bluuebunny/crossref_metadata_2025_split huggingface dataset:
Avalanche Dynamics. Review of Experiments and Theoretical Models of Flow and Powder-Snow Avalanches
Authors: Scheiwiller Thomas , Hutter Kolumban 
Published: September 2017

AbstractThe paper of which this is an extended abstract reviews theoretical formulations for flow and airborne powder-snow avalanches. First powder-snow avalanches are considered as plane turbulent gravity currents. Then we propose a two-phase model describing powder-snow avalanches as turbulent binary mixtures of snow granules and air. An analogy is postulated between flow avalanches and the rapid shear flow of granular materials which leads to a non-polar continuum with microstructure taking into account the fluctuation energy of the snow granules.
Equations for Determining the Gas and Brine Volumes in Sea-Ice Samples
Authors: Cox G. F. N. , Weeks W. F. 
Published: September 2017

AbstractEquations are developed that can be used to determine the amount of gas present in sea ice from measurements of the bulk ice density, salinity, and temperature in the temperature range of −2 to −30 °C. Conversely these relationships can be used to give the density of sea ice as a function of its temperature and salinity, considering both the presence of gas and of solid salts in the ice. Equations are also given that allow the calculation of the gas and brine volumes in the ice at temperatures other than that at which the bulk density was determined.
On the Thermal Regime of an Arctic Valley Glacier: A Study of White Glacier, Axel Heiberg Island, N.W.T., Canada
Authors: Blatter Heinz 
Published: September 2017

AbstractFrom 1974 to 1981, a total of 32 bore holes was drilled on White Glacier and vertical ice-temperature profiles measured. The data obtained allowed the construction of three longitudinal and four transverse profiles of the two-dimensional temperature distributions. Thus, an extensive layer of temperate or near-temperate ice was discovered close to the bedrock in the lowest part of the glacier tongue. It was also found that the temperature distribution cannot be in a steady state, since there is a temperature minimum 100–150 m below the glacier surface in the accumulation area. A simple numerical model calculation shows that this minimum can be mostly explained by the general climatic warming since 1880. The 10 m temperatures show diffuse relations to climatic conditions and balance zones. A simple scheme for extrapolating “surface temperatures” is discussed.
Accumulation and Temperature Measurements on the James Ross Island Ice Cap, Antarctic Peninsula, Antarctica
Authors: Aristarain A.J. , Pinglot J.F , Pourchet M 
Published: September 2017

AbstractBasic glaciological measurements from the James Ross Island ice cap are presented, including mean annual accumulation and firn temperature. In addition to the well-known radioactivity levels of January 1955 and 1965 in Antarctic snow, two new radioactivity levels corresponding to January 1969 and January 1974 are used in determining the accumulation values. The measurements reveal certain climatic features of this ice cap.
Experiments on the Growth of Spongy Ice Near a Stagnant Point
Authors: Lock G.S.H. , Foster I.B. 
Published: September 2017

AbstractThe paper presents experimental observations on the growth of spongy ice in the vicinity of the forward stagnation point of a disc situated in a cross flow containing supercooled water droplets. Following some preliminary observations, the discussion focuses on two quantities: the ice fraction and the rate of growth of the accretion. The data presented reveal the effects of air speed, air temperature, liquid-water content, and salinity. They also suggest two morphological regimes: at higher air temperatures, the growth appeared to be crystalline columnar; at lower temperatures, smaller crystals appeared to be randomly distributed, producing a mushy accretion.
Ice-flow and mass changes of Lewis Glacier, Mount Kenya, East Africa, 1986–90: observations and modeling
Authors: Hastenrath Stefan 
Published: September 2017

