Ice-core drilling to depths of 200–300 m is an important part of research studies concerned with paleoclimate reconstruction and anthropogenic climate change. However, conventional drilling methods face difficulties due to firn permeability. We have developed an electromechanical ice-core drill with air reverse circulation at the hole bottom. We believe that the new drilling system will recover ice cores faster than shallow auger drills, with high efficiency and low energy consumption. The theoretically estimated up-hole speed of the airflow should be not <7.7 m s−1 to allow proper removal of ice cuttings from the borehole bottom. The computer simulation and test results showed that the design of the new ice-coring drill is feasible. The maximum allowed penetration rate depends by square law on airflow.

Compressive strain-rates in discrete layers of a sub-alpine snow cover are analyzed. Individual layers are identified according to density and the dominant type of metamorphism which contributed to their formation. Data were collected during four winter seasons at the Institute of Arctic and Alpine Research (INSTAAR) snow-study site (3 400 m), Red Mountain Pass, south-western Colorado, U.S.A. At average densities of less than 250 kg m₋3 the influence of metamorphism on strain-rate is not apparent. However, at densities greater than 250 kg m₋3, two separate relationships emerge for strain as a function of crystal type and density. While two adjacent layers may exhibit comparable densities, a layer of sintered, fine grained (ET) snow indicates a strain-rate approximately one order of magnitude greater than an adjacent layer of cohesionless, coarse-grained (TG) snow.

Theories of the dielectric constant in ice differ in three fundamentally different ways that are often confused with each other. First, there is the choice of interactions to include in the model, notably whether to try to include long-range dipolar interactions as in the Kirkwood theory or to include only the short-range ice-rule interactions. Second, there is the choice of the kind of statistical quantity calculated, e.g. the Kirkwood correlation factor g or the polarization factor G, which Stillinger and Cotter showed to be different. Finally, there is the choice of the kind of computational tool used, and in original papers this choice often obscures the first two differences. With these distinctions in mind a review is given of current theoretical calculations of the dielectric constant and the residual entropy and how the different theories relate to each other and to experiments.

Reorientation of individual crystal glide planes, as isotropic surface ice is deformed during its passage to depth in an ice sheet, creates a fabric and associated anisotropy. We adopt an evolving orthotropic viscous law which was developed to reflect the induced anisotropy arising from the mean rotation of crystal axes during deformation. This expresses the deviatoric stress in terms of the strain rate, strain and three structure tensors based on the principal stretch axes, and involves one fabric response function which determines the strength of the anisotropy. The initial isotropic response enters as a multiplying factor depending on a strain-rate invariant and incorporating a temperature-dependent rate factor. The fabric response function has been constructed by correlations with complete (idealized) uniaxial compression and shearing responses for both ‘cold’ and ‘warm’ ice. The possible effects of such fabric evolution are now illustrated by determining steady radially symmetric flow solutions for an ice sheet with a prescribed temperature distribution and subject to an elevation-dependent surface accumulation/ablation distribution, zero basal melting and a prescribed basal sliding law. Comparisons are made with solutions for the conventional isotropic viscous law, for a flat bed, for a bed with a single modest slope hump and for a bed with a single modest slope hollow, for both cold and warm ice.

After a brief review of factors relevant to the propagation of radio waves in ice, problems of profiling the upper and bedrock surfaces of ice sheets are considered. These include deconvolution of echo traces and accurate navigation. Results already available not only provide knowledge of sub-ice geomorphology, but also confirm our general ideas on interaction of temperature and flow in large ice sheets. Difficulties encountered in the study of temperate glaciers appear to be due to irregular dielectric properties of the ice mass, which in turn suggest an irregular distribution of water. In the future, application of radio-echo methods should lead to more detailed knowledge of accumulation and ablation over ice masses, improve our understanding of temperatures at great depths in polar ice sheets, and give data on ice movement from central areas of ice sheets.

Using a Monte Carlo (MC) method, we determine the accumulation-rate profile along a flowband, the influx of ice into the upstream end of the flowband and the age of an internal layer. The data comprise the depth profile of the internal layer, a few velocity measurements at the surface and the average accumulation at one location. The data in our example were collected at Taylor Mouth, a flank site off Taylor Dome, Antarctica. We present three alternative formulations of this inverse problem. Depending on the formulation used, this particular inverse problem can have up to four solutions, each corresponding to a different spatial accumulation-rate pattern. This study demonstrates the ability of a MC method to find several solutions to this inverse problem, and how to use a Metropolis algorithm to determine the probability distribution of each of these different solutions. The only disadvantage of the MC method is that it is computationally more expensive than other inverse methods, such as the Gradient method.

