bluuebunny/crossref_metadata_2025_split huggingface dataset:
Annual Moraine Ridges at Skàlafellsjökull, South-East Iceland
Authors: Sharp Martin 
Published: September 2017

AbstractMoraine ridges have formed annually at Skálafellsjökull, south-east Iceland since about A.D. 1912. These ridges are asymmetrical with a steeper distal slope, and their surface morphology reflects their internal structure. Most ridges are formed at the glacier margin, and they form a series of concentric arcs about it. Their plan form reflects small details of the ice-front morphology. Some ridges are composed of boulders released from the ice by ablation and swept together by glacier re-advances, but most have a core of deformed till. Those which were ice-cored have a surface veneer of resedimented debris consisting of ice-slope colluvium and sediment-flow deposits. Lodgement tills at Skálafellsjökull have a two-layer structure, with a weak upper horizon apparently formed by dilation during subglacial shearing of the till. Ridges are composed of this sheared material and overlie undisturbed lodgement till at depth. Subglacial shearing results in a discharge of till towards the glacier margin and its accumulation there when glacier retreat ceases in winter. Till may also be extruded from beneath ice at the margin as a result of loading by the ice, and subsequently bulldozed into a ridge by a winter readvance of the glacier.
Stable Isotope Analysis of a Submarine Ice Cliff at Explorers Cove, McMurdo Sound, Antarctica
Authors: Stockton William L. , DeLaca Ted E. , Deniro Michael J. 
Published: September 2017

AbstractStable isotope ratios and salinities of ice samples obtained from a submarine ice cliff at Explorers Cove demonstrate that the upper parts of the ice cliff have frozen directly from sea-water and are an underwater expression of permafrost, whereas the lower parts appear to be partially glacial in origin. These results indicate that there may be ice cores in the moraines of Explorers Cove, in which case the coastline of McMurdo Sound is more extensively ice-cored than previously known.
Mass Balance and Thermal Regime of Laika Ice Cap, Coburg Island, N.W.T., Canada
Authors: Blatter Heinz , Kappenberger Giovanni 
Published: September 2017

AbstractDuring the North Water Project of the late F. Müller, glaciological studies were carried out on Laika ice cap. In addition to the main climatological investigations, surveying, mapping, mass-balance studies, and englacial temperature measurements were carried out. The mass-balance distribution is strongly determined by the orography. Strong westerly winds erode and transport snow from exposed surfaces, whereas prevailing easterly winds, during precipitation, deposit snow on lee slopes. The balance is negative under the present climate. The history of the glacier-tongue geometry is reconstructed using geomorphological observations and photogrammetric mapping for 1959 and 1971. Englacial temperature measurements revealed a finite layer of temperate basal ice in the ablation zone. The temperature distribution in the accumulation area around the summit of the ice cap is not stationary.
The Topography and Surface Characteristics of the Larsen Ice Shelf, Antarctica, Using Satellite Altimetry
Authors: Ridley Jeff , Cudlip Wyn , McIntyre Neil , Rapley Chris 
Published: September 2017

AbstractA comprehensive survey of the Larsen Ice Shelf has been conducted using precise orbit and retracked Seasat radar-altimeter data with editing of erroneous values resulting from intrumental artefacts. Contour maps of elevation and radar back-scatter (with absolute accuracies of 1 m and 2 dB, respectively) have been produced and it has also been possible to map rifts, grounding points, rough terrain, and about 30% of the ice shelf’s seaward margin. Ice thicknesses derived from these elevation data show broad agreement with those derived from previous airborne radio-echo surveys. The maps of parameters measured by Seasat represent a very substantial improvement over those previously available. They thus provide a reference against which comparison may be made with a view to detecting substantial climatic changes. This is of particular interest since, as the most northerly major ice shelf in Antarctica, the Larsen Ice Shelf may be more sensitive than others to global climatic trends.
Time–Scale for Adjustment of Glaciers to Changes in Mass Balance
Authors: Jóhannesson Tómas , Raymond Charles , Waddington Ed 
Published: September 2017

