bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pressure-Melting Within The Basal Ice of an Alpine Glacier Indicated by The Chemical Composition of Regelation Ice
Authors: Souchez R. , Lemmens M. , Lorrain R. , Tison J.-L. 
Published: September 2017

AbstractIn the heat-pump effect developed by Robin (1976), pressure-melting within the basal ice mass, as distinct from processes at the ice–bedrock interface, can be responsible for the formation of excess water in zones of high-pressure ice up-stream of obstacles. This water is squeezed out of the ice by the pressure and can refreeze at the interface to form regelation ice down-stream.The peculiar chemical characteristics of regelation ice at the base of Glacier de Tsijiore Nouve in the Swiss Alps can only be explained by refreezing of this squeezed water. Melting at the interface up-stream of bed protuberances and refreezing of these melt waters downstream, as implied in weertman’s theory, can be excluded in this case.This paper is published in full in Nature, Vol. 273, No. 5662, 1978, p. 454–56,
Characteristics and Origins of the Debris and Ice, Matanuska Glacier, Alaska
Authors: Lawson D.E. 
Published: September 2017

AbstractThe physical characteristics of the ice and debris of the Matanuska Glacier, Alaska (lat. 61° 47’, long. 147° 45’) and their consistent variation in a vertical stratigraphic column of the glacier indicate multiple origins for both. The two zones of ice recognized in the glacier are the upper englacial zone, which comprises the bulk of the glacier (est. 300 m thick), and the thin (3 to 15 m thick) basal zone, which contains an estimated 97% of the sediment transported in the glacier. The physical characteristics of the ice and the quantity and mode of distribution of debris in it define two ice facies in each zone. The englacial zone consists mainly of the debris-poor (0.002 volume per cent) diffused facies. White coarse-bubbly ice and blue coarse-clear ice (2 to 10 cm diameter) comprise most of this facies. The bubble-rich banded facies (debris bands) contains abundant debris (25 to 50 volume per cent), varies in lateral and vertical extent, and occurs randomly in the diffused facies.
On the Temperature Response in Ice Sheets to Radioactive Waste Deposits
Authors: Philberth K. 
Published: September 2017

AbstractDisposal of the the radioactive waste from the peaceful use of nuclear energy in the central region of the ice sheet of Greenland or Antarctica has been proposed. This paper demonstrates that an area only 100 km2 on the ice divide is sufficient to dispose of the high-level waste of the whole world for the next 30 years without hazard. The thermal power of the radioactive decay makes the waste containers melt down to a depth of 2 km. Thus the total disintegration heat is spread through a volume of 100 km2 × 2 km. The mean temperature increase in this volume is a few degrees. The temperature increase does not influence the rheology of the ice sheet at any time: for a few ten-thousand years after the dumping the area concerned is too small; later the temperature increase is too small.
Measured and Computed Temperature Distributions in the Law Dome Ice Cap, Antarctica
Authors: Budd W.F. , Young N.W. , Austin C.R. 
Published: September 2017

AbstractBy 1969 considerable data had been collected over Law Dome from surface measurements. These included surface elevation, ice thickness, accumulation rates, ice movement and strain-rates, surface mean temperatures, and several temperature-depth gradients. Since then core drilling up to 380 m in depth has been carried out from the summit to the coast where the cores reached close to the bed. The bore holes have been concentrated on two main flow lines: one to Cape Folger and the other to Cape Poinsett. The bore-hole temperatures give a clear indication of the temperature distribution throughout the ice cap.Numerical modelling shows that the measured deep temperatures closely match the steady-state temperature distribution calculated from the present regime. The variations in the temperature profiles over the dome are primarily associated with the flow regime.The Cape Folger line has low accumulation rates and low velocities which results in positive surface temperature-depth gradients increasing towards the coast. By contrast the Cape Poinsett line has high accumulation rates and high velocities which result in a large negative temperature-depth gradient there. The profile at the Dome summit is close to isothermal primarily due to the high accumulation rates and lack of horizontal motion.
Some Thermal Effects of Bubbles in Temperate Glacier Ice
Authors: Raymond C.F. 
Published: September 2017

