bluuebunny/crossref_metadata_2025 huggingface dataset:
The Distortion of a Water Molecule in Ice
Authors: Whalley E.
Published: September 2017

The 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

Ice 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

The 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

Positron 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

The 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

Ice 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

The 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.
The Radio-Frequency Birefringence of Polar Ice
Authors: Hargreaves N. D.
Published: September 2017

Radio-echo observations have shown that polar ice in situ is birefringent. The most likely explanation of the birefringence is an anisotropy in the radio-frequency dielectric constant of the ice single crystal, combined with the ordering of the orientations of the ice crystals in polar ice. It is possible to calculate the birefringence of ice which has a distribution of crystal orientations using a technique similar to that used to derive the dielectric properties of heterogeneous media. The experimentally observed birefringence may then be shown to be consistent with the crystal orientation fabric at the site of the observations if the anisotropy of the dielectric constant is slightly less than 1%, that is, slightly less than the accuracy of the laboratory measurements which have failed to detect any anisotropy. Further experimental observations might be used to obtain information on not only the level of anisotropy of the single crystal but also on the crystal orientation fabric of the ice.
The Core Structure and the Mobility of Dislocations in Ice
Authors: Whitworth R. W.
Published: September 2017

The evidence concerning the velocity of glide of dislocations on the (0001) plane of ice Ih is reviewed and related to atomic processes occurring within or near the dislocation core. The velocity is directly proportional to stress at low stress, with a value of the order of 500 Burgers vectors per second at — 18°C and a stress of 105 N m-2. The usual idea of a dislocation core is that it is “crystalline” in the sense that the linkages between molecules are as far as possible the same as those in the normal lattice. For such a model the disorder of protons presents an obstacle to dislocation movement, and recent theories predict that dislocations should not be able to glide as fast as they are observed to do. Various ways of avoiding this difficulty within the context of a crystalline core are discussed, but none seems likely to be successful. An alternative model is that the core is “non-crystalline”, with a disordered arrangement of mobile molecules within it. The movement of such dislocations should not be seriously impeded by proton disorder. Dislocation mobility would then be limited at least in part by anelastic loss due to the stress-induced order of protons in the surrounding lattice.
X-Ray Topographic Studies of Dislocations in Vapor-Grown Ice Crystals
Authors: Mcknight C. V. , Hallett J.
Published: September 2017

Ice crystals grown from the vapor under controlled conditions have been examined by X-ray topography. Plates grown in the region — 1.5°C to —3°C and at — 15°C near water saturation were often free of defects, as were plates grown at smaller supersaturations (1.5% at — 3°C, 6% at — 15°C). It is inferred from these observations that growth was occurring by two-dimensional nucleation on the prism plane. It is suggested that multilayer adsorption on the crystal surface was responsible for growth at the low values of supersaturation, compared with higher values predicted by the Burton—Cabrera—Frank theory. Ice crystals dependent on dislocations for growth could only occur at supersaturations lower than these values. The crystal habit is interpreted as being dependent on differential two-dimensional nucleation on prism or basal faces. Rib structure is often associated with dislocation loops; stacking faults were evident in some crystals.
A Deformation Mechanism Map of Ice
Authors: Shōji H. , Higashi A.
Published: September 2017

A deformation mechanism map for pure polycrystalline ice of 2 mm grain diameter is constructed, New sub-regions in the dislocation glide region are proposed: dislocation glide with crack formation, dislocation creep, and fracture at high stresses above about 1 MPa. The boundary between the dislocation creep and DGC regions is determined by the onset of cleavage cracks due to piled-up dislocations near grain boundaries. The fracture region is that area of the map where fracture occurs readily when the ice is subjected to a rapid deformation rate exceeding 10-3 s-1. Experimental results of the stress dependence of the compressive deformation rate of polycrystalline ice are compared with the map. The effect of changes in the creep activation energy near the melting point is discussed together with those of other factors.
The Effect of Anisotropy on the Creep of Polycrystalline Ice
Authors: Lile R. C.
Published: September 2017

Quantitative effects of crystallographic orientation fabrics are incorporated into the flow law for isotropic polycrystalline ice by the introduction of an enhancement factor applied to the isotropic fluidity. An aggregate is viewed to a first approximation as a collection of grains deforming independently by basal glide. The influence of preferred orientations on the mean intragranular rate of strain is treated in terms of a redistribution of the magnitude and orientation of resolved basal shear stress. A quantitative measure of this effect on the fluidity of the aggregate is provided through the development of a geometric tensor and a stress configuration parameter. Intergranular interference is then considered as a dissipative process modifying the fluidity of the aggregate.

