Studies that had been started in 1971 were continued in the summer of 1972 in order to gather information on the intraglacial run-off system in the ablation region of Hintereisferner, In a long-term test of 30 h, the daily fluctuations of the inflow into a moulin and the discharge at the glacier mouth were measured. A number of injections of dye tracers were made to measure the curve of concentration versus time. Finally, a test was made to compare with last year's results, in which the inflow was marked with dye at three different points on the glacier. From the long-term measurements, the daily fluctuations of the average velocity of flow in the intraglacial run-off system and the dispersion coefficient were determined. The results confirm the experiments of last year, showing that the melt water reaches the glacier bed taking the shortest possible route without passing through cavities within the glacier, flowing mostly in an open channel.

Boudinage structures have only rarely been reported in glacier ice, yet they seem to be widespread in Swiss glaciers. They form in debris-free, strongly foliated ice by the stretching, necking and rupture of layers or groups of layers, when the principal compressive strain axis lies at a high angle to the layering. Two main types of boudinage are distinguished. The first results from the difference in competence between fine-grained and coarse-grained ice, and indicates that the former is more resistant to flow than the latter. The second occurs in more equigranular ice which shows a strong planar anisotropy; associated with the necking of such ice is the development of shear planes, along which the layers are displaced. As in deformed rocks, it is not possible to determine the directions of the finite principal strain axes from the boudinage structures alone. Although the boudins described here all occur in longitudinal foliation, it is suggested that they are likely to form in other situations also.

In Svalbard and Iceland there appears to be much more debris entrained in glaciers that surge than in those which do not. Conditions particularly favourable for the basal incorporation of debris develop as a consequence of the high flow velocities attained by a surge. These are increased cavitation in the lee of obstacles and an increased supply of basal melt water resulting from frictional heat and from the trigger zone. Layers of regelation ice incorporating debris can thus develop to a much greater vertical and horizontal extent than in non-surging glaciers. Excessive shearing, and the distortion of foliation structures in the terminal zone of compressive flow, enhance the vertical development of the debris-rich regelation layers. Glaciers that surge over outwash and/or fjord-bottom sediments become particularly rich in debris.

This study was undertaken to determine the sources of debris and methods of transportation and deposition in and on a small cirque glacier. Data were collected on the amount of debris, stone roundness, the presence of striations and polish, and till fabric. Lichenometry gave relative ages of the tills, and suggests that the Gannett Peak till is of at least three ages and probably overlies Audubon till.

Debris originating from subglacial erosion can be differentiated from that from rockfall or avalanches on stone roundness, polish and striations. A maximum of 70% of the present glacial load derives from subglacial erosion, as compared to 88% during the Gannett Peak stade. Rockfall rates are 35-50 m3/year at present and were 290–485 m3/year during the Gannett Peak stade. Data on present-day processes and on the volume and age of Gannett Peak moraines can be used to make comparisons on present and past rates of denudation. The denudation rate in the cirque at present is 95–165 mm/1 000 year; in the past it was 4 920-8 160 mm/ 1 000 year. The denudation rate and the glacial effects on debris are comparable to rates from other glacial areas and effects on debris carried by valley glaciers and continental ice sheets.

An approximate analysis of (he processes of inciting and freezing of a drill hole, 500 m depth and 0.15 m m initial radius, through an ice shelf was made. Results are expressed in graphical form showing the time available for experimentation under the hole as a function of heating duration. It was also found that refreezing has a much slower rate than melting.

The concentration of microparticles in the 2 164 m long ice core from “Byrd” station Antarctica, varies cyclically. Highest concentrations of 0.65 μm diameter microparticles occur where oxygen-isotope studies show lowest paleotemperatures. The age of the bottom ice estimated from microparticle-concentration variations, assuming an annual cycle, is 27 000 years, much less than from oxygen-isotope studies.

The study of ice in the upper Great Lakes, both from the operational and the scientific points of view, is receiving continued attention. Quantitative and qualitative field work is being conducted to provide the needed background for accurate interpretation of remotely sensed data. The data under discussion in this paper were obtained by a side-looking multiplexed airborne radar (SLAR) supplemented with ground-truth data.

Because of its ability to penetrate adverse weather, radar is an especially important instrument for monitoring ice in the upper Great Lakes. It has previously been shown that imaging radars can provide maps of ice cover in these areas. However, questions concerning both the nature of the surfaces reflecting radar energy and the interpretation of the radar imagery continually arise.