AbstractGas bubbles in core samples from the Blue Glacier, Washington, were observed to be partially filled with liquid. The time and spatial dependence of liquid content in the bubbles demonstrates that the in situ liquid content of the bubbles was small and liquid appeared in the bubbles as a consequence of heat flow into the sample after collection. An effective bulk heat capacity for wet bubbly ice is derived and used to analyze the relaxation process and it is shown that the warming of samples is controlled by an effective heat capacity two or more orders of magnitude larger than for pure ice. The relaxation process presents a practical difficulty for measurement of in situ water content from core samples and the behavior of the bubbles indicates that at positions in a temperate glacier where bubbles have pressure in excess of the ice stress, bubbles may control the ice temperature and significantly restrict water flow through veins.
Is the Basal Ice of a Temperate Glacier at the Pressure Melting Point?
Authors: Robin G. de.Q. 
Published: September 2017

AbstractCertain aspects of the flow of glaciers suggest that molecular adhesion contributes to basal friction of glaciers sliding at speeds below those of surging glaciers. Laboratory experiments indicate that this will only occur if some part of the ice-rock contact is “cold”, that is below the pressure melting point (p.m.p.), a few tenths of a degree being sufficient. Field evidence is scanty, but suggests that such cold patches may exist at the base of a temperate glacier.Discussion of pressure-melting within the basal ice mass, as distinct from processes at the ice-rock contact, indicate that excess water is formed in zones of high-pressure ice up-stream of obstacles. If this water is squeezed out of the ice by the pressure, we have a simple heat pump that will tend to cool the basal ice. The ice will warm again as the result of thermal conduction and internal friction, but before reaching the p.m.p. it can produce "cold" patches of the ice-rock contact, roughly estimated to be from 0. 1 to 1.0 m in extent.Another factor that could cause intermittent cold patches at the ice-rock interface arises from changes of basal water pressures with time beneath a glacier. If a major part of the weight of a glacier is supported by a thin water film at a relatively low pressure and by a small proportion of water film in which pressures are high, then over a large area the water pressures must balance the weight of ice. If however the pressure in the low-pressure film rises, the smaller high-pressure areas of stress concentration will suffer a proportionately greater decrease of pressure to maintain the total balance between pressure and weight, If changes take place rapidly, in a matter of hours, then in areas of stress concentration of the order of a metre or more across, the water film will freeze to the bed as stresses are relieved. This could cause stick-slip motion in a temperate glacier.Pressure-temperature effects at the ice-rock interface can help to explain certain features of glacial erosion, such as intense grinding on the top surface of a roche moutonée and plucking on the down-stream side.
15m Deep Temperatures in the Glaciers of Mont Blanc (French Alps)
Authors: Lliboutry L. , Briat M. , Creseveur M. , Pourchet M. 
Published: September 2017

AbstractThe top of Mont Blanc is a dry snow zone. The cold infiltration zone extends between about 4 300 and 3 800 m. Its lower limit is lined by large cracks and ice cliffs, similar to bergschrunds. Near rock faces this limit is the bergschrund, which can descend as far as the 0°C isotherm of the mean annual air temperature, 3 100-3 200 m- At Col du Dôme (c, 4 250 m), 15 m deep temperature has increased 1.8 deg between the years 1911 and 1973, probably due to infiltration which happened there in the last few years. The ice in the ablation area is entirely temperate, while in dryer areas of the Alps it may be at 1°C to — 3°C in the vicinity of the firn line.
Thermal Regulation of Glacier Surging
Authors: Clarke Garry K.C. 
Published: September 2017

