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  • 1
    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-202-329
    In: Research report
    Description / Table of Contents: CONTENTS: General Introduction. - Part I. Spatial and temporal variations in sea ice deformatfon. - Introduction. - Approach. - Site location and data collection procedures. - Data analysis. - Strain results. - Comparison of mesoscale deformation with macroscale deformation. - Nature of the ice pack rotation. - Conciusion. - Literature cited. - Part Il. Comparison of mesoscale strain measurements with linear drift theory predictions. - Introduction. - List of symbols. - Linear drift equations. - Ice drift solutions. - Comparison of theory with mesoscale measurements. - A more general linear constitutive law. - Conclusions. - Literature cited. - Appendix Relative magnitudes of differential drift forces. - Abstract.
    Description / Table of Contents: Measurements of mesoscale sea ice deformation over a region approximately 20 km in diameter were made over a five-week period in the spring of 1972 at the main AIDJEX camp in the Beaufort Sea. They have been analyzed to determine nonlinearities in the ice velocity field (due to the discrete small-scale nature of the ice pack), as well as a continuum mode of deformation represented by a least squares strain rate tensor and vorticity. The deformation rate time series between Julian day 88 and 113 exhibited net areal changes as large as 3% and deformation rates up to 0.16% per hour. In the principal axis coordinate system, the strain rate typically exhibited a much larger compression (or extension) along one axis than along the other. Persistent cycles at ~12-hour wavelengths were observed in the divergence rate. A comparison of the average residual error with the average strain rate magnitude indicated that strains measured on a scale of 10 km or greater can serve as a valid measure of the continuum motion of the sea ice. This conclusion is also substantiated by a comparison between the mesoscale deformation, and macroscale deformation measured over a ~100-km-diameter region. Vorticity calculations indicate that at low temporal frequencies ( 〈 0.04 hr^-1 ) the whole mesoscale array rotates essentially as an entity and consequently the low frequency vorticity can accurately be estimated from the rotation of a single floe. (Part I) A comparison of mesoscale strain measurements with the atmospheric pressure field and the wind velocity field indicated that the ice divergence rate and vorticity followed the local pressure and wind divergence with significant correlation. For low atmospheric pressures and converging winds, the divergence rate was negative with the vorticity being counterclockwise. The inverse behavior was observed for high pressures and diverging winds. This behavior agreed with predictions based upon the infinite boundary solution of a linearized drift theory in the absence of gradient current effects and using the constitutive law proposed by Glen for pack ice. The best least squares values of the constitutive law parameters [Eta] and [Zeta] were found to be given by ~10^12 kg sec^-1. Using typical divergence rates, these values yielded compressive stresses of the magnitude of 10^5 N m^-1, which are similar to values suggested by the Parmerter and Coon ridge model. In general, the infinite boundary solution of the linear drift equation indicates that in a low pressure region that is reasonably localized in space, the ice would be expected to converge for high compactness (winter) and diverge for low compactness (summer). Calculations were also carried out using a more general linear viscoelastic constitutive law that includes memory effects and that includes a generalized Hooke's law as well as the Glen law as special cases. A best fit of this more general calculation with strain measurements indicates, overall, a better agreement with viscous behavior than with elastic behavior, with the frequency behavior of the estimated "viscosities" similar to the Glen law behavior at temporal frequencies less than ~0.01 hr^-1 (Part II)
    Type of Medium: Series available for loan
    Pages: v, 37 Seiten , Illustrationen
    Series Statement: Research report / Cold Regions Research and Engineering Laboratory, CRREL, US Army Material Command 329
    Language: English
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  • 2
    Series available for loan
    Series available for loan
    Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory
    Associated volumes
    Call number: ZSP-201-83/21
    In: CRREL Report, 83-21
    Description / Table of Contents: The probability density function of the gouge depths into the sediment is represented by a simple negative exponential over four decades of gouge frequency. The exceedance probability function is, therefore, e to the -lambda d, where d is the gouge depth in meters and lambda is a constant. The value of lambda shows a general decrease with increasing water depth, from 9/m in shallow water to less than 3/m in water 30 to 35 m deep. The deepest gouge observed was 3.6 m, from a sample of 20,354 gouges that have depths greater than or equal to 0.2 m. The dominant gouge orientations are usually unimodal and reasonably clustered, with the most frequent alignments roughly parallel to the general trend to the coastline. The value of N(bar) sub 1, the mean number of gouges (deeper than 0.2 m) per kilometer measured normal to the trend of the gouges, varies from 0.2 for protected lagoons to 80 in water between 20 and 38 m deep in unprotected offshore regions. The distribution of the spacings between gouges as measured along a sampling track is a negative exponential. The form of the frequency distribution of N sub 1 varies with water depth and is exponential for lagoons and shallow offshore areas, previously skewed for 10 to 20 m depths off the barrier islands, and near-normal for deeper water. As a Poisson distribution gives a reasonable fit to the N sub 1 distributions for all water depths, it is suggested that gouging can be taken as approximating a Poisson process in both space and time. The distributions of the largest values per kilometer of gouge depths, gouge widths, and the heights of the lateral embankment of sediments plowed from the gouges are also investigated.
