bluuebunny/crossref_metadata_2025_split huggingface dataset:
Spatial and temporal patterns in snow accumulation, western Dronning Maud Land, Antarctica
Authors: Isaksson Elisabeth , Karlén Wibjörn 
Published: September 2017

AbstractDuring the Swedish Antarctic Expedition to Dronning Maud Land, Antarctica, 1988–89 the net accumulation was estimated for an area from the coast to about 400 km inland. Stake measurements were used to obtain the spatial variability and firn cores were used for the temporal variability. The mean annual accumulation for the period 1976–88 is about 0.4mw.e. for Riiser-Larsenisen and about 0.3mw.e. for the area above the grounding line. The accumulation rate at higher altitudes, > 2500 m a.s.1., is about 0.1 m w.e. for 1955–88. One record from the ice shelf covers the period 1957–88, and suggests an increase in accumulation of about 12%. Between 1976 and 1988, the accumulation has decreased by about 50%, most likely due to lower temperatures as suggested by the temperature record from Halley.
Radio Echo-Sounding Studies of Englacial Water Movement in Variegated Glacier, Alaska
Authors: Jacobel Robert , Raymond Charles 
Published: September 2017

AbstractRadio-echo returns from internal reflectors were monitored for three weeks during surge motion on Variegated Glacier, Alaska in July 1982. A monopulse transmitter with 3 MHz center frequency was fixed on the glacier surface near the equilibrium line. Data were recorded on magnetic tape approximately three times daily and contain both amplitude and phase information. The frequency spectrum of returned radiation from englacial scatterers shows peaks in the 12 to 30 MHz range which places constraints on the size and geometry of the scatterers. Timing of variations in the amplitude and frequency of returned radiation were found to coincide with changes in glacier velocity, basal water pressure, and surface melt rate. These changes in the echo pattern are interpreted in terms of the redistribution of water in englacial channels and cavities connected to the bed some distance down-glacier. This connection has large hydraulic resistance compared to a bore hole connected vertically to the bed. The inflow of water to the cavities from surface melt and rain and the drainage are generally in equilibrium except in times of changed surface input and during surge pulses. In the latter case, water may fill these cavities due to increased pressure at the bed associated with the motion pulse. The information obtained is therefore complementary to bore-hole water pressure levels but cannot duplicate it. This is apparently due to fundamental differences in the hydraulics of the natural cavity and conduit system, and a bore hole connected vertically to the bed.
Sedimentary Processes and Buried Ice Phenomena in the Pro-Glacial Areas of Spitsbergen Glaciers
Authors: Hambrey M. J. 
Published: September 2017

AbstractObservations at the snouts of several glaciers in Spitsbergen indicate that, between their present apparent limits and the moraines dating from the maximum Holocene extent of ice, wide areas of outwash deposits underlain by dead glacier ice occur. Such ice was visible at a number of localities. Indirect evidence of dead ice includes kettle-holes, collapse structures and, in one case, a subglacial melt stream emerging as a fountain within one such plain. Aufeis, formed in early winter, can sometimes also be preserved in the long term if covered by fluvio-glacial material. The presence of such ice has implications for the interpretation of soft-sediment structures in glacigenic successions. Previously, many folds and faults have been interpreted as resulting from active ice overriding or pushing the sediment. Simple ablation beneath the sedimentary layer in question also gives rise to similar structures.
Relation between the Mass Balance of Western Canadian Mountain Glaciers and Meteorological Data
Authors: Letréguilly Anne 
Published: September 2017

AbstractThe mass balance, summer balance, winter balance, and equilibrium-line altitude of three Canadian glaciers (Peyto, Place, and Sentinel Glaciers) are compared with the meteorological records of neighbouring stations for the period 1966—84. While Peyto Glacier’s mass balance is almost entirely related to summer temperature, Sentinel Glacier’s mass balance is mostly controlled by winter precipitation. Place Glacier is influenced by both elements. Statistical reconstructions are presented for the three glaciers, using the best regression equations with the meteorological records since 1938.
A Stochastic Model of Atmospheric Rime Icing
Authors: Gates E.M. , Liu A. , Lozowski E.P. 
Published: September 2017

