Accumulation on the Meighen Ice Cap appears to be about normal for the region, but ablation seems abnormally low. Statistical analyses of several years’ data reveal the following trends: accumulation increases towards the north; ablation decreases with increase of elevation, decreases towards the north and west, and is greater on south-facing slopes than elsewhere. Because ice movement is very small, these trends explain the surface topography of the ice cap quite well. Other topics discussed are the significance of changes in the margins of a stagnant ice cap, and the rate at which net mass balance changes with elevation.

The stresses and strains in a limited region of a temperate glacier are approximated by polynomials. In this case it seems that we can replace Glen’s law by the more convenient law . We initially consider a plane problem with a flat glacier surface. In a simple example the theoretical possibility of very important deviations from the classical relation τxz = ρgz sin α is demonstrated. The calculation is then extended to the more general case when the surface of the glacier is no longer a plane (the contours remaining always parallel) and where the width of the glacier varies.

Starting from a precise survey of the surface and measurements of surface velocity, one can then obtain velocities and stresses at depth, and extrapolate the bedrock profile into regions inaccessible by seismic sounding. A provisional calculation has been made for the ice fall between the Glacier du Géant and the Glacier du Tacul (Mont-Blanc massif). In the lower part, the existence of a gorge near the right bank and the fact that the various ice streams partially superpose instead of flowing side by side, make the calculations uncertain.

In this way the law of friction can be determined experimentally. Proceeding down-glacier, the sliding velocity decreases from about 830 m/year to about 250 m/year, while the normal pressure increases from about 2.8 to about 18.5 bar. At the same time the friction increases from about 1.1 to about 4.3 bar, approximately proportional to the pressure, which seems to be in agreement with the author’s theory of friction.

There are four major glacier regions in the U.S.S.R.: the Atlantic-Arctic, Atlantic-Eurasian, East Siberian and Pacific-Asian, which can be divided into 19 separate glacier areas. The total area of the glaciers in the country amounts to 81 900 km2, and the volume of water stored in them to 13 750 km3.

The main characteristic features of glacier regime, such as the elevation of the equilibrium line, the value of the total accumulation at the equilibrium line, the vertical gradients of net balance, the “glacier ratios”. etc., are estimated for the majority of the glacier areas. The data on mass balance of the glaciers in the Polar Urals and Tien Shan which were obtained by direct measurement during the last decade are tabulated and compared. It has been found that the glacier balance changes in the two areas are nonsynchronous.

A comparison of the variations in mass balance of the Lednik IGAN in the Polar Urals, and the Grosser Aletschgletscher in the Swiss Alps, over a period of several decades suggests a cyclic trend of the variations in both regions (with a wave-length of about 22 years), and the direct opposition in their phase. The analogy of 22-year cycles of the balance variations with the cyclic fluctuations of the same wave-length in solar activity seems to be quite evident, whereas the atmospheric circulation appears to be one of the main intermediate variables in the chain sun-glaciers responsible for the out-of-phase relationship in glacier variations of certain areas.

In conclusion, some data on the present changes in glacier regime are given, as well as general information on glaciological studies carried on in the U.S.S.R. within the framework of the I.H.D. programmes. The latter include the compilation of the Soviet Union inventory of perennial snow and ice masses, the continuous measurement of glacier variations, and the research on combined heat, mass and water balances at selected mountain glacier basins.

The lower one-third of “Sioux Glacier” in south-central Alaska was buried beneath a debris slide during the 27 March 1964 earthquake. Investigations to determine the effect of this cover on the regimen of the glacier revealed that it has increased in thickness by as much as 28 m, primarily as a result of the insulating effect of this debris cover. In areas where debris has continuously veneered the surface, at least since 1938, the ice is also thicker. A longitudinal profile reveals that the area near the upper extent of the slide debris has become intensely crevassed and has been lowered as much as 8 m between 1965 and 1966, while the terminal area is up to 5 m higher and is characterized by thrusting. It is concluded that a kinematic wave passed through this glacier sometime between 1965 and 1966.

The upper zone of debris-veneered ice is moving at 175 m/year while the terminal area is flowing at only 21 m/year. The rate of down-glacier decrease in velocity is about 0.06 m/year per meter of horizontal distance except for an area approximately 1 km from the terminus. Here, the rate of decrease in velocity is 0.1 m/year per meter. The change in rate is presumed to be related to topographic control caused by the recent thinning of the ice here.

