Two models are presented for the formulation of abrasion and basal drag due to rock–rock friction (debris drag) for the case of sparse debris entrained in the basal layers of a temperate glacier resting on a bedrock bed. The first model is formulated in terms of average basal melting rate, va, and the concentration, C, of basal debris fragments which make intermittent bed contact. The second model is formulated in terms of vn the component of ice velocity normal to the bed flowing around rock fragments contacting the bed, and Cc, the concentration of debris actually in contact with the bed. The relationship between the two models is given for the case of a sinusoidal bed. Generalizations are discussed as well as potentially important physical processes which remain to be investigated.

When plotted on a δD-δ18O diagram, the isotope values of basal ice formed by refreezing of melt water beneath the cold-based margin of a corrie glacier lie on a straight line with a slope of 5.5. This freezing slope differs from a slope of 7.2 for the basal ice layer of the cold-based ice cap, Balgesvarri, which has not undergone refreezing. The latter slope is similar to that of 7.7 for the local precipitation. Co-isotope measurements from the two glaciers support the association of subglacial debris entrainment with refreezing processes.

The main perturbation in the mass balance of Storglaciären during the twentieth century was caused by a sudden 1°C increase in the summer mean temperature around 1910. Later perturbations of the climate have been of minor importance in relation to the mass balance. Annual field surveys suggest that the mass budget on Storglaciären has been in near balance for the last 15 years. Because of this major step-like change, we can establish the validity of theoretical models giving response times for Storglaciären of the order of 50 years. According to these models, Storglaciären could by now have reached a profile in balance with the present climate. To study this problem, the emergence velocity was calculated and compared with the net balance. The result shows that the emergence velocity either balances or exceeds the net balance for the entire tongue except for the lowermost part, where it decreases to about half of the net balance. A slight further recession of the front position would thus be expected with today’s climate.

Calculated balance velocities also suggest that most of the present profile is close to a steady-state profile, if the mean annual sliding velocity is about 50% of the surface velocity. Lower sliding velocities would imply a thickening of the tongue and a thinning of the accumulation area during years of balanced mass budget.

Observations of the physical properties of the snow cover and underlying young fast ice in Resolute Passage, N.W.T., Canada, were made during the winter of 1982. Detailed measurements of snow density, and ice and snow temperatures, salinities, and brine volumes were made over a period of 46 d, beginning when the ice was 0.4 m thick and about 8 d old. The recorded values are used in a theoretical mixture model to predict the dielectric properties of the snow cover over the microwave frequency range. The results of this analysis are then used to investigate the effects of the snow properties on the radar back-scatter signatures of young sea ice. The results show that back-scatter is a function of the incidence angle and can change significantly over short periods of time during the early evolutionary phase of ice and snow-cover development. This has important consequences for the identification of young ice forms from Synthetic Aperture or Side Looking Airborne Radar images.

Depth hoar in polar firn forms when large temperature gradients act on low-density firn, but high-density firn does not develop into depth hoar. Low densities in firn may be depositional (burial of surface hoar or still-air snowfall) or diagenetic (mass loss to the free atmosphere, typically in autumn); however, diagenesis is sufficiently strong to cause significant mass loss only in the top 50–100 mm of firn. Between about 50–100 mm and 2 m depth, grain growth and densification are accelerated strongly by temperature-gradient effects; from 2 to 5 m, temperature gradients have a small but measurable effect on rates of processes in firn, and below 5 m rates essentially have isothermal values.

Diagenetic depth-hoar layers typically develop in the autumn, are relatively thick, and have smooth bases. Depositional depth-hoar layers may develop at any season, are relatively thin, and have irregular bases. In low-accumulation regions, visual stratification may preserve only an annual signal, but in high-accumulation regions individual storms or other features may be recognizable.

Creep curves obtained from the polycrystalline ice samples containing low concentrations of antifreeze glycopeptides (AFGPs) do not show the re-accelerating or tertiary creep that is found in pure ice samples. Previous work has shown that AFGPs inhibit grain-boundary migration in ice and the present results are consistent with this, as tertiary creep is associated with nucleation and growth of new ice grains.

It is believed that water-filled cavities on the scale of decimetres are present in a number of glaciers in Spitsbergen. The evidence for this hypothesis comes from airborne radio echo-sounding records collected by the Scott Polar Research Institute in 1983. The size of these cavities prevents the use of Rayleigh scattering theory and requires a more general analysis. Mie scattering theory is used to investigate the scattered power providing some unexpected results, the most significant of which is that for water bodies greater than approximately 0.25 m in radius the returned power from the volume illuminated is greater than that from a perfectly reflecting plane boundary.