AbstractThe accumulation of rime ice on structures, due to the impact and freezing of small water droplets, has been modelled as a stochastic process. Individual droplets are introduced into the flow field about the structure at a random position. Their trajectories are then calculated to determine the position of impact on the structure, or on previously impacted droplets. By assuming that the droplets maintain their shape on impact, the modelled accretion is gradually built up, one droplet at a time.In the present paper, attention has been limited to a circular cylinder as the collecting structure, and it has been assumed that the flow field and the ice accumulation are strictly two-dimensional. With these assumptions, the influence of the droplet/cylinder diameter ratio and of the air speed upon the resulting predictions has been investigated. The main feature of interest in the model prediction is the development, near the edges of the accumulation, of discrete structures called “rime feathers”. The mechanism for the growth of these rime feathers is described, and a comparison is made between the characteristics of the predicted structures and of some natural rime feathers grown in an icing wind tunnel.
Ice-shelf Response to Ice-stream Discharge Fluctuations: II. Ideal Rectangular Ice Shelf
Authors: Macayeal Douglas R. , Lange Manfred A. 
Published: September 2017

AbstractAbstract. Ice-shelf thickness and velocity anomalies resulting from ice-stream discharge fluctuations are calculated for an ideal ice shelf fed by a single ice stream and confined within a rectangular coastal geometry. Ice-shelf response to periodic forcing is found to be linear (thickness and velocity anomalies oscillate at the forcing frequency, and response scales with the forcing). Thickness anomalies are trapped near the ice-stream outlet and propagate down-stream at a slow, advective time-scale. Velocity anomalies tend to be widespread and propagate instantaneously throughout the ice-shelf environment. Ice-shelf response is sensitive to ice-stream fluctuation time-scale in the manner of a low-pass filter; longer forcing time-scales produce more widespread ice-shelf response. If ice-stream velocity and thickness fluctuations are in phase, thickness-anomaly maxima typically occur down-stream of the ice-stream outlet. This effect may determine where ice rumples and rises are likely to form in response to stochastic ice-stream variability.
Apron Entrainment at the Margins of Sub-Polar Glaciers, North-West Ellesmere Island, Canadian High Arctic
Authors: Evans David J.A. 
Published: September 2017

AbstractFrom observations on the sub-polar glaciers of Phillips Inlet, north-west Ellesmere Island, neither complex basal thermal regimes nor internal thrusting need be invoked to explain all types of debris distribution in the basal ice of sub-polar glaciers. Debris is present in the terminal ice cliffs as: (1) debris-poor folia expressing internal flow patterns; (2) debris-rich bands of various thickness; and (3) augens or clots. Debris-rich bands and augens are concentrated predominantly in the basal ice, contain a wide range of grain-sizes, cut across debris-poor folia, rarely extend >1 m laterally, and are irregularly spaced.Observations on patterns of entrainment and contemporary processes at ice margins, together with clast-shape analyses, suggest that the recycling and re-incorporation of fluvial/deltaic sediment, aprons, and pro-glacially thrusted blocks at the ice face are an alternative process of debris entrainment to basal plucking and large-scale freeze-on at the base of the glacier. The most active processes observed at the glacier margins are fluvial, and the origins of some debris-rich bands and augens are linked to thermal-erosional niches and abandoned meanders in the base of the glacier cliff face. Because the large-scale accumulation of ice-cored debris at glacier snouts represents periods of increased run-off and snout recession (specifically during the early Holocene), basal and englacial debris concentrations resulting from glacial over-riding and re-incorporation have great palaeoclimatic significance.
An Energy and Mass Model of Snow Cover Suitable for Operational Avalanche Forecasting
Authors: Brun E. , Martin Ε. , Simon V. , Gendre C. , Coleou C. 
Published: September 2017