AbstractThe length of time TMover which a glacier responds to a prior change in climate is investigated with reference to the linearized theory of kinematic waves and to results from numerical models. We show the following: TMmay in general be estimated by a volume time-scale describing the time required for a step change in mass balance to supply the volume difference between the initial and final steady states. The factorfin the classical estimate of τM=ƒl/u, whereIis glacier length anduis terminus velocity, has a simple geometrical interpretation. Ft is the ratio of thickness change averaged over the full lengthIto the change at the terminus. Although bothuandfrelate to dynamic processes local to the terminus zone, the ratiof/uand, therefore, Tmare insensitive to details of the terminus dynamics, in contrast to conclusions derived from some simplified kinematic wave models. A more robust estimate of Tmindependent of terminus dynamics is given by TM=h/(–b)wherehis a thickness scale for the glacier and–bis the mass-balance rate (negative) at the terminus. We suggest that Tmfor mountain glaciers can be substantially less than the 1O2–103years commonly considered to be theoretically expected.
On the Development of Transverse Ridges on Rock Glaciers
Authors: Loewenherz Deborah S. , Lawrence Christopher J. , Weaver Richard L. 
Published: September 2017

AbstractThe stability of a low Reynolds number flow on an inclined plane is investigated with respect to modelling the initiation of transverse wave-like ridges which commonly occur on the surfaces of rock-glacier forms. In accordance with field observations indicating the presence of stratification in rock glaciers, two models of rock-glacier structure are considered, each stratified and possessing a lower layer which is treated as a Newtonian fluid. An upper, less compliant layer is treated, alternatively, as a Newtonian fluid of viscosity greater than that of the lower layer, or as an elastic solid under longitudinal compression induced by a decrease in the slope of the underlying incline. A linear stability analysis is used to examine the behaviour of each of the proposed models, and both are found to generate instabilities at wavelengths comparable to those associated with transverse surficial ridges on rock glaciers. The growth rates of a flow disturbance predicted by the viscous-stratified model appear to be too slow to account fully for the development of wave forms of finite amplitude, suggesting that other mechanisms are involved in the amplification of an initial disturbance. The results of the stability analysis of the elastic lamina model indicate that finite surficial ridges may develop on rock glaciers as a product of a buckling instability in the surface region if there is a decrease in the slope of the underlying incline. Both of the analyses illustrate that transverse ridges can occur on the surface of a rock glacier in the absence of any variations in debris supply to the system. The results further imply that the use of these features in the paleoreconstruction of Holocene climatic conditions must entail an assessment of the relative roles of external climatically driven forcing versus internal Theologically derived instability.
Airborne UHF Radio Echo-Sounding of Three Yukon Glaciers
Authors: Narod B. B , Clarke G. K. C. 
Published: September 2017

AbstractA high-resolution radio echo-sounder operating at a frequency of 840 MHz has been developed for airborne sounding of small and medium-sized polar glaciers and ice caps. The sounder uses a compact,, high-gain antenna which suppresses valley-wall echoes and simplifies operation from light aircraft, Successful field trials were carried out on Rusty, Trapridge, and Hazard Glaciers, Yukon Territory, Canada. Results compare well with ice depths obtained from earlier ground-based soundings on Rusty and Trapridge Glaciers. The maximum ice thickness encountered was 200 m on Hazard Glacier.Owing to the high operating frequency, random scattering from inhomogeneities within the ice is a major cause of signal degradation. For this reason the sounder cannot penetrate great thicknesses of temperate or debris-rich ice. Spatial averaging, an immediate result of operating from a moving platform, reduces the effects of back-scattered “clutter”.
Nivation: An Arctic-Alpine Comparison and Reappraisal
Authors: Thorn Colin E. , Hall Kevin 
Published: September 2017