Trace elements in ice samples taken from Law Dome, Antarctica, were analysed using an instrumental neutron-activation analysis technique. A Jupiter multichannel analyser-computer system coupled to a Ge(Li) detector was used for the acquisition of γ-spectra and for data reduction. “Blanks” in water and in nitric acid, which were used in pre-concentration and sample transfer, were also analysed. To check the validity of this analytical procedure, a U.S. Environment Protection Agency water standard for trace elements was also analysed. The observed values agreed with the certified values.

The results (in ppb) of eight elements are:

Na   209         Mn   0.42   Mg  26   Fe  14

Sc    0.0017   Co   0.028   Al   9.6   Se   0.02

The enrichment factors for these eight elements relative to the Earth’s crust were calculated. These elements can be subdivided into three groups or sources according to their enrichment factors. The variations of elemental concentrations with depth show no positive tendency towards a systematic increase or decrease over the past 5000 years.

The mechanical behaviour for the geometrical properties of two-dimensional deformation has been investigated. The Mohr formulation of failure, which is based on the concept of slip at the plane of weakness, is used in this study. It is shown that alteration of the shear stress τn at the plane of weakness requires self-similarity of features in deformation patterns. A general relationship between the angle of internal friction and the breaking angle of deformation patterns is derived. Using imagery data, this relationship is used to find the angle of internal friction from selected sea-ice deformation patterns. The value obtained for this angle is Φ = 15° ± 2° for deformation on a scale from 100 m to 100 km.

The isotopic composition of river water discharging from the Norwegian glacier, Austre Okstindbreen, in summer varies on both daily and longer-term scales. Most δ18o values of samples from the principal river are within the range −12.5 to −14.0‰). Because new snow tends to be relatively depleted of 8180, water leaving the glacier early in the summer has low δ18O values. Subsequently, values rise as contributions of old snow, glacier ice, and their melt waters, which are isotopically heavier (median δ18O values generally above −12.0‰) dilute the δ18O depleted base-flow component of discharge, a mixture of waters with different histories of formation, storage, and transit. Accumulation-area melting contributes significantly to river discharge. Towards the end of the summer, as surface melting declines, δ18O values tend to fall. Between-year differences of within-summer trends reflect differences of development of the glacier’s drainage systems. The drainage systems are affected by outbursts from a glacier-dammed lake. During fine weather, δ18o variations follow the diurnal cycle of surface melting: they are strongly correlated with, but lag behind, air temperatures. Perturbations during rainfall cannot be explained simply in terms of the isotopic composition of the precipitation, since low values may be associated with isotopically heavy rainfall. Displacement of water previously stored within or below the glacier may account for the anomaly. Contrasts of composition characterize different rivers leaving the glacier, because the relative contributions of various water sources differ.

During fast indentation tests on ice sheets at constant rates, crushing is commonly observed at appropriate combinations of speed and aspect ratio. An analysis is made of this mode of failure, using as a basis a recently conducted test on an ice sheet under controlled conditions. The variation of load with time is given special attention, and cyclic variation of load is associated with periodic crushing (pulverization) events, followed by clearing of the crushed ice particles. An analysis of the clearing process is summarized in the paper, treating the crushed ice as a viscous material. A detailed analysis of the energy exchanges during the indentation process is given. Elastic variations of stored energy in the indenter and in the ice sheet are calculated; these are relatively minor. The dissipation of energy during a typical load cycle (3 mm movement during 0.05 s) is about 8 J. The energy required to create surfaces of the crushed ice particles is small (0.006 J), as is the work of crushing based on mechanical testing (0.09 J). It is concluded that the process of viscous extrusion of crushed ice is the main seat of energy dissipation, basically as a frictional process. A relationship for the mean thickness of the crushed ice layer is developed, based on energy-balance considerations.

Glaciated valleys of the Dalton Range in the south-west Yukon Territory are dominated by rock glaciers identified as glacier ice-cored debris systems. The two rock glaciers studied have different amounts of deformation at present, resulting from post-formation mechanics.

