bluuebunny/crossref_metadata_2025_split huggingface dataset:
Interference Phenomena in Deformed Single Crystals of Ice
Authors: Readings G. J. , Bartlett J. T. 
Published: September 2017

AbstractWhen rectangular single crystals of ice were subjected to uniaxial compression parallel to their Long axes and viewed between crossed polarizers, interference fringes were often observed. Some of these interference bands were associated with grain boundaries formed as a result of “kinking”. These can be explained in terms of the known anisotropic optical properties of ice and the change in the orientation of the optic axis across the boundary. This case has been analysed in detail with the aid of Jones’ calculus and good quantitative agreement exists between the theory and the experimental observations.Other interference bands were observed parallel to the trace of the basal plane on the surface of some deformed crystals. Alternative hypotheses for the explanation of this phenomenon have been considered and it seems probable that these bands are a result of slight random misorientations between adjacent slip lamellae. Applying Jones’ calculus to a simple model of such a deformed crystal indicates that the required misorientations are of the order of 1º If this explanation is correct, it implies that dislocations with non-basal Burgers vectors (probably c[0001]) make an active contribution to the deformation.
Calculation of Grain-Boundary Thickness in Polycrystalline Ice of Low Salinity
Authors: Chatterjee Amiya K. , Jellinek H.H.G. 
Published: September 2017

AbstractGrain-boundary thickness in polycrystalline ice is a function of time (age), salinity, tempera-turf ·, and mode of sample preparation. It is directly proportional to the salinity of the ice and the number-average grain diameter (spheres) or edge-length (cubes). Practically the total salt content resides in the grain boundary for low salinity ice samples. The gram-boundary thickness S is also directly proportional to growth time of the grains raised to a power n(n = 0.25 to 0.3) and increases exponentially with absolute temperature for constant salinity and age. The energy of activation for growth increases with salinity. The results of the grain-boundary thickness calculations are useful for evaluating grain-boundary diffusion coefficients.
The Effect of Subglacial Chemical Processes on Glacier Sliding
Authors: Hallet Bernard 
Published: September 2017

Abstract
The glacier sliding theory of Nye is modified to include the effect of solutes in
subglacial regelation waters on the sliding process. Motivation for this development stems
from studies of subglacially formed chemical deposits that appear to be widespread on rock
surfaces recently exposed by retreating temperate glaciers. These deposits indicate clearly
that considerable local concentration of solutes commonly occurs subglacially as a result of
the selective rejection of solutes into the melt during the freezing associated with
regelation sliding. Because solutes accumulate where regelation waters refreeze, they tend to
lower the temperature there and hence inhibit the heat transport away from these areas that is
essential for regelation sliding. For a simple sinusoidal bed and solute distribution in the
regelation water film, the modified theory shows that a maximum excess of solutes of, for
example, several millimoles/1 of dissolved CaCO3 along lee surfaces
relative to stoss surfaces impedes basal sliding significantly, especially if the bed
roughness wavelength does not exceed about one meter.
A Concise Method for Analyzing the Ice-Melting Performance of a Heated Disc
Authors: Lea J.F. 
Published: September 2017

Abstract
Shreve (1962) evaluated the performance of solid-nose hotpoints of various geometries.
A more concise method for analysis of the special case of a flat disc melting into ice is
presented here. In contrast to the numerical solution presented by Shreve, this method results
in a closed analytical solution, based on constant properties, which is corrected using a
property ratio scheme. This technique allows the substitution of various fluid properties into
the solutions as might be required when considering contaminated or saline ice or other
liquids. Shreve's method would require some additional numerical work to evaluate various
properties because the temperature dependence of the viscosity of water is integrated into the
results.
Results obtained for the flat disc using this method are shown to compare favorably
with Shreve's, indicating that this type of analysis may be applicable to other melt-unit
geometries.
The Spatial Distribution of 10 m Temperatures in the Antarctic Peninsula
Authors: Martin P. J. , Peel D. A. 
Published: September 2017

