A variety of frost-crystal forms found growing from the vapor in ice caves and tunnels in the Antarctic are described and illustrated. Complex layered structures found within large, skeletal crystals are ascribed to the action of the temperature gradient. Some novel c-axis growth forms and a rare type of bicrystal growth – accelerated growth in a particular direction along a particular grain boundary – are also shown.

The mechanism by which blower fences can protect roads from snow-drifts is investigated, and the variation of the drift-free width behind a blower fence with the dimensions and inclination of the fence and with terrain features has been determined. The results are presented in the form of an equation and a nomogram to help in the design of blower fences.

Dry snow on the surface of polar ice ice sheets is first densified and metamorphosed to produce firn. Bubbly ice is the next stage of the transformation process which takes place below the depth of pore closure. This stage extends to the transition zone where, due to high pressures and low temperatures. air trapped in bubbles and ice begins to form the mixed air clathrate hydrates, while the gas phase progressively disappears. Here we develop a model of bubbly-ice rheology and ice-sheet dynamics taking into account glacier-ice compressibility. The interaction between hydrostatic compression of air bubbles, deviatoric (uniaxial) compressive deformation of the ice matrix and global deformations of the glacier body is considered. The ice-matrix pressure and the absolute-load pressure are distinguished. Similarity theory and scale analysis are used in examine the resultant mathematical model of bubbly-ice densification. The initial rate of bubble compression in ice sheets appears to be relatively high, so that the pressure (density) relaxation process takes place only 150-200 m in depth (below pore close-off) to reach its asymptotic phase, wherein the minimal drop between bubble and ice pressures is governed by the rate of loading (ice accumulation). This makes it possible to consider densification under stationary (present-day) conditions of ice formation as a special case of primary interest. The computational tests performed with the model indicate that both ice-porosity and bubble-pressure profiles in ice sheets are sensitive to variations of the rheological parameters of pure ice. However, only the bubble-pressure distinguishes between the rheological properties at low and high stresses. The porosity profile at the asymptotic phase is mostly determined by the air content in the ice. In the companion paper (Lipenkov and others, 1997), we apply the model to experimental data from polar ice cores and deduce, through an inverse procedure, the rhelogical properties of pure ice as well as the mean air content in Holocene and glacial ice sediments at vostok Station (Antarctica).

This paper provides a review of the characteristics of airborne laser profilometry and its application to quantitative characterization of cold-regions terrain. The limitations of profilometry due to the profiler instrumental characteristics and instability of the aircraft platform (resulting from variations in aircraft altitude and attitude) are discussed. For typical aircraft speeds of the order of 100 m/s these limitations restrict the accurately measured roughness content to the approximate wavelength range 2 m to 300 m. Digital filtering and hardware techniques for removing the aircraft motion, and hence extending the long wavelength validity of the profile, are discussed.

Regarding terrain characterization, particular attention is given to Arctic, sea ice. Ridge height and spacing distribution models for sea ice in conjunction with digitally processed laser profiles allow efficient characterization of sea-ice ridging using only a few parameters. In particular, a single ridging intensity parameter has been found to allow reasonable estimation of the number of ridges encountered at any height level along a straight-line path. Examination of spectral characteristics of first-year and multi-year ice suggest that laser profiles may be used to identify the ice type of floes and ridges. Comparisons of laser data and submarine sonar data are made which suggest that ratios of c. 6.5: 1 can be used to estimate ridge keel depths from laser data. Use of laser profilometry to characterize tundra and indirectly 10 measure variation in snow depth is briefly discussed.

We present the Raman spectra in natural and polarized light of ice Ih monocrystals in the region of the translational frequencies. These spectra are of better quality and higher resolution than previous spectra from monocrystals, and demonstrate the value of the investigation of single crystals by this technique, in spite of the proton disorder. In order to explain the observations we use the model of simultaneous activity of the modes allowed in D6h symmetry and the modes allowed by the proton disorder. By analogy with the interpretation of the phenomena observed in ordered piezoelectric crystals, we suggest that the existence of translation frequencies up to c. 320 cm-1 is due to the splitting between transverse and longitudinal optical modes. On this basis, an initial simple dynamical model using only three parameters permits an interpretation of the Raman spectrum. The probable presence of directional effects in ice Ih argues in favour of the proposed explanation.

A three-dimensional model of the temperature and velocity distribution within any arbitrary-shaped ice mass is described. There is a mutual interaction in the model between the flow of the ice and its thermodynamics, since the flow law used in the model is temperature-dependent.

Ice growth in three dimensions is governed by mass accumulation through precipitation, by mass depletion through loss of ice over the ocean, and by continuity requirements. Phase changes at the base of the ice are accounted for. The model has been applied in art exploratory manner to the Greenland ice sheet. Changes in the ice shape and temperature are presented and discussed. The basic shortcoming of the model as here presented appears primarily due to the coarse finite-difference mesh used, and to an unsophisticated approach to modelling the boundary ice.

The problem of improving the spatial resolution of ice-sheet elevations derived from satellite-altimeter observations is investigated theoretically in two dimensions. An equation for the echo is described that allows the elevation to be determined In linear operations on the echo. An approximate solution of the equation is explored to illustrate the behaviour of the solution. The modifications necessary to consider a regularly sampled solution are described and the effects of echo fluctuations on the reconstructed surface are considered. Numerical examples are described. It is shown that, in general terms, the resolution may be limited by sampling or by echo fluctuations but that in the case of current practical measurements it is the sampling that determines the resolution. This resolution is smaller than has been considered possible hitherto. Limitations of the method are discussed together with extensions to a wider class of problems including three-dimensional reconstructions.