Robin (1967) and Budd (1968, unpublished) have succeeded in connecting the variations in surface slope of an ice sheet with variations in the gradient of the longitudinal strain-rate. This paper tries to improve the theoretical basis of their work. By choice of a suitable coordinate system and suitable redefinition of the variables, Budd’s formula for the basal shear stress is derived with a minimum of restrictive assumptions. The resulting formula, containing the gradient of a longitudinal stress, is thought to be of high accuracy for the two-dimensional flow of cold ice sheets, and is valid for slopes of any magnitude.

A flow model is described for the Camp Century area in Greenland. The horizontal velocity profile along the core is assumed to be uniform from the surface down to y = 400 m above the bottom. Below this level, the horizontal velocity vx, is assumed to decrease proportionally to y. Furthermore, at a given y, vx is assumed to be proportional to the distance x from the ice divide. The resulting vertical strain-rate under steady-state conditions gives the age of the ice as a function of y. The flow model has explained the measured temperature profile, and the time scale has been verified by comparison between observed stable isotope variations and past climatic changes (at least 70 000 years back in time) estimated by other methods.

D.C. ice-resistivity measurements on the polar Paris Gletscher in East Greenland are presented. It is found that the observed profile is well described by a four-layer system. Near the surface there are two layers resulting from the penetration of the summer temperatures into the polar ice. Below this the ice has constant resistivity until the bed is reached, where contrary to expectation a high-resistivity layer is found.

The results of the present study support the conclusion that the former ice cover of northern Ellesmere Island was very much more extensive than the present, although the age of maximum glaciation is not known. In the Tanquary Fiord area the conclusion is based on bathymetric data indicating considerable overdeepening of the fiords; morphology of the main valleys; and the presence of moraines, erratics and glacial lake deposits at high levels. Tanquary Fiord became free of glacial ice at least 6 500 years ago and peat was forming in the valleys by this time. A long period of river erosion followed the main retreat of the ice. Subsequently, and within the last 4 000 years, glaciers advanced to re-occupy V-shaped valleys, and at the same time small ice caps were probably regenerated. In the last 900 years, however, there has been little change in the terminal position of most of the major glaciers, which appear to be advancing slightly, although in the last 40 years the side glaciers have receded from well-marked terminal moraines.

This paper is devoted to the causes of initiation and development of the Quaternary glaciation and climatic fluctuations connected with it. There are many hypotheses on this problem. The most interesting of them are those suggesting the evolution of glaciers and ice sheets, and variation of climate as a self-regulating process.

The first person to offer a definite mechanism for such self-regulation was the Russian sailor, Captain E. S. Gernet, whose book about this was published in 1930. The book is of great scientific importance, but so far few people appear to have known anything about it. This paper gives a brief summary of the book, shows the similarity between the main ideas of Captain Gernet and the American geologists, W. L. Stokes, M. Ewing and W. L. Donn (the theory of the two latter authors has become well known recently), and justifies naming this concept after Gernet and Stokes in honour of the men who first proposed it.

The climatic snow line is a little above the highest peaks in this region (Mir Samir, 5 809 m, lat. 35° 35′ N., long. 70° 10′ E.) but steep north-facing slopes provide a topographie reason for small glaciers persisting, with a snow line a little below 4 900 in (16 000 ft). Snow accumulation at this height averages 1 300 kg m−2, most of this falling in late winter and spring. Gross ablation reaches 40 kg m−2 d−1. Net ablation (July–August), measured as stream discharge, averages 3 600 m3 d−1 = 9 kg m−2 d−1. Slow recession is the average condition. Halt stages at 4 800, 4 600 and 4 000 m are interpreted from the topography. Dating of moraines by lichen distribution indicates for the highest of these a minimum age of 400 years.

The vertical flux of heat and of water vapour were calculated through an air layer 30–100 cm over a melting firn surface for 24 h. The source of heat available at the surface expressed as a percentage of the total was: net radiation 87, condensation 5, forced convection 1, conduction through snow 6 and unexplained 1. The heat sink was: long-wave radiation 4, evaporation 6, forced convection 6, conduction into snow 2 and melting 82%.

Forbes Glacier, one of the outlet ice streams from the Antarctic ice sheet, is located 20 km west of Mawson, Mac.Robertson Land, east Antarctica. In the uppermost part of the glacier near Casey Range, the velocity at the centre of the glacier is 59 m year−1 and the strain-rate at seven strain grids ranges from −6.7 to 6.7×10−3 year−1 on the surface of the glacier. The fabric types of this area are characterized by single-maximum and small-girdle fabrics. It is confirmed that the single-maximum fabric is an original pattern which changes gradually to a small girdle fabric about the maximum compressive axis in association with grain growth. The patterns predicted by Brace (1960) can be adapted to the small-girdle fabrics of this area.

