bluuebunny/crossref_metadata_2025_split huggingface dataset:
Crystalline Texture of the 2083 m Ice Core at Vostok Station, Antarctica
Authors: Lipenkov V.Ya. , Barkov N.I. , Duval P. , Pimienta P. 
Published: September 2017

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.
The Age-Depth Profile in the Upper Part of a Steady-State Ice Sheet
Authors: Reeh Niels 
Published: September 2017

AbstractSimple analytical models are developed in order to study how up-stream variations in accumulation rate and ice thickness, and horizontal convergence/ divergence of the flow influence the age and annual layer-thickness profiles in a steady-state ice sheet. Generally, a decrease/increase of the accumulation rate and an increase/decrease of the ice thickness in the up-stream direction (i.e. opposite to the flow direction) results in older/younger ice at a given depth in the ice sheet than would result if the up-stream accumulation rate and ice thickness were constant along the flow line.Convergence/divergence of the up-stream flow will decrease/increase the effect of the accumulation-rate and ice-thickness gradients, whereas convergence/divergence has no influence at all on the age and layer-thickness profiles if the up-stream accumulation rate and ice thickness are constant along the flow line.A modified column-flow model, i.e. a model for which the strain-rate profile (or, equivalently, the horizontal velocity profile) is constant down to the depth corresponding to the Holocene/Wisconsinan transition 10 750 year BP., seems to work well for dating the ice back to 10 000–11 000 year B P. at sites in the slope regions of the Greenland ice sheet. For example, the model predicts the experimentally determined age profile at Dye 3 on the south Greenland ice sheet with a relative root-mean-square error of only 3% back to c. 10 700 year B.P. As illustrated by the Milcent location on the western slope of the central Greenland ice sheet, neglecting up-stream accumulation-rate and ice-thickness gradients, may lead to dating errors as large as 3000–000 years for c. 10 000 year old ice.However, even if these gradients are taken into account, the simple model fails to give acceptable ages for 10 000 year old ice at locations on slightly sloping ice ridges with strongly divergent flow, as for example the Camp Century location. The main reason for this failure is that the site of origin of the ice cannot be determined accurately enough by the simple models, if the flow is strongly divergent.With this exception, the simple models are well suited for dating the ice at locations where the available data or the required accuracy do not justify application of elaborate numerical models. The formulae derived for the age-depth profiles can easily be worked out on a pocket calculator, and in many cases will be a sensible alternative to using numerical flow models.
Two Models for Estimating Climate‒Glacier Relationships in the North Cascades, Washington, U.S.A.
Authors: Tangborn Wendell 
Published: September 2017

AbstractTwo models based on standard observations of precipitation, temperature, and run-off at low-altitude weather and gaging stations have been devised to calculate annual glacier balances in the North Cascades of Washington. The predicted glacier balances of the Thunder Creek basin glaciers, determined by a run-off–precipitation (RP) model during the 1920–74 period, are compared with balances predicted by a precipitation–temperature (PT) model for the same period. Annual balances determined by the PT model are also compared with balances measured by field techniques at South Cascade Glacier since 1958. In the PT model, winter snow accumulation (winter balance) is determined by winter (October–April) precipitation observed at the Snoqualmie Falls weather station. Summer (May–September) ablation (summer balance) on the glaciers is estimated by a technique which utilizes maximum and minimum air temperatures, also observed at Snoqualmie Falls. Ablation calculations incorporate summer cloud cover as a variable by using a relationship between cloud cover and the range in daily maximum and minimum air temperatures.Annual mass changes for the 1884–1974 period in both South Cascade Glacier and the Thunder Creek glaciers were reconstructed by utilizing the PT model. The fluctuations in glacier mass during this period generally agree with historical observations and show that a definite change in glacier activity from marked recession to stability or an advancing state occurred about 1945. During the 1900–45 period, South Cascade Glacier lost mass at a rate of 1.4 m per year and the Thunder Creek glaciers (which are at a higher altitude) at 1.1 m per year.These models suggest that the relationship of glacier mass balance to precipitation and temperature is a very sensitive one. It appears from these studies that a decrease in summer air temperature of just over 0.5 deg or an increase in winter accumulation of slightly more than 10% (350 mm) from the 1920–74 average would cause these glaciers to grow continuously.
A Thermohydrodynamic Model of an Ice Sheet
Authors: Verbitsky M. Ya. , Chalikov D. V. 
Published: September 2017

