The generalized Glen’s law έ = έ0Tn exp (kθ ) is used to calculate die horizontal and vertical velocity profiles and from these the temperature and age profiles of cold ice sheets. It is shown that, by substituting for θ a function increasing linearly with height, velocity profiles for all ice sheets are obtained which represent excellent approximations to the true ones, since, above a critical height he where the deviation from linearity becomes large, the influence of temperature on ice flow becomes negligible. In a comparison of the present theory with Robin’s (1955) treatment a larger temperature difference ΔT of up to 30% is obtained. Furthermore the present theory yields an age considerably increased compared with Nye’s model; e.g. more than 50% at a relative height of h\H = 0·1.

A temperate glacier is defined as a glacier containing liquid inclusions in which the concentration of salts is not too high. Nevertheless these salts suffice to produce a depression in temperature comparable with that due 10 the pressure, and much greater than that due to interfacial energies. Because of this a large part of the liquid water present in the ice is not mobile, contrary to the theory of Nye and Frank. Deformation and recrystallization is bound to close off capillary intergranular channels, for glacier ice is usually impermeable. An explanation is given of why firn, at a depth which the annual cold wave does not reach, is nevertheless transformed relatively suddenly into practically impermeable ice. Saline inclusions will migrate with a velocity inversely proportional to the potential temperature (difference from the melting point of pure ice at the pressure in question) and proportional to the gradient of this potential temperature. This velocity, the salinity, the liquid water content, and the ice temperature, parameters which are all functions of the depth, are calculated for a steady state in a stagnant or moving glacier. Under the action of anisotropic stresses, isolated inclusions perpendicular to the maximum compressive stress will enlarge at the expense of their neighbours. If however the two inclusions are connected by a capillary channel, no enlargement occurs, but instead the salt content decreases, evacuated to the other inclusion. This process would constitute an objection to the theory of glacier sliding by melting and refreezing around small obstacles, unless new subglacial mechanisms were to occur.

The value of the basal shear stress is derived for two-dimensional and three-dimensional cirque glaciers. It is assumed that a cirque glacier moves primarily by a rigid-body rotation over a bed of cylindrical or spherical shape. In the region of maximum ice thickness the new value of the basal shear stress is only about one half that derived from equations in common use in the literature. The new expression for the basal shear stress of a cirque glacier is used to correct a data point in Paterson’s recent compilation of measured sliding velocities and basal shear stresses of glaciers.

A method for the determination of the three-dimensional velocity field in a glacier is described, Measurements in three or more bore holes arranged in an appropriate array are needed for its application. Surface motion measured by triangulation and tape measure, bore-hole profiles given by inclinometry, and the geometry of the bed are all considered simultaneously in order to determine the velocity field. The basic assumption is that velocity between the bore holes can be represented by suitable interpolation based on the measurements in the holes. Ice displacement parallel to bore holes is calculated indirectly from incompressibility and the constraint that velocity normal to the bed be zero. As an example, the method is applied to an array of 9 bore holes in Athabasca Glacier.

Measurements of ice deformation at the surface and at depth in the Athabasca Glacier, Canada, reveal for the first time the pattern of flow in a nearly complete cross-section of a valley glacier, and make it possible to test the applicability of experimental and theoretical concepts in the analysis of glacier flow. Tilting in nine bore holes (eight holes essentially to the bottom at depth about 300 m) was measured with a newly developed electrical inclinometer. The new instrument permitted bore-hole configurations to be determined with greater speed and accuracy than possible with earlier methods. The measurements define the distribution of the velocity vector and the strain-rate tensor over about 70% of the area of the glacier cross-section.

The main longitudinal component of flow has the following general features: (1) basal sliding velocity which exceeds 70% of the surface velocity over half of the width of the glacier, (2) marginal sliding velocity (not more than a few meters per year) much less than basal sliding velocity at the center-line (about 40 m a-1), (3) marginal shear strain-rate near the valley walls two to three times larger than the basal shear strain-rate near the center-line (0.1 a-1).