    Type of Medium: Series available for loan
    Pages: 40 Seiten , Illustrationen, 1 Karte
    Series Statement: CRREL Report 83-21
    Language: English
    Note: CONTENTS Abstract Preface Introduction Background and environmental setting Data collection and terminology Data analysis Gouge depths Gouge orientation Gouge frequency Extreme value analysis Applications to offshore design Gouge depth Extreme value statistics Burial depths Conclusion Literature cited Appendix A: Detailed bathymetric map of the Alaskan portion of the Beaufort Sea
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  • 3
    Series available for loan
    Series available for loan
    Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory
    Associated volumes
    Call number: ZSP-202-101
    In: Research report / Cold Regions Research and Engineering Laboratory, 101
    Description / Table of Contents: Partial Summary: This paper is a pilot study of interrelations between structural features readily observed in horizontal thin sections of sea ice under low magnification. The core studied was 31.4 cm in length and was collected from Elson Lagoon at Point Barrow, Alaska on 26 October 1960.
    Type of Medium: Series available for loan
    Pages: iv, 11 Seiten , Illustrationen
    Series Statement: Research report / Cold Regions Research and Engineering Laboratory 101
    Language: English
    Note: CONTENTS Preface Summary Introduction Petrographic characteristics Intercrystalline features Intracrystalline features References
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  • 4
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    Series available for loan
    Hanover, NH : U. S. Cold Regions Res. and Eng. Laboratory
    Associated volumes
    Call number: ZSP-201-79/8
    In: CRREL Report, 79-8
    Description / Table of Contents: Sea ice ridging statistics obtained from a series of laser surface roughnessprofiles are examined. Each set of profiles consists of six 200-km-long flight tracks oriented approximately perpendicular to the coastline of the Chukchi and Beaufort Seas. The landward ends of the profiles were located at Point Lay, Wainwright, Barrow, Lonely, Cross Island and Barter Island. The flights were made in February, April, August, and December 1976, and one additional profile was obtained north of Cross Island during March 1978. It was found that although there is a systematic variation in mean ridge height (h) with season (with the highest values occurring in late winter), there is no systematic spatial variation in h at a given time. The number of ridges/km (micron) is also high during the late winter, with the highest values occurring in the Barter and Cross Island profiles . In most profiles, the ice 20 to 60 km from the coast is more highly deformed (higher micron values) than the ice either nearer the coast or farther seaward. The Wadhams model for the distribution of ridge heights gives better agreement with observed values in the higher ridge categories than does the Hibler model. Estimates of the spatial recurrence frequency of large pressure ridges are made by using the Wadhams model and also by using an extreme value approach. In the latter, the distribution of the lagest ridges per 20 km of laser track was found to be essentially normal
    Type of Medium: Series available for loan
    Pages: iv, 28 S. : Ill.
