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.

Carrying on from the work initiated over the I.G.Y. period by the United States glaciological parties at Wilkes (cf. Hollin and Cameron, 1961), members of the Australian National Antarctic Research Expeditions have continued accumulation stake measurements to 80 km. inland on the plateau (lat. 66° 31′ S.) and extended them south 480 km. (to lat. 71° S.). These stake measurements, supplemented by pit data and surface observations, supply a comprehensive account of the accumulation in this region; how it builds up during the year, how it varies from year to year and how it is affected by topography.

An analysis is made of the time required to build up an ice-age ice sheet and of the time required to destroy such an ice sheet. The calculations are based on the approximation that the theory of perfect plasticity is valid. It is concluded that the time required to build up an ice-age ice sheet is longer than the time required to eliminate it. If it is assumed that the accumulation rate of an ice-age ice sheet lies in the range of 0.2 to 0.6 m./yr., it is found that the growth time of a large ice sheet is of the order of 15,000 to 30,000 yr. Ablation rates of to 2 m./yr. lead to shrinkage times of the order of 2,000 to 4,000 yr., provided ablation occurs over an appreciable area of the ice sheet.

Compaction of different types and mixtures of snow including snow collected from the natural snow cover and waste from an ice milling machine, was carried out in a cold room with a small model compactor. Density, cone hardness and shear strength were measured, generally 24 hours after compaction, for specimens compacted in different ways. When the snow was compacted to maximum, densities between 0.55 and 0.60 g./cm.3 were achieved, except for mixtures including more than one third new snow for which densities were lower. For snow collected from the natural cover the highest hardness values after compaction were found for new snow and for mixtures including more than 50 per cent of new snow or fine-grained granular snow. The maximum hardness was obtained with specimens prepared from fine-grained mill waste.

The influence of temperature on density and hardness was also studied.

The permittivity and loss tangent of naturally occurring ice and snow are considered. The direct-current conductivity is considered only when it is of importance to the alternating-current and radio-frequency properties. Laboratory measurements on pure ice, and deliberately contaminated ice, are included to help in explaining and extrapolating the behaviour of natural ice and snow. The lower band of frequencies from 10 c./sec. to 1 Mc./sec. is occupied by a relaxation spectrum in which the relative permittivity falls from approximately 100 to 3. The loss tangent reaches a maximum at a frequency which varies from 50 c./sec. to 50 kc./sec. as the temperature increases from −60°C. to 0°C. We are interested in the effect of snow density, impurities, stress, crystal size, and orientation. For frequencies much greater than 1 Mc./sec., the relative permittivity is 3.17±0.07. The loss tangent reaches a minimum value at approximately 1,000 Mc./sec. beyond which the dominant influence is infrared absorption. The minimum is 10−3 at 0°C or 2×10−5 at −60°C. These values are greatly increased by impurities or free water. Some possible applications to glaciological field measurements are mentioned.

The physical setting of the Athabasca Glacier is described. Ablation of ice from the glacier contributes roughly 40 per cent of the annual outflow from the lake at the terminus. Variations of ice velocity, measured over periods ranging from a week to four months, are discussed. Few if any of these variations can be explained by changes of ice thickness. Variations in the amount of water at the glacier bed provide a plausible explanation however, and the data lend some support to Weertman’s ideas on this subject. Variations in annual velocity of the glacier are not correlated with stream flow, but passage of a kinematic wave provides an explanation of these variations. The wave is attributed to a climatic change which began about 1938.

The techniques and results of a heat-balance programme on Sørbreen, Jan Mayen, are presented and discussed. Estimates of 24 hr. heat-transfer totals under frontal and non-frontal weather conditions are then made. Transfer is found to be higher during frontal conditions, due to an increase in latent and to a lesser extent sensible heat transfer. Consideration of upper air temperatures and humidities suggests this higher transfer is experienced by the glacier as a whole. It is then proposed that summer rainfall totals will provide an index of frontal activity which may be used to indicate relative ablation from one summer to another. A statistical comparison of ablation measured on the glacier and rainfall recorded at the Jan Mayen meteorological station supports this suggestion.