AbstractThe long-term monitoring of Lewis Glacier on Mount Kenya serves as a basis for the study of glacier evolution in response to climatic forcing through modeling of its ice flow and mass budget. Following up on an earlier modeling and prediction study to 1990, this paper examines the ice-mass and flow changes in relation to the net-balance conditions over 1986–90. A model experiment using as climatic forcing the observed 1978–86 vertical net-balance profile yielded a volume loss and slow down of ice flow more drastic than observed during 1986–90. The causes of this discrepancy were examined in successive model experiments. Realistic simulations of mass-budget and thickness changes over 1986–90 are obtained using as input the net-balance forcing for the same period rather than for the preceding 1978–86 interval, and approximate flow velocities. With the same net-balance forcing and a completely stagnant Lewis Glacier, the elimination of mass redistribution by ice flow acts to mitigate the loss of volume and thickness in the upper glacier, and to accentuate it in the lower glacier. Accordingly, the observed 1986–90 net-balance profile along with the 1990 ice-flow velocities provide suitable input for the modeling of Lewis Glacier changes to 1994. Under continuation of the 1986–90 climatic forcing, ice thinning ranging from less than 1 m in the upper glacier to more than 7 m in the lower glacier, and a total volume loss of order 57 × 104 m3, are anticipated over the 1990–94 time interval.
Interpretation of borehole-inclinometer data: a general theory applied to a new instrument
Authors: Blake Erik W. , Clarke Garry K. C. 
Published: September 2017

AbstractBorehole inclinometers are standard equipment for field glaciologists and are commonly used for investigating the flow law of ice and for measuring the spatial position of englacial and sub-surface sensors. The recent development, at the University of British Columbia (UBC), of a prototype inclinometer that employs a three-component fluxgate magentometer to obtain a compass bearing has stimulated our interest in borehole inclinometry. Following a review of various approaches to glacier inclinometry, we present a unified theory of data interpretation that can be applied to all inclinometers, discuss the application of the theory to the UBC inclinometer, and discuss the sensitivity of the theory to error in the data.
Analysis of Multiple-Angle Microwave Observations of Snow and Ice Using Cluster-Analysis Techniques
Authors: Rotman Stanley R. , Fisher Arthur D. , Staelin David H. 
Published: September 2017

AbstractThe Nimbus-6 satellite carries the Scanning Microwave Spectrometer experiment (SCAMS) which continuously maps the Earth’s surface at two frequencies (22.235 and 31.65 GHz) and at six angles besides nadir. Cluster analysis was applied to these observations to determine the influence of various geophysical parameters on the radiometric brightness temperatures.Characteristic microwave signatures for a variety of terrain were obtained by this method; discrete clusters were distinguished for sea ice (with sub-classes for ice age and fractional ice cover) and firn (with accumulation-rate sub-classes). The availability of the angular data greatly facilitated separate determinations of the extent of continuous sea ice and mixtures of sea ice and water.
Creep and Fabrics of Polycrystalline Ice Under Shear and Compression
Authors: Duval Paul 
Published: September 2017

AbstractCreep tests were performed in torsion and torsion–compression on polycrystalline ice at temperatures near the melting point. Syntectonic recrystallization occurs at strains of the order of 2–3%, leading to a rapid increase in strain-rate. It is shown that the increase of creep-rate during tertiary creep arises from the development of fabrics favouring the glide on basal planes but also from the softening processes associated with recrystallization. The c-axis fabric of recrystallized ice developed in simple shear consists of two-maxima, one at the pole of the permanent shear plane and the other between the normal of the second plane of maximum shearing stress and the principal direction of compression. In torsion–compression, a three- or four-maximum fabric is formed according to the intensity of different components of the stress tensor. The maxima are clustered around the principal direction of compression. Processes of fabric formation are discussed. The experimentally developed fabrics are probably produced by the strain-induced recrystallization, for which the driving force is provided by differences in stored plastic strain energy. However the degree of preferred orientation of ice c-axes must be a function of the total strain when syntectonic recrystallization becomes less important. In this case, fabrics are principally formed by plastic flow and a steady state is obtained for very high strains.
Preliminary Experiments on the Formation of Elongated Air Bubbles in Glacier Ice by Stress
Authors: Nakawo Masayoshi , Wakahama Gorow 
Published: September 2017

AbstractBiaxial compression tests on glacier ice with bubbles revealed that elongated air bubbles were developed with long axes in the direction of free expansion. The elongated bubbles were not only derived from spherical bubbles but also created by the healing of cracks that were developed during compression. Formation of elongated bubbles and foliations in natural glacier ice are discussed here in the light of results obtained experimentally.
The Effect of the Subglacial Water Pressure on the Sliding Velocity of a Glacier in an Idealized Numerical Model
Authors: Iken Almut 
Published: September 2017