The observed longitudinal flow is significantly different from that expected from theoretical analysis of flow in cylindrical channels (Nye, 1965). The relative strength of marginal and basal shear strain-rate is opposite to that expected from theory. In addition, the longitudinal flow velocity averaged over the glacier cross-section (which determines the flux of ice transported) is larger by 12% than the average flow velocity seen at the glacier surface, whereas it would be essentially the same if the theoretical prediction were correct. These differences are caused to a large extent by the contrast between the actual distribution of sliding velocity and the constant sliding velocity for which the theoretical analysis holds. The observed relation between marginal and basal sliding velocity is probably a general flow feature in valley glaciers, and may be caused by lateral variation of water pressure at the ice-rock contact. The observed pattern of longitudinal velocity over the section also shows in detail certain additional features incompatible with the theoretical treatment, even after the difference in boundary conditions (distribution of sliding velocity) is taken into account.

Longitudinal strain-rate (a compression of about 0.02 a-1 at the surface) decreases with depth, becoming nearly o at the bed in the center of the glacier, which confirms a prediction by Savage and Paterson (1963). The depth variation cannot be explained completely by overall bending of the ice mass as a result of a longitudinal gradient in the curvature of the bed, and is at variance with existing theories, which require the longitudinal strain-rate to be constant with depth.

Motion transverse to the longitudinal flow occurs in a roughly symmetric pattern of diverging margin-ward flow, with most of the lateral transport occurring at depth in a fashion reminiscent of extrusion flow. The observed lateral velocities averaged over depth (up to 1.9 m a-1) are compatible with the lateral flux required to maintain equilibrium of the marginal portions of the glacier surface under ablation (about 3.7 m of ice per year) and are driven by the convex lateral profile of the ice surface.

Untersteincr and Nye (1968) calculated the possible future movement of Berendon Glacier, B.C. These calculations are repeated using much improved data and a slightly different method for computing the datum state. The predictions that result are very similar to those found in the earlier work. It is concluded, however, from mass-balance data, that the chance of the glacier rising sufficiently in the next 25 years to be a danger to the mining installations situated near the snout of the glacier is much greater than was previously considered. The sensitivity of the theory to changes in input data is discussed.

Oxygen-isotope and chlorinity determinations, as well as petrographie observations, indicate that the basement we of the Ward Hunt Ice Shelf is largely composed of a unique brackish ice, which interdigitates with sea ice. Some iced firn occurs near the top of the Basement Ice, below an unconformity.

stratification in brackish and sea ice represents annual increments to the bottom of the ice shelf The c-axis vertical orientation and small-angle grain-boundary relations in brackish ice are explained by nucleation and floating of ice dendrites from the undercooled brackish water zone to the bottom of the ice shelf, where they attach themselves sub-parallel to the plane of the undersurface.

Ice island T-3 did not come from a break-up of the main part of the Ward Hunt Ice Shelf, but probably originated in a nearby area to the west.

Two Kipp hemispherical radiometers mounted back to back and suspended by an 18 m cable from a helicopter flying at an altitude of about 90 m were used to make measurements of incident and reflected short-wave radiation. The helicopter was brought to a hovering position at the instant of measurement to ensure that the radiometers were in the proper attitude and a photograph of the ice cover was taken at the same time. The observations were made in 1969 during 16 flights out of Tuktoyaktuk, Northwest Territories (lat. 69° 26’N., long. 133° 02’W.) over the fast ice extending 80 km north of Tuktoyaktuk. Values of albedo of the ice cover were found to decrease during the melting period according to the equation A = 0.59 —0.32P where P is the degree of puddling of the surface.

In contrast to the extensive and rapidly growing body of knowledge on permafrost in the Eurasian and North American Arctic and sub-Arctic, little is known about permafrost occurrence in the high mountain regions of the world. Preliminary results of permafrost studies from the Colorado Rocky Mountains are presented.