AbstractA numerical model has been developed to simulate energy and mass evolution of snow cover at a given location, as a function of meteorological conditions: precipitation, air temperature, humidity, wind velocity, and incoming short-wave and long-wave radiation.This model, named CROCUS, was first tested on a well-instrumented field during a whole winter, showing its ability to simulate the important phenomena affecting the evolution of the snow layers: high temperature gradients, wetting, compaction, and melting-freezing cycles. A second test was conducted at two locations in the French network used for operational avalanche forecasting. Though the weather observations are made there only twice daily, the snow profiles calculated by the model were very close to those obtained once a week by a pit observation. CROCUS proved itself sufficient to be considered now as a useful objective tool for operational avalanche forecasting.
Mass-Balance Gradients and Climatic Change
Authors: Oerlemans J. , Hoogendoorn N.C. 
Published: September 2017

AbstractIt is generally assumed that the mass-balance gradient on glaciers is more or less conserved under climatic change. In studies of the dynamic response of glaciers to climatic change, one of the following assumptions is normally made: (i) the mass-balance perturbation is independent of altitude or (ii) the mass-balance profile does not change — it simply shifts up and down. Observational evidence for such an approach is not convincing; on some glaciers the inter-annual changes in mass balance seem to be independent of altitude, on others not at all. Moreover, it is questionable whether inter-annual variation can be “projected“ on different climatic states.To see what a physical approach might contribute, we developed an altitude-dependent mass-balance model. It is based on the energy balance of the ice/snow surface, where precipitation is included in a parameterized form and numerical integrations are done through an entire balance year (with a 30 min time step). Atmospheric temperature, snowfall, and atmospheric transmissivity for solar radiation are all dependent on altitude, so a mass-balance profile can be calculated. Slope and exposure of the ice/snow surface are taken into account (and the effects of these parameters studied). In general, the calculations were done for 100m elevation intervals.Climatological data from the Sonnblick Observatory (Austria; 3106 m a.s.l.) and from Vent (2000 m a.s.l.; Oetztal Alps, Austria) served as input for a number of runs. Simulation of the mass-balance profiles for Hinterseisferner (north-easterly exposure) and Kesselwandferner (south-easterly exposure) yields reasonable results. The larger balance gradient on Kesselwandferner is produced by the model, so exposure appears to be an important factor here.Sensitivity of mass-balance profiles to shading effects, different slope, and exposure are systematically studied. Another section deals with the sensitivity to climatic change. Perturbations of air temperature, cloudiness, albedo, and precipitation are imposed to see their effects on the mass-balance profiles. The results clearly show that, in general, mass-balance perturbations depend strongly on altitude. They generally increase down-glacier, and are not always symmetric about the reference state.For typical climatic conditions in the Alps, we found that a 1 K temperature change leads to a change in equilibrium-line altitude of 130 m. Three factors contribute to this large value; turbulent heat flux, longwave radiation from the atmosphere, and fraction of precipitation falling as snow. Here, the albedo feed-back increases the sensitivity in a significant way.
Early Discoverers XXXVI: W.J. McGee On Glacial Erosion Laws and the Development of Glacial Valleys
Authors: Harbor Jonathan M. 
Published: September 2017

AbstractIn work presented in 1883 and published in full in 1894, W.J. McGee made one of the first clear attempts to outline the main morphologic differences between glaciated valleys and valleys developed by processes dominant in more temperate areas. Moreover, with an unprecedented analysis of glacial erosion, he attempted for the first time to explain the evolution of glacial land forms in terms of theoretical predictions of patterns of erosion under valley glaciers. In the latter half of the nineteenth century, there was fierce debate over whether glaciers were even capable of significant erosion, so it is perhaps not surprising that McGee’s analysis of glacial erosion processes and land-form development received little attention in his own time. Despite this, McGee’s work provided some of the first really convincing glacial explanations for the development of land forms such as hanging valleys and U-shaped valleys, and these were developed more fully in later work by Davis (1900) and Gilbert (1903). In modern research, the use of theoretical erosion laws and a knowledge of ice dynamics to develop models of land-form development is emerging as a major theme in glacial geomorphology, marking a return to the methodology pioneered by W.J. McGee.
Field Techniques for Experimental Stress Analysis in Arctic Sea Ice
Authors: Cochran G. V. B. 
Published: September 2017