AbstractNivation is a collective noun identifying a set of geomorphic processes, comprised of an indeterminate number of elements and of unknown relative importance, for which there is little likelihood of ever producing a precise definition. Instead, attention should first be directed towards the relationships between snow-packs and individual geomorphic processes. The relationship between freezing amplitude in the bedrock, snow cover, and aspect at an Arctic site in northern Norway and an alpine site in the Front Range, Colorado, U.S.A. is complex. Comparison of field data and laboratory criteria permit several conflicting interpretations. If oscillations across 0°C, regardless of freezing amplitude, are critical, the alpine site is potentially a more active freeze-thaw weathering regime, with a primary springtime peak and a secondary fall peak. If a freezing amplitude of –5°C is required for effective freeze-thaw weathering then the alpine site is largely inactive and the Arctic active (but with only a single fall peak). Chemical weathering is much more important at snow-patch sites than has traditionally been recognized. Mass wasting at colluvial sites subject to snow patches is dominated by interaction between overland flow and solifluction when the site is unvegetated, and by solifluction when it is vegetated. Given contemporary knowledge of snow and glacial geomorphology, there appears to be no threshold, only differences of intensity. Resolution of the disruptive mechanism associated with bedrock freezing and its constraining temperature and moisture requirements is the most pressing present problem in the field of snow geomorphology.
Does the Permanent Creep-Rate of Polycrystalline Ice Increase with Crystal Size?
Authors: Duval Paul , Gac Hugues Le 
Published: September 2017

AbstractUniaxial compression creep tests were performed on artificial and natural polycrystalline ices at temperatures near –7°C. The grain-size range investigated was from 1 to 10 mm. Contrary to previous results, the permanent creep-rate was not found to increase with crystal size. Only the transient creep appears to be sensitive to variations in crystal size.
Elastic Constants of Ice by Brillouin Spectroscopy
Authors: Gammon P. H. , Kiefte H. , Clouter M. J. 
Published: September 2017

AbstractBrillouin spectroscopy has been used to measure the adiabatic elastic constants of laboratory-grown pure monocrystalline ice Ih at – 3°C. The values obtained were (in units of 108 N/m2): c11 = 136.96 ±0.60, c12 = 69.66± 0.45, c13 = 56.28±0.31, c33 = 147.02±0.68, c44 = 29.59±0.15. Comparison of these values with ultrasonic measurements quoted in the literature reveals no significant acoustic dispersion in ice over frequencies ranging to 1010 Hz. However, the results suggest that the elastic constants of ice may depend on the precise crystal quality and age of a given sample. The low experimental error in the values obtained, along with the inherent versatility of the method, indicate that Brillouin spectroscopy is an effective technique for systematically investigating the elastic properties of ice samples formed under natural conditions.
The University Course in Snow Dynamics —A Stepping-Stone to Career Interests in Avalanche Hazards
Authors: Montagne John 
Published: September 2017

AbstractThe principles of snow dynamics, including practical field work, constitute a feasible university-level course where seasonal snowfall and terrane of varying steepness are accessible. Two to three lectures or discussions per week are combined with one full afternoon in the field to provide a workable course format. We have successfully used the U.S. Department of Agriculture Forest Service Agriculture Handbook 489 (Avalanche handbook) as a text but also assign readings in diverse world literature.Field work has centered on standard techniques for snow study in a realistic alpine setting but could easily be adapted to more simple “roadside” conditions if necessary. Student interest during and following the course usually leads to spontaneous and practical research that tends to develop life-long skill and application in the subject.Our experience indicates that one instructor can manage a maximum of 25 students in the field, considering proper logistics, safety, and necessary adaptibility of field procedures to changing weather conditions.
Snow Stratigraphy and Water Equivalence Measured With an Active Microwave System
Authors: Ellerbruch D. A. , Boyne H. S. 
Published: September 2017

AbstractThis paper reports on research on the relationship between the electromagnetic scattering properties and physical properties of snow-pack. An FM-CW active microwave radar system operating in the frequency range 8-12 GHz is used to scatter electromagnetic radiation from surface and subsurface stratigraphic layers in the snow-pack. The amplitude of the scattered radiation as a function of depth in the snow-pack can be correlated with such physical characteristics as density, hardness, stratigraphy, and moisture content. A direct determination of snow-pack water equivalence can be made from these observations.
Propagation of Stress Waves in Alpine Snow
Authors: Brown R. L. 
Published: September 2017