Two new methods have been devised for measurement of crystallographic lattice orientations of individual crystals in polycrystalline ice. The first uses edge-length ratios of etch pits. The second uses a combination of optical measurement on a thin section and etch-pit technique. Although the second method does not work for crystals with their c-axis oriented parallel to the thin section, it is much simpler and more practical than the first method. When used on polycrystalline glacier ice, this method gave the three a-axes orientations as well as c-axis orientation for each crystal with an accuracy of 5°.

Recent measurements of snow accumulation on undulating surfaces around “Byrd station”, Antarctica indicate that the undulations are tending to be filled in. These results are discussed in the light of current knowledge of the origin and migration of such features.

Collected data on the mean annual surface values for δ18O over Antarctica have been tabulated and also presented in map form. An additional map shows contours of constant δ18O values.

Low-elevation blue-ice areas in Antarctica can contain significant amounts of subsurface liquid water during summer and may experience internal melt–freeze cycles due to absorption of shortwave radiation. An existing 2-D (x-z) model has been used to study the phenomenon and this is improved by changing the lower boundary condition from a no-flux condition to one that lets heat through, and by changing the bulk optical properties to spectral values. Both changes made the model more realistic. The optical and thermal boundary conditions, together with the optical attenuation coefficient, have a large effect on the amount of water produced in the ice. Our results show that if the lower boundary condition is changed from no flux to radiating, subsurface melting is reduced dramatically. Using a spectral albedo produces less melting than using a corresponding bulk albedo, the other variables left unchanged. If optical properties are changed to spectral values, the melting is different than using bulk values. If the linear extent of the blue-ice area is <0.6 m, subsurface melting is diminished. We found the spatial variability of snow has a significant effect on subsurface melting. Subsurface melting was found to be impossible for albedos >0.7 and the subsurface ponds can persist over the winter if the albedo is <0.4.

“Avalanche-type” medial moraines are described on four Torngat Mountains glaciers with single, rather than compound, firn basins. They form from debris avalanching down couloirs and are exposed by ice melt to form extensive debris covers on glacier snouts in the Torngat Mountains. The debris may play an important part in helping the glacier survive periods with warm summers and/or dry winters since, in the Torngat Mountains, average ice melt on debris-covered sites is approximately one-third that on exposed ice.

Velocities have been derived from motion-picture film of two different avalanches falling in known terrain. These data are used to calculate avalanche behavior according to the method of Voellmy and the method of Lang and others. Results suggest that Voellmy’s coefficient of turbulent flow may be related to snow density and temperature as much as it is to terrain roughness. For avalanche flow modelled as a transient, viscous process, specification of friction coefficient and kinetic viscosity over a limited range of values successfully predicts a wide range of avalanche behavior.

A method of estimating siding velocity is presented. It rests on few assumptions, one of which is that longitudinal strain-rate varies linearly with depth. The flow law of ice is not used. To apply it, the sliding velocity at one point must be known. The method is used to calculate the sliding velocity at twelve points on Athabasca Glacier. These values are not related to calculated basal shear stresses. Thus one or more of the following statements must be true: (1) basal shear stress cannot be calculated by the conventional formula, (2) the roughness of the glacier bed varies from place to place, (3) sliding velocity does not obey Weertman's formula. Analysis of seven published measurements of sliding velocity leads to the same conclusion.

In the summer of 1962 a completely portable and relatively simple electrically heated thermal core drill of new design was constructed and used to obtain 16 oriented samples of ice 2.5 cm. in diameter by 120 cm. in length from depths ranging from 12 m. to 137 m. in lower Blue Glacier, Mount Olympus, Washington, U.S.A. The thermal element is a 0.260-in. (0.66-cm.) diameter 300-W. 150-V. tubular heater bent to form an annulus with an external diameter of 5.0 cm. Opposed ratchet-like teeth break off and hold the core inside the tubular core barrel. Orientation is recorded photographically by a commercial inclinometer modified to show azimuth and to be controlled from the surface.

We investigate relationships between synoptic-scale atmospheric variability and the mass-balance of 13 Andean glaciers (located 16–55° S) using Pearson correlation coefficients (PCCs) and multiple regressions. We then train empirical glacier mass-balance models (EGMs) in a cross-validated multiple regression procedure for each glacier. We find four distinct glaciological zones with regard to their climatic controls: (1) The mass-balance of the Outer Tropics glaciers is linked to temperature and the El Niño-Southern Oscillation (PCC ⩽ 0.6), (2) glaciers of the Desert Andes are mainly controlled by zonal wind intensity (PCC ⩽ 0.9) and the Antarctic Oscillation (PCC ⩽0.6), (3) the mass-balance of the Central Andes glaciers is primarily correlated with precipitation anomalies (PCC ⩽ 0.8), and (4) the glacier of the Fuegian Andes is controlled by winter precipitation (PCC ≈ 0.7) and summer temperature (PCC ≈ −0.9). Mass-balance data in the Lakes District and Patagonian Andes zones, where most glaciers are located, are too sparse for a robust detection of synoptic-scale climatic controls. The EGMs yield R2 values of ~ 0.45 on average and ⩽ 0.74 for the glaciers of the Desert Andes. The EGMs presented here do not consider glacier dynamics or geometry and are therefore only suitable for short-term predictions.

Uniaxial compression experiments at –10°C at 10−3s−1 on fresh-water, granular ice have established through the use of high-speed photography that internal cracks nucleate preferentially away from the ice/platen (i/p) interface under conditions of i/p contraint, but near the interface under conditions of i/p expansion. Under conditions of little i/p interaction, cracks nucleate more or less randomly throughout the specimen. Correspondingly, the brittle-fracture strength decreases as the i/p interaction changes from compressive to tensile. These effects are explained in terms of the spatial variation of the maximum shear stress and the crack density.