AbstractIncreasing interest is being directed toward studies involving measurement of strain and strain-rates in sea and glacier ice. A number of techniques for obtaining these data over gauge lengths ranging from 1 m to several kilometers have been reported, but there has been little experience with shorter lengths. Use of commercially available electrical resistance strain-gauges (length 5–20 cm) intended for embedment in concrete offers a new approach in which multiple gauge, two- and three-dimensional arrays can be installed in ice with minimum effort and monitored with portable equipment. This report describes a pilot study designed to demonstrate the use of three types of electrical resistance strain gauges in sea ice under exposed field conditions. Results include detection of variations in strain fields related to tidal currents.
Simultaneous Measurements of Stability Indices and Characteristic Parameters Describing the Snow Cover and the Weather in Fracture Zones of Avalanches
Authors: Gubler H. 
Published: September 2017

AbstractStability indices at different slope aspects and characteristic parameters describing the snow cover and the weather conditions are recorded simultaneously and automatically in potential fracture zones of avalanches during the whole winter season. A remote, solar-powered system including measurements of snow depth, mass flux of wind-blown snow and of the snow temperature profile as well as on-line and off-line data processing has been developed and tested. The results show that this type of data-recording and processing system makes quantitative case studies of natural stability variations possible.
Calculations of Avalanche Friction Coefficients from Field Data
Authors: Martinelli M. , Lang T. E. , Mears A. I. 
Published: September 2017

AbstractThe friction coefficients needed to solve Voellmy’s avalanche-dynamics equations and as input to the numerical, finite-difference computer program AVALNCH are calculated from case studies. The following coefficients of internal frictionvand of surface frictionfworked well for program AVALNCH: for midwinter dry snowv =0.5 to 0.55 m2/s andf= 0.5 to 0.55; for hard slabv =0.7 to 0.8 m2/s andf =0.7 to 0.8; for fresh, soft slabv= 0.4 to 0.5 m2/s and f = 0.4 to 0.5. The program predicted run-out distance well for a variety of conditions but performed less well in cases of sharp, adverse grade in the run-out zone. For the Voellmy approach, large design-size avalanches required turbulent friction coefficients ξ of 1200 to 1600 m/s2and kinetic friction coefficients of 0.15. Two hard-slab avalanches, a slow-moving,wet-slab avalanche, and a soft-slab avalanche that ran through scattered mature timber required ξ of 700 to800 m/s2and μ of 5/V whenVis velocity in m/s. The coefficient of sliding friction for a hard-slab avalanchethat encountered damp snow in the run-out zone was computed directly from movies to be 0.35, 0.43, and 0.32 for three measured sections of the run-out zone.
Observed Maximum Run-Out Distance of Snow Avalanches and the Determination of the Friction Coefficients µ and ξ
Authors: Buser Othmar , Frutiger Hans 
Published: September 2017

AbstractTo fix the limits of different hazards in the avalanche-hazard maps one uses criteria pertaining to avalanche dynamics. These criteria are at present the velocity and the run-out distance of a given avalanche for a given place. In 1955 A. Voellmy published his theory of avalanche dynamics which has widely been used in practical map preparation. Since 1962 his equations have also been used by the Eidg. Institut für Schnee- und Lawinenforschung (EISLF) to calculate avalanche pressures and run-out distances. Furthermore B. Salm (EISLF) developed another equation for the calculation of run-out distances in 1978. Both the equations of Voellmy and of Salm contain two friction coefficients, µ and ξ. Little is known about them and opinions, even among specialists, differ on what values should be given to them.This paper presents field observations on very long run-out distances. These observations are used to calculate values for pairs of µ and ξ. For avalanche zoning, only extreme values are of interest, i.e. very low values for µ and very high values for ξ. For the calibration of those coefficients, ten avalanches from the winters 1915–16, 1967–68, 1974–75, and 1977–78 have been used. Those avalanches occurred during heavy and intense snowfalls. For those avalanches, the pair µ= 0.155, ξ = 1 120 m/s2 was found for the Voellmy equation and the pair µ = 0.157, ξ =1 067 m/s2 for the Salm equation. These values only partially agree with those used up to date by EISLF. It is recommended for example that for extreme flowing avalanches (newly fallen snow, soft slabs) the pair µ = 0.16,ξ = 1 360 m/s2 be used.
Modeling of Snow flow
Authors: Dent J. D. , Lang T. E. 
Published: September 2017

