The U.S. IGY program in glaciology is reviewed in two parts: Antarctica and northern latitudes. The objectives of the program are outlined and the results of each investigation are briefly summarized. A separate discussion of observations related to changes in the Earth’s ice cover is included.

To resolve some of the factors causing strength variation in natural sea ice, fresh water and five different NaCl–H2O solutions were frozen in a tank designed to simulate the one-dimensional cooling of natural bodies of water. The resulting ice was structurally similar to lake and sea ice. The salinity of the salt ice varied from 1‰ to 22‰. Tables of brine volumes and densities were computed for these salinities in the temperature range 0° to −35° C. The ring-tensile strength σ of fresh-water ice was found to be essentially temperature independent from −10° to −30°C., with an average value of 29.6±8.5 kg./cm.2 at −10° C. The strength of salt ice at temperatures above the eutectic point (–21.2° C.) significantly decreases with brine volume v;. The σ–axis intercept of this line is comparable to the a values determined for fresh ice indicating that there is little, if any, difference in stress concentration between sea and lake ice as a result of the presence of brine pockets. The strength of ice containing NaCl.2H2O is slightly less than the strength of freshwater ice and is independent of the volume of solid salt and the ice temperature. No evidence was found for the existence of either phase or geometric hysteresis in NaCl ice. The strength of ice at sub-eutectic temperatures, however, is decreased appreciably if the ice has been subjected to temperatures above the eutectic point; this is the result of the redistribution of brine during the warm-temperature period. Short-term cooling produces an appreciable (20 per cent) decrease in strength, in fresh-water and NaCl.2H2O ice. The present results are compared with tests on natural sea ice and it is suggested that the strength of freshwater ice is a limit which is approached but not exceeded by cold sea ice and that the reinforcement of brine pockets by Na2SO4.10H2O is either lacking or much less than previously assumed.

Ogives form beneath active ice falls whose heads are situated near or below the firn line. They consist of curved bands of alternating white, bubbly, less dense ice and darker, denser ice with fewer bubbles, extending throughout the thickness of the glacier. The difference in character is held to be due to the different conditions in the upper ice fall, through which the ice passes in one year at high speed. In summer the thin and shattered ice is exposed to high temperatures and melt water, while in winter the conditions are of Arctic-type throughout the thickness of the attenuated ice. A lane of ice on the Gornergletscher, originating as cold, dry snow with no melt water present, illustrates the character and origin of the white bubbly ice. The greater elevation of this cold-snow ice and the waves formed beneath the ice falls are considered to be the result of the lesser thermal conductivity and greater albedo of the white bubbly ice.

In the coastal mountain chain of southern Victoria Land approximately 4,000 km.2 of glacier-cut valleys and dividing ranges are almost completely ice-free, while the surrounding areas are fully glacierized.

In the ice-free Wright Valley and Victoria Valley systems evidence of four glaciations is recognized. The earliest two glaciations were the most extensive; glaciers flowed eastwards from the ice plateau through the coastal ranges and cut broad valleys extending to McMurdo Sound and the Ross Sea. The moraines of these glaciations are thin and highly weathered. The third glaciation was less extensive, consisting of advances by smaller glaciers derived from the inland ice plateau, the Wilson Piedmont Glacier and névé fields in the dividing ranges. The surfaces of moraines of this glaciation are now partly covered by saline lakes, evaporite deposits and extensive areas of desert pavements strewn with ventifacts. The fourth and youngest glaciation comprised small advances by remnants of the plateau-fed valley glaciers. Thick boulder moraines of this glaciation overlie earlier deposits.

During each glaciation the greatest volume of ice was derived from the inland ice plateau. The volume of ice entering the valleys was dependent on the difference in altitude between the plateau surface and subglacial rock thresholds at the valley heads. Decrease in the surface level of the inland ice plateau caused the rock thresholds to increasingly hinder the eastward flow of plateau ice until practically no ice could flow down into the valleys, thereby terminating the glaciation. Such a condition exists at the present time.

