During the North Water Project of the late F. Müller, glaciological studies were carried out on Laika ice cap. In addition to the main climatological investigations, surveying, mapping, mass-balance studies, and englacial temperature measurements were carried out. The mass-balance distribution is strongly determined by the orography. Strong westerly winds erode and transport snow from exposed surfaces, whereas prevailing easterly winds, during precipitation, deposit snow on lee slopes. The balance is negative under the present climate. The history of the glacier-tongue geometry is reconstructed using geomorphological observations and photogrammetric mapping for 1959 and 1971. Englacial temperature measurements revealed a finite layer of temperate basal ice in the ablation zone. The temperature distribution in the accumulation area around the summit of the ice cap is not stationary.

The initial conditions needed for formation of moulins are crevasses and a supply of melt water. Water pouring into a crevasse may fill it until it overflows at the lowest point, which is normally near the margin. However, as the crevasse deepens, it intersects englacial channels through which the water can drain. These channels may be finger-tip tributaries in a dendritic system such as that described by Shreve (1972) and observed by Raymond and Harrison (1975). When the crevasse closes, heat in the melt water keeps the connection open and a moulin is formed. The englacial channel enlarges rapidly by melting, utilizing mechanical energy released by the descending water.

Descents into moulins, and mapping of structures exposed at the surface after many years of melting, demonstrate that the drainage channels leading down from the bottoms of the moulins have inclinations of 0–45° from the vertical. These channels trend in the direction of the original crevasse but appear to be deeper than the expected depth of the crevasse. They have not, even at depths of 50–60 m, become normal to the equipotential planes described by Shreve.

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.

Inexpensive add-on boards are currently available that enable personal computers to be used as digital image-processing systems. The capabilities of one such system are illustrated by two specific cases examining the surface characterization of a sea-ice cover and the statistical description of sea-ice structure. The unit discussed digitizes video input into a 512 × 512 array of pixels, assigning each a gray shade from 0 to 255. A key feature of the system is that the primitive commands of the board can be accessed through higher-level programming languages. This allows users to customize easily the system for their own needs.

Wide-angle seismic reflections from a glacier bed are sensitive to the presence of subglacial water and to the mechanical strength of the basal zone. The phase of a compressional to shear (P-SV) converted wave is particularly sensitive to the shear coupling between the glacier and its bed. Both shear (SV) and compressional (P) reflections from the bottom of Variegated Glacier were obtained before the 1982–83 surge event using explosive sources, and the phases of these reflections (relative to the source) were positive as expected for an ice/bedrock interface. During surge, P-wave reflections from the deepest part of the glacier bed were phase reversed, while somewhat shallower P-wave reflections were not. SV reflections were not clearly observed during surge and cannot be interpreted with confidence, even though the experiments were designed to detect them using three-component geophones. The unexpected P-wave phase reversal might be explained by a thin, mechanically weak or fluidized basal debris layer during surge which acts as a strong seismic absorber and suppresses multiple reflections within the layer. However, the required amount of seismic attentuation in the layer seems unreasonably large. An alternative explanation requiring ∼4–8 m or more of water or water-saturated debris (without strong attenuation) is implausible.

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.

Ice-stream discharge fluctuations constitute an independent means of forcing unsteady ice-shelf behavior, and their effect must be distinguished from those of oceanic and atmospheric climate to understand ice-shelf change. In addition, ice-stream-generated thickness anomalies may constitute a primary trigger of ice-rise formation in the absence of major sea-level fluctuations. Such triggering may maintain the current ice-rise population that, in turn, contributes to long-term ice-sheet stability. Here, we show that ice-stream-generated fluctuations of an ideal, two-dimensional ice shelf propagate along two characteristic trajectories. One trajectory permits instantaneous transmission of grounding-line velocity changes to all points down-stream. The other trajectory represents slow transmission of grounding-line thickness changes along Lagrangian particle paths.

Abstract. Ice-shelf thickness and velocity anomalies resulting from ice-stream discharge fluctuations are calculated for an ideal ice shelf fed by a single ice stream and confined within a rectangular coastal geometry. Ice-shelf response to periodic forcing is found to be linear (thickness and velocity anomalies oscillate at the forcing frequency, and response scales with the forcing). Thickness anomalies are trapped near the ice-stream outlet and propagate down-stream at a slow, advective time-scale. Velocity anomalies tend to be widespread and propagate instantaneously throughout the ice-shelf environment. Ice-shelf response is sensitive to ice-stream fluctuation time-scale in the manner of a low-pass filter; longer forcing time-scales produce more widespread ice-shelf response. If ice-stream velocity and thickness fluctuations are in phase, thickness-anomaly maxima typically occur down-stream of the ice-stream outlet. This effect may determine where ice rumples and rises are likely to form in response to stochastic ice-stream variability.

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.