]c and the modulus values was noted at bulk densities greater than 0.830 g/cm^3. This increase is presumably caused by the close-off of the air passages.
    Note: MAB0014.001: ZSP-202-276 , Online frei verfügbar
    In: Research report
    Language: English
    Keywords: Forschungsbericht
    URL: http://www.worldcat.org/oclc/5974547
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