In western North America 204 surging glaciers have been identified by aerial photographic observations. These glaciers exhibit either intense crevassing and rapid ice displacements during surges or distinctive surface features which have resulted from past surges. Distribution of these unusual glaciers is not random throughout the glacierized areas, as they occur only in the Alaska Range, eastern Wrangell Mountains, eastern Chugach Mountains, Icefield Ranges, and the St Elias Mountains near Yakutat and Glacier Bay. No surging glaciers have been identified in the Brooks Range, Kenai Mountains, west and central Chugach Mountains, west and central Wrangell Mountains, Coast Mountains, Rocky Mountains, Cascade Range, Olympic Mountains, or Sierra Nevada. No definite reason for this restricted distribution is apparent. Surging glaciers are found in maritime to continental and temperate to subpolar environments. Practically all physical forms of glaciers are represented. The restricted distribution does not relate to topography, bedrock type, altitude, orientation, or size of glacier. Some surging glaciers are associated with fault-related valleys, but neither recent faulting nor earthquakes have initiated surge activity. Possible causes for the limited distribution of surges are unusual bedrock roughness or permeability in certain areas, anomalously high ground-water temperatures, and/or abnormal geothermal heat flow.

By means of modern geodetic observation techniques the ice movement along an east-west and a north-south profile across the Ross Ice Shelf, Antarctica, was measured during the two Antarctic summers, 1962–63 and 1965–66. 103 markers were placed on the 910 km long traverse. Distances were measured by tellurometer, and traverse angles by a precision theodolite between all consecutive markers, normally 8 to 9 km apart. For this type of observation method, six men distributed into three groups of two men each were necessary.

The main part of the paper deals with data processing and with the computation of the ice movement. As the ice moves, the geometrical configuration of the traverse changes during the epoch of observation. For this “reduction to epoch” problem two methods are described in detail: (1) time reduction of observations, and (2) time reduction of positions. Between the two field journeys, only linear ice movement can be assumed. It is possible, however, to determine acceleration and curvature of the ice flow at all traverse points where the traverse angles differ considerably from 180°.

The result of all computations is the field of velocity vectors along the traverse. Obvious characteristics are the rapid increase of velocity between the McMurdo Ice Shelf and Ross Ice Shelf, the uniform and nearly parallel movement in the middle of the ice shelf (maximum velocity 935 m year−1), the decrease of velocity along the north-south profile, and the systematic increase of divergence of the flow lines towards the ice margins. Careful study of the velocity vector field shows some deviations from an entirely uniform distribution.

Several analyses are given for the flexure of a floating polar ice tongue with the general dimensions of several kilometers wide by 200 in in thickness. The lengths considered are from 2 km to in excess of 10 km which is referred to as a long slab. The analyses are made under the separate assumptions that ice behaves as (1) an elastic material, (2) an elastic-plastic material, and (3) a fully plastic material, when reacting to flexure due to changes in sea-level. The elastic analysis shows that hinge-line stresses could become very high of the order of 15 bar) for slab lengths up to about 3·5 km reacting to sea-level changes of the order of ±50 cm. For slab lengths greater than this, the stresses at the hinge, as well as being significantly less than before, become independent of the length of the slab, dependent only on the slab thickness and the amount of deflection of sea-level. In the elastic-plastic analysis, the hinge-line stress cannot exceed a value of about 2 bar. This yield value is reached when sea-level departs about 50 cm from the mean. The fully plastic analysis requires more accurate knowledge of the constants in the flow law and their variation with density, temperature and salinity within the ice. However, the theory may be tested by measuring the diurnal change in strain-rate across the hinge-line zone. The process of calving of large tabular icebergs from such glacier tongues may demand sea-level changes of more than ± 1 m, or bending about more than one axis of the shelf.

The size of firn crystals as a function of age has been investigated in thin sections to a depth of 49 m at the South Pole. Grain cross-sections increased in size from 0.24 mm2 at 0.1 m depth to 0.63 mm2 at 10 m. Crystals, as distinct from grains, increased in size from 0.18 to 0.43 mm2 over the same interval, implying that grains are generally composed of just one or two crystals rather than several as is frequently contended. The mean crystal cross-section increased linearly with the age of the firn at a rate of 0.0006 mm2 year−1; in 388 year old firn at 49 m the crystal size measured 0.63 mm2. Analysis of crystal-growth data from other locations in Antarctica and Greenland also revealed a strong linear relationship between the mean cross-sectional arcas (D2) of crystals (in mm2) and their ages in years (t), i.e. . The fact that the temperature dependence of the crystal growth rate K can be expressed very satisfactorily in an equation of the form K = K0 exp (E/RT) confirms predictions that crystal growth in firn is essentially analogous to grain growth in metallic and ceramic sinters. An extrapolation of available data indicates that crystal growth rates in dry firn could be expected to vary by two orders of magnitude (0.0003 to 0.03 mm2 year−1) over the temperature range −60° to −15°C. A method of utilizing crystal growth-mean annual temperature data to determine accumulation rates in snow is demonstrated.