Observations are presented on a particularly unusual sequence of flood events witnessed at Bas Glacier d’Arolla, Switzerland, in July 1987. The sequence was triggered by heavy rain storms, and involved a supraglacial “overflow event” (water cascading from moulins over the snout of the glacier) succeeded, following a series of “mini-floods”, by a subglacial “outburst event”. Available hydrological and geomorphological data are used to assess the significance of the floods and to deduce likely explanations for each phase of the flood-event sequence. Bottom-up surcharging of a poorly developed subglacial drainage system is the preferred explanation for the overflow event. The subglacial outburst is explained as an extreme “spring event”. Hydraulic jacking is implicated, but not proven, during both events. Whilst the flood sequence was triggered by an intense storm, englacially stored waters are believed to have contributed most of the flood waters.

An analysis of records of annual mean temperatures around Antarctica shows large-scale anomalies of thousands of kilometers extent with typical variations of a deg from one year to another From 1967 on, composite satellite photographs are available which show considerable variation in the sea-ice extent in different years up to about 5º of latitude. These largest differences seem to persist over entire seasons. In general there seems to be considerable association between the region around the Antarctic with the coldest temperatures and the regions of greatest sea-ice extent. An analysis of long-term records at a single location near the edge of the Antarctic sea ice indicates a strong correlation between variations in the annual mean temperature and the duration of the sea ice, such that a change of 1 deg in the annual mean temperature corresponds to about 70 d variation in the duration of the sea ice. A relation is obtained between variations of annual mean temperature and the mean extent of the sea ice, viz. a 1 deg change corresponds to approximately 2.5º latitude variation in the maximum sea-ice extent. The magnitude of the variations in the sea-ice extent observed from the satellite data in comparison with the large-scale temperature anomalies is compatible with the above relations, although some rotational shifts appear to take place.

A new laboratory device is used to investigate the resistance to clast ploughing at the base of glaciers. In experiments in which a ploughing tip is dragged at different velocities and effective normal stresses through water-saturated sediment from Unteraargletscher, Switzerland, pore pressures above and below the hydrostatic level develop around the tip. The absolute magnitude of these nonhydrostatic pore pressures increases with the ploughing velocity but remains small compared to the sediment yield strength, so that the pore pressures do not significantly weaken the sediment. The shear stress on the tip is independent of the velocity but scales with the applied effective normal stress, in agreement with a Coulomb-plastic behavior of the sediment. The results indicate that, depending upon position close to the object, both sediment compaction and dilation can influence the pore-pressure distribution and thus the sediment yield strength. Comparison with other studies of clast ploughing suggests that the significance of sediment weakening in front of ploughing clasts may depend on the relative magnitudes of the non-hydrostatic pore pressures. Therefore, depending on the dominant pore-pressure response of the deforming sediment, clast ploughing may have the potential to either trigger ice-flow instabilities or stabilize glacier motion.

Statistical results of measurements of glacier variations in Switzerland 1891–1965 are compared with deviations from average temperature and precipitation in summer for stations above 2000 m. The result is interpreted in terms of meso-scale glacier–weather relations. A correlation between glacier mass budget and deviation from the average height of the 500 mbar surface indicates the importance of cyclonic and anticyclonic conditions during the ablation period, and therefore of the frequency of certain Grosswetterlagen which has been studied for the period 1881–1965. The pattern of the difference of Grosswetterlagen favourable and unfavourable for glaciers resembles the pattern of glacier variations and also of mass-budget data. Atmospheric circulation in zonal and meridional forms, as expressed by the frequency of Grosswetterlagen has to be considered by seasons. There is no simple relation between the intensity of zonal circulation and glacier variation. Glacier recession of the last few decades seems to be caused by the fact that meso-scale weather conditions mainly in the ablation season have become much less cyclonic than in the decades 1886–95 and 1906–15.