AbstractThe purpose of this paper is to consider an ice-sheet model based on joint solution to the dynamic equations and equations of heat conductivity in which the surface relief is one of the unknown functions. The proposed model is applicable to calculations of the Antarctic ice sheet. Results of a numerical experiment for present values of the temperature of the ice surface and precipitation as well as for their separate and simultaneous increase by 2, 4, or 6 deg and 10, 20, or 30% are given.
The Pendular-Funicular Liquid Transition in Snow
Authors: Denoth A. 
Published: September 2017

AbstractThe way free water is distributed around contact points of ice grains is recorded by measuring the dielectric constant of the porous system which constitutes snow. Within the saturation range of 11% to 15% of the pore volume, a transitional range from the “pendular” to the “funicular” mode of distribution of free water occurs. By measuring the drainage-flow of free water through snow, additional information as to the upper limit of the pendular distribution is obtained. This upper limit is reached at a saturation of approximately 14% of the pore volume.
Dynamic Behaviour of Dislocations in HF-Doped Ice Ih
Authors: Perez J. , Maï C. , Tatibouët J. , Vassoille R. 
Published: September 2017

AbstractA model of dislocation glide in ice Ih was recently proposed. This model was developed on certain assumptions, namely that transitions occur through cooperative movements of H2O molecules in the non-crystalline core of dislocations. A relation between the velocity vd of linear defects and shear stress τ or temperature T is obtained. This relation shows that vd varies linearly with τ at low values of τ and (or) T but varies more rapidly at higher stresses; this non-linearity is more pronounced the higher the temperature. Such an analysis is extended in order to take into account doping effects. The case of HF-doped ice is considered: it is shown that there is a strong accumulation effect of HF molecules in the dislocation cores, which induces an increase of the rate of transitions. The results are in agreement with experimental data concerning both the velocity of dislocations and high-temperature internal friction in HF-doped ice.
Bottom Crevasses
Authors: Weertman J. 
Published: September 2017

AbstractAn approximate calculation is made of the rate at which a bottom crevasse in a cold ice shelf or tabular iceberg can close shut by freezing of water and can creep open through the creep deformation of ice. In all but the thickest ice shelves and icebergs, those with a thickness greater than about 400 m, the freezing process is the more important mechanism if the ice is cold (< – 10°C). Consequently in a cold iceberg or ice shelf a bottom crevasse, once formed, will freeze shut.
Frequency of Major Avalanche Winters
Authors: Fitzharris B.B. , Schaerer P. A. 
Published: September 2017

AbstractA 70-Year record has been compiled for avalanches affecting the Canadian Pacific Railway at Rogers Pass, British Columbia. Time series are presented for avalanche frequency, avalanche mass, and length of avalanche debris on the rail line for 26 avalanche paths as well as for winter snow-fall. Winters with the heaviest avalanche activity were 1971-72, 1934-35, 1919-20, 1932-33, and 1953-54. Time-series analysis indicates that the size of avalanches has decreased in recent decades. Spectral analysis shows avalanche activity to the similar to white noise but with a weak periodicity of about 18 years. An examination of the climatology of big avalanche winters reveals two distinct circulation patterns: a strong zonal flow with frequent Pacific storms and heavy snow-fall; or a pronounced meridional flow, Arctic air outbreaks, and catastrophic avalanching released by rapid advection of warm moist Pacific air. Major avalanche winters need not be big snow-fall winters.
The Fundamental Processes in Conventional Alavalanche Forecasting
Authors: LaChapelle Edward R. 
Published: September 2017

