In sub-level caving mining operations, the lateral walls cave in. This results in dilution of the mineral content of the produced ore by 15%-20% waste rock. Also 15%-20% of the valuable ores are lost in the caved wall material that is left behind in the mined-out rooms. Placing ice, in the form of a small glacier, in the mine-room before the lateral walls start to cave, permit complete recovery of ore reserves without dilution. The glacier will advance at a rate permitted by ore extraction processes, in accordance with glaciological theories and laws.

Volumes of ice that are required may be calculated from ore extraction rates, power consumed in the mine, ventilating air volumes and temperatures, specific heat and thermal conductivity of the lateral rock. The required ice volumes can be produced through natural freezing of water, where the winter temperatures regularly fall below 0°C for a predictable period every winter. Use of ice as a mining aid reduces costs of the ore extraction process by about one-third and increases value of the produced ore by about 20%. Thus, the value of a given orebody is increased by about 30% relative to the values experienced in the most efficient mines of today.

The study of subglacial movements taking place in regions of cavitation beneath the Glacier d’Argentière, has demonstrated the necessity for using several cavitometers. The very unusual conditions in which such apparatus is installed to measure simultaneously the velocity and the position of the ice vault have led us to design and produce a prototype of a portable cavitometer which records the data on magnetic tape (cassettes).

Since the mid-20th century, ice shelves around the Antarctic Peninsula have declined in extent and thickness, and some have shown signs of structural instability. Here, using satellite imagery from 1999/2000 to 2019/20 (Landsat 7 and 8, Sentinel-2 and ASTER), we measure areal changes, calculate surface flow speeds, and quantify structural changes of Bach, Stange and George VI ice shelves, located in the southwest Antarctic Peninsula. We recorded a total area loss of 797.5 km2 from 2009/10 to 2019/20, though spatial and temporal patterns varied at individual ice fronts. Flow speeds remained largely stable over the observation periods, but notable acceleration was calculated for Bach Ice Shelf, and at the northern and southern extents of George VI Ice Shelf. Open fractures widened and lengthened between 2009/10 and 2019/20 on all three ice shelves. We conclude that Stange Ice Shelf is stable, and not under any immediate threat of enhanced recession. Continued ice-mass loss and consequential speed up of George VI South may cause further fracturing and destabilisation in the coming decades. Of more immediate concern are the glaciological changes noted for Bach Ice Shelf and George VI North; substantial areas of stabilising ice have already, or will soon be removed, that may lead to enhanced recession within the next decade.

Forty years ago, Ahlmann considered the thermo-physical character of ice masses as a basis for differentiating glaciers into two broad geophysical groups: (1) polar and (2) temperate. About the same time, Lagally sub-divided glaciers into corresponding thermodynamic categories: (1) kalt and (2) warmen. By this it was understood that the temperature of a polar, or “cold”, glacier was perennially sub-freezing throughout, except for a shallow surface zone which might be warmed for a few centimeters each year by seasonal atmospheric variations. Conversely, in a temperate, or “warm”, glacier, the temperature below a recurring winter chill layer was consistently at the pressure melting point. As these terms are thermodynamic in connotation, glaciers of the polar type may exist at relatively low altitudes if their elevations are sufficiently great. Temperate glaciers may be found even above the Arctic Circle at elevations low enough that chilling conditions are not induced by the lapse rate.

In these distinctions, it is implied that regardless of geographical location a glacier’s mean internal temperature represents an identifiable characteristic which can be shown critically to affect the mass and liquid balance of ice masses and significantly to relate climatic influences to glacier regimes. The importance of these implications, and the fact that they are based on a gross, sometimes changing, and always difficult to measure, thermo-physical characteristic, makes some explicit terminology desirable.

To some extent Ahlmann addressed this problem by introducing a subordinate classification, sub-polar glaciers. In these, the penetration of seasonal warmth involved only a shallow surface layer at 0°C, but still to a depth substantially greater than the superficial warming experienced in summer on polar glaciers. Lagally also recognized an intermediate type which he called “transitional”, characterized by a relatively deep penetration of 0°C englacial conditions during the summer. These pioneering efforts reflect Ahlmann’s experience with glaciers in the high Arctic and Lagally’s with the Alpine glaciers of southern Europe. Although some confusion has resulted from alternate application of these different terms, both definitions can be useful. Further to refine the classification, a modified terminology is suggested by the writer. This involves introducing a fourth category, substituting the term sub-temperate for Lagally's “transitional” type on the basis that it is etymologically more consistent with the Ahlmann terminology which has remained most commonly in use. Thus, two distinct transitional categories are identified. These categories, sub-polar and sub-temperate, typify ice sheets during changes from fully polar to fully temperate englacial conditions—a situation pertaining during the waning and waxing stages of deglaciation and reglaciation,