AbstractTemperatures from 10 m bore holes have been analysed to determine the spatial variation of mean annual surface temperature over the Antarctic Peninsula. In general there is a decrease in temperature of 0.84 deg per degree latitude southwards combined with an altitude lapse rate of 0.68 deg per 100 m. There is a sharp divide between the continental type climate of the east coast and a maritime climate of the central and western regions. Temperatures are approximately 7 deg lower along the east coast compared with those at sites of a similar altitude and latitude on the west.
An Alternate Statistical Interpretation of the Strength Snow
Authors: Gubler H. 
Published: September 2017

AbstractThe basic features of the statistical models to describe brittle and ductile strength of snow are outlined and discussed. The concept of the "fundamental unit" is introduced. The models are applied to estimate the development of slab stability during heavy snowfalls and to simulate measurements of the tensile strength of snow using the centrifugal method as a function of the load rate. The models developed in this paper are compared with Sommerfeld’s applications of statistical methods to estimate the strength of snow in the starting zone of a slab avalanche.
Glacial Erosion by the Laurentide Ice Sheet
Authors: Sugden D. E. 
Published: September 2017

AbstractThe aim of the paper is to analyse landscapes of glacial erosion associated with the Laurentide ice sheet at its maximum and to relate them lo the three main variables affecting glacial erosion, namely former basal thermal regime of the ice sheet, the topography of the bed, and the geology of the bed. The key to the analysis is the comparison of the distribution of landscape types with the simulated pattern of the basal thermal regime of the former ice sheet.Landscapes of areal scouring are found to be associated with zones of basal melting and occur beneath much of the former ice-sheet centre and in those places where the topography favoured converging ice flow. The landscape type may also have formed beneath cold-based ice when it was carrying debris inherited from an up-stream zone of regelation. Areas with little or no sign of glacial erosion occur primarily in the north in the Queen Elizabeth Islands but they also occur on uplands associated with diverging ice flow; they coincide with areas calculated to have been covered by cold-based ice devoid of debris. Landscapes of selective linear erosion are common on uplands near the eastern periphery of the ice sheet. In these situations, pre-existing valleys channelled ice flow and created a situation where there was warm-based ice over the valleys and cold-based protective ice over the intervening plateaux. Variations in the permeability of the bedrock base have modified the landscape pattern, mainly in those areas where there was a change from one basal thermal regime to another. In general, permeable rocks tend to have experienced less erosion than impermeable rocks.Using lake-basin density as an indication of the intensity of glacial erosion, a zone of maximum erosion is identified and this forms a ring between the centre of the former ice sheet and its periphery. This ring coincides with a zone where melt water from the ice-sheet centre is calculated to have frozen on to the bottom of the ice sheet. This regelation incorporated basal debris into the ice, forming a basal layer 20-50 m thick and afforded an efficient means of debris evacuation.A conceptual model is developed and hangs round the following postulates:
(1)Landscapes of glacial erosion are related primarily to the basal thermal regime of the ice sheet.(2)Landscapes of glacial erosion are equilibrium forms related to maximum glacial conditions. This implies that at some stage in the Pleistocene the Laurentide ice sheet was in a stable maximum condition for a long period of time.(3)Mechanisms allowing evacuation of debris rather than those of abrasion or fracture may be the most important in influencing the amount of erosion achieved by an ice sheet.(4)Cold-based ice may accomplish erosion if it contains debris.
Application of Numerical Transient Fluid Dynamics to Snow Avalanche Flow. Part II. Avalanche Modeling and Parameter Error Evaluation
Authors: Lang T. E. , Martinelli M. 
Published: September 2017