AbstractConventional avalanche forecasting is practiced as a mix of deterministic treatment for snow and weather parameters and inductive logic to reach actual forecast decisions. Inductive logic of the scientific method dominates, making frequent use of iteration and redundancy to minimize decision uncertainties. The mental processes involved are holistic rather than analytical. Elementary information theory can be used rationally to sort data categories for minimum entropy and optimize inductive reasoning. Recognizing these principles affords a chance to improve the practice and teaching of conventional forecasting techniques.
Snow-Slab Studies at Whistler Mountain, British Columbia, Canada
Authors: Stethem C. , Perla R. 
Published: September 2017

AbstractA study of 30 slab avalanches at Whistler Mountain ski area, British Columbia, indicates that slab instability initiates with highest frequency on 40° slopes, that the temperature at the slab bed surface is about –5°C averaged for the 30 cases, and that on the average the slabs have a snow density of about 220 kg/m3. These results agree well with results from earlier studies. A rich variety of crystals appear in photomicrographs of samples extracted from the bed surfaces of the 30 slabs. In many cases, crystals extracted from the plane of critical weakness do not differ markedly from crystals extracted from adjacent strata.
A Fragment–Flow Model of Dry–Snow Avalanches
Authors: Mears Arthur I. 
Published: September 2017

AbstractField data on dry–slab avalanches obtained during the period 1975–79 from several snow climates suggest the following: (1) most of the mass of the typical avalanche studied consisted of fragments with lengths greater than 5 cm, (2) transverse and longitudinal shear planes formed during deceleration in the avalanche run–out zone, and (3) the flow height exceeded the slab height in most cases. No correlation was found between the run–out distance and the track or run–out zone slope, or between the run–out distance and the released slab height.The field data suggest that avalanche motion is best described as a flow of fragments in which boundary shearing stresses are sensitive to fragment size distributions and volumetric solids concentrations. These factors may be more important than the roughness of the avalanche boundary in determining maximum velocity and run–out distance.
Seismic and Impact–Pressure Monitoring of Flowing Avalanches
Authors: Schaerer P. A. , Salway A. A. 
Published: September 2017

AbstractContinuous records have been made during the passage of dry–snow avalanches of both seismic signals, which allows the avalanche speed to be estimated, and impact pressures on load cells with surface areas of 645 and 6 450 mm2. The impact pressure recordings show an initial peak followed by a base pressure. The observed initial and base pressures vary strongly within avalanches and from one avalanche to another, but, on average, they can be correlated with the frontal speed and the density of the deposited avalanche snow. It is concluded that well–developed dry–snow avalanches have an unsteady wave motion similar to the slug flow observed in ultra–rapid flow of water, and that they consist of three stratified components: dense flowing snow at the bottom, light flowing snow, and powder snow.
A Two–Parameter Model of Snow–Avalanche Motion
Authors: Perla R. , Cheng T. T. , McClung D.M. 
Published: September 2017

AbstractVoellmy’s (1955) method for computing the run-out distance of a snow avalanche includes an unsatisfactory feature: the a priori selection of a midslope reference where the avalanche is assumed to begin decelerating from a computed steady velocity. There is no objective criterion for selecting this reference, and yet the choice critically determines the computed stopping position of the avalanche. As an alternative, a differential equation is derived in this paper on the premise that the only logical reference is the starting position of the avalanche. The equation is solved numerically for paths of complex geometry. Solutions are based on two parameters: a coefficient of friction μ; and a ratio of avalanche mass–to–drag, M⁄D. These are analogous to the two parameters in Voellmy’s model, μ and ξH. Velocity and run-out distance data are needed to estimate μ and M⁄D to useful precision. The mathematical properties of two–parameter models are explored, and it is shown that some difficulties arise since similar results are predicted by dissimilar pairs of μ and M⁄D.
An analysis of compressive strain in adjacent temperature-gradient and equi-temperature layers in a natural snow cover
Authors: Armstrong Richard L. 
Published: September 2017