The theory of the sliding of glaciers presented by the author in earlier papers has been generalized (1) by taking into account the resistance to sliding offered by obstacles both smaller and larger than the controlling obstacles and (2) by relaxing the assumption that ice is always in intimate contact with the bed at the down-stream side of an obstacle. The sliding velocities and controlling obstacle sizes which are found from the generalized theory are approximately the same as those found from the earlier theory. A new result obtained from the present theory is that a water layer an order of magnitude smaller in thickness than the height of the controlling obstacles can cause an appreciable increase in the sliding velocity. The generalized theory contains Lliboutry’s sliding theory as an extreme limiting case. For certain thicknesses of a glacier the sliding velocity is a double-valued function of the shear stress exerted at the bed.

Ice island ARLIS II, which is adrift in the Arctic Ocean, is a 1.3 km. wide and 3.8 km. long fragment of shelf ice 12–25 m. thick, which preserves several structural features heretofore undescribed in ice. The island is composed of an irregular central block of foliated, locally debris-rich, grey glacial ice bordered in part by extensive areas of stratified bluish sea ice. The central block contains a series of narrow, elongate, sub-parallel dike-like septa of massive fresh-water ice and a large tongue-like body of tightly folded, coarse banded ice. Both the septa and the tongue cut across the foliation and debris zones of the grey ice.

The margins of the central block are penetrated by a series of elongate, crudely wedge-shaped re-entrants occupied by salients of bluish sea ice. Two broad, arch-like plunging anticlines deform the stratified sea ice along one margin of the block.

The foliation and debris zones in the glacial ice are relict features inherited from the source glacier. The septa formed as crevasse and basal fracture fills. Salients represent fills formed in the irregular re-entrants along the margins of the glacial ice mass. The tongue of tightly folded, banded ice represents an earlier generation salient deformed by compressive forces as the fill built up. The broad anticlines are apparently the result of warping in response to differential ablation but the small, tight plunging folds on their noses and limbs are probably the result of compressive forces.

Ice velocity, net mass budget and surface elevation change data were collected over the length and width of a small (3.4 km. long) valley glacier from 1957 to 1964. Ice velocities range up to about 20 m./yr.; three prominent velocity maxima along the length of the glacier correspond to maxima in surface slope. Net mass budgets averaged over the glacier surface range between − 3.3 m. of water equivalent (1957–58) and +1.2 m. (1963–64). Except for the year 1960–61, curves of net budget versus altitude are parallel. During the period 1958–61 the glacier became thinner at a rate averaging 0.93 m./yr. The net budget and thinning data are internally consistent. Relations between emergence velocity, net budget and surface elevation change are examined at four specific points on the glacier surface and as functions of distance along the length of the glacier. Emergence velocity averages about −0.5 m. in the upper part of the glacier and about +1.0 m. in the lower part. Ice discharge and ice thickness are also calculated as functions of distance. The discharge reaches a peak of 8.8 × 105 m.3 of ice per year 2.2 km. from the head of the glacier. The mean thickness of the glacier is about 83 m. A steady-state distribution of net budget is used to calculate a steady-state discharge, which is 2.2 times larger than the present discharge.

Meighen Island lies in the centre of the north coast of the Queen Elizabeth Islands and fronts on the Arctic Ocean. An ice cap of about 76 km.2 covers about one-tenth of the island. Its greatest thickness of 150 m. occurs under the summit, near the south end, which was 268 m. above sea-level in 1960. The northern half of the ice cap is less than 30 m. thick; and the total volume is of the order of 2,000 × 106 m.3.