A review of the literature reveals further problems. Flint and others have considered geophysically temperate glaciers as most typical of the inland glaciation which covered much of Europe, northern North America and Siberia during the expanded phases of the Pleistocene, whereas others including Ahlmann have suggested that the massive continental glaciers of the Pleistocene were geophysically polar. Thus, the latter advocates consider that present-day Antarctic and Greenland ice sheets represent conditions comparable to those which pertained in the Laurentide and Cordilleran ice sheets. New insights have developed, however, through deep drilling and englacial temperature measurements carried out in a number of different geographical locations in recent years. Such research has shown that each of the geophysical categories can pertain in a glacier system if there is sufficient range of latitude, area and elevation for the requisite climatological factors to pertain.

Because of the foregoing considerations, it is probable that polar, sub-polar, sub-temperate and temperate thermal conditions coexisted in different parts of continental glaciers during the Pleistocene maxima. At times of greatest extension, the ice sheet’s peripheries could have been thermo-physically polar and sub-polar, as on the margins of today’s Greenland icc sheet. But in their most regressive phases, the lower latitude margins were more than likely temperate, with only high interior sectors remaining “cold”. Such combined conditions characterize a fifth thermo-physical category, which in the geophysical sense may be termed polythermal. To some extent all glaciers are poly thermal, except in the final wasting temperate phase when they are fully isothermal.

To elucidate the characteristics of each of these five categories and to identify prototypes with suggested thermal parameters, selected held studies on existing glaciers are discussed and thermal measurements and characteristics illustrated. From the sampled data, arbitrary englacial temperature limits are suggested: for the main body of polar glaciers (—10 to — 70°C); for sub-polar glaciers (—2 to —10°C); for sub-temperate glaciers (-0.1 to —2°C); for temperate glaciers (in summer, 0°C throughout); and for polythermal glaciers (a range across at least two of the foregoing temperature zones). The significance of thermal anomalies, temperature sandwich structures, diagenetic ice zones, and measured shifts in thermodynamic characteristics over a number of years are considered as they aid in the interpretation of ice morphology, glacier regimes, and climatic change.

Type thermo-physical examples are briefly compared from the following areas: the Antarctic and Greenland ice sheets (polar and polythermal), the Nepal Himalaya, Svalbard (polar to sub-polar), Lapland (sub-polar), sub-Arctic Norway (sub-temperate), the Alps (polythermal to temperate), the Canadian Rockies (sub-temperate), the Juneau Icefield, Alaska (sub-temperate to temperate), the Alaskan-British Columbian coast (temperate), glacier systems on Mount Rainier, Washington State (polythermal), and icefields in the St Elias Mountains, Yukon Territory (temperate to polythermal).

The relationship of thermal anomalies is clarified and illustrated within (he defined framework of each category. It is noted how these are manifest by deformation irregularities, differing salinities, and varying heat capacities within the ice. Also discussed is the relationship of changes in thermo-physical characteristics to the sensitivity of ice flow, revealed by changes in entropy and negentropy of glacier systems and by observable shifts from parabolic to rectilinear to surging flow. Finally considered is the long-term implication of secular changes in climate and their influences on englacial thermal regimes which affect the hydrological capacity and fluvial discharge of glaciers as well as their terminal fluctuations. The strong interdependence of all these factors and the total systems analysis which they represent underscore the mandate for a rational thermo-physical classification of glaciers.

Three experiments were conducted to assess acoustic properties of hard-pack snow. One test involved transmission of acoustic signals in the frequency range 100-20 000 Hz through natural snow-pack in order to measure signal loss of a point acoustic source. At all frequencies the relatively high-energy input signal decays rapidly by energy dissipation, with nominal diffusion occurring at large distances from the source. Signal persistence is greatest in the frequency range 100-200 Hz, In a second test, acoustic bursts in snow columns under deformation were recorded. Spectrum analysis in the frequency range 500-14000 Hz reveals dominance of signal amplitudes at frequencies between 1 000 and 10 000 Hz. This dominance is attributed to the strong attenuation properties of snow and suggests the use of waveguide or collector techniques to monitor natural acoustic emissions in snow-pack. In a third test several waveguide geometries and materials were evaluated for their acoustic signal interception and transmission characteristics. In general, metallic waveguides show the least attenuation of the configurations tested.