Empirical justification for the model at low octahedral shear stresses is provided by several laboratory creep tests on naturally anisotropic bore-hole specimens under both in situ and anomalous stress situations. Predicted enhancement factors ranged from approximately 0.2 to 2.8 and agree well with measured values. The tests were carried out in uniaxial compression and simple shear.
On the Relationships between Low-Density Amorphous Solid Water and Ice Ih
Authors: Rice Stuart A. , Madden William G. , McGraw Robert , Sceats Mark G. , Bergren Michael S.
Published: September 2017

New experimental and theoretical studies of low-density amorphous solid water (H2O(as)) and of polycrystalline ice lh are reported and integrated with other available data. A variety of evidence is put forward to support the conclusion that low-density H20(as) is derived from ice lh by slightly increasing the dispersion in the O—O separation and by introducing a distribution O—O—O angles (width c. 8°). Our theoretical analysis focusses attention on the consequences of strong intermolecular coupling of OH oscillators. The vibrational modes of both ice lh and H20(as) are found to be complex mixtures of molecular motions, so the identification of regions of the Raman or infrared spectra of these materials with particular isolated molecule modes is not useful. The theory developed gives a good, but not perfect, account of the OH stretching regions of the observed Raman and infrared spectra of ice lh and, to a lesser degree of low-density H20(as).
Dynamical Processes at the Ice-Water Interface During Solidification
Authors: Bilgram J. H. , Güttinger H.
Published: September 2017

The dynamics of the freezing process is studied at the surface of growing ice crystal by means of Rayleigh spectroscopy. Light is scattered quasi-elastically at the interface. The line width is proportional to the square of the scattering vector. For a scattering angle of 90° one measure, about 2 krad/s. The line width does not depend on the growth rate or thermal gradients at the interface. Light is scattered isotropically, which indicates that the correlation length is small compared with the wavelength of the scattered light. The intensity depends on the growth rate and shows a hysteresis in that dependence; at a minimum growth rate one observes the onset of fluctuations.
Charge Separation by Collision of Ice Particles on Metals: Electronic Surface States
Authors: Buser Othmar , Jaccard Claude
Published: September 2017

The charge separation of ice particles colliding with metals was investigated in a wind tunnel (air speed 10 m/s) at a temperature of —45°C for different metals as a function of an applied external electric field. The ice particles (to μm radius) collided with the metal target at a rate of 105 per second. The charge separation produced by different metals can be explained by the contact potential difference between the metal and the ice introducing electronic surface states on the ice. A lower limit for their density (1016m–2) is found. The influence of the electric field is explained by an interaction between Bjerrum defects and the electrons of the metal, the transfer probability depending on the charge in the surface states.
Optical Absorption Spectra of H2O Ice Doped with Ytterbium Chloride YbCl3
Authors: Couture L.
Published: September 2017

Near-infrared absorption spectra of a frozen dilute solution of ytterbium chloride have been obtained at 77 K, 20 K, and 4.2 K. They contain two broad lines revealing a Stark splitting of 60 cm-1 of the excited 2F5/2, level of the Yb3+ ion. Such spectra indicate that in frozen solutions of ytterbium chloride the Yb3+ ions have crystalline or quasi-crystalline surroundings which are similar for most ions; different possibilities are discussed.
Structure and Behaviour of Grain Boundaries in Polycrystalline Ice
Authors: Higashi Akira
Published: September 2017