Rapid changes in time and space in the micro-relief of an ablating glacier surface and radiation-induced melt within the uppermost ice layer, termed the “weathering crust”, seriously affect the accuracy of the short-term ablation measurements. The various measuring techniques commonly used (stakes, ablatometers, ablatographs) and some new methods (measurement of discharge from a small supra-glacial drainage basin, and mass loss directly measured on core samples) are critically reviewed and assessed in the light of these phenomena. The implications for studies of heat and mass balance are discussed.

It appears that the direct measurement of mass flux is the most accurate means of assessing short-terni ablation rates. The errors in short-term ablation measurements by any method are largely compensatory and consequently do not influence long-period mass-balance estimates.

Measurements of the attenuation of acoustic waves in sea ice at frequencies f between 10 kHz and 500 kHz have been made on the ice cover at Tanquary Fiord, Ellesmere Island (lat. 81° 25′ N., long 76°50′ W.). A horizontal transmission path at a depth of 4 ft (1.3 m), mid-way between the top and bottom surfaces of the ice cover, was used at ranges varying from 25 ft (7.6 m) to 4 ft (1.3 m) between piezoelectric transducers immersed in oil-filled bore holes. The attenuation coefficient α was found to fit the equation a α = c1f+c2f4 with c1 = 4·45 × 10−2 db m−1 kHz−1, and c2 = 2·18 × 10−10 db m−1 kHz−4. Over the frequency band covered, the linear term was predominant and the Rayleigh scattering term relatively insignificant.

Measurements of strain-rates on a temperate glacier in a region of initial transverse fracturing indicate a critical strain-rate of 3.5±0.5 × 10−5 d−1, associated with a regional strain-rate gradient of 5 × 10−8 d−1 m−1. At only one section of the glacier is the theoretical longitudinal strain-rate (Nye, 1959[c]) in approximate agreement with the value measured at the surface at that point. Corresponding measurements on a polar glacier (temperature −27.9°C at 10 m depth during the summer) indicate that the critical strain-rate is about 0.6±0.05 × 10−5 d−1, which is associated with a gradient of strain rate of about 3 × 10−9 d−1 m−1. At one section there is close agreement between the theoretical and measured longitudinal strain-rate. For the temperate glacier crevasse depths ranged from 23.5 to 28 m; in the polar glacier one crevasse was 23.9±0.5 m deep, assuming a wedge form. Only an approximate agreement with the measured values of depth is obtained by using the regional strain-rate values in Nye’s crevasse-depth formula.

Over a distance of 1.2 km the temperate glacier transverse crevasse spacings are very variable, ranging from 30 m to 96 m, but initially the spacings range from 55 m to 96 m, and for the first four cases the spacing s varies from 2.7 d to 3.3 d, where d is the crevasse depth. In the cold ice, crevasse spacings are far more uniform, ranging from 57 m to 66 m. A value of s ≈ 2.5 d is obtained in only one case. This greater uniformity of spacing may be explained in terms of the dynamics of flow. Despite large differences in thermal, dimensional and strain-rate parameters between the two glaciers, (1) the crevasse depths are closely similar, and (2) the spacings of crevasses are similar. It has been demonstrated from two lines of evidence that the assumption that the strain on an intercrevasse block is negligible is not correct. The direction of the principal extending strain-rate is, in the most reliable cases, perpendicular to the crevasse traces within 2° to 7°.

Continuous measurements of incident and reflected short-wave radiation have been obtained from 12 May to 17 June 1968 on the ice cover at Tanquary Fiord, Ellesmere Island (lat. 81° 25′ N., long. 76° 50′ W.). The observations were made with radiometers suspended between two towers at a height of 50 ft (15 m) to sample an area large enough to be representative of the surface of the ice cover. From the start of surface melting, time-lapse photographs were taken at intervals of 3 h with a camera mounted on one of the towers at a height of 20 ft (6 m) and slanted below the horizontal.

Values are presented, for the observation period, of incident short-wave radiation, albedo, air temperature at screen height and percentage of surface covered with melt pools. It is shown that the albedo decreases linearly with increasing area of water puddles.