This paper is a synthesis of glaciological investigations conducted in Terre Adélie, mainly during the LG.Y. The surface and bedrock profiles have been obtained along a 500 km. line roughly perpendicular to the coast; the mean annual temperature has been studied as a finnction of altitude, and mean accumulation has been related to distance from the coast and surface slope. Stratigraphic studies made at Station Charcot again raise the problem of the determination of mean accumulation in certain parts of the Antarctic plateau; they provide a quadratic relationship between density and depth. The snow-drift studies lead to the Mowing conclusions: wind velocity and density of drifting snow are functions of height above the surface, and the total transport depends on wind velocity. Lastly, measurements have been made of glacier flow near the coast. The paper ends with a schematic study of the mass balance in Terre Adélie; accumulation seems to be slightly larger than ablation, a result that is to be contrasted with the obtervrd coastal retreat near Dumont d’Urille base.

“Fresh-looking” moraines lying within a mile of glaciers in the lowlands of the McMurdo Sound area, Victoria Land, Antarctica have been interpreted by some to be only 50 or 100 yr. old and to have been left by recent glacier retreats. The present author believes that these moraines are considerably older because a comparison of the position of existing glacier fronts in the area with positions on photographs of 50 yr. ago shows no movement of the front or appreciable thickening or thinning of the glaciers during the last 50 yr.

Radiocarbon dating of mummified seal carcasses lying near glacier fronts indicates that the glaciers have not been more extensive for at least 1,000 yr. The youngest moraines in the area are ice-cored moraines to the existing glaciers. Radiocarbon dates of algae from extinct ephemeral ponds in the ice-cored moraines indicate the moraines to be at least 6,000 yr. old.

Additional evidence for the antiquity of the near-glacier moraines is the presence of a rather uniformly well-developed micro-relief pattern of sand-wedge polygons on both the end moraines and the ground moraines extending up to the existing glacier front. Studies show that it requires hundreds if not thousands of years for such well-developed polygonal patterns to form.

A drilling operation and core investigations at Base Roi. Baudouin (lat. 70° 25′ 5″ S., long. 24° 18′ 38″ E.) in January 1961 are discussed. The drilling, undertaken with light equipment, attained a depth of 115.72 m. From the start serious difficulties were encountered so that it was decided to use a SIPRE auger driven by the mechanism of the drilling machine. Core recovery was close to 100 per cent. Below a depth of 43.70 m., since the drill had reached the zone of high ice density (0.85 g./cm.3), a 3 m. double core barrel was used with air circulation. A depth of 79.33 m. was reached with a core yield close to 100 per cent. From this level downwards to the final depth of 115.72 in. the core yield was only 55 per cent.

Preliminary observations were made at the site. A stratigraphie profile of the first 43 m. showed an al terna-ion of coarse-grained summer layers with ice formation and fine-grained winter deposits. From the seasonal alternations of the last six years, an average annual accumulation of 38.3 cm. of water was calculated. No coloured or dust layers were observed. Between 9 and 16 m. and between 41 and 44 m. an intense formation of ice was noticed. The depth-density curve is similar to those found by the. Norwegian-British-Swedish Antarctic Expedition at Maudheim and by the Americans at Little America V. If an average annual accumulation of 38 cm. of water is assumed, the whole depth drilled corresponds to approximately 240 yr. Temperature measurements could not he carried out b;rcause of the limited time available.

Detailed stratigraphie and morphological studies of the cores, which are stored at −15°C. in Brussels, are planned, as well as chemical and isotopic investigations.

Observations in the glaciological pit of Little America III (1939–41), carried out in March 1957 and in January 1958, are discussed. Of particular interest is the analysis of the settling of firn over a period of 17.6 years. The observed data, including those of Wade taken in 1940 and of Howard in 1947, were fitted best by a logarithmic expression, which proved useful as an interpolation formula. From the computed values of the rate of settling, and the observed density-depth relation, the average accumulation is calculated, using Sorge’s law. For the undisturbed period 1947–58 an average annual accumulation of 19 g./cm.2 is found for Little America III (position in 1958 about lat. 78° 26′ S., long. 163° 52′ W.).

An ice surface map of central Marie Byrd Land has been compiled from aero-altimetric data taken on 14,000 km. of flight lines during the Antarctic summer of 1960–61 using standard aircraft equipment. A large depression sloping down towards the Filchner Ice Shelf was determined and earlier known features in the area are shown in greater detail.