AbstractThe propagation of pressure waves in low-density snow is investigated analytically to determine the variation of wave pressure and wave speed with density and frequency. The results show that, for pressure waves that produce finite volumetric deformations, both pressure jump across the wave and wave-speed increase with initial density and final density. The pressure jump was also found to increase with the wave frequency if other parameters were held constant, although the dependence on frequency is not as strong as the dependence on the initial and final densities. The relationship between pressure jump and frequency implies that high-frequency waves would tend to dissipate more quickly than lower-frequency waves, although like pressure, the attenuation rate would not be strongly frequency dependent.
Tensile strain and fracture of snow
Authors: Watanabe Zempachi 
Published: September 2017

AbstractMeasurements over several hours of the tensile strain of snow have been carried out, and the strain-rate e can be expressed in terms of stress σ, elapsed time t, and (Celsius) snow temperature T as . It is evident from this expression that a creep fracture does not happen without either an increase of stress or a rise of temperature. We observed the phenomenon of creep fracture of snow by these two methods.
History and Actual State of Legalization of Avalanche Zoning in Switzerland
Authors: Frutiger Hans 
Published: September 2017

AbstractTourism in the Swiss Alpine region has developed rapidly in the last 20 years. Many new routes transport systems, and tourist resorts have appeared for which the planning and construction have inadequately considered the avalanche danger. The local authorities are responsible for the safety and welfare of the inhabitants and visitors. This is especially true with respect to land-use control and the issue of building permits. Since property values have risen considerably since the second World War, speculation in land that is not safe from hazard has become widespread. This speculation has led to numerous conflicts between property owners and the municipal government as well as between sellers and buyers of land which is later found to have an avalanche hazard. In Swiss law a legal basis is required to prohibit building in unsafe places. This basis did not exist in many Swiss cantons when these fateful developments began. This study will show how the legal basis for avalanche zoning has been developed at the federal, cantonal and communal levels and what the actual state of jurisdiction is. Of special interest are the “precedents” or “case law” which are presented and discussed in this paper. It also gives definitions of the terms “zone”, “avalanche zoning”, “avalanche hazard map”, and “avalanche zone plan”.
Natural-Hazard Maps for Land-Use Planning in Norway
Authors: Hestnes E. , Lied K. 
Published: September 2017

AbstractProblems concerning natural-hazard mapping have been discussed by the Norges Geotekniske Institutt in pilot projects sponsored by the National Fund for Natural Disaster Assistance. Hazard-registration maps, geomorphic hazard maps and hazard-zoning maps are defined. Hazard-zoning maps are preferable in land-use planning. Both survey maps (1 : 50000) and detailed maps (1:5000) are of interest. A survey map (c. 600 km2) would be mainly based on airphoto interpretation and could be prepared in about 150 h. Detailed mapping is more time consuming and should be limited to development areas. Mapping of “marine deposits” and “other areas” are handled by separate groups, mainly because of differences in technical and professional problems. This gives rise to two parallel series of survey maps and detailed maps.The proposed programmes for survey mapping states that 80% of the marine areas should be evaluated in 5 years (1980-84), and that one-third of the country should be examined for rockfalls, rock slides, and snow avalanches in 10 years. Other hazard types are impossible to identify by survey mapping. There is a rising demand for detailed maps but as yet there has been no research project to standardize methods.The hazard maps are intended primarily to be an aid in land-use planning.
Vertical profile and Horizontal Increase of Drift-Snow Transport
Authors: Takeuchi Masao 
Published: September 2017

AbstractThere are a number of published empirical formulae for drift-snow transport as a function of wind velocity. Comparing these formulae at the same wind velocity, however, results in considerable disagreement. It is hypothesized that the disparity arises from snow conditions and the various stages of development of drifting snow.The horizontal distribution of drift flux was measured with snow traps along a transect parallel with the wind, beginning at an up-wind boundary that served as the starting point of drifting snow. Results indicate that drift-snow transport cannot be defined uniquely unless the drifting snow attains equilibrium (i.e. the snow profile is saturated).Saltation of snow particles is thought to prevail near the snow surface. However, the vertical flux profile of saltating snow has never been measured. Vertical profiles of drift flux from the snow surface to a height of 30 cm were measured at nine levels, using snow traps composed of nine streamers (compartments). It appears that the saltation flux prevails up to a height of 7-9 cm above the surface, and the suspension flux gradually takes over as the drifting snow develops.
Constant Strain-Rate Tensile Testing of Natural Snow
Authors: Singh H. , Smith F.W. 
Published: September 2017