Precipitation is low in the northern Queen Elizabeth Islands, and Meighen Island lies in an area where summer temperatures are lowest. In the winters of 1959–60, 1960–61 and 1961–62, the snow accumulation was 12.6, 18.2 and 14.1 cm. of water equivalent. Some snowfall remained on the higher part of the ice cap in the cold summer of 1961; but the ice cap diminished in volume in each year; by 36 × 106, 72 × 106, 22 × 106 and 91 × 106 m.3 in the 1959, 1960, 1961 and 1962 ablation seasons.

If the conditions of these four seasons were maintained the ice cap would disappear in about 100 yr. However, a radio-carbon dating of a saxifrage exposed by the retreat of the ice from a small nunatak near the northern edge gave a date of less than 100 yr., and it appears that the existence of the ice cap might be sensitively related to recent climatic change.

Careful surveys were made in 1959, 1960 and 1961 in an attempt to detect movement in the ice cap. Unequivocal evidence is not available from these surveys; but the stake network has been maintained and another survey has recently been completed.

At the head of a tunnel driven to bedrock in Blue Glacier, Washington, the mechanism of sliding of the glacier over bedrock has been investigated. This mechanism involves (1) regelation-slip, which operates through the combined action of heat transport and mass transport (liquid and solid) in the immediate neighborhood of the glacier sole; (2) plastic flow, promoted by stress concentrations in the basal ice. We have observed and/or measured the following features of the basal slip process: 1. Slip rate in relation to internal deformation of the ice; 2. Time-variations of the slip rate; 3. Freezing of basal ice to bedrock upon release of overburden pressure; 4. Formation of a regelation layer in the basal ice, and detailed behavior of this layer in relation to bedrock obstacles and to incorporated debris particles; 5. Local separation of ice from bedrock and continuous formation of regelation spicules in the open cavities thus created; 6. Plastic deformation of basal ice as recorded in the warping of foliation planes and of the regelation layer. Simple experiments to test our interpretation of the regelation layer have been carried out, in which regelation flow of solid cubes of different materials frozen into blocks of ice was produced. The field measurements and laboratory results are used to test the theory by Weertman (1957, 1962) of the basal slip mechanism. It is found that the theoretical “controlling obstacle size” and “controlling obstacle spacing” that should correspond to our observations are about an order of magnitude too small. This quantitative failure represents an overemphasis in the theory on the importance of plastic flow as compared to regelation. A new theory has been constructed which gives results in better agreement with observation.

A four-man party representing the Arctic Institute of North America and the Department of Geology, Dartmouth College, went to the Ward Hunt Ice Shelf in 1960 to obtain ice cores for subsequent laboratory analysis. The overall objective of the project was to study the structural and stratigraphic history of the shelf and its relationship to the environment through laboratory analysis of the cores, using stratigraphic. petrologic, chemical, and physical methods.

The four cores obtained were logged, packed, and shipped to Dartmouth College for detailed study. The stratigraphy and structure of the ice were studied under natural and plane polarized light conditions. The results of this initial work showed that the cores were composed of four ice types: glacier ice, lake ice, sea ice, and transition ice. Chlorinity, sulfate, and density profiles complemented megascopic studies and were most useful criteria for plotting stratigraphie changes in ice type.

Results of the investigations thus far have yielded new information about the gross structure and stratigraphy of the ice shelf and re-entrant. They have also shown that the physical and chemical techniques employed will be useful in future ice-core analysis.

The history of glaciological studies in the Svartisen area is outlined, and observations made by earlier workers are summarized. The present position of the ice limit in the area is indicated and is compared with those of the past Evidence of extensive, and almost continuous, retreat of the glaciers is presented, and emphasis is placed on the rapidity of the changes since the 1930’s. In the present century, the formation of marginal lakes and the detachment of glacier tongues have characterized the decay of many of the Svartisen outlets.