Our analysis of ice in Whitefish Bay (Lake Superior) indicates that the combination of the ice/water interlace and the ice/air interface is the major contributor to the radar backscatter as seen on the imagery. At these frequencies the ice has a very low relative dielectric permittivity (< 3.0) and a low loss tangent. Thus, this ice is somewhat transparent to the energy used by the imaging SLAR system. The ice types studied include newly formed black ice, pancake ice, and frozen and consolidated pack and brash ice.

Although ice thickness cannot be measured directly from the received signals, it is suspected that by combining the information pertaining to radar backscatter with data on the meteorological and sea-state history of the area, together with some basic ground truth, better estimates of the ice thickness may be provided. In addition, certain ice features (e.g. ridges, ice-foot formation, areas of brash ice) may be identified with reasonable confidence. There is a continued need for additional ground work to verify the validity of imaging radars for these types of interpretations.

A calorimetric experiment was performed to determine empirically the dependence of the specific heat of ice with salinity 0-10‰ over the temperature range from –23° C to the melting point The experimental results agree with the theoretical model determined by Schwerdtfeger (1963) for calculating the specific heat except within several degrees of the melting point and for very pure ice.

A section-plane preparation technique and an operational definition of a snow grain bond are developed to allow the quantitative analysis of bonding in snow structure. Values for three-dimensional grain size, grain-bond size and number density, and related bonding measurements are presented for equi-temperature metamorphosed snow. These results from mutually orthogonal planes within a given snow block show that the assumptions of randomness and isotropy of grain and grain-bond location and orientation, necessary for stereological analysis from one plane, are satisfied to within ± 10% even after 30% uniaxial plastic deformation of the snow block. The idealization of a grain bond as a circular plane disk yields self-consistent results. The number of bonds per grain cannot be accurately determined from two-dimensional studies due to variations in the shape and size of snow grains within a given sample.

New and felt-like snow was sieved and sintered at a constant temperature in order to produce homogeneous samples of fine, rounded-grain snow with a density in the range 270–340 kg m−3. The structure of single samples was changed in stages by non-destructive uniaxial compression. This deformation, which amounted to 30%, took place within 8 hours (thus limiting temperature metamorphism). At each stage the Young’s modulus was measured quasi-statically and the creep behaviour under constant uniaxial compression was recorded. Stereological analysis of sections from the samples provided mean values for both grain-bond and grain properties. The Young’s modulus increased with density slightly more strongly than linearly, whereas the low-stress viscosity in unconfined compression increased nearly exponentially for densities less than 380 kg m−3. The maximum densification resulted in a 15-fold increase in the measured visco-elastic properties. However, the number of grain bonds per unit mass increased linearly by a factor in the range 1.5 to 2 while the average grain-bond size remained constant. It is concluded that only a fraction of the grain bonds in a snow sample transmit an applied stress, and that the new grain bonds formed during the deformation of a snow sample determine the visco-elastic properties of snow. The hypothesis that chains, defined as series of stress-bearing grains, are the basic units of snow structure is developed. Semi-quantitative calculations developed from the chain concept explain the observed variations in the visco-elastic properties.

The remote sensing of snow-pack characteristics with surface installations or an airborne system could have important applications in water-resource management and flood prediction. To derive some insight into such applications, the electromagnetic response of multi-layered snow models is analyzed in this paper. Normally incident plane waves at frequencies ranging from 106 to 1010 Hz are assumed, and amplitude reflection coefficients are calculated for models having various snow-layer combinations, including ice layers. Layers are defined by a thickness, permittivity, and conductivity; the electrical parameters are constant or prescribed functions of frequency. To illustrate the effect of various layering combinations, results are given in the form of curves of amplitude reflection coefficients versus frequency for a variety of models. Under simplifying assumptions, the snow thickness and effective dielectric constant can be estimated from the variations of reflection coefficient as a function of frequency.

The heat conduction of ice single crystals is measured by a steady-state heat-flux method between 1.7 K and 100 K. For temperatures higher than 16 K all experimental points are found to be on the same curve. For temperatures lower than 16 K the heat conduction curves depend on the material of the crystallization vessel, the ageing of the sample and the cooling rate between the temperature of the mount (≈ 260 K) and liquid-nitrogen temperature. No anisotropy can be found for temperatures higher than 9 K. Computer fits are made, based on Callaway’s model of heat conduction in dielectric crystals. An attempt is made to explain the observed extrinsic heat conduction by the presence of microstructures in ice. It is shown that heat-conduction measurements can be used to establish a “quality-list” of samples studied in laboratories.