The primary formation of lobes of the rock glaciers resulted from periods of glacier activity in the Neoglacial, although older lobes, probably late Pleistocene in age, occur below the Neoglacial lobes. The hydrological systems of the rock glaciers have played a major role in the post-formation deformation of the land forms and the present drainage system is entirely sub-surface. The explanation for the extensive occurrence of rock glaciers in the Dalton Range is lithological as a result of the high susceptibility of the Upper Jurassic/Lower Cretaceous sediments to frost action and glacier erosion.

Glacier variations during the last few centuries have shown a marked coherence over the globe. Characteristic features are the maximum stand somewhere in the middle of the nineteenth century, and the steady retreat afterwards (with some minor interruptions depending on the particular region). In many papers, qualitative statements have been made about the causes of these fluctuations. Lower temperatures associated with solar variability and/or volcanic activity are the most popular explanations. In particular, the statistical relation between glacier activity and major volcanic eruptions appears to be strong.

In this paper, an attempt is made to simulate recent glacier fluctations with a physics-based model. A simple climate model, calculating perturbations of surface-radiation balance and air temperature (not necessarily in phase!), is coupled to a schematic time-dependent glacier model. The climate model is forced by volcanic activity (Greenland acidity and/or Lamb’s dust-veil index) and greenhouse warming. Solar variability was not considered, because its effect on climate has still not been demonstrated in a convincing way. The output is translated into variations in equilibrium-line altitude, driving the glacier model.

The simulated variations in glacier length show good agreement with the observed record, but the amplitude is too small. This is improved when mass-balance gradients are assumed to be larger in warmer climates. Compared to recently published modelling studies of particular glaciers, in which series of local parameters (e.g. tree-ring width and temperature) were used as forcing, the present simulation is better. This suggests that the radiation balance is a decisive factor with regard to glacier variations on longer time-scales. The model experiments lend support to the results of Porter (1986), who concluded from a more qualitative study that a strong relation exists between periods of increased volcanic activity and glacier advances.

A comparison of some selected runs shows that, according to the present model, the greenhouse warming would be responsible for about 50% of the glacier retreat observed over the last 100 years.

Scheuchzer’s dilatation theory and Altmann’s rigid sliding theory were the first glacier-flow theories to receive serious scientific attention. When Agassiz began a research program at Unteraargletscher in 1839, he held several incorrect notions about glacier flow. Forbes understood the difficulties with the existing theories, and in the early 1840s he and Agassiz acquired motion, temperature, and structural data that were incompatible with the dilation and sliding theories but were suggestive of flow analogous to that of a viscous fluid. How an apparently brittle rigid solid like ice could flow became the central paradox requiring explanation. Some of the most able physicists of the mid-nineteenth century went through contortions in their largely misguided efforts to explain the viscous behaviour in terms of the known physics of rigid solids. Personality and speculation played a far larger part in their debates than we see in scientific discussions today.

We have built a radio-echo sounder which utilizes a low-frequency broad-band impulse transmitter and a microprocessor-based digital-recording system. The unit is mounted on skis and power is delivered by a small generator and batteries. The receiver uses a portable digital storage oscilloscope which passes data via a microprocessor unit to a cassette tape for off-line analysis on a personal computer. Though originally intended primarily for sounding temperate ice, the system has been tested in the Antarctic during the 1987–88 field season with good results. The radar performed well there and also in field tests and subsequent studies on South Cascade Glacier, Washington, and many interesting results were obtained. An oblique incidence profile, where transmitter-receiver separation varied, was used to study the dielectric permittivity of the ice and to locate internal layers at shallow depths. The sounder was also deployed in conjunction with hot-water drilling experiments attempting to create cavities at known locations within the ice. Wave forms from different transmitter–receiver orientations around the bore hole were combined in the off-line analysis to produce a more directional synthetic aperture emphasizing returns from the bore-hole region. Changes in the radar echoes from within the ice were not seen during these experiments, possibly because the drilling was not able to create regions with dimensions or orientations approximating those of naturally occurring cavities.

SIPRE-style hand augers usually recover core sections whose bottom is somewhat shallower than the drill depth. A procedure for calculating the range of possible core depths is presented.

A technique is described for measuring melt-water outflow from snowbanks that develop a basal ice layer. The method involves excavation of channels across ice exposed at the lower edge of a snowbank in order to divert run-off into a portable flume. Since discharges are measured before the water comes into contact with the soil, sub-surface flow and soil-moisture changes do not have to be assessed. Outflow discharges recorded at a perennial snowbank site on Melville Island, N.W.T., Canada, compare favourably with energy-balance calculations and measurements of ablation.