AbstractIn order to interpret observed short-term variations of the sliding velocity of a glacier the effect of a variable subglacial water pressure on the sliding velocity has been studied using an idealized numerical model. In particular the transient stages of growing or shrinking water-filled cavities at the ice-bedrock interface were analysed. It was found that the sliding velocity was larger when cavities were growing than when they had reached the steady-state size for a given water pressure. The smallest sliding velocities occurred while cavities were shrinking. When cavitation is substantial a small drop of water pressure below the steady-state value (e.g. by 0.5 bar) can temporarily cause backward sliding. A limiting water pressure at which sliding becomes unstable is derived. The consequences of more realistic assumptions than those of the model are discussed.
Bottom Melting under George VI Ice Shelf, Antarctica
Authors: Bishop J. F. , Walton J. L. W. 
Published: September 2017

AbstractBottom melting rates have been calculated for a large number of sites on George VI Ice Shelf from measurements of its kinematic behaviour. No simple explanation for the melt-rate pattern was found in terms of ice-shelf parameters, assuming steady-state conditions. Values of apparent melt rates varied from 1 to 8 m a−1 of ice. Along different flow lines the melt rate would sometimes increase with distance from the grounding line and sometimes the melt rate would decrease with distance. Large melt rates were found both where ice flowed off Palmer Land and where the ice shelf butted against Alexander Island. Although oceanographic conditions probably control bottom melting rates the complex pattern with large spatial variation seems to indicate that some areas of ice shelf are changing in thickness.
Tracing Particle Paths in the Antarctic Ice Sheet
Authors: Doake C. S. M. 
Published: September 2017

AbstractA layer of moraine within the Antarctic ice sheet has been detected in the course of airborne radar ice soundings. The moraine was injected at the margin of the ice and can serve as a tracer to pick out a particle path within the ice. When combined with surface measurements, the ability to trace particle paths should allow detailed modelling of the dynamic behaviour in limited areas.
A Cirque-Glacier Chronology Based on Emergent Lichens and Mosses
Authors: Calkin Parker E. , Ellis James M. 
Published: September 2017

AbstractRecession of “Golden Eagle” glacier in the central Brooks Range is exposing undisturbed lichen-covered boulders. Radiocarbon analysis of dead moss surrounding these boulders dates a Neoglacial advance across this site at 1120±180 years b.p Measurements of the preserved lichens indicate that a minimum ice-free period of 1500–2500 years preceded this glacial expansion.
Summer Heat and Ice Balances on Hodges Glacier, South Georgia, Falkland Islands Dependencies
Authors: Hogg I. G. G. , Paren J. G. , Timmis R. J. 
Published: September 2017

AbstractThe heat and ice balances of a temperate sub-Antarctic cirque glacier were measured through the 1973–74 melt season at an altitude midway between the climatic firn limit and the snout. The melt calculated from mean daily measurements at a single level of net radiation, wind-speed, temperature, and humidity agreed with that observed at nearby budget stakes. In the central ablation zone, radiation provided (54 ± 6)% and sensible fluxes (46 ± 6)% of the heat income through the summer, which was exceptionally warm and sunny. Latent-heat fluxes made no significant contribution to the heat balance. The calculation by Smith (1960) that the radiative, sensible, and latent heat fluxes contribute about equally to ablation in this zone has not been substantiated by measurement. The measured partition of the glacier’s heat balance suggested that maritime influences on its regime are mitigated by its position in the lee of a major mountain range.
Stability of Sheet Flow of Water Beneath Temperate Glaciers and Implications for Glacier Surging
Authors: Walder Joseph S. 
Published: September 2017

AbstractA mathematical model is presented for the stability of sheet flow of water beneath a temperate glacier. Enhanced viscous heat dissipation in thick parts of the sheet tends to make sheet flow unstable, the instability increasing as sheet thickness and pressure gradient increase. However, incipient channels may be destroyed as the glacier slides over protuberances on its bed. Quasi-stable sheet flow may be possible for sheets up to several millimeters in thickness, especially beneath glaciers that have relatively gentle surface slopes and slide at moderate to high speeds. Such water sheets may somewhat reduce the effective roughness of glacier beds, but probably not enough to allow surge initiation. Furthermore, the presence of numerous water-filled cavities at the glacier bed will tend to reduce the sheet thickness and lessen the degree of “lubrication” of the glacier bed by the water sheet.
Short-Term Variations in Velocity of South Cascade Glacier, Washington, U.S.A.
Authors: Jacobel Robert W. 
Published: September 2017