AbstractA necessary condition for a glacier to surge by thermal instability is that the glacier be cold with basal ice at or near the melting point. Deep temperature measurements show that two small surge-type glaciers in the Yukon Territory meet this requirement, but shallow measurements in three other surge-type glaciers suggest a temperate regime. If the latter observations are accepted, not all surges are thermally controlled: if a single mechanism accounts for all surges it cannot be thermal instability.In this paper it is argued that thermal instability remains a viable mechanism for explaining surges of many cold glaciers, and that regardless of the underlying mechanism, thermal processes must at least have a major influence on the surge behavior of cold glaciers.Two numerical modelling experiments are described. The first involves a one-dimensional model which shows that thermal control can account for the remarkably constant surge cycle found in some glaciers. The second, a two-dimensional model of the time-dependent temperature structure of a surge-type glacier, shows that the relative amounts of temperate and cold basal ice can change considerably as the surge cycle progresses. This variation alone may be sufficient to explain surges, but even if this is not the case, thermal processes must affect the timing of surges in many cold glaciers.A compelling feature of the thermal instability mechanism is that it offers an explanation of the factors controlling the non-random geographical distribution of surge-type glaciers. For a glacier to have a cold surface and near-temperate bed, the ice thickness, temperature, and geothermal flux must be fortuitously related.
Post-Surge Temperatures in Steele Glacier, Yukon Territory, Canada
Authors: Clarke Garry K.C. , Jarvis Gary T. 
Published: September 2017

AbstractDeep ice temperatures measured at four widely spaced sites on Steele Glacier show that the thermal regime was profoundly influenced by the 1965-66 surge advance. Three of four measured temperature profiles are "anomalous" in that the upper 100 m of ice is far from thermal equilibrium. Water penetration during the surge is the probable cause of these anomalies. Insufficient data are available to predict the basal ice temperature.
Reports on Current Work Temperatures in the Devon Island Ice Cap, Arctic Canada
Authors: Paterson W.S.B. 
Published: September 2017

AbstractTemperatures have been measured in a 299 m bore hole that reaches the base of the ice near the divide of the main ice cap on Devon Island in the Canadian Arctic Archipelago. Temperature ranges from — 23.0°C at a depth of 20 m to — 18.4°C at the bottom. The difference between surface and bottom temperatures is about 1.5 deg less than expected for a steady state. Recent climatic warming seems the most likely explanation of the discrepancy. The temperature gradient in the lowest 50 m is approximately linear and corresponds to a geothermal heal flux of 1.5 h.f.u. This value may be invalid, however, because temperatures at and below this depth have probably been perturbed by changes of surface temperature during the past several thousand years, particularly by the warming at the end of the last glaciation. A detailed analysis of the results is in progress.
Creep Instability of Ice Sheets
Authors: Clarke Garry K.C. 
Published: September 2017

AbstractThe equation governing the growth or decay of a temperature perturbation T’ in an ice slab under shear stress σxy iswhere K and k are respectively the thermal conductivity and diffusivity of ice, KB-v is the advection velocity normal to the bed andis the rate of increase of strain heating with temperature assuming a power law for flow. For a slab of infinite thickness under constant stress and at constant ambient temperature, T Fourier analysis gives -k2+a/k < o as the condition for stability where k is the wave number of a sinusoidal perturbation. When the slab has finite thickness the stability depends on the sign of the eigenvalues λm of the perturbation equation and on the boundary condition at the ice-rock interface. In general the eigenfunctions and eigenvalues must be found by approximate methods such as the Rayleigh-Ritz procedure but in the case where the stress and ambient temperature are constant over the slab thickness and there is no advection the eigenfunctions are either sines or cosines depending on the boundary conditions.In this special case the stability condition isif the bed is frozen andif it is at the melting point. The eigenvalue associated with the smallest value of m is the least stable so the maximum stable thickness is thus h = ½ π(a/K)1/2 if the bed is frozen or h = π (a/K)1/2 if it is at the melting point. For typical flow-law parameters these depths are around 250 m and 500 m respectively. The eigenvalues are related in a simple way to the growth or decay rates of the eigenfunctions: (K λm)–1 is the time constant for the mth eigenfunction.Depth-dependent stress, temperature, and advection have a marked effect on stability. A slab in which stress and temperature increase to values B and TB at the bed is considerably more stable than a slab held at constant stressσB and a constant temperature TB. Advection normal to the bed also has a major influence on stability. If the advection velocity is taken to vary linearly with depth and the bed is frozen, the effect of upward advection is to decrease stability and of downward advection to increase it. When the bed is temperate the effect of advection is more complex: downward advection increases stability but upward advection may increase or decrease it depending on the magnitude of the advection velocity.
Abstracts of Papers Presented at the Symposium but not Published in Full in this Volume Computer: Modelling of Temperature Distributions in Polar Ice Sheets
Authors: Budd W.F. , Young N.W. 
Published: September 2017

