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  • 1
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    The brine zone in the McMurdo Ice Shelf, Antarctica (1982)
    Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory
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    Call number: ZSP-201-82/39
    In: CRREL Report, 82-39
    Description / Table of Contents: Observations of a 4.4-m-high brine step in the McMurdo Ice Shelf, Antarctica, show that it has migrated about 1.2 km in 4 years. The present brine wave is overriding an older brine-soaked layer. This migration is proof of the dynamic nature of the step, which is the leading edge of a brine wave that originated at the shelf edge after a major break-out of the McMurdo Ice Shelf. The inland boundary of brine penetration is characterized by a series of descending steps that are believed to represent terminal positions of separate intrusions of brine of similar origin. The inland boundary of brine percolation is probably controlled largely by the depth at which brine encounters the firn/ ice transition (43 m). However, this boundary is not fixed by permeability considerations alone, since measurable movement of brine is still occurring at the inland boundary. Freeze-fractionation of the seawater as it migrates throught the ice shelf preferentially precipitates virtually all sodium sulfate, and concomitant removal of water by freezing in the pore spaces of the infiltrated firm produces residual brines approximately six times more concentrated than the original seawater.
    Type of Medium: Series available for loan
    Pages: v, 35 Seiten , Illustrationen
    Series Statement: CRREL Report 82-39
    URL: https://apps.dtic.mil/docs/citations/ADA124516
    URL: https://hdl.handle.net/11681/9319
    Language: English
    Note: CONTENTS Abstract Preface Introduction Objectives Analytical techniques Radio echo profiling Core drilling Results and discussion Brine infiltration survey Brine layer steps Brine infiltration characteristics Brine infiltration mechanisms at inland boundary Confirmation of brine depths by drilling Density and temperature profiles Ice shelf freeboard Brine upwelling Brine chemistry Conclusions Literature cited
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  • 2
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    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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    Call number: ZSP-201-91/12
    In: CRREL Report, 91-12
    Description / Table of Contents: 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.
    Type of Medium: Series available for loan
    Pages: iv, 23 Seiten , Illustrationen
    Series Statement: CRREL Report 91-12
    URL: https://apps.dtic.mil/dtic/tr/fulltext/u2/a240974.pdf
    URL: https://hdl.handle.net/11681/9126
    Language: English
    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
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  • 3
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    Investigations of sea ice anisotropy, electromagnetic properties, strength, and under-ice current orientation (1980)
    Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory
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    Call number: ZSP-201-80/20
    In: CRREL Report, 80-20
    Description / Table of Contents: Results of impulse radar studies of sea ice give support to the concept of a sea ice model in which the ice bottom is composed of an array of lossy parallel plate waveguides. The fundametal relation between the average bulk brine volume of sea ice and its electrical and strength properties is discussed as is the remote detection of under-ice current alignment. It was found that 1) the average effective bulk dielectric constant is dependent upon the average bulk brine volume of the sea ice; 2) sea ice anisotropy, arising from a bottom structure of crystal platelets with a preferred c-axis horizontal alignment, can be detected by radio echo sounding measurements made not only on the ice surface but also from an airborne platform; 3) the effective coefficient of reflection from the seaiIce bottom decreases with increasing average effective bulk dielectric constant of the ice, decreases with increasing bulk brine volume, and is typically one to two orders of magnitude lower dhan the coefficient of reflection from the ice surface; and 4) the losses In sea ice increase with increasing average bulk brine volume.
    Type of Medium: Series available for loan
    Pages: v, 18 Seiten , Illustrationen
    Series Statement: CRREL Report 80-24
    URL: https://apps.dtic.mil/dtic/tr/fulltext/u2/a092089.pdf
    Language: English
    Note: CONTENTS Abstract Preface Introduction Field program Results and discussion Conclusions Literature cited Appendix: Data analysis procedures
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  • 4
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    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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    Call number: ZSP-201-82/42
    In: CRREL Report, 82-42
    Description / Table of Contents: 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.
    Type of Medium: Series available for loan
    Pages: iv, 19 Seiten , Illustrationen
    Series Statement: CRREL Report 82-42
    URL: https://apps.dtic.mil/dtic/tr/fulltext/u2/a124456.pdf
    URL: https://hdl.handle.net/11681/9323
    Language: English
    Note: CONTENTS Abstract Introduction Profiling system Theoretical considerations Field program Discussion Literature cited
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  • 5
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    Electromagnetic property trends in sea ice; Part I (1987)
    Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory
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    Call number: ZSP-201-87/6
    In: CRREL Report, 87-6
    Description / Table of Contents: Two-phase dielectric mixing model results are presented showing the electromagnetic properties of sea ice versus depth. The modeled data are compared with field measurements and show comparable results. It is also shown how the model data can be used in support of impulse radar and airborne electromagnetic(AEM) remote sensing of sea ice. Examples of the remote measurement of sea ice thickness using impulse radar operating in the 80- to 300-MHz frequency band and low-frequency (500 to 30,000 Hz) sounding techniques are presented and discussed. Keywords: Polar regions; Radar pulses.