AbstractUnder evaluation is the range of the parameters of internal viscosity and surface friction of flowing avalanches in order to represent the flow numerically by computer program AVALNCH. Nominal values of these parameters are determined to be in the range 0.4 to 0.6 for, snow flowing on snow, with values as high as 0.8 to 0.9 for snow flowing on rough ground. Using a nominal avalanche path, the basic parameters: (1) depth of initial release slab, (2) viscosity and friction, (3) adverse grade, and (4) flow spreading are determined to be in the order listed as regards their relative effect on avalanche runout distance. Program AVALNCH, which permits treatment of flow parameters separately from geometric parameters, provides a versatile tool for the prediction of avalanche runout, as well as for related studies of avalanche dynamics.
A Recommendation for the Application of the Roch Index for Slab Avalanche Release
Authors: Sommerfeld R. A. , King R. M. 
Published: September 2017

AbstractDetailed measurements on several avalanches verify that a Daniels’ (1945) type statistical correction to Roch’s (1966) stability index would accurately predict snow-slope instability. It is recommended that one-half the median of at least 50 shear-strength measurements be used as a measure of the strength of a weak layer.
Snow–Avalanche Impact on Structures
Authors: Lang Theodore E. , Brown Robert L. 
Published: September 2017

AbstractTwo–dimensional hydrodynamic equations for laminar, viscous flow, and admitting a frictional slip-plane lower boundary are applied to the modeling of snow-avalanche impact on rigid wall structures. Predicted maximum pressures and pressures versus time are compared with published experimental results, and general correspondence is established. Impact pressure versus time is found to depend upon the shape of the avalanche leading edge, for which general information is lacking. Computer modeling of more complex structural configurations is feasible using the methodology reported.
Instruments and Methods: Radio-Echo Equipment for Depth Sounding of Temperate Glaciers
Authors: Sverrisson Marteinn , Jóhannesson Ævar , Björnsson Helgi 
Published: September 2017

AbstractRadio echo-sounding equipment has been designed, and used for depth sounding on temperate glaciers in Iceland. Two devices have been built. Mark I operates in the frequency band 2 to 5 MHz. The overall range is 100 to 1000 m. The arrival of the echo can be timed with an accuracy which corresponds to 20 m resolution. The equipment has been used for routine soundings on Mýrdalsjökull and Vatnajökull for the last two years. Mark II operates at 2 to 10 MHz. The range is from 30 to 400 m and the range resolution is 8 m. The equipment has been used for successful soundings on valley glaciers.The power consumption of the whole system is 18 W plus 72 W for the oscilloscope (Tektronix Model 465). The voltage is supplied from 12 V car batteries. The total weight of the equipment is about 35 kg plus the weight of batteries. The antennae are contained in 16 mm plastic tubes. The equipment is placed on two sledges and towed behind a snowmobile or a skidoo. A continuous sounding record is photographed from the oscilloscope.
“Global Dynamics” of a Temperate Valley Glacier, Mer De Glace, and Past Velocities Deduced from Forbes’ Bands
Authors: Lliboutry Louis , Reynaud Louis 
Published: September 2017

AbstractTransverse profiles and velocities which have been measured on the ablation zone of Mer de Glace more or less continuously since 1891 contradict the Weertman–Nye theory of glacier kinematic waves. Faint broad waves, which undoubtedly result from fluctuations in the balance, travel down the glacier faster than this theory predicts. (This theory having first been completed by taking changes in width with time and with distance down the glacier into account.) On the other hand, velocity fluctuations are synchronous and more or less the same over the entire length studied (6 km).These discrepancies result from bottom friction being of the solid type, i.e. independent of sliding velocity. Friction should also be almost insensitive to discharge in subglacial waterways, since in the steady state energy for keeping them open, not entirely flooded, and at atmospheric pressure, is superabundant. The sliding velocities at all cross-profiles are thus controlled by some areas where the body of the glacier suffers strong deformation because the valley shape is far from cylindrical. One such controlling zone exists on Mer de Glace owing to the existence of a subglacial transverse shoulder. A new perturbation equation and a new rough expression for wave velocity are given.Intervals between Forbes’ bands were plotted on seven aerial surveys between 1939 and 1979. Progressive tilting of the slices of blue, dusty ice from the position from which these dark bands proceed and progressive lowering of their exposed edge must be taken into account. This analysis confirms the validity of our simple model for velocity fluctuations and allows us to estimate the entire series since the year 1888.
Mass Balance of “Vesper” Glacier, Washington, U.S.A.
Authors: Dethier David P. , Frederick Jan E. 
Published: September 2017

