Several aspects of space glaciology are considered in the paper. Estimates of the water content of the Earth, Mars, and the Galilean moons of Jupiter are corrected. A considerable proportion of the total amount of water in the solar system is localized near Jupiter; part of this water is contained as ice in glaciations, glacial caps, and ice crust on the planets. Ice is one of the main components of the surface of some planets. The major amount of ice on Mars is contained in a permafrost layer of mean thickness about 3 km. The model of an ice crust floating on a water mantle is considered for Jupiter’s moon Europa. It is shown that for definite values of certain parameters this crust may be subject to destruction due to the instability of its proper oscillations, which explains the numerous systems of fractures and cracks observed on Europa’s surface. The stress-strain state of such an ice crust is calculated within the framework of a non-linear thermo-elasticity model. The role of short-period temperature variations at Europa’s surface is estimated and the peculiarities of relief observed on this planet are analysed.

In the last decade deposition on lateral moraine embankments of glacier de Tsidjiore Nouve has been re-activated on a large scale. An attempt has been made to reconstruct, from the dimensions of the embankments, average rates of debris accumulation on the moraines during the Neoglacial period. These are compared with rates of deposition over the period 1977–82, calculated from detailed changes in moraine profiles (surveyed by ground- and air-based photogrammetry) and measured rates of ice-margin ablation. At present total output of sediment, by marginal deposition and transport by melt-water streams, from glacier de Tsidjiore Nouve is in the order of 6400–9500m3/a; this suggests the possibility of a high average erosion rate within the glacier catchment of 1.55–2.29 mm/a.

In 1983 three directional surveys were made in the bore hole from which a deep ice core was obtained in the summers of 1979–81. The inclination and azimuth of the bore hole were measured on three surveys, temperature was included on two surveys, fluid pressure and hole diameter on one of the surveys. Fluid-pressure measurements show that the ice-overburden pressure was undercompensated in the upper few hundred meters and overcompensated at the bottom of the hole. Diameter measurements show closure in the upper portion and expansion near the bottom beginning at the transition from the Holocene to Wisconsin ice at 1784 m. The hole expansion and increase in inclination correlate with dust and silt content in the Wisconsin ice. Changes in azimuth are due to flow of the ice and are consistent with the direction of flow at the surface. Temperature measurements show that the hole is at or near equilibrium. The gradient of 0.012 K/m below 1400 m is less than the 0.018 K/m at Camp Century. There is a slight reduction in gradient near the bottom from internal friction in the silty ice.

Georesistivity soundings have been carried out at four sites in the Antarctic Peninsula. The objective of the work was to investigate the electrical behaviour of ice from an area where substantial melting occurs in summer and from contrasting thermal regimes. Electrical measurements made at three sites along a flow line within George VI Ice Shelf reveal that:

• (a) the resistivity of deep ice is similar to that of other Antarctic ice shelves,

• (b) the resistivity of the ice-shelf surface, which is affected by the percolation and refreezing of melt water, is similar to that of deep ice and hence the ice is polar in character.

A compilation of published resistivities of deep ice from polar regions shows that the range of resistivities is very narrow (0.4 –2.0) x 105 Ω m between –2 and – 29°C, irrespective of the physical setting and history of the ice. Typically, resistivity is within a factor of two of 80 kΩ m at –20° C with an activation energy of 0.22 eV. In contrast, the resistivity of surface ice at Wormald Ice Piedmont, where the ice is at 0°C throughout, is two orders of magnitude higher and falls at the lower end of the range of resistivities for temperate ice.

A mathematical model for the formation of perched blocks on glaciers due to differential ablation is developed by considering energy balances. The model is applied to naturally positioned rocks on Bersærkerbræ, Greenland. The model predicts correctly whether a rock will perch or sink in eleven out of twelve cases. For artificially positioned small rocks of mean dimension 0.2 m, the model has a 53% success rate. The reduced performance is probably due to the thicknesses of the rocks being of similar magnitude to the range of relief of the glacier surface.

Researchers have analyzed various properties of drumlins within individual drumlin fields in order to provide evidence to help in identifying the processes involved in drumlin formation. One property which has been examined is the spatial distribution of drumlins within a field. Traditionally, in such endeavours the individual drumlins have been represented as points and their distribution examined using techniques of point-pattern analysis. We suggest that not only is such a representation inappropriate at this scale, it also introduces statistical bias which makes the results of such analyses questionable. Consequently, we propose an alternative approach which involves representing individual drumlins as areal phenomena and considering their pattern as a two-phase mosaic. The advantages of such an approach are discussed and it is illustrated by applying it to two different drumlin fields.