    Series Statement: CRREL Report 79-8
    Language: English
    Note: CONTENTS Abstract Preface Introduction Data collection and processing Analysis General Variations in ridging Ridge height distributions Occurrence of high ridges The tail of the distribution Extreme values Applications to offshore design Conclusions Literature cited Appendix A. Tabulated ice ridge data ILLUSTRATIONS Location and orien!ation of the laser sampling tracks Mean ridge height has a function of distance from shore for all loca-tions and sampling times in 1976 Number of ridges p per 20-km interval as function of distance fromshore for all locations and sampling times in 1976 p and h values obtained in March 1978 by NASA plotted as a func-tion of distance from shore Ridging intensity I, as a function of distance from shore for all loca-tions and sampling times in both 1976 and 1978 Histograms of predicted versus observed ridge heights separated in-toclassintervalsofo.3m Total x1 values for each ridge sail height class interval The Wadhams ridge height distribution function parameters a and 13 plotted as a function of distance from the shore of Cross Island dur-ing February, April and December 1976 The Hibler ridge height distribution function parameters N0 and Aplotted as a function of distance from the shore of Cross Island dur-ing February, April and December 1976 Plot of log~0 vs ridge sail height Semilog of P,(h), the probability that a ridge encountered at randomwill have a height of at least h meters, versus ridge sail height Ridge sail heights versus spatial recurrence intervals Monte Carlo simulation of the extreme ridge heights generated bythe Wadhams and Hibler models using p and h from the Beaufort Sea February and April tracks TABLES Least-squares constants a, 13 and ~3’
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  • 5
    Series available for loan
    Series available for loan
    Hanover, NH : U. S. Cold Regions Res. and Eng. Laboratory
    Associated volumes
    Call number: ZSP-201-78/13
    In: CRREL Report, 78-13
    Description / Table of Contents: Field observations of the growth fabrics of the fast and near-fast ice along the coasts of the Beaufort and Chukchi Seas show that, at depths of more than 60 cm below the upper ice surface, the sea ice crystals show striking alignments within the horizontal plane. At one site this alignment was well developed at a depth of 15 cm and in all cases the degree of preferred orientation increased with depth, with the strongest orientations occurring at the bottom of the ice sheet. In general the c-axes of the crystals were aligned roughly E-W parallel to the coast. In the vicinity of islands the alignment roughly paralleled the outlines of the islands and in narrow passes between islands the alignment paralleled the channel. Our observations, as well as similar observations made in the Kara Sea by Cherepanov, can be explained if it is assumed that the c-axes of the crystals are aligned parallel to the 'long-term' current direction at the sea ice/sea water interface. The alignments are believed to be the result of geometric selection among the growing crystals, with the most favored orientation being that in which the current flows normal to the (0001) plates of ice that make up the dendritic ice/water interface characteristics of sea ice. It is hypothesized that current flow in this direction reduces the thickness of the solute boundary layer as well as the salinity in the liquid at the interface. This lowered salinity allows crystals in the favored orientation to extend farther into the melt than neighboring crystals with less favored orientations. In addition the current tends to induce a continuous flux of supercooled seawater against the sides of the crystals that extend ahead of the interface.
    Type of Medium: Series available for loan
    Pages: v, 29 S. : graph. Darst.
    Series Statement: CRREL Report 78-13
    Language: English
    Note: CONTENTS Abstract Preface Introduction Locale and techniques Observations Vertical variations in crystal orientation Regional variations in crystal orientation Summary of observations Causes Initial ice skim Earth’s magnetic field Currents Conclusions and consequences Literature cited ILLUSTRATIONS Figure Vertical thin section of ice from the upper part of the columnarzone; Site 15, 47t o 57cm Map of Beaufort Sea coast in the vicinity of Prudhoe Bay, Alaska, showing sampling sites and mean c-axis orientation in the horizon-tal plane at each site C-axis orientation plotted on a Schmidt net for six different sampl-ing sites shown on Figure 2 C-axis orientation obtained at six different depths in the ice sheet at site 6 Mean crystal orientation in the horizontal plane X0 and standard deviation s, as a function of vertical location in the ice sheet for sites 6 and N76 Schmidt net plots of individual c-axis orientations and the meanorientation at two different levels at Sites 2 and 7 Standard deviation s, of the c-axis as measured in the horizontalplane as a fuoction of vertical location in the ice sheet C-axis orientations measured in the vicihity of Cross Island C-axis orientations measured in the vicinity of the McClure Islands C-axis orientations measured at Site 20 offshore from Barrow. Alaska, in the Chukchi Sea C-axis orientations as determined by Cherepanov (1971) in the Kara Sea region of the U.S.S.R Progressive vector diagrams for the currents measured beneath the ice at sites C1 and C2
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  • 6
    Series available for loan
    Series available for loan
    Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory
    Associated volumes
    Call number: ZSP-201-78/2
    In: CRREL Report, 78-2
    Description / Table of Contents: Many of the technical questions relating to iceberg transport are given brief, but quantitative, consideration. These include iceberg genesis and properties, the mechanical stability of icebergs at sea, towing forces and tug characteristics, drag coefficients, ablation rates, and handling and processing the iceberg at both the pick-up site and at the final destination. In particular the paper attempts to make technical information on glaciological and ice engineering aspects of the problem more readily available to the interested planner or engineer. Specific conclusions include: (1) No unprotected iceberg, no matter how long or wide, would be likely to survive the ablation caused by a long trip to low latitudes. (2) Icebergs that have a horizontal dimension exceeding 2 km may well be prone to breakup by long wavelength swells. (3) To avoid the dangers associated with an iceberg capsizing, the width of a 200-m thick iceberg should always be more than 300 m. (4) For towing efficiency the length/width ratio of a towed iceberg should be appreciably greater than unity. (5) For a pilot project, the selected iceberg would have to be quite small, if for no other reason than the practical availability of tug power.