The meteorological records for Jan Mayen have been examined on a seasonal basis in order to obtain a clearer understanding of the fluctuations of the Beerenberg glaciers from 1920 to the present day. Summer and winter have been arbitrarily defined as including those months with mean monthly temperatures, at sea-level, above and below 0°C., respectively. The results indicate that the retreat of Sørbreen prior to 1940 was associated with high summer temperatures and high summer precipitation, and relatively low winter precipitation. A rapid rise in winter precipitation followed, which culminated about 1950. The advance of Sørbreen since about 1954 is thought to have been caused by this rapid rise of precipitation and has also been associated with a slight drop in summer temperature, which is considered to be of secondary importance. The most recent trends of rising summer temperature since 1956 and falling winter precipitation since 1958, if they continue, must lead to a renewed retreat of the glaciers. Studies on Sørbreen in the summer of 1963, which show that the recent advance has ceased, support this view.

The theory developed in previous papers to represent the response of a glacier to changes in the rate of accumulation and ablation has been used for a number of applications. A method of integrating the differential equations for a fixed frequency was programmed for a high-speed digital computer. This provides a better way of finding the frequency response than the earlier method which used series approximations or high and low frequencies. Results are given for (a) an artificial glacier showing varying amounts of diffusion of the kinematic waves, (b) South Cascade Glacier, Washington, U.S.A., as a check on previous results, and (c) Storglaciären, Kebrekaise, Sweden. The response curves of Storglaciären are very similar in shape In those of South Cascade Glacier but, since. Storglaciären moves more slowly, the curves are shifted in frequency (by a factor of two). The phase of the response at the terminus of Storglaciären plotted against frequency shows a double peak.

Certain mathematical results for the artificial case of no diffusion are given in an Appendix.

A computer programme was also written for calculating λ and μ coefficients and applied to South Cascade Glacier and Storglaciären.

Strain-rate and surface velocity measurements were made on a valley glacier. The measured strain-rates were used to calculate the stress condition and velocity distribution in the glacier. The measured velocity is in reasonable agreement with that calculated from Nye’s plasticity solution.

Measurements have been made of the flow rates of two adjacent glaciers in Westland, New Zealand. A longitudinal flow foliation is developed in one (Franz Josef Glacier) and this was found to be associated with more or less constant rates of flow down the length of the glacier tongue. In the other (Fox Glacier) the foliation is of the transverse type and is associated with a high strain-rate in ice under compression with markedly decreasing rates of flow being found down the length of the glacier. The highest strain-rates are associated with tectonic dirt bands and thrusts.

A highly deformed area in the Ross Ice Shelf near the Bay of Whales was studied during the 1958–59 Antarctic summer season. A series of snow-firn folds up to 8 m. high and with a wavelength of approximately 100 m. occurs here. Along one of these folds, a unique ice layer formed during the 1952–53 season through refreezing of melt water. From sites along this layer approximately 2,300 ice grains were measured using the root mean square method with the least circle diameter. The data obtained indicate the following:

1. The mean diameter of the ice grains ranges from 4.5 mm. in the ice from the crest of the anticline to 2.5 mm. in the zone of maximum shear stress and/or in sections having a high air bubble content.

2. The large diameter of the ice grains at the crest is attributed to greater solar radiation resulting from their proximity to the 1958–59 snow surface, and because they are near the surface of the exposed crevasse wall.

3. The area of maximum shear stress, which is represented by small ice grains and the presence of secondary folds, is located almost halfway between the crest and the trough.

4. Grains in the trough are larger than those in the shear zone because of less stress, and smaller than those at the crest because of deeper burial and the presence of a crevasse bridge which eliminates all direct radiation here.

5. The growth of the ice grains is therefore controlled by temperature, stress and impurities.

The practical analysis of the growth of a sea-ice cover is discussed with initial reference to the classical work of Stefan, whose basic equation connecting surface temperature with the growth of a uniform ice cover of negligible specific heat and hence infinite diffusivity is extended to cover “real” cases. The separate effects of a finite heat content and thermal diffusivity are derived theoretically and semi-empirically respectively, and combined in a more general ice-growth equation which is then tested in the analysis of annual sea-ice growth on Hudson Bay.