Avalanche tarns are a particular morphological form of avalanche impact and sixteen of these features are described from the Fiordland region of New Zealand. Average area of the tarns is 11000 m2. Profiles are given for eight of the avalanche paths where such tarns occur. All are found at the base of very steep avalanche tracks (slopes 38–59°), where there are no fans, so that there is an abrupt change of slope with the valley floor. The plunging avalanches which cause the tarns may have a mass of up to 300000 tonnes and impact pressures of more than 600 kN/m2, although no direct measurements are available.

The natural modes of oscillation of an infinitely long, ice covered channel are considered, using the hydrostatic approximation, and assuming the ice to behave elastically. The dispersion relation, mode shape, and associated force on the channel wall are found for the lowest three modes. Special attention is paid to the limitations associated with the hydrostatic and elastic approximations.

Field tests have been developed to measure the shear and tensile strengths of large volumes of snow. Basal shear strengths were measured across and down some slabs of snow, giving highly variable strengths. These measurements support the idea that the basal region of an avalanche may contain zones where the basal shear strength exceeded the gravitational shear stress (i.e. pinning areas) with weak zones between (deficit areas) where the shear strength was less than the gravitational shear stress. The slab tensile stresses induced by these deficit areas would become high if either the deficit length (down-slope) was large, or the deficit itself was large. Measurements of tensile strengths of slabs above weak layers, together with the down-slope gravitational stress of a snow slab, suggest that deficit lengths of only several metres are often sufficient to cause a local tensile failure. In some cases, this local failure may propagate across the remainder of the slope (depending on the pinning distribution) and cause an avalanche. We propose that the maximum local deficit, rather than the mean slope deficit of basal shear stress, and the maximum length of the local deficit, are the first important parameters to consider when evaluating slope stability in the field, since the magnitude of these factors determine the probability of a local tensile failure.

Two air-permeability devices were developed and measurements were made to study the relationship between air permeability and structure of different snow types. Permeabilities varied both with position and direction in the snow-pack, and changed with time as metamorphic changes occurred. A marked increase of air permeability was noted as faceted crystals grew due to radiation recrystallization. In other observations, as a snow-pack densified and crystals became more rounded (destructive metamorphism) the air permeability decreased. Measurements were made of air permeability of snows that had been subjected to a creeping tensile strain, and initial tests indicated that the changes in air permeability due to strain, even to rupture, were significant, but small compared with the intrinsic variability of snow.

A model for glacier flow is developed which incorporates longitudinal deviatoric stress contributions to the field equations. The underlying assumptions may be applied to develop models for various situations. Here, they are developed for steady-state and non-steady-state sliding glaciers in plane flow. The models reduce to a proper generalization of plane-flow pseudo-hydrostatic theory if longitudinal deviatoric stresses are neglected in comparison to basal shear stresses. Solution of this simpler reduced model allows an estimate to be made of the magnitude of the longitudinal deviatoric stress to test if it is negligible or, more generally, investigate under what conditions it can be neglected. The steady-state model predicts that longitudinal deviatoric stresses are negligible for very arbitrary non-uniform sliding-law distributions provided that the following conditions exist: the region must be distant from an ice divide or terminus and subject to normal (not extreme) accumulation or ablation. On the other hand, examples are produced where, under non-steady conditions, longitudinal deviatoric stresses are important and even dominant.

Nye’s theory of glacier sliding, when modified to incorporate Gilpin’s model of the liquid layer adjacent to foreign solids in ice, predicts non-zero sliding speeds at subfreezing temperatures. Although the predicted speeds are too small to affect glacier motion or even to be observed readily, the total distance of sliding of large glaciers should be adequate to produce bedrock striations. Dissolved solutes in the liquid layer increase the sliding speeds slightly. At temperatures below about – 1° C, 90% of the drag comes from the part of the bed-roughness spectrum at wavelengths between 0.2 and 20 mm regardless of solute concentration. If no more basal ice melts than refreezes (as in a cold glacier), the average liquid-layer thickness and, concomitantly, the sliding speed for given drag and roughness are governed by the ambient temperature. With net melting (as in a temperate glacier), on the other hand, they are governed by the rate of escape of the excess water and no conflict arises between the thickness requirement for run-off water flow and that for regelation water flow. Thus, the proper distinction is not between temperate and cold, but between net melting and no net melting. The theory applies to both cases.