    Type of Medium: Series available for loan
    Pages: v, 31 Seiten , Illustrationen
    Series Statement: CRREL Report 78-2
    Language: English
    Note: CONTENTS Abstract Preface Introduction Sources and properties of tabular icebergs Sources Characteristics of ice shelves near the ice front Characteristics of tabular icebergs Towing Geophysical and engineering considerations Tug characteristics Handling and processing Cutting and boring with thermal devices Penetration with electrothermal devices Electrothermal cutting Making vertical cuts by pre-split blasting Primary fragmentation by blasting Primary fragmentation by mechanical sawing Comminuting ice with machines Slurry pipelines Conclusion Literature cited
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  • 7
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    Series available for loan
    Hanover, NH : U.S. Army Corps of Engineers, Cold Regions Research and Engineering Laboratory
    Associated volumes
    Call number: ZSP-202-276
    In: Research report
    Description / Table of Contents: 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.
    Description / Table of Contents: 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.
    Type of Medium: Series available for loan
    Pages: 35 S. : graph. Darst.
    Series Statement: Research report / Cold Regions Research and Engineering Laboratory, CRREL, US Army Material Command 276
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  • 8
    Call number: ZSP-201-76/18
    In: CRREL Report, 76-18
    Description / Table of Contents: Three surface elevation and ice thickness profiles obtained during the 1972 Arctic Ice Dynamics Joint Experiment on a multiyear ice floe were analyzed to obtain relationships between surface elevation, thickness and physical properties of the ice. It was found that for ice freeboards from 0.10 m to 1.05 m above sea level a linear relationship between ice density and freeboard could be postulated. The equation for the regression line is: Ice density = -194f' + 974 kg/cu m where f' is the ice freeboard plus snow depth in ice equivalent at the point in question. This statistical relationship is consistent with observed physical properties, which indicate that as the ice freeboard increases, ice salinity decreases and the higher freeboard or thicker ice therefore decreases in density. Using this variable density with freeboard relationship, a model was constructed to predict ice thickness, given ice freeboard and snow depth alone. This prediction is desirable, since snow depth and freeboard are relatively easy to obtain, whereas ice thickness can usually be obtained only by drilling through the ice. The model was compared with two other models. It was found that the variable density prediction model gave the best approximation to observed ice thickness, with a standard error between the measured and predicted value of about 0.4 m, compared with errors from 50 to 100% higher for the other two models.