AbstractDisplacement of an array of eight stakes was measured at approximately 12 h intervals on South Cascade Glacier, Washington, for a period of 638 h during July and August 1979. The array was located on the glacier center-line and had overall dimensions comparable to the 200 m ice thickness in this part of the glacier. Variations in velocity for individual stakes was typically 100% for periods of 12 h but decreased for longer time intervals in accordance with reports in the literature. The constraint of requiring compatible motion for the entire array reduces the averaged short-term fluctuations to the same order as the variations between stakes for a given 12 h period. This implies that non-uniformity in individual stake motion does not represent true velocity variation of the studied portion of the glacier.
Surging of Fisher Glacier, Eastern Antarctica: Evidence From Geomorphology
Authors: Wellman Peter 
Published: September 2017

AbstractA study of the geomorphology of the Prince Charles Mountains using colour vertical air photographs shows well–preserved old moraines throughout much of the outcrop area. Along Fisher Glacier, lower Lambert Glacier and the Amery Ice Shelf, within the altitude range 50–2 000 m, the old moraines show that the ice level had risen 150–200 m above the present level at least three times. Old moraines elsewhere show that none of the other glaciers had risen significantly in their upper parts; the rise of their lower parts was caused by the rise of lower Lambert Glacier and the Amery Ice Shelf. The changes in ice level are unlikely to be due to climatic change because this would not repeatedly affect only one glacier draining central Antarctica. It is thought that the changes in ice level are caused by repeated surges of Fisher Glacier.
Ice Movement through Smith Sound in Northern Baffin Bay, Canada, Observed in Satellite Imagery
Authors: Ito Hajime , Müller Fritz 
Published: September 2017

AbstractMovement of pack ice in Smith Sound in northern Baffin Bay was observed for April 1975 using the satellite imagery obtained by Landsat. Mean velocity was found to be directed to the south with a magnitude of 4 km d−1. The influence of the wind is discussed and the amount of ice transported from Smith Sound evaluated. The findings show that on a daily average 600 km2 of pack ice was carried out of the area.
Fracture Criterion for Ice Using a Dislocation Model
Authors: Parameswaran V.R. 
Published: September 2017

AbstractThe propensity for crack formation on basal and prismatic planes and twin nucleation on two pyramidal planes in hexagonal ice is examined on the basis of fracture theories and anisotropic elastic theories of dislocations. Calculations show that the ease of crack formation is almost the same in the basal and prismatic planes, whereas it is almost impossible to produce mechanical twinning in ice by stress alone.
Preparation of Section Planes in Snow Specimens
Authors: Perla R. 
Published: September 2017

AbstractDiethyl phthalate, dimethyl phthalate, ethyl anisate, and α-tetralone are examples of liquids that can be used to fill the pore space of snow specimens. After the pore space is filled, the specimen is frozen solid. A section plane is microtomed and polished. Photomicrographic contrast of the section plane is improved by gently rubbing on to the plane a water–insoluble powder, such as carbon powder, or by rubbing on a water–soluble stain such as powder of acid fuchsin. Photomicrographic contrast is also improved by adding a water–insoluble dye such as oil blue N or oil red O to the pore–space filler.
Stress-Gradient Coupling in Glacier Flow:III. Exact Longitudinal Equilibrium Equation
Authors: Kamb Barclay 
Published: September 2017