The effect of ice content and normal load on the shear strength characteristics of a frozen coarse granular debris was investigated. 31 shear tests were carried out in a modified shearbox allowing a sample temperature of (–1.0 ± 0.2)° C and a load rate of 9.63 × 10−4 cm/min. The tests showed that as the ice content of the frozen debris was increased from 0% (under-saturated) to 25% (saturated), sample shear strength was markedly increased. In contrast, sample shear strength was reduced as ice content was increased from 25% (saturated) to 100% (supersaturated). The changes in shear strength with increasing ice content were attributed directly to changes in internal friction and the cohesive effects of the pore ice. The shear tests also indicate that shear strength increases with increasing normal load up to a critical limit. Above this limit, dilatancy is suppressed causing the shear strength to decrease or remain relatively constant with increased normal load.

The stress-strain curves of the 31 tests indicated that samples with higher ice contents tended to reach peak strength (τP) with less displacement during shear. Moreover, the difference between τp and τr (residual strength) was lowest for pure polycrystalline ice and highest for ice-saturated samples. The Mohr-Coulomb failure envelopes displayed very distinctive parabolic curvilinearity. The degree of curvature is thought to be a function of ice creep at low normal loads and particle fracture and crushing at high normal loads.

A new extraction system has been designed and constructed which allows the extraction of gases from air bubbles in ice without melting it. The ice sample of about 500 g is crushed an evacuated container by a milling cutter, and the gas escaping from the opened bubbles is collected by condensation at 15K. Results of CO2 analyses of extracted gases are discussed with respect to possible contamination risks by the system.

The fluorescent dye dilution method for determining the liquid-water content in snow is based on measuring the concentration change of a solution when it is mixed with snow. Samples for analysis can be obtained rapidly and reliably, and, unlike calorimetric or equilibrium-temperature methods, field use requires no on-site data analysis.

The possibility of replacing or supplementing direct measurements of mass balance by estimates calculated from equilibrium-line altitude (ELA) measurements is investigated by statistical analyses of data from 31 glaciers. A linear relationship between mass balance and ELA in terms of two parameters, the effective balance gradient and the balanced-budget ELA, is tested. It is concluded that existing mass-balance series can be usefully extrapolated by using ELA data for additional years. However, accurate mass balance cannot be calculated for glaciers where no such measurements have been made because of the difficulties in prescribing the two model parameters with sufficient accuracy. For example, the effective balance gradient is of the order of 5 mm water/m so that errors of only a few decametres in the estimation of the balanced-budget ELA can have a great effect upon calculations of mass balance.

Experiments on progressive unidirectional freezing are conducted to determine the evolution in δD and δ18O of successive water samples and ice layers taken during the course of freezing. Results indicate that this evolution takes place, in a δD–δ18O diagram, along a straight line with a characteristic slope. This slope, different from that due to the precipitation effect, gives a finger-print of the occurrence of a freezing or of a melting–refreezing process in the studied reservoir.

Electrical resistivity sounding, using electrodes which are lowered directly to the ice–rock interface in bore holes, is proposed as a technique for studying the exact position of glacier beds, as well as their lithological characteristics. A test study is described on Grubengletscher, a partially cold Alpine glacier in Switzerland. Results of soundings along a 400m long profile indicate that previous depth determinations, based on radio echo-soundings, were in general accurate to within less than 5% of the actual ice thickness. The results also show that the glacier rests on non-consolidated sediments of considerable thickness. The proposed method could add substantial information about glacier sliding and glacier erosion, if applied alongside conventional deep drilling projects.

Position fixes made at the British Antarctic Survey station, Halley, on the Brunt Ice Shelf are considered for the period 1968–82. These show an initial westward velocity of approximately 400 ma−1 rising to over 700 m a−1 by the end of the period. The data are well fitted by two straight lines. The first for 1968–71 has a slope 430 m a−1 in agreement with that found by Thomas (1973) for the period up to 1968. The second for 1972–83 has a slope 740 ma −1, a large increase sustained for up to 10 years.

The identification of a small region of grounded ice in the north-western sector of the Ross Ice Shelf has forced a re-evaluation of the mass-balance calculations carried out by Thomas and Bentley (1978). Those authors concluded that the Ross Ice Shelf up-stream of Crary Ice Rise was thickening, but they did not take into account the effects on the velocity field of grounded ice (of which they were unaware), which is located near the input gate to their volume element. Reasonable estimates of the degree to which the ice velocity just up-stream of the grounded ice is diminished indicate that it is no longer possible to conclude that the ice shelf is thickening using Thomas and Bentley’s original flow band. Therefore, a new flow band was chosen which was grid east of Thomas and Bentley’s band and unaffected by any nearby grounded areas. The mass balance in this flow band was found to be zero within experimental error; a difference exceeding about 0.2 m a−1 in magnitude between the thickening and bottom freeze-on rates is unlikely.