Large subglacial lakes manifest themselves as flat regions on the ice surface. ERS-1 satellite radar altimetry of the Dome C region of East Antarctica was analyzed to correlate unusually flat areas on the ice surface with known locations of subglacial lakes identified from airborne radio-echo sounding (RES) data. The mean length of subglacial lakes which have an expression in the ice-sheet surface was ~8.3 km, whilst those that did not exhibit a surface morphological manifestation had a mean length of ~3.3 km. Thus, lakes up to about 4 km in length arc unlikely to be detected from satellite radar altimetry of the ice surface. Given that the spacing of radio-echo flight tracks within the SPRI-NSF-TUD Antarctic database is 50-100 km in many areas, a number of subglacial lakes probably lie undetected beneath the ice sheet. RES information from two large, flat surface regions within Dome C, and a further flat area located at 80° S, 127° E, indicates the absence of subglacial lakes beneath the ice-surface features. However, these areas are characterised by relatively strong radio-echo returns which may indicate the presence of water-saturated basal sediments. We suggest that (1) blankets of water-saturated basal sediments may cause similar surface morphological features to those produced by subglacial lakes; and (2) misidentification of subglacial lakes from satellite altimeter observations of the ice-sheet surface is possible without the support of RES information relating to the ice-sheet base. Furthermore, our study indicates a lack of subglacial lake signals from RES data over relatively thick regions of East Antarctica such as the Adventure Subglacial Trough. We conclude that subglacial water produced in such regions may be transported by a basal hydrological system, driven by overburden pressure, to less thick regions of the ice sheet where subglacial lakes have been identified.

Glacial mass-balance reconstruction for a long-term time-scale requires knowledge of the relation between climate change and mass-balance fluctuations. A large number of mass-balance reconstructions since the beginning of the century are based on statistical relations between monthly meteorological data and mass balance. The question examined in this paper is: are these relationships reliable enough for long-term time-scale extrapolation? From the glacier de Sarennes long mass-balance observations series, we were surprised to discover large discrepancies between relations resulting from different time periods. The importance of the albedo in relation to ablation and mass balance is highlighted, and it is shown that it is impossible to ignore glacier-surface conditions in establishing the empirical relation between mass-balance fluctuations and climatic variation; to omit this parameter leads to incorrect results for mass-balance reconstruction in the past based on meteorological data.

To better understand apparent stratigraphic disturbances in ice cores such as Greenland Ice Sheet Project 2 (GISP2), we examine how ice-sheet flow can transform gentle open folds into order-disturbing recumbent folds. The initial disturbances in the stratigraphy have their roots in transient dynamic processes and local rheological inhomogeneities, but the kinematics of even a simple ice-flow model can deform these disturbances enough to alter paleoclimatic interpretation of an ice core. The local vorticity number suggests which structures can be passively overturned, but analyzing the finite strain along particle paths gives a more complete picture, especially when taken relative to a hypothetical core location. Core-relative isochrones, or “pre-cores”, predict which stratigraphic disturbances will appear as obviously overturned layers in a core. The deformation-gradient tensor along particle paths allows us to calculate the rotation of segments of various reference slopes. These calculations suggest that observed 20° dips in the GISP2 core are rotating on a time-scale of a few hundred years and could result from distortions with much smaller slopes produced upstream. The time during which they can be recognized to be overturning is short because the rotation rate is high. Once overturned they are flattened further and may be hard to recognize, especially in the small cross-section of a core.

A commonly accepted distinction between snow-patches and glaciers is the slow mass movement of the latter with consequent abrasion of stones and rock surfaces. However, the observations of some workers do not support this distinction. The present study, in a snow-patch area on Mount Twynam in the Snowy Mountains (Australia), presents positive evidence of slow mass sliding of snow, causing transport, abrasion and detachment of stones and abrasion of the bedrock surface. Consequently, no sharp separation is possible between the erosional effects of snow-patches and small cirque glaciers. In areas such as the Snowy Mountains the relative importance of glacial and nivational processes becomes more difficult to evaluate.