AbstractIt is now practicable to construct complete three-dimensional primitive- equation models of ice flow in which all the input may be time dependent. The input consists of bedrock and ocean distribution, accumulation net balance, ice-surface elevation- temperature relation, and the thermal and flow parameters of the ice. The main limitations on this type of model is the extensive demand of computation time. Thus simplified two-dimensional models have been developed for detailed flow-line studies, and single-column models have been used extensively for analysing the few deep bore-hole temperature profiles.The main feature of the measured temperature profiles reflect the current steady-state regime at each location. Deviations from the steady state are caused by time variations of any of the variables such as surface temperature, accumulation rate, ice thickness, velocity, etc.Measurements of stable-isotope ratios in the ice cores provide an indication of past temperatures which has been confirmed by the analysis of the temperature profiles. However the temperature changes could be either due to surface elevation changes or climate changes. Gas volumes in the core show promise of providing an indication of past elevations. Annual variations of the isotopes give indications of past accumulation rates. The determination of past velocities, however, requires velocity-temperature coupled models with more precise flow-law information.Three-dimensional models are necessary to study past variations of the flow-line pattern. Finally the sliding and surging models recently developed need to be incorporated into the cold ice-sheet models.
The Distortion of a Water Molecule in Ice
Authors: Whalley E. 
Published: September 2017

AbstractThe experimental evidence for the distortion of a water molecule when it is condensed to form ice is reviewed. The specific distortions considered are the changes in inter-nuclear distances, energy and its derivatives with respect to nuclear motion, and electrical moments and polarizabilities and their response to nuclear motion. Some of the properties of ice can be expanded as Fourier or Taylor series in the ratio r/R of the O–H to the O—O distances, and these expansions are used to relate various properties of the intermolecular potential energy, of the electrical dipole moments, and of the polarizability. For example, the amplitude of the orientation polarization can be related to the infrared intensity of the fundamental and first overtone infrared bands.
X-Ray Determination of the Structure of Ice IV
Authors: Engelhardt Hermann , Kamb Barclay 
Published: September 2017

AbstractIce IV, a wholly metastable ice phase, has a structure based on a framework of tetrahedrally hydrogen-bonded water molecules in a rhombohedral unit cell. The structure involves two non-equivalent types of water molecules and four non-equivalent types of hydrogen bonds. A novel structural feature is a hydrogen bond that passes through the center of a 6-ring of water molecules and links non-adjacent structural layers. The bond network is proton-disordered, even after quenching.
Origin of the High-Frequency Translational Bands of Ice I
Authors: Klug D. D. , Whalley E. 
Published: September 2017

AbstractThe translational vibrations of hypothetical ordered forms of ice Ic and ice Ih have been predicted and correlated with the known spectra of the actual disordered phases. The TO–LO splittings have been predicted by assuming that the changes of mean refractive indexes across the translational band is the same in all phases, and equal to the known change for ice Ih. Both ordered phases are predicted to have LO components at c. 275 and c. 310 cm-1. These predicted bands are assumed to be related to the bands at the same frequencies in the disordered phases. These bands are therefore LO components corresponding to the TO translational vibrations.
Vacancies in HF-doped and in Irradiated Ice by Positron Annihilation Techniques
Authors: Eldrup M. , Mogensen O. E. , Bilgram J. H. 
Published: September 2017