Radio-echo signals travel faster in firn than in ice, which affects the analysis of ice-mass thickness. If this effect is neglected, then the calculated thickness of an ice mass may be in error by an amount of the order of one-tenth of the firn thickness. An exact formulation is derived for the path of the signal through the firn and the ice. Explicit solutions are given for constant, linear, and quadratic profiles of the refractive index in the firn layer.

A morainal sequence in south-west Yukon Territory, Canada, records at least four major, successively less extensive glaciations from ice fields in the St. Elias Mountains south of the glaciated area.

The Nisling Moraine flanks the Klondike Plateau in a belt t km. wide to an altitude of 1,040 m., 12 km. north-east of Snag. The northernmost lobe of this moraine terminates at the junction of the Donjek and White Rivers, 120 km, from the nearest source of ice, Klutlan Glacier. 11 km. north-east of Snag, the prominent front of the Donjek Moraine lies 180 m. below the front of the Nisling Moraine. The northernmost lobe of the Donjek Moraine terminates 106 km. north of Klutlan Glacier and occupies the lower courses of canyons cut into the Nisling Moraine. The front of the Snag Moraine crosses the White River valley 210 m. below the front of the Donjek Moraine and 96 km. north of Klutlan Glacier. The Tchawsahmon Moraine, 38 km. north-west of Klutlan Glacier. consists of a series of concentric ridges, the oldest of which impounded Tchawsahmon Lake.

Provisional correlations suggest that the Nisling Moraine is pre-Illinoian; the Donjek, Illinoian; the Snag, pre-classical Wisconsin; and the Tchawsahmon, classical Wisconsin.

The authors describe a new method that allows an accurate, cheap and quick characterization of snow grains from natural snowpacks. The method is based on stopping all metamorphism of snow grains by immersing them in cold isooctane. Snow grains are then carried from the field, stored in a cold room and easily observed through a microscope. It then makes possible recording of snow-grain pictures in a state similar to their natural state, even after storage of several months.

The report describes an experiment to evaluate the use of geophysical (Cambridge-type) wire strainmeters for the rapid acquisition of strain-rate data and to compare strains on a large ice mass over gauge distances of 5 m, 50 m, and 1 km.

Three continuously recording wire strainmeters were installed at the centre of two separate arrays of strain poles 10.6 km and 19.5 km from the ice divide on the Barnes Ice Cap. Data was collected between 24 April and 15 May 1976. The 1 km strain arrays had previously been measured in 1974 and 1975. The results show good agreement between the strainmeter data and the larger strain arrays at the 10.6 km site but differ at the 19.5 km site. When the daily means are calculated for the strainmeters at the 19.5 km site, the strain-rates show a possible periodic variation with an apparent period ofabout 11 d. Since there appears to be no direct correlation between the strainmeter signal and either temperature or pressure, the result is assumed to represent real varying strain within the ice.

Many developed areas in British Columbia are exposed to snow-avalanche hazards. Avalanche-hazard zoning has been undertaken by the British Columbia Ministry of Transportation, Communications, and Highways during the past five years. Recommendations from these zoning studies are forwarded to those agencies responsible for land-use zoning and development approval. Existing and possible legislation are described, as well as problems associated with implementation of the legislation. Technical considerations are outlined; interpretation of vegetation is a very important factor in evaluating each avalanche site. Calculation of run-out distances and consideration of other factors serve as a check on the vegetation interpretation. A special safety factor has been developed.

Socio-political considerations with respect to British Columbia are described. Existing developments have the most wide-ranging implications.

At lat. 7° S. the fern line was at about 3,500 m. during the Riss glaciation, at 3,650 m. during the Würm maximum and at 3,700 m. during a later stage (Würm II?). The moraines were deposited by equatorial-type glaciers from which there was relatively little melt water.

At lat. 14° S., during the Riss glaciation, an important ice cap covered a 3,900–4,000 m. high plateau, the firn line being at about 3,950 m. The role of melt waters was important in the formation of the moraines, suggesting their deposition from tropical-type glaciers. From the evidence of periglacial gravels it appears that this southern region has not been glaciated since Riss times.