AbstractDuring 1974–75 glaciologic and geologic studies were conducted on a small (0.17 km2) avalanche-nourished glacier in the North Cascade Range of Washington. The approximate equilibrium-line altitude (ELA) for this ice body, informally called “Vesper” glacier, lies at 1475 m, some 300 m below the regional ELA value. Estimated annual accumulation was 6 100±675 mm during the two years of study; 15 to 30% of this flux resulted from avalanche and wind–transported snow. Average annual ablation during the period was 5 350 mm, giving a total net balance of + 1 600 mm for the two-year study period. “Vesper” glacier persists well below the regional snow-line because of excessive local precipitation, substantial avalanche contributions, and a favourable north-facing aspect.Neoglacial moraines indicate that maximum ELA lowering in this period was approximately 165 m and occurred prior to a.d. 1670. Minor re-advances occurred during the nineteenth century. These reconnaissance measurements are consistent with the sparse geologic data reported from other glaciers in the Cascade Range. While the relationship between regional lowering of snow-line and avalanche activity is uncertain at present, these data suggest that avalanche-nourished glaciers provide a useful record of climatic fluctuations.
A Method for Growing Large Single Crystals of Sea Ice
Authors: Kawamura Toshiyuki 
Published: September 2017

AbstractA simple technique is presented for growing large single crystals of sea ice. Using this technique, crystals with dimensions of 20 cm × 20 cm × 10 cm or more can be readily obtained within an orientational accuracy of 3°. Such crystals can then be used to investigate the physical properties of sea ice.
Thermo-mechanically coupled ice-sheet response — cold, polythermal, temperate
Authors: Hutter Kolumban 
Published: September 2017

AbstractClassical mixture concepts are the appropriate vehicle for describing the dynamics of ice masses containing some water. We review and derive, respectively, the theoretical formulations of cold, polythermal and temperate ice masses, emphasize the peculiarities of the model equations and point to difficulties that were encountered with the proposed models. The focus is both on the adequate physical motivation of the models and the consistency of their mathematical representation. The paper also has a tutorial character.As usual, cold ice is treated as a single-component incompressible heat-conducting viscous fluid, while two different models are presented for temperate ice. When it arises in a polythermal ice mass, the water content is small and a simple diffusive model for the moisture content suffices. This diffusive model is further simplified by taking its appropriate limit, when the moisture diffusivity tends to zero. Temperate ice in a wholly temperate — Alpine — glacier is treated as a two-phase flow problem, i.e. the momentum-balance laws of both constituents ice and water are properly accounted for. Such Darcy-type models are suggested because the water arises in a greater proportion; so its dynamic role can no longer be ignored.The constituent ice is treated as an incompressible non-linearly viscous isotropic body with constitutive properties similar to those of cold ice. The interstitial water is a density-preserving ideal or perfect fluid. The two interact with an interaction force that is proportional to the “porosity” and the seepage velocity. Internal melting that arises will lead to a generalization of the familiar Darcy law.When water is present, the boundary and transition conditions across internal singular surfaces take special, more complicated forms and involve statements on drainage to the base. These conditions are also discussed in detail.
Analysis of synthetic aperture radar Data collected over the southwestern Greenland ice sheet
Authors: Jezek K. C. , Drinkwater M. R. , Crawford J. P. , Bindschadler R. , Kwok R. 
Published: September 2017