    Type of Medium: Series available for loan
    Pages: v, 25 Seiten , Illustrationen
    Series Statement: CRREL Report 76-18
    Language: English
    Note: Contents Abstract Preface Summary Introduction Previous work Results Models for predicting thickness from ice freeboard Comparison between measured and predicted thicknesses Spectral behavior of measured and predicted profiles Comparisons of ice thickness using airborne laser profilometry Conclusions Literature cited Appendix A: Misgivings on isostatic imbalance as a mechanism for sea ice cracking
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  • 9
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    Series available for loan
    Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory
    Associated volumes
    Call number: ZSP-202-345
    In: Research report / Cold Regions Research and Engineering Laboratory, 345
    Description / Table of Contents: CONTENTS: Abstract. - Preface. - List of symbols. - Introduction. - Previous work. - Experimental design. - The radioisotope 22Na. - Description of apparatus. - Experimental procedure. - Correction of profiles. - Assumptions. - Decay correction. - Boundary correction. - Error analysis. - Results. - Salinity data. - Temperature data. - Growth velocity. - Discussion. - Brine and ice properties. - Brine salinity. - Brine density. - Brine volume. - Brine latent heat of freezing. - Brine viscosity, specific heat, and thermal conductivity. - Ice properties. - Theoretical brine expulsion model. - Continuity equations. - Thermal energy equation. - Simplified brine expulsion equations. - Brine expulsion in NaCl ice. - Results. - Discussion. - Gravity drainage in NaCl ice. - Application of results to natural sea ice. - Effective distribution coefficient. - Previous work. - Experimental procedure and results. - Conclusions. - Literature cited. - Appendix A: Profile correction data. - Appendix B: Program "correct" and sample output. - Appendix C: Tabulation of salinity data. - Appendix D: Tabulation of profile data. - Appendix E: Time-ice thickness equations (Runs 2 and 3). - Appendix F: Tabulation of distribution coefficient data.
    Description / Table of Contents: To obtain a better understanding of the desalination of natural sea ice, an experimental technique was developed to measure sequential salinity profiles of a growing sodium chloride ice sheet. Using radioactive 22Na as a tracer, it was possible to determine both the concentration and movement of the brine within the ice without destroying the sample. A detailed temperature and growth history of the ice was also maintained so that the variation of the salinity profiles could be properly interpreted. Since the experimental salinity profile represented a smoothed, rather than a true salinity distribution, a deconvolution method was devised to restore the true salinity profile. This was achieved without any significant loss of end points. In all respects, the salinity profiles are similar to those of natural sea ice. They have a characteristic C-shape, and clearly exhibit the effects of brine drainage. Not knowing the rates of brine expulsion or gravity drainage, the variation of the salinity profiles during the period of ice growth could be explained by either process. To determine the relative importance of the desalination mechanisms, a theoretical brine expulsion model was derived and compared to the experimental data. As input for the model, equations describing the variation of some properties of NaCl brine with temperature were derived. These included the brine salinity, viscosity, specific heat, thermal conductivity, and latent heat of freezing. The theoretical brine expulsion model was derived by performing mass and energy balances over a control volume of NaCl ice. A simplified form of the model, when compared to the experimental results, indicated that brine expulsion was only important during the first several hours of ice growth, and later became a minor desalination process relative to gravity drainage which continued to be the dominant mechanism for the remainder of the study period (up to 6 weeks). The rate of gravity drainage was found to be dependent on the brine volume and the temperature gradient of the ice. As either the brine volume or temperature gradient was increased, the rate of change of salinity due to gravity drainage increased. The equation commonly used to calculate the effective distribution coefficient (Weeks and Lofgren 1967) was modified and improved by taking brine drainage into account. An expression was also derived to give the distribution coefficient at very low growth velocities.
    Type of Medium: Series available for loan
    Pages: vii, 85 Seiten , Illustrationen
    Series Statement: Research report / Cold Regions Research and Engineering Laboratory 345
    Language: English
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  • 10
    Call number: ZSP-202-337
    In: Research report
    Description / Table of Contents: Contents: Introduction. - Surface ice observations. - Imagery interpretation. - Side-looking airborne radar. - Infrared. - Conclusions. - Literature cited.
    Description / Table of Contents: Ice conditions during mid-January 1974 in the Gulf of St. Lawrence and in the estuaty as far upstream as Rimouski are described utilitizing side-looking airborne radar, infrared and photographic imagery. The interpretations were verified by simultaneous surface observations on the ice by investigators operating from the CSS Dawson. The ice examined was undergoing rapid drift and deformation and showed a wide variety of thin ice (0-40 cm) features formed under the influence of strong winds and currents. These observations should serve as a guide in interpreting ice conditions in similar areas where ground truth data are not available.
    Type of Medium: Series available for loan
    Pages: 41 Seiten , Illustrationen
    Series Statement: Research report / Cold Regions Research and Engineering Laboratory, CRREL, US Army Material Command 337
    Language: English
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