AbstractCompressive strain-rates in discrete layers of a sub-alpine snow cover are analyzed. Individual layers are identified according to density and the dominant type of metamorphism which contributed to their formation. Data were collected during four winter seasons at the Institute of Arctic and Alpine Research (INSTAAR) snow-study site (3 400 m), Red Mountain Pass, south-western Colorado, U.S.A. At average densities of less than 250 kg m₋3 the influence of metamorphism on strain-rate is not apparent. However, at densities greater than 250 kg m₋3, two separate relationships emerge for strain as a function of crystal type and density. While two adjacent layers may exhibit comparable densities, a layer of sintered, fine grained (ET) snow indicates a strain-rate approximately one order of magnitude greater than an adjacent layer of cohesionless, coarse-grained (TG) snow.
Thermodynamics of snow metamorphism due to variations in curvature
Authors: Colbeck S. C. 
Published: September 2017

AbstractIn the absence of imposed temperature gradients, the metamorphism of dry snow is dominated by the slow process of vapor diffusion between surfaces of different radii of curvature. This process is so slow in a seasonal snow cover (where temperatures normally change on the scale of hours or days) that vapor migration is usually dominated by the imposed temperature gradient. Thus radius of curvature contributes to but does not control metamorphism except for short periods in very fresh snow. As opposed to dry snow, liquid-saturated snow (i.e. pore space filled by the melt) is metamorphosed by heat flow arising from relatively large temperature differences among the particles. Grain growth in liquid-saturated snow is rapid because of the large temperature differences at nearly constant liquid pressure. In wet snow with low liquid content (2-5% by volume), grain growth is dominated by vapor diffusion (as in dry snow) so grain growth is much slower than under conditions of liquid saturation.
Avalanche Zoning in France –Regulation and Technical Bases
Authors: Crécy L. de 
Published: September 2017

AbstractAvalanche zoning in France comprises two main parts:1. A map of the probable location of avalanches was produced between 1970 and 1976, at a scale of 1 : 20000, and covering nearly 600000 ha. This was prepared by using a novel method based on:
(i)the photo-interpretation of air photographs: the relief, extent of vegetation, notably forests the structure of deposits and alluvia, the comparison of several areas, thus enabling the zones …. which appear to have been struck by avalanches in the past to be identified;(ii)information acquired from inhabitants and the study of archives;(iii)a detailed inspection of the ground which can reveal physical or anthropogenic signs not disclosed by photo-interpretation.This map is only concerned with the past and gives no indication of frequencies.2. French law places an obligation on the State to define the limits of the zone subject to natural risk betore a building permit can be obtained.Consequently, since 1974 when France ventured into zoning, plans have been made on a large scale (1 : 2000) showing the zones exposed to avalanches. Plans are made in three colours: white presumed to be without danger, red dangerous and therefore prohibited to constructors, and blue zones, doubtful.Blue zoning, the most difficult to establish, relics on the evaluation of specialists, supported by the classical calculation of Voellmy, as well as by some first results received from experiments in a water channel for powder-snow avalanches, or from numerical simulations for other avalanches.The blue zone includes heavy avalanches with a time of return greater than 300 years and slightly more frequent avalanches (return time 30-50 years) but of very little importance.According to circumstances in every blue zone, several types of measure are recommended: police measures (evacuation or regulation in the home), architectural measures of reinforcement protective structure construction or annual checking by the authorities that natural (forest) or artificial (structures) defences are in a good state.
Snow Avalanche Hazard Zoning in British Columbia, Canada
Authors: Freer G. L. , Schaerer P. A. 
Published: September 2017