AbstractA numerical computer model, based on the finite differencing of the Navier-Stokes fluid equations, is used to simulate snow-avalanche flow. In order to verify and calibrate the numerical model, snow-flow tests 0.20 m deep with flow velocities between 0-18 m/s were conducted. Data concerning position, velocity, and flow depth versus time were collected and compared to model runs on the computer. The frictional force on moving snow is investigated and found to be modeled by a term that is proportional to the square of the flow velocity.
Scale Modeling of Snow–Avalanche Impact on Structures
Authors: Lang T. E. , Dent J.D. 
Published: September 2017

AbstractSmall–scale modeling of flow and impact of snow avalanches is demonstrated to be both feasible and accurate. Geometric, kinematic, and force variables are scaled correctly under equivalence of Froude number between prototype and model using sifted snow as the model fluid. Physical and computer–simulated impact processes show correspondence, so that computer modeling is demonstrated to be a viable tool in flow and impact predictions.
A Model For Snow-Slab Failure Under Conditions Of Dynamic Loading
Authors: Johnson Jerome B. 
Published: September 2017

AbstractA stress-wave model is used to describe snow-slab failure under dynamic loading conditions. This model indicates that dilational waves and shear waves can interact with a thin, weak bedding layer underlying a snow slab causing dilatational and shear stresses in the layer. The magnitude and distribution of stresses in the layer are shown to depend strongly on the height of the loading source above the bedding plane, the difference in impedance between the slab and the loading source, the difference in impedance between the slab and its substratum, and the initial stress magnitude of the loading source. Failure occurs in the bedding layer when the generated stresses exceed the strength of the layer. This causes a loss of shear strength capacity at the bedding plane and a re-distribution of stress in the slab. If the shear capacity is reduced sufficiently the body-force loading of the slab will cause snow-slab failure.
An Experimental Study of Temperature-Gradient Metamorphism
Authors: Marbouty D. 
Published: September 2017

AbstractThe present study was carried out with a view to quantifying the effects of the main parameters ot temperature-gradient metamorphism. Cold-room simulation tests showed crystal growth to be an increasing function of the temperature-gradient modulus with a lower limit of around 0.25 deg/cm. This growth also proved to be a function of temperature itself reaching a maximum at around –5°C Furthermore the shape of depth-hoar crystals was also shown to depend on temperature and to resemble approximately that obtained when crystals are formed in the atmosphere. Temperature-gradient metamorphism is observed to take place at constant density. Increase in crystal size is a decreasing function of density with a lower limit of around 150 kg/m3, below which destructive metamorphism occurs accompanied by packing (similar to ET metamorphism): the upper limit is situated at approximately 350 kg/m3 and no depth-hoar crystals occur above this value. The series of Cold-room simulations enabled a highly simplified model of crystal growth to be constructed.
Municipal Avalanche Zoning: Contrasting Policies of Four Western United States Communities
Authors: Mears Arthur I. 
Published: September 2017

AbstractFour communities in the western United States (Vail, Colorado; Ketchum, Idaho; Ophir, Colorado; and Juneau, Alaska) have detailed avalanche–hazard mapping available. In response to this detailed information, Vail restricts building in a red (high hazard) zone but permits specially designed buildings in the blue (moderate hazard) zone. Ketchum allows single–family dwellings in red or blue zones regardless of design but will not permit such structures to be rented from the period 15 November through 15 April of each year. Multi–family dwellings in Ketchum hazard zones must be designed for avalanche forces. Ophir will restrict buildings from the red zone and permit specially designed structures in the blue zone. Juneau does not restrict development in any avalanche–hazard zone.
Research on Prevention of Snow-drifts by Blower Fences
Authors: Zhonglong Wang , Yuan Chen 
Published: September 2017

AbstractThe mechanism by which blower fences can protect roads from snow-drifts is investigated, and the variation of the drift-free width behind a blower fence with the dimensions and inclination of the fence and with terrain features has been determined. The results are presented in the form of an equation and a nomogram to help in the design of blower fences.