AbstractAnalyses of the first aircraft multi-frequency, Polarimetric synthetic aperture radar (SAR) data acquired over the southwestern Greenland ice sheet are presented. Data were collected on 31 August 1989 by the Jet Propulsion Laboratory SAR using the NASA DC-8 aircraft. Along with curvilinear patterns associated with large-scale morphologic features such as crevasses, lakes and streams, frequency and polarization dependencies are observed in the P-, L-and C-band image products. Model calculations that include firn grain-size and volumetric water content suggest that tonal variations in and between the images are attributable to large-scale variations in the snow-and ice-surface characteristics, especially snow wetness. In particular, systematic trends in back-scatter strength observed at C-band across regions of changing snow wetness are suggestive of a capability to delineate boundaries between snow facies. Ice lenses and ice pipes are the speculated cause for similar trends in P-band back-scatter. Finally, comparison between SEASAT SAR data collected in 1978 and these airborne data collected in 1989 indicate a remarkable stability of surface patterns associated with the locations of supraglacial lake and stream systems.
Steady flow of a viscous ice stream across a no-slip/free-slip transition at the bed
Authors: Barcilon Victor , MacAyeal Douglas R. 
Published: September 2017

AbstractAn exact, analytic description of the steady, downhill flow of a viscous ice stream across a no-slip to free-slip transition in basal boundary condition suggests ways in which such transitions might be detected by observations of ice-stream surface properties. We find that the best expression of this transition is in the free-surface profile, which dips over the point of transition and becomes horizontal far downstream. The streamwise velocity at the surface shows a gradual change across the transition, and this is in disagreement with previous studies which suggest a marked change. Basal shear stress and basal pressure exhibit singularities at the point of transition. As concluded in previous study, the former singularity is a likely point of strong basal erosion. The latter singularity is problematical, however, because it violates the assumptions which make the exact solution possible. It is not clear how this problem can be overcome without appealing to thermodynamics, non-Newtonian material properties, cavitation or wake separation.
How many reservoirs? An analysis of flow recessions from a glacier basin
Authors: Gurnell Angela M. 
Published: September 2017

AbstractAnalysis of hydrograph-recession curves from temperate catchments has frequently been directed towards identifying a linear-storage element with mean residence time Κ which characterizes the delayed-flow component. This paper presents the results of applying such an analysis to recession curves from 11 years of discharge records from a glacier basin. Four reservoirs are identified but their estimated recession coefficients (K values) are found to vary with discharge and with time in the ablation season. This implies that the reservoirs are non-linear. Whilst it may be helpful for the interpretation of glacier-hydrological processes to identify several reservoirs, it appears that a single non-linear reservoir may provide an adequate representation of the glacier for operational forecasting purposes.
Niche Glaciers in Bünsow Land, Vestspitsbergen
Authors: Groom G. E. 
Published: September 2017

AbstractSmall glaciers lying in funnel-shaped hollows on steep slopes have been variously described as wall-sided glaciers, cascade glaciers, cliff glaciers and niche glaciers. This type of glacier and the landforms associated with them in Bünsow Land, central Vestspitsbergen are described and their possible mode of origin is discussed. The theory that they were formed by an overspill of plateau ice and that they are thereby genetically related to hanging glaciers is rejected. It is suggested that they are formed by an accumulation of snow in an initially water-worn gully and that as the small glacier develops the original form of the gully is modified by nivation to a rounded, funnel-shaped hollow. Niche glaciers may thus be considered as glacier types genetically related to cirque glaciers, forming an early stage in corrie development.
Errors in Ablation Measurements from Settlement and Sub-Surface Melting
Authors: LaChapelle E. 
Published: September 2017

AbstractBoth long and short-term snow ablation measurements usually contain errors when made with a simple ablation stake. Ablations measured over long periods for glacier regimen studies are subject to a settlement error in even dense snow, corrections for which may be made by simultaneous measurements with stakes of different lengths. For observation periods in the order of twenty-four hours or less, both mass loss and ice melt are often poorly represented by the simple product of mean bulk density and change in surface level. These quantities may be measured directly by successive determinations of bulk density and ice density profiles in the surface snow layer. Under certain favorable conditions, they may also be derived by observing directly the total and ice mass changes in a sampled area of the snow surface.