Recent progress in studies of the structure and behaviour of grain boundaries in ice are reviewed. As a lattice geometrical model of the boundary, the coincidence-site lattice (CSL) model is considered for ice crystals. Some evidence of the validity of this model is presented through observations of special shapes of natural snow, results of grain-boundary energy measurements, and direct microscopic observations of boundaries by X-ray diffraction topography. Although methods of measurement of grain-boundary energy have been developed recently, results are still not adequate to be analysed in terms of real energetics for comparison with models of atomic bonding. Modern methods of observing grain boundaries in ice using X-ray diffraction topography are described. Observations of migrating boundaries have revealed that faceting along most closely packed CSL points impede the migration of the CSL boundaries whilst increased numbers of steps among facets with boundaries of other kinds enhance it. The mobility of a fast-moving boundary has been determined to be of the order of 10-10 cm3 dyn-1 s-1 (10-11 m3 N-1 s-1) either in the case when the driving force is the capillary force due to the boundary energy or when it is the stored energy of dislocations.
Fracture Toughness of Ice: A Preliminary Account of Some New Experiments
Authors: Goodman D. J. , Tabor D.
Published: September 2017

This paper describes the first results from an experiment to measure the fracture toughness of ice. Two experimental techniques have been used; fracture of pre-notched rectangular specimens in three- and four-point bending, and from the observation of the cracks which form underneath an indenter forced into the ice surface. In the latter test the indenter behaves like a wedge. We have observed that for indenters with large interior angles the plastic zone beneath the indenter may itself behave like a wedge. Data obtained over a range of temperatures has been compared with the little other data available. We find a decrease of fracture toughness as the temperature is lowered, which is the reverse of that observed by H. W. Liu and L. W. Loop.
Anisotropy of the Kinetic Friction on a Single Crystal of Ice
Authors: Tusima Katutosi
Published: September 2017

Measurements were made of the kinetic friction which occurs when a tungsten carbide ball slides in various directions on the surface of a single crystal of ice, the track width produced on the surface was also measured. Anisotropies were detected in both the friction coefficient and the track width. The track width φ was at a maximum when the ball was slid normal to the basal plane and a minimum when it was moving parallel to (0001) in the temperature range —5 to —30°C. Although the friction coefficient was at a minimum when slid normal to (0001) and maximum in parallel to (0001) at temperatures of —19°C and below, this relation was found to be reversed at temperatures of —10°C and above. Anisotropy in track width can be explained in terms of the amount by which a slip system contributes to deformation in a specimen. However, our understanding of frictional anisotropy calls for knowledge of the ploughing strength p defined by the adhesion theory of friction. It was found that p reached a maximum in parallel to (0001) and a minimum normal to (0001) and that the frictional anisotropy on (0001) was influenced by the value . A remarkable frictional anisotropy was also observed on the surface inclined to the basal plane at 30°; the maximum friction coefficient was twice the minimum, whereas the maximum track width was only 1.3 times the minimum.
The Dielectric Properties of Antarctic Ice
Authors: Fitzgerald W. J. , Paren J. G.
Published: September 2017

Two 0.5 m cores from "Byrd" station, Antarctica have been studied in the laboratory, one from a shallow depth (155 m) and the other from the zone where recrystallization has given a vertical c-axis fabric, and the air in situ is thought to be in clathrate form (1 424 m). The dielectric response has been studied in the frequency range 60 Hz to 10 kHz, and in the temperature range — 6° C to —6o° C. The behaviour observed is markedly different from that of "pure" polycrystalline ice such as may be made by slowly freezing distilled de-ionized water and is thus at variance with the conclusions of Rogers (unpublished) who deduced, from measurements of the admittance of a dipole probe lowered through the fluid-filled drill hole at "Byrd", that the ice surrounding the hole had a dielectric response similar to that of "pure" ice. The Antarctic ice is shown to have properties similar to those of the ice from "Camp Century" and "Site 2" in Greenland studied by Paren (1973). In an attempt to discover what factors determine the difference in electrical behaviour between polar ice and pure ice, some samples were melted and subsequently refrozen slowly. Their dielectric response was similar to that of pure polycrystalline ice. These results are discussed in connection with the impurity content and growth conditions of the ices.
Theory of Radio Echoes From Glacier Beds
Authors: Berry M. V.
Published: September 2017