    Type of Medium: Series available for loan
    Pages: vii, 55 Seiten , Illustrationen
    Series Statement: CRREL Report 87-6
    URL: https://hdl.handle.net/11681/9041
    Language: English
    Note: Contents Abstract Preface Nomenclature Introduction Sea ice growth and structure Model sea ice Brine salinity Seawater and model brine conductivity Complex dielectric constant of brine Electromagnetic properties of model sea ice at 100 MHz Electromagnetic properties of model sea ice at 100 and 500 MHz and 1 and 5 GHz Example of impulse radar sea ice profiling results Example of frequency-domain electromagnetic sea ice thickness sounding Concluding remarks Literature cited
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  • 6
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    Detection of cavities under concrete pavement (1983)
    Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory
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    Call number: ZSP-201-83/18
    In: CRREL Report, 83-18
    Description / Table of Contents: An evaluation of an impulse radar system for detecting cavities under concrete pavement is discussed, and field results are presented. It was found that a dual antenna mode of surveying was ideal for void detection. In this mode one antenna operated in a transceive mode and a second, offset from the first, operated in a receive-only mode. This arrangement allowed a refraction-type profile survey to be performed, which enabled subpavement voids to be easily detected. Field trails were held at Plattsburgh Air Force Base, where 28 cavities were detected and mapped. Drilling of holes verified that a cavity existed and allowed cavity depth to be measured. The cavities varied from 1.5 in. to 23 in, depth and were up to 20 ft. long.
    Type of Medium: Series available for loan
    Pages: 49 Seiten , Illustrationen
    Series Statement: CRREL Report 83-18
    URL: https://cdm16021.contentdm.oclc.org/digital/collection/p266001coll1/id/7120/rec/1
    URL: https://hdl.handle.net/11681/9301
    URL: https://apps.dtic.mil/docs/citations/ADA131851
    Language: English
    Note: CONTENTS Abstract Preface Introduction Plattsburgh Air Force Base Radar sounding system Survey procedure Cavity inspection Radar cavity detection test Radar profile results Falling-weight deflectometer tests Discussion and conclusions Literature cited
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  • 7
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    Electromagnetic properties of sea ice (1984)
    Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory
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    Call number: ZSP-201-84/2
    In: CRREL Report, 84-2
    Description / Table of Contents: Investigations of the in situ complex dielectric constant of sea ice were made using time-domain spectroscopy. It was found that (1) for sea ice with a preferred horizontal crystal c-axis alignment, the anisotropy of polarizing properties of the ice increased with depth, (2) brine inclusion conductivity increased with decreasing temperature down to about -8 C, at which point the conductivity decreased with decreasing temperature, (3) the DC conductivity of sea ice increased with increasing brine volume, (4) the real part of the complex dielectric constant is strongly dependent upon brine volume but less dependent upon the brine inclusion orientation, (5) the imaginary part of the complex dielectric constant was strongly dependent upon brine inclusion orientation but much less dependent upon brine volume. Because the electromagnetic (EM) properties of sea ice are dependent upon the physical state of the ice, which is continually changing, it appears that only trends in the relationships between the EM properties of natural sea ice and its brine volume and brine inclusion microstructure can be established.
    Type of Medium: Series available for loan
    Pages: vi, 38 Seiten , Illustrationen , 1 Beilage
    Series Statement: CRREL Report 84-2
    URL: https://apps.dtic.mil/docs/citations/ADA140330
    URL: https://hdl.handle.net/11681/9287
    Language: English
    Note: CONTENTS Abstract Preface Nomenclature Introduction Dielectric properties of sea ice Time-domain spectroscopy measurement Laboratory measurements Field measurements Analysis of ladder data Conductivity of brine and sea ice Complex dielectric constant of brine and sea ice Discussion and conclusions Literature cited
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  • 8
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    Radar anisotropy of sea ice due to preferred azimuthal orientation of the horizontalcaxes of ice crystals (1978)
    American Geophysical Union
    Details
    Publication Date: 1978-01-01
    Print ISSN: 0148-0227
    Electronic ISSN: 2156-2202
    Topics: Geosciences
    Published by American Geophysical Union
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  • 9
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    Sounding sea ice thickness using a portable electromagnetic induction instrument (1991)
    Society of Exploration Geophysicists
    Details
    Publication Date: 1991-12-01
    Print ISSN: 0016-8033
    Electronic ISSN: 1942-2156
    Topics: Geosciences , Physics
    Published by Society of Exploration Geophysicists
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