Above tree line (about 3 500 m) in the Front Range, scattered patches of permafrost begin to occur under wet sites blown free of snow in winter with a mean annual air temperature of about — 1.0°C. At greater elevations, with correspondingly lower mean annual air temperatures (extreme case — 9.0°C and 4400 m), permafrost becomes more extensive and probably exceeds 60 m in thickness. These initial results are derived from a skeleton ground-temperature observation program supplemented by indirect evidence and by data gathered from engineering and mining operations in the high country. It is probable that under the higher summits and ridge crests the alpine equivalent of the continuous zone of Arctic permafrost can be anticipated.

Refraction seismic studies conducted on the Zemu Glacier in Sikkim at an altitude of 4 570 m (15 000 ft), indicate that the thickness of the glacier ice varies from about 125 m at the edge of the glacier to about 300 m at the centre. The bedrock section across the glacial valley as drawn on the basis of the seismic data corroborates the fact that the glacier has undergone considerable lateral shrinkage. The observed seismic velocity in the glacier ice, which ranges between 3 500 m/s and 3 700 m/s is in good agreement with the values obtained on glaciers in various parts of the world.

The presence of 49 cirques on the Falkland Islands indicates that glacial conditions were prevalent during the Pleistocene. Cirque moraines and glacially eroded valleys also occur. There appear to have been three phases: a period of cirque formation, the growth of local ice caps and subsequent cirque development. Periglacial landforms such as stone runs, stone terraces and stone lobes also developed during the Pleistocene and attained very large dimensions because of the lithology, the relatively small scale of glacierization and the presence of rotted bedrock.

A newly developed bore-hole inclinometer permits the determination of bore-hole configurations with greater accuracy and efficiency in comparison with earlier systems of inclinometry. Instrument orientation is given to within 0.1° in magnitude of tilt and 10° in azimuth of tilt by an electrical output which can be read remotely from the surface.

In ice-fabric studies, use of an accessory plate is necessary in conjunction with the Rigsby universal stage to discriminate between the a- and c-axes of an ice crystal when the orientation of the c-axis is parallel or nearly parallel to the stage. The techniques described permit orientation of the c-axis regardless of its orientation.

A strain-tree grooving method has been developed for surface self-diffusion studies of ice. This method utilizes a hot-wire grooving engine and is capable of obtaining a uniform spacing between grooves ranging from 15.9 μm to 159 μm in increments of 15.9 μm.

Neoglacial deposits in the Indian Peaks section of the Colorado Front Range have been dated lichenometrically by recourse to a growth-rate curve developed for Rhizocarpon geographicum and three glacial fluctuations of the Temple Lake (4500–2700 B.P. ), “Arikaree” (1900–1000 B.P.) and Gannett Peak (300–50 B.P.) have been recognized and identified by Benedict (1968). Recent soil investigations on neoglacial deposits suggest the need to define an alternative type “Arikaree” in the Indian Peaks.

In many areas of glaciology, cumulative degree days, either positive or negative, are regressed against another cumulative value, such as ablation or lake-ice growth. Very strong functional relationships are frequently found with high correlation coefficients. This note shows that, if pairs of random numbers are cumulated, the resulting correlation coefficients are extremely high with a Fisher transformed mean of r = 0.986 and standard error of ±0.001 (based on 50 individual computations of r which in turn were based on 20 cumulated pairs of random numbers between 0 and 99). These results indicate that caution must be exercised in the physical interpretation of data of this kind.

Two corrective terms in the mass balance between two cross-sections are computed. The first results from the fact that balances are measured at moving stakes. The second correction arises since the discharges are calculated through summer cross-sections which are smaller than their mean values during the whole year.

Preliminary data indicate that fabric is developed in river ice. Crystal orientations are usually sub-parallel to the ice surface, and develop partly in response to stress generated by stream flow.