AbstractMany developed areas in British Columbia are exposed to snow-avalanche hazards. Avalanche-hazard zoning has been undertaken by the British Columbia Ministry of Transportation, Communications, and Highways during the past five years. Recommendations from these zoning studies are forwarded to those agencies responsible for land-use zoning and development approval. Existing and possible legislation are described, as well as problems associated with implementation of the legislation. Technical considerations are outlined; interpretation of vegetation is a very important factor in evaluating each avalanche site. Calculation of run-out distances and consideration of other factors serve as a check on the vegetation interpretation. A special safety factor has been developed.Socio-political considerations with respect to British Columbia are described. Existing developments have the most wide-ranging implications.
Avalanche zoning in alaska, U.S.A.
Authors: Hackett Steve W. , Santeford Henry S. 
Published: September 2017

AbstractOver 30% of Alaska’s 586 400 squares miles (1 518900 km2) is subject to snow-avalanche activity. For a state-wide avalanche hazard evaluation, Alaska has been divided into six major snow— avalanche regions on the basis of topography, climatological data, dominant snow—pack conditions, and typical avalanche activity. They are: Arctic Slope, Brooks Range, Western, Interior, South—central, and South—east.Mountainous terrain was studied at scales of 1 : 250 000 and 1 : 1 584000; final compilation was at a scale of 1 : 2 500 000. Regional snow—pack and climatic conditions were cross—correlated with relief zonation of each avalanche region to produce a map of Alaska's provisional snow—avalanche potential.Most of the mountainous areas in the South—central and South—east regions, because of their northern latitude, closeness to large masses of water, and large orographic and cylonic weather processes, are susceptible to major avalanche activity. For areas near population centers, the potential avalanche terrain has been identified from data on known and suspected avalanche activity through air photographs, terrain analysis, and documented snow—avalanche occurrences compiled at scales of 1 : 250 000 and 1 : 63 360.The state—wide regional data compilation and study are initial steps toward avalanche zoning in Alaska. Local land—use planning and detailed investigations are needed to establish effective natural—hazard zoning in municipal areas as related to snow avalanche activity.
Drifting-Snow Similitude—Transport-Rate and Roughness Modeling
Authors: Iversen J. D. 
Published: September 2017

AbstractThis paper reports on results from a series of experiments in a boundary-layer wind tunnel concerning snow-drift control adjacent to grade separations on interstate highways. A new application of similitude principles making use of theoretical relationships involving drifting particulate material is presented. The primary modeling parameters are considered to be a mass-rate parameter and an aerodynamic roughness parameter. They are derived by considerations of mass-transport rate of material in saltation and the equivalent roughness height of material in saltation. The parameters are combined empirically to correlate model snow-drift data successfully as well as to predict equivalent full-scale wind speeds and storm durations. The combined parameter has been used to compare and evaluate a variety of drift-control techniques adjacent to an interstate highway grade-separation crossing.
Geometry and Density of Drifts Formed by Snow Fences
Authors: Tabler Ronald D. 
Published: September 2017

AbstractThis paper presents results from studies of snow-drifts formed by vertical-slat “Canadian” and horizontal-slat “Wyoming” snow fences having 50% porosity and heights H from 0.8 to 3.8 m, on nearly level terrain. Characteristics of equilibrium lee drifts behind the Wyoming fence include cross-sectional area 19.3H 2, length 30H, maximum depth 1.20H. and water-equivalent volume 6.8H 2.18. Up-wind drift dimensions include maximum depth 0.5H and length 12H. Drifts behind Canadian fences are about 25% smaller than for the Wyoming design. Polynomial regression equations are fitted to drift profiles for both fence types. Relationships are presented for the effects of wind orientation and curvature of drifts near fence ends, as well as empirical equations describing pre-equilibrium geometry relative to degree of saturation. Mean density ρ (kg/m3) of drifted snow having depth y (m), is given by ρ = 376+158 log y.