AbstractThe “vertically” integrated, exact longitudinal stress-equilibrium equation of Budd (1970) is developed further in such a way as to yield an equation that gives explicitly and exactly the contributions to the basal shear stress made by surface and bed slope, surface curvature, longitudinal stress deviators, and longitudinal stress gradients in a glacier flowing in plane strain over a bed of longitudinally varying slope. With this exact equation, questions raised by various approximate forms of the longitudinal equilibrium equation can be answered decisively, and the magnitude of errors in the approximations can be estimated. To first order, in the angle δ that describes fluctuations in the surface slope α from its mean value, the exact equilibrium equation reduces towhere G and T are the well-known stress-deviator-gradient and “variational stress” terms, K is a “longitudinal curvature” term, and B is a “basal drag” term that contributes a resistance to sliding across basal hills and valleys. Except for T, these terms are expressed in simple form and evaluated for practical situations. The bed slope θ (relative to the mean slope) is not assumed to be small, which allows the effects of bedrock topography to be determined, particularly through their appearance in the B term.
Changes in the Salinity and Porosity of Sea-Ice Samples During Shipping and Storage
Authors: Cox G.F.N. , Weeks W.F. 
Published: September 2017

AbstractA theoretical examination of salinity and porosity changes introduced in sea-ice samples by brine expulsion and gas entrapment caused by thermal cycling during shipping and storage shows that in extreme cases such effects can be significant, resulting in 15% reductions in porosity (n) More representative scenarios give porosity changes of less than 2% which, assuming that ice-property variations scale with n1/2, result in property variations of less than 1%.
A Preliminary Assessment of Glacial Ice Profiling Using Vlf Surface-Impedance Measurements
Authors: Thiel David V. 
Published: September 2017

AbstractVLF surface-impedance measurements have been used in the past for sub-surface mapping. The application of this technique to glacial ice probing is discussed theoretically and results of measurements on Brewster Glacier, New Zealand, are presented. Results were fitted to a three-layer model and a section profile is given. Dramatic changes in the phase of the surface impedance were observed in the vicinity of crevasses. Results indicate that the technique has potential as a tool for quick, reliable, and non-invasive ice-thickness measurements.
Evidence of Cirque Glaciation in the Falkland Islands
Authors: Clapperton Chalmers M. 
Published: September 2017

AbstractThe presence of 49 cirques on the Falkland Islands indicates that glacial conditions were prevalent during the Pleistocene. Cirque moraines and glacially eroded valleys also occur. There appear to have been three phases: a period of cirque formation, the growth of local ice caps and subsequent cirque development. Periglacial landforms such as stone runs, stone terraces and stone lobes also developed during the Pleistocene and attained very large dimensions because of the lithology, the relatively small scale of glacierization and the presence of rotted bedrock.
An Analysis of the Relation Between the Surface and Bedrock Profiles of Ice Caps
Authors: Budd W.F. , Carter D.B. 
Published: September 2017

AbstractResults art, presented of spectral analyses of the surface and bedrock profiles along a flow line of the Wilkes ice cap and the surface along the Greenland E.G.I.G. profile. Although the bedrock appears irregular over all was velengths studied, the ice-cap surface is typically characterized by a smooth curve with small-scale surface undulations superimposed on it. The following relations of Budd (1969, 19701 are confirmed. The “damping factor" or ratio of the bedrock amplitude to the surface amplitude is a minimum for wavelengths λ about 3.3 times the ice thickness. The surface lags the bed in the direction of motion by λ/4. The magnitude of the minimum damping factor φm is typically least near the coast, and increases inland depending on the ice thickness Z, the velocity V, and the mean ice viscosity η (which is a function of stress and temperature) according to
where p is the mean ice density and g is the gravitational acceleration. Thus the determination of the damping factors provides a valuable means of estimating the ice flow parameter η.
Movement of the Ward Hunt Ice Shelf, Ellesmere Island, N.W.T., Canada
Authors: Dorrer E. 
Published: September 2017

AbstractThe movement at a marginal location on the Ward Hunt Ice Shelf, northern Ellesmere Island, was determined by repeated survey measurements with theodolite and geodimeter. The purpose and duration of the field work, and reduction of the observational data are described, and the resulting mean ice velocity of 0.53 m year-1 is discussed. Strain-rates of a 1 km by 1 km deformation figure are determined. The parameters n and B of Glen’s power flow law are determined by using the equations given by Nye and Weertman. The results are compared with experimental data. Computed ice stresses show that the “ridge-and-trough" structure on the ice shelf surface is not originated by internal ice forces. The elevations of all survey markers have been determined from vertical-angle measurements, and the peculiarities of atmospheric refraction in near-surface layers are discussed.