A numerical treatment of the heat conduction in ice sheets subject to vertical shrinking, geothermal and frictional heating from below, and surface accumulation or ablation, is outlined and illustrated with results computed for an arbitrary ice thickness profile. The movement of the ice is found to increase its basal temperature when the ice is thick, and to decrease it in the fringe zone where the ice becomes thin. The treatment seems capable of extension to cover both the thermal and dynamic aspects of ice motion.

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.

The performance of a thermal ice-drill having a smooth, solid, impervious frontal surface, termed a “solid-nose hotpoint”, is determined by the velocities, pressures, and temperatures in the thin layer of warm melt water between the hotpoint and the ice. The efficiency, the speed of penetration, the temperature of the frontal surface, and the distribution of pressure on it can be calculated from the equations of non-turbulent fluid flow. For hotpoints whose frontal surfaces are isothermal and axially symmetric, these quantities are functions of the total input of power Q of the weight W on the hotpoint, of the radius a and “shape factor” S of the frontal surface, and of the pertinent physical properties of water and ice. The calculation shows that with increasing “performance number” the efficiency E decreases and the surface temperature θ0 increases. Thus, for example, E = 1·00 and θ0 = 0°C. when N = 0.0 E = 0·76 and θ0 = 48°C when N = 1.4; and E = 0·60 and θ0 = 103°C. when N = 3.0. The coefficient Λ is