AbstractIn conducting tension and compression tests on snow samples, strains and strain-rates are usually determined from the displacements of the ends of the samples. In this work, a strain-gage which mounts directly onto the snow sample during testing, was developed and was found to give accurate and direct measurements of strain and strain-rates.A commercially available 0-28 pF variable capacitor was modified to perform the required strain measurements. It is a polished metallic plunger sliding inside a metal-coated glass tube. The plunger and tube were each soldered to the end of a spring-steel wire arm. To the other end of these arms were soldered to 10 mm square pads made of thin brass shim stock. The whole device weighs 2.5 g and the low coefficient of friction in the capacitor resulted in a very low actuation force. To mount the strain gage, the pads are wetted and frozen onto the snow sample.A high degree of sensitivity was achieved through the use of “phase-lock-loop” electronic circuitry. The capacitance change caused by the strain in the sample, changes the frequency of output signal from an oscillator and thus causes the change in output from the system. In the locked state, to which the system is constantly driven by a feed-back loop, the system output is almost ripple free.The strain gages were calibrated in the field in order to take into account the effects of very low field temperatures. The calibration curves were almost linear over the travel of 15 mm, the maximum limit. The sensitivity of the system is 4 mV per strain unit, but this could be increased by an order of magnitude by minor adjustments in the circuit.Constant strain-rate tensile tests were performed on natural snow at Berthoud Pass, Colorado, U.S.A., in the density range of 140-290 kg m-3. Four strain gages were mounted onto the samples to sense any non-uniform deformation which otherwise would have gone unnoticed or caused scatter in the data. The average indication of these gages was used to construct stress—strain curves for various types of snow at different strain-rates. The effect of strain-rate on the behavior of snow was studied.“Ratcheting” in the stress-strain curve in the region where the snow becomes plastic was observed first by Kinosita in his compression tests. A similar phenomenon was observed in these tension tests. It was found that directly measured strain is quite different from that which would be calculated from sample end movement. Strain softening was not observed in these tests up to total strains of 8%. The strain-rate effects found were comparable to the results of other investigators.
Monolithologic erosion of hard beds by temperate glaciers
Authors: Lliboutry Louis A. 
Published: September 2017

AbstractThe old problem of erosion by temperate glaciers is reviewed. We restrict ourselves to a monolithologic erosion of hard beds where chemical weathering is almost negligible. Rock fracture, either subglacial or otherwise, may have occurred during a previous cold episode, allowing long-lasting quarrying by the temperate glacier, but, once all the loosened material had been dragged away, grooving becomes the main erosional process. The theory of locally stress-controlled temperatures leads to the idea that very small particles found in the bottom ice cannot reach the bed. Therefore, abrasion and polishing come from rock chips due to grooving or sand grains freed by suglacial chemical weathering. In the steady regime, clasts that are able to groove come from the surrounding rock walls. Most of them do not enter the bergschrund, but are embedded in a bottom layer, which melts progressively over several kilometres. After being in contact with the bed over some distance, they are sufficiently blunted to become unable to groove. This distance. λ, increases with the boulder size, and the largest ones are not yet worn out at the glacier terminus. The mechanics of grooving is roughly modelled to estimate, for any stone size, the grooved volume per unit time and the grooving distance λ. From these estimations, and the size distribution, the erosion rate without quarrying as a function of the distance from the head wall, is calculated. It goes through a maximum when all the debris-laden bottom layer has just melted, and thus an overdeepening might form in a steady way. However, two unknown parameters enter the theory the probability ∏ for a stone able to groove which is in contact with the bed to groove and the ratio k of the volume of grooved rock before the stone is worn out to the volume of the stone. Experiments that may allow us to determine them are indicated below.