This paper examines the deterioration of an iceberg grounded outside St. John’s Harbour, Newfoundland, Canada, in terms of its initial velocity prior to grounding. Theoretical expressions for the lifting of the iceberg and hence its buoyancy loss during grounding are derived as a function of initial iceberg velocity and ocean-bottom slope. Wave erosion and calving are two of the most significant mechanisms for iceberg deterioration. With wave erosion occurring on the seaward side of the grounded iceberg, model simulations are compared with observational data from a field study conducted on the grounded iceberg between 10 and 17 June 1983. Model–simulated time of re-flotation of the iceberg agrees with observations, for initial iceberg velocity of 0.3–0.5 m/s. Model simulations of the deterioration of the iceberg beyond the point of re-flotation are also compared with observations. Allowing for a 10% error in the observed above-water volume of the iceberg on 10 June, the model-simulated mass losses are in good agreement with observations. Best results are obtained for the model initialized with data observed on 14 June 1983, the first day for which detailed observational data are available following re-flotation of the iceberg.

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.

Bering Glacier lacunas are steep-sided flat-floored depressions ranging from 40 to 60 m wide, 80 to 120 m long and 35 to 50 m deep. They are confined within a band of debris-free ice (1.5 km wide, 5 km long) parallel to the eastern margin of the Bering piedmont lobe. After the 1993–95 surge displaced the lacuna band several kilometers onto the foreland, a new band of lacunas began to form 5–6 years later in the same location as occupied by the displaced band. Conditions essential to lacuna formation were initiated during the surge, as overriding ice was thrust into position across the trend of a subglacial trough, leading to stagnation deep within the trough. It is proposed that stagnation combined with englacial water movement altered ice crystal fabric and resistance to ablation. Exposure of this ice through normal ablation led to differential ablation and the formation of lacunas.

Victoria Lower Glacier is a complex structure of ice from two distinct sources (Schultz Glacier to the north and a local névé of Victoria Lower Glacier) that join at a broad median shear zone. Evidence from the margins suggest that both are currently retreating. Algae in a block of frozen stratified sediment from within the ice of the terminal margin has a radiocarbon age of 20 200 ± 2400 year BP (NZ 6531 A), indicating that the glacier has advanced since that time. Superposition of ice levels of Ross Sea I glaciation on a radio echo–sounding profile of bedrock beneath the glacier indicates that it is unlikely that Ross Sea I ice entered the valley. The radiocarbon date supports this finding.

In November and December 1965 accumulation measurements were made at 3 km. intervals and at networks of poles at six photogrammetric arrays on an oversnow traverse from Mount Chapman to “Byrd” station. The results at the photogrammetric arrays, which yield a mean accumulation of 16.4 g. cm.−2 yr.−1 for 1963–65, are compared with values determined from stratigraphic investigations in 1958–59 and in 1962–63, which gave 12.2 g. cm.−2 yr.−1 and 13.2 g. cm.−2 yr.−1, respectively.

An outdoor sea-ice tank system for measuring the microwave properties of sea ice has been developed. With the natural cooling and the help of a cooling unit in the movable roof attached to the tank, the system can grow sea ice to about 50 cm thickness continuously without the effects of snowfall and/or melting. Portable microwave radiometers are attached beside the tank to measure the brightness temperature of the ice. As sea ice grows, the system can measure microwave brightness temperature, and seawater/ice temperature at each depth and thickness of sea ice. The bulk salinity of sea ice is measured by sampling. The following results were obtained from experiments conducted during two winters. (1) Rapid desalination was observed during the early stages of growth with ice thicknesses of 0–5 cm. (2) A new relational expression between ice thickness and bulk salinity at this thickness was obtained. (3) The rapid rise in microwave brightness temperature associated with the increase in sea-ice thickness during the early stages of sea-ice growth was captured in each frequency band. The microwave measurements from the sea-ice tank system are expected to provide new insights into the microwave properties of sea ice.

An algorithm is developed for adjusting glacier surface-velocity vectors, given on the nodes of a square grid, so that they obey a central-difference approximation of the continuity equation. Also required on the grid nodes are the glacier thickness, the ratio of the surface-velocity to the average velocity in the column, and the difference between the mass balance and the thickness change. All these other variables are assumed to be known exactly, and only the surface-velocity field is adjusted. The result is optimum in the sense that the magnitude of the adjustment is minimized. Either the relative or the absolute adjustment can be minimized, depending on how weights are specified. No restriction is placed on the shape of the solution region, and no boundary condition is required. The algorithm is not iterative. The algorithm first forms a parallel flow field that satisfies the continuity equation, and then uses a stream function to add a divergenceless field to it. The stream function that leads to the minimum velocity adjustment is obtained as four independent, interlacing solutions covering the solution region. For each of the four, a well-conditioned, sparse-matrix system of simultaneous linear equations is solved. A compact, sub-optimum, well-behaved iterative procedure is also developed for transforming part of the velocity adjustment into an adjustment of the thickness field.