We review the theory of interpreting the echoes received back at the source from a glacier bed illuminated with a wide-angle beam of quasimonochromatic radio waves. It is convenient wherever possible to separate bed relief into “geography” and “roughness”. “Geography” is the surface that results from horizontally smoothing the bed over distances comparable with the mean height h of the source above the bed. The geography can be deduced from the lime delays of specular reflections, provided these can be identified, “Roughness” is the statistics of the departures of the actual bed from the geography on scales down to about one-tenth of the predominant wavelength in the travelling pulse. The average height S and horizontal dimension L (where these quantities can be defined) of the irregularities can be deduced from measurements of the average value of the echo envelope p as a function of time delay. It is also possible to distinguish qualitatively different beds with the same S and L. If the source-receiver unit moves keeping h constant, then p fluctuates about its mean value. This “spatial fading” can be used to detect horizontal ice displacements of less than one hundredth of a wavelength. To detect vertical ice motion it is necessary to observe the phase of the echo.
Glacier Sliding Measured by a Radio-Echo Technique
Authors: Doake C. S. M.
Published: September 2017

An attempt to measure the surface velocity of a glacier by observing radio-echo fading patterns appears to have yielded instead a measure of the bottom sliding velocity.
Radio-echo sounding of the lambert glacier basin
Authors: Morgan V. I. , Budd W. F.
Published: September 2017

Several seasons of aerial ice-thickness soundings over the region of the Prince Charles Mountains, the Lambert Glacier system, the Amery Ice Shelf, and their drainage basin in east Antarctica have now been completed. The measurements provide detailed maps of surface topography and ice thickness over an area of about 2 X 105 km2. The equipment used consisted of a 100 MHz echo sounder designed and constructed by Antarctic Division and carried in a Pilatus Porter aircraft. ERTS imagery provides a valuable background for portraying the echo-sounding results. These results show that an extensive, deep subglacial valley system forms the basis of the large drainage basin with concave ice surface topography which channels the ice flow into the Amery Ice Shelf. Deep glacial streams penetrate a long way into the ice-sheet basin. The rock relief is considerable, varying from 3 000 m above (present) sea-level to 2 000 m below sea-level. A very deep subglacial trench exists in the region of the confluence of the Fisher, Mellor, and Lambert Glaciers where the ice thickness reaches 2 500 m. The low surface slope and high ice velocity are suggestive of high melt production in this region. The strong echo, together with the high bedrock back-slope, suggests that the deep trench may contain a basal melt lake.
Velocity of radio waves in ice by means of a bore-hole interferometric technique
Authors: Robin G. DE Q.
Published: September 2017

Radio waves of fixed frequency, which had passed through ice and firn from a transmitting antenna lowered down a bore hole, were monitored on the surface. By mixing the received signal with the fixed frequency, the beats which were produced as the antenna was lowered gave a value for the wavelength in ice at the depth of the antenna. This was multiplied by the frequency to give the velocity of radio waves m ice. Measurements averaged over 10 m and longer intervals were related to density values from bore holes in the same location. Results above 50 m were difficult to interpret, but at greater depths the velocities fitted a linear relationship between refractive index and density. A small extrapolation gives a velocity of radio waves in pure ice of 167.7±0.3 /μs at — 20° C.
Comparison of Sea-ice Type Identification Between Airborne Dual Frequency Passive Microwave Radiometry and Standard Laser/Infrared Techniques
Authors: Tooma S. G. , Mennella R. A. , Hollinger J. P. , Ketchum R. D.
Published: September 2017

During December 1973, the Naval Oceanographie Offirc (NAVOCKANO) and the Naval Research Laboratory (NRL) conducted a joint remote-sensing experiment over the sea-ice fields off Scoresby Sound on the east coast of Greenland using NAVOCEANO’s RP3-A Birdseye aircraft, laser profiler, and infrared scanner, and NRL’s 19.34 and 31.0 GHz nadir-looking radiometers. The objectives of this mission were: (1) to develop skills for interpreting sea-ice passive microwave data. (2) to expand, if possible, the two-category capability (multi-year ice and first-year ice) of passive microwave sensors over sea ice, (3) to compare two frequencies (19 and 31 GHz) to determine which may be more useful in a scanning radiometer now under development at NRL, and (4) to determine the value of multi-frequency as compared to single-frequency study of sea ice.

Since, because of darkness and remoteness, no photography or in situ ground truth were possible for this mission, it was necessary to rely on the interpretations of the laser and infrared (IR) data to evaluate the performance of the microwave radiometers. Fortunately, excellent laser and IR data were collected, and a confident description of the ice overflown was possible.