AbstractPositron annihilation techniques, which are specifically sensitive to vacancy-type defects have been used to study the effect on ice of irradiation and HF doping. Main conclusions are that immobile water-molecule vacancies can be created at low temperatures by either irradiation or HF doping. Upon heating, the vacancies become mobile at about 100 K. Some of them cluster into di- and multi-vacancies which grow in size with temperature up to at least 145 K. A vacancy migration energy of 0.34 ± 0.07 eV is deduced, about three times higher than previously assumed. Possible mechanisms for vacancy formation by HF doping are discussed. Out-diffusion of HF is followed at –26°C over several weeks. The diffusion constant derived agrees within uncertainty (a factor of two) with the large value obtained by Haltenorth and Klinger. In particular two results seem important for other parts of ice physics. One is that HF doping creates an appreciable increase in the vacancy concentration, the influence of which should be considered in models for other defects in ice. The other is that vacancies migrate at about 100 K, a fact which might be important for the interpretation of some of the many “anomalous” effects observed in ice at about that temperature.
The Electrical Properties of Ice Surfaces
Authors: Maeno Norikazu , Nishimura Hiroshi 
Published: September 2017

AbstractThe surface conductivity of monocrystalline ice was measured as a function of temperature impurity concentration, field-strength, and other variables. At temperature, below about –6°C the surface conductivity was found to follow the Arrhenius equation with an activation energy of 33±2 kcal mol−1 (1.43±0.09 eV). Small amounts of impurities contained within the ice increased the surface conductivity and decreased the actuation energy: for HF-doped ice the activation energy was reduced to 10.0 kcal mol−1 (0.44 eV). Mechanical treatment of the ice surface increased the surface conduction. At temperatures above about —6°C the surface conductivity increased more rapidly with the rise in temperature; this is explained in terms of the appearance and development of a quasi-liquid layer on the ice surface. The electrical behaviour of sublimed ice surfaces was found to vary at a temperature around —9°C. At higher temperature a sharp, instantaneous current increase was observed as evacuation began; this was considered to be caused by the formation of ionic states due to the rapid evaporation of quasi-liquid layers. It was concluded that the temperature above which the ice surface was covered with a quasi-liquid layer lay in the range — 6 to — 9°C.
Measurements of the Electrical Properties of Ice Ih Single Crystals by Admittance and Thermally Stimulated Depolarization Techniques
Authors: Loria Arturo , Mazzega Ezio , Pennino Umberto del , Andreotti Giovanni 
Published: September 2017

AbstractIce Ih single crystals were investigated by complex admittance and thermally stimulated depolarization (TSD) techniques, in the relaxation-time ranges 10–5–10 s and 10–104 s respectively.The relaxation spectrum was resolved and three components of it were studied. Second-order kinetics had to be assumed for two of the TSD spectra to obtain Arrhenius-type relaxation times. The “Debye spectrum” had an activation energy for the relaxation time of 0.64 eV at the high temperatures and its dielectric strength revealed a possible defect cross-over at Tc = 190 K. Far below this temperature the activation energy was 0.38 eV, that is about half of that necessary for a pair of ion defects to form. In comparison with the results of other authors, a lower concentration of ionic defects, or possibly of Bjerrum–ion aggregates, was deduced to occur in our crystals.Inert-gas host molecules were proposed as a possible origin of the two other spectra, having relaxation times shorter than the “Debye spectrum” and energies of 0.33 eV and 0.37 eV. Moreover the 0.33 eV spectrum, whose dielectric strength appears at a temperature below Tc, might alternatively be related to the cross-over of the “Debye spectrum”.
The Influence of the Rate of Deformation on the Electrical Properties of Ice Monocrystals
Authors: Noll G. 
Published: September 2017

AbstractThe influence of plastic deformation on the electrical properties of ice monocrystals has been measured in the frequency range 10-2 to 105 Hz as a function of strain-rate and strain. The crystals have been tested mainly under uniaxial compression, their orientation being for glide in the basal glide system (0001)[1120]. The resolved shear strain-rate ranged from 2 × 10-5 to 1 × 10-3 s-1, the resolved shear strain from 3 to 60%u. Transient as well as bridge methods have been used for the electrical measurements before, during and after the deformation, Plastic deformation reduces the electrical conductivity in the space-charge dispersion range. The decrease depends strongly on the strain-rate; the size of the strain has practically no influence. After the end of the deformation recovery processes have been observed, which restored the original conductivity if the total strain was small. Rapid and large deformations however leave permanent changes. The changes of the d.c. conductivity and of the dispersion strength in the space-charge region are discussed and attributed to the increase of the dislocation density and the change of character of the dislocation network.