Brillouin spectroscopy has been used to measure the adiabatic elastic constants of laboratory-grown pure monocrystalline ice Ih at – 3°C. The values obtained were (in units of 108 N/m2): c11 = 136.96 ±0.60, c12 = 69.66± 0.45, c13 = 56.28±0.31, c33 = 147.02±0.68, c44 = 29.59±0.15. Comparison of these values with ultrasonic measurements quoted in the literature reveals no significant acoustic dispersion in ice over frequencies ranging to 1010 Hz. However, the results suggest that the elastic constants of ice may depend on the precise crystal quality and age of a given sample. The low experimental error in the values obtained, along with the inherent versatility of the method, indicate that Brillouin spectroscopy is an effective technique for systematically investigating the elastic properties of ice samples formed under natural conditions.

During the winter of 1987–88, an average of seven tensile tests was made for each of 66 snow layers in the Rocky Mountains of western Canada. The precision of the mean strength for seven tests, expressed in terms of the coefficient of variation, was 15% with 90% confidence. Snow with a faceted micro-structure was approximately half as strong as partly settled or rounded snow of the same density. Notch sensitivity in the strength data and critical strains of 1% or less indicate that the test fractures were essentially brittle.

Profile surveys are presented of four ice rises on the east coast of the Antarctic Peninsula. On Butler Island velocity measurements were also made. The ice rises behave as miniature ice caps frozen to flat horizontal bedrock and provide a simple system for the study of laws of ice flow. Deformation is principally by shear through the ice mass. Velocity measurements provide a value of n = 3.13±0.52 for the flow law . Each ice rise is bounded on one side by ice shelf and on the other side by open sea. Towards open sea the profiles are found to agree well with steady-state theoretical profiles and they supply a value of for temperature – 13.5°C and stress range 0.5–1.3 bar. Towards ice shelf the profiles are elongated and they deviate from the theoretical profile. This may be due to compressive stress in the ice shelf causing migration of the grounding line down sloping bedrock. No significantly anomalous behaviour is found in the summit region.

The future contributions of the Antarctic Ice Sheet to sea level rise will depend on the evolution of its surface mass balance (SMB), which could amplify/dampen mass losses increasingly observed at the ice sheet's edge. In situ constraints of SMB over annual-to-decadal timescales consist mostly of firn/ice cores that have a surface footprint $\sim$cm$^{2}$. SMB constraints also come from climate models, which have a higher temporal resolution but a larger surface footprint of several km$^{2}$. We use ice-penetrating radar data to obtain an intermediate spatial and temporal resolution SMB record over three ice rises along the Princess Ragnhild Coast. The co-located ice cores allow us to obtain absolute radar-derived SMB rates at a multi-annual-to-decadal temporal resolution. By comparing the ice core SMB measurements and the radar-derived SMB records, we determine that pointwise measurements of SMB are representative of a small surface area, $\sim 200-500$ m radius extending from the ice core drill site for the ice rises studied here, and that the pointwise measurements are systematically 7–15 cm w.e. a$^{-1}$ lower than the mean SMB value calculated for the whole ice rises. However, ice core records are representative of an entire ice rise's temporal variability at the temporal resolution examined.

As part of the Ross Ice Shelf Geophysical and Glaciological Survey, a detailed map of ice thickness has been produced from airborne radar measurements closely tied to the network of survey stations on the ice-shelf surface. The map, drawn with a 20 m contour interval, reveals a highly complex pattern of thickness variations reflecting presumably, at least in part, complex ice-shelf dynamics. Many features of the thickness variation pattern appear to be associated with zones of grounded ice, but not all. Features of interest include many ice thickness minima, with closures up to 120m; a narrow, greatly elongated ridge-trough system 450 km or more in length; a few ice thickness maxima; steep regional gradients of 10 m/km in freely floating ice; highly contorted contours suggesting a large-scale “turbulence”; and at least two remarkable step-like changes in ice thickness. The irregularity of many of these features suggests dynamic non-equilibrium, i.e. the existence of transients in the dynamic system, so that the ice shelf as a whole suggests a state of rather rapid change. Flow-bands constructed on the basis of the strengths of the echo from the ice-water interface clearly delineate the outflow from the main East Antarctic outlet glaciers in the grid eastern part of the shelf. A discontinuous flow band originating in a small mountain glacier (Robb Glacier) suggests a variable mesoclimate in the vicinity of the glacier within the last thousand years. Strong reflections near the ice front suggest bottom melting of saline ice previously frozen on to the underside of the ice. Several rifts or incipient rifts in the ice shelf characteristically show two lateral bands of strong reflections with a non-reflecting zone in between.