Five ice conditions: (1) open water/new ice, (2) smooth first-year ice, (3) ridged first-year ice, (4) multi-year ice, and (5) a higher brightness temperature form of multi-year ice interpreted as second-year ice were identifiable, regardless of weather conditions, by comparing the average of the two microwave brightness temperatures at the two frequencies with their difference.
Application of remote-sensing techniques to the study of seasonal snow cover
Authors: Meier Mark F.
Published: September 2017

This paper discusses the measurement of important snow properties using electromagnetic radiation. Snow areal extent can be measured using manual, optical, electronic, or digital techniques from data supplied by visible and near-visible light sensors carried on Earth resources and meteorological satellites, but these techniques cannot routinely detect snow under clouds or a forest canopy. Gamma-ray techniques used at stations or from low-flying aircraft permit measurement of water equivalent of snow (depth times density). Active or passive microwave systems may permit this to be done over larger areas, but the physics of this possible technique is not yet sufficiently understood. Wetness or temperature, of a snow surface is measurable with thermal infrared radiometers; wetness throughout a snow pack may be measurable with microwave radiometers. Much research needs to be done on the electrical (including scattering) properties of snow before efficient, all-weather, remote-sensing systems can be designed.
Significance of Surface Temperature in the Thermal Infrared Sensing of Sea and Lake Ice
Authors: Poulin Ambrose O.
Published: September 2017

Thermal infrared sensing can provide much information about sea ice, and some of the physical conditions associated with sea ice suggest that surface temperature may be a good indicator of ice thickness. However, steady-state heat-flow calculations suggest that the variable thickness of the snow-cover and its low. variable thermal conductivity would preclude the use of surface temperature alone as a suitable indicator of ice thickness. Measurements of surface temperature, snow depth, and ice thickness suggest that, in an area of relatively uniform ice thickness, surface temperature might be useful as an indicator of snow depth if some surface data can be obtained.
Geophysical studies of floating ice by remote sensing
Authors: Campbell W. J. , Weeks W. F. , Ramseier R. O. , Gloersen P.
Published: September 2017

This paper presents an overview of recent remote-sensing techniques as applied to geophysical studies of floating ice. The current increase in scientific interest in floating ice has occurred during a time of rapid evolution of both remote-sensing platforms and sensors. Mesoscale and macroscale studies of floating ice are discussed under three sensor categories: visual, passive microwave, and active microwave. The specific studies that are reviewed primarily investigate ice drift and deformation, and ice type and ice roughness identification and distribution.
Satellites—New Global Observing Techniques for Ice and Snow
Authors: Gloersen P. , Salomonson V. V.
Published: September 2017

Starting with the TIROS-2 weather satellite in 1961 which permitted synoptic viewing of large-scale areas with an 011-board television camera system, the capabilities of satellite observations for assessing snow and ice resources on Earth have been greatly improved through the utilization of higher resolution imaging systems and multispectral images in the wavelength range from 0.4 μm to 1.55 cm. The possibility that the variation in areal extent of the snow cover may be related by empirical means to the average monthly run-off in a given watershed was demonstrated by comparing run-off records from the Indus River Basin in south-east Asia with a series of snow-cover maps obtained from Nimbus-3 and 4 imagery. Similar studies using the higher spatial resolution available with ERTS-I imagery were carried out for the Wind River Mountains watersheds in Wyoming, where it was found that the empirical relationship varied with mean elevation of the watershed. In addition, digital image-enhancement techniques are shown to be useful for identifying glacier features thought to be related to extent of snow cover, moraine characteristics, debris coverage, and the like. Finally, longer wavelength observations using sensors on board the Nimbus-5 satellite are shown to be useful for indicating crystal size distributions and onset of melting on glacier snow cover.
Glacier Applications of Erts Images
Authors: Krimmel R. M. , Meier M. F.
Published: September 2017

The ERTS satellite’s sun-synchronous orbit covers the entire Earth horn lat. 81° N. to 81° S. every 18 d at approximately 10.00 a.m. ground time. The scanners on board have continued to relay images to Earth from the launch on 23 July 1972 to the present (summer 1974). Images from four spectral bands (0.5-1.I μm), with ground resolution of about 100 m. cover an area 185 km on a side. The resulting images have proved to be very useful for collecting certain basic data from glaciers.

Long-term surface velocities are readily determined by comparison of recent ERTS images with maps that have been produced from earlier data. Images have been used 10 measure velocities on the Malaspina Glacier over a 10 year period, surge displacements on the Lowell, Tenas Tikke. and Tweedsmuir Glaciers and Lednik Medvezhiy, and velocity at the margin of the Hubbard Glacier. Many surging glaciers are readily identifiable on (he images. Coverage from the satellite will allow surging glaciers to be identified world-wide which may help glaciologists to understand their peculiar geographical distribution. Images of large glaciers taken under conditions of low sun angle and complete snow cover show previously undetected subtle slope changes which can be interpreted as dynamic How features or reflections of subglacial topography.

ERTS imagery is providing new glacier data for several reasons: very large areas are covered repetitively with sufficient consistency to show subtle tonal changes, conditions of maximum and minimum snow cover, subtle morphologic features at low sun angle, and changes in position of glaciers.
Bottom Crevasses in the Ross Ice Shelf
Authors: Clough John W.
Published: September 2017

Bottom crevasses were detected at many locations in the southern portion of the Ross Ice Shelf during the 1973-74 austral summer. The crevasses which extended up about 100 m from the bottom of the shelf were detected by radio-echo sounding. These linear features were mapped in some detail at the RISP Camp. Wide-angle reflection velocity measurements, airborne radio-echo sounding, and other results of the R1GGS program will be included in the discussion.
Electromagnetic Reflection from Multi-Layered Models
Authors: Linlor William I.
Published: September 2017

The remote sensing of snowpack depth, density, and wetness with an airborne system would have important applications in water resource management and flood prediction. In this paper, the electromagnetic response of multi-layered models is analyzed. Normally-incident plane waves are assumed at frequencies ranging from 106 to 1010 Hz, and reflection amplitudes are calculated for models having various layer combinations. Each layer can have arbitrary thickness, and its own dielectric constant and conductivity, each of which can vary with frequency. Thus “lossy” media as well as “perfect” dielectrics can be employed in the models. An outline of the theory for the calculations is presented for an n-layered model. Because of the complexity of the equations, interpretation is accomplished by illustrative models, selected from seven snow types and seven earth types. The objective of this type of calculation is to establish the dependence of the reflection coefficient on the impedance transitions between two half-spaces. This paper is a theoretical study only, and does not include consideration of the size, weight, estimated cost, and other physical attributes of a flight system. These, and other matters of a practical nature, are being treated in other papers.

A revised version of this paper is being published in full in another issue of the Journal of Glaciology.
On Some Aspects of the Interaction of the Pulse and the Medium during the Vertical Echo Sounding of Glaciers
Authors: Trepov G. V. , Fedorov B. A. , Khokhlov G. P.
Published: September 2017

The paper discusses three aspects of the interaction of a radar pulse and the medium which is being sounded, that is the glacier proper and the lower scattering surface. These aspects are:

Radar signals attenuation during vertical sounding.

The rale of radar signal propagation through the glacier.

Fluctuations of radar signals during horizontal movements.

Representative samples of signal attenuation were chosen for two points in the vicinity of Mirny station in Antarctica, these samples were obtained under roughly constant temperature conditions of the ice. The scattering properties of the bedrock are shown to be the controlling factor. Histograms of attenuation for these two points are given; effective temperatures of the ice were estimated.

The measurements of the propagation velocity of electromagnetic waves were made along paths near “Molodezhnaya” station. Interesting results were obtained. The curves of the variation of the amplitude of reflected pulses were obtained for a number of short-distance paths with the radar moving horizontally, the working radar frequencies were 60, 213 and 440 MHz. Radii of autocorrelation of signal fluctuations were estimated. The fluctuation pattern along each of the paths is shown to be stable in time provided the distance is short enough. Measurement of the surface velocity of ice sheet movement by the transition of the fluctuation pattern in time seems quite promising.
Statistical Method of Radio-Echo Sounding Temperate Mountain Glaciers and Portable Equipment for That
Authors: Suchanov L. A.
Published: September 2017

Field experimental data show the possibility of using standard radio-echo sounding equipment of relatively low power to sound through a temperate mountain glacier. The main problem of sounding is the interpretation of echo signals, because they are a mixture of visually indiscernible echoes from the bed and from inhomogeneities in the body of the glacier. To get information about ice thickness and other things from such echo data, a method based on a statistical analysis of echo-signal fluctuations is proposed. As a main criterion the stability of echo-signal statistical characteristics is used.

Special portable equipment was designed based on this method. The equipment makes the interpretation of radio-echo sounding data simple. It eliminates distortions of echo signals because of receiver overloading by powerful impulses, automatically records the form and intensity of signals, makes its amplitudes proportional to reflection characteristics of the ice bed and inhomogeneities of the glacier body, and makes automatic statistical analysis. The thickness of a glacier, and the position of inhomogeneities within its body, are determined given more than ten radio-echo signal positions.

The method and the equipment have been used to determine thicknesses of Lednik Dzhankuat (Caucasus). Radio-echo sounding data have been compared with data obtained by other geophysical methods and thermal drilling. There is a good agreement (±10 m when the ice thickness is about 100 m).
Evaluation of ERTS-I Imagery for Inventory Work of Perennial Snow Patches in Central Japan
Authors: Higuchi Keiji
Published: September 2017

In order to make the inventory of perennial snow patches in central Japan as a part of the I.H.D. world inventory of perennial ice and snow masses, observations have been continued by the author and collaborators by taking photographs of snow patches from the air every autumn since 1968. The results obtained during the period from 1968 to 1970 were published as the Atlas of perennial snow patches in central Japan (Higuchi and Iozawa, 1971). The flight for observation in 1972 was made on 13 October, just after 5 October 1972 when the Earth resources technology satellite (ERTS-I) imagery of central Japan was obtained. Therefore it was possible to compare the ERTS imagery of perennial snow patches in central Japan with aerial photographs of them.

The perennial snow patches can be classified as (a) snow patches developed mainly from avalanching, (b) those developed mainly from snow drifting, and (c) those developed from both. The perennial snow patches in central Japan are mainly those of types (a) and (b). Since the prevailing wind direction in winter is north-west in this area, snow drifting and also avalanching of drifted snow occur at the eastern side of the mountains running southwards from the Sea of Japan. Therefore, 65% of the perennial snow patches of type (a) and 70% of those of type (b) are located at the eastern side of mountains. Fortunately, the ERTS imagery of this area was obtained at a local time when the solar azimuth was 143° so that many of the snow patches were in sunshine. Therefore, comparison of the ERTS imagery of snow patches with aircraft photographs in this case can be used as the data to discuss the limit of observation of small ice and snow masses by this satellite.

It was found from comparisons between the ERTS-I MSS imagery of band 4 (0.5 to 0.6 μm), band 5 (0.6 to 0.7 μm) and band 6 (0.7 to 0.8 μm) that the band 4 imagery was best to distinguish snow patches. Snow patches of type A were most clearly seen on the imagery. Since they are located in the valleys where avalanching occurs, the contrast between the white snow surface and the dark valley walls was quite clear. For instance, it was easy on the imagery to find four long snow patches (No. 12 701, 12 708, 12 718 and 12 720 in the Atlas) at the eastern slope of the mountain Tsurugi Dake (2 998 m above sea-level), their width being 30-50 m and their length 1 000-l 500 m. It was difficult on the imagery to distinguish snow patches of type (b) from an exposed surface, since they are not so long as those of type (a), but circular and small. However, big ones of type (b) can be found on the imagery when they are located near ridges in the sunshine. For instance, the snow patch No. 18 509 in the Atlas was seen on the imagery, its size being 200 m X 100 m. Snow patches of type (c) are few and this type seems most difficult to find on the imagery, since they located at the bottom of cirque valleys in the shadow.
Hydraulic run-away: a mechanism for thermally regulated surges of ice sheets
Authors: Fowler A. C. , Johnson Clare
Published: September 2017

By using a simple parameterized model of thermomechanically coupled flow in cold ice sheets, together with a physically based sliding law which includes a description of basal drainage, we show that relationships between ice flux and ice thickness can realistically be multi-valued, and hence that hydraulically induced surges can occur. We term this mechanism hydraulic run-away, as it relies on the positive feed-back between sliding velocity and basal melt production. For this feedback to operate, it is essential that water pressure increases with water storage. This is consistent with various recent ideas concerning drainage, under ice sheets, be it through a system of canals, a distnbuted film or a subglacial aquifer. For confined flows, such as valley glaciers (e.g. Trapridge Glacier) or topographically constrained ice streams (e.g. Hudson Strait in the Laurentide ice sheet), which are underlain by sufficiently deformable sediment, we can expect thermally regulated surges to occur, while in a laterally unconfined drainage basin (such as that which flows into the Ross Ice Shelf), we might expect ice streams to develop.
Changes in continental and sea-salt atmospheric loadings in central Greenland during the most recent deglaciation: model-based estimates
Authors: Alley R. B. , Finkel R. C. , Nishiizumi K. , Anandakrishnan S. , Shuman C. A. , Mershon G. , Zielinski G. A. , Mayewski P. A.
Published: September 2017

By fitting a very simple atmospheric impurity model to high-resolution data on ice accumulation and contaminant fluxes in the GISP2 ice core, we have estimated changes in the atmospheric concentrations of soluble major ions, insoluble particulates and 10Be during the transition from glacial to Holocene conditions. For many species, changes in concentration in the ice typically overestimate atmospheric changes, and changes in flux to the ice typically underestimate atmospheric changes, because times of increased atmospheric contaminant loading are also times of reduced snowfall. The model interpolates between the flux and concentration records by explicitly allowing for wet- and dry-deposition processes. Compared to the warm Preboreal that followed, we estimate that the atmosphere over Greenland sampled by snow accumulated during the Younger Dryas cold event contained on average four–seven times the insoluble particulates and nearly seven times the soluble calcium derived from continental sources, and about three times the sea salt but only slightly more cosmogenic 10Be.
Ice-thickness measurements of Taku Glacier, Alaska, U.S.A., and their relevance to its recent behavior
Authors: Nolan Matt , Motkya Roman J. , Echelmeyer Keith , Trabant Dennis C.
Published: September 2017

Using radio-echo soundings and seismic reflections, we measured cross-sections of Taku Glacier, near Juneau, Alaska, to resolve inconsistencies in previous measurements and to understand better the glacier’s dynamics. The maximum thickness is about 1477 m and the minimum bed elevation is about 600 m below sea level, which establishes Taku Glacier as the thickest and deepest temperate glacier yet measured. Our data indicate that, during the 19th century, the terminus of Taku Glacier may have begun its rapid advance at a position where the ice bed was greater than 300 m below sea level and more than 25 km from the inland end of its submarine trough; this behavior is uncharacteristic of temperate tide-water glaciers. The glacier, which no longer calves, has eroded a sediment layer 100 m thick since 1890 at an average rate of about 3 m a−1 since 1948; this high erosion rate retards advance by entrenching the glacier into the terminal moraine. Calculations based on ice-deformation theory indicate significant basal ice motion near the terminus and high basal shear stress (140–220kPa) along much of its length. Estimated differences between ice flux and balance flux are consistent with observed thickening and positive net mass balance; these data indicate that ice volume is increasing and that further advance is likely.
Aerodynamic stability and turbulent sensible-heat flux over a melting ice surface, the Greenland ice sheet
Authors: Braithwaite Roger J.
Published: September 2017

The turbulent sensible-heat flux to a melting ice surface is calculated from wind speed and air temperature at 2 m over the ice surface, assuming a certain wind profile with the appropriate surface roughness. The aerodynamic stability of the boundary layer over melting ice is examined by comparing sensible-heat fluxes for logarithmic and log–linear wind profiles, where the logarithmic profile is strictly valid only for neutral conditions. Increasing stability reduces the sensible-heat flux to the glacier surface and introduces a non-linear relation between heat flux and air temperature. The stability effect is greatest at low wind speeds and fairly small at the high wind speeds that are common over the ice sheet. Earlier estimates of ablation by energy-balance modelling may be too large due to neglect of stability but this was almost offset by using a surface roughness that was too small. The log–linear wind profile should he used in future energy-balance models to take account of stability but more research is needed on the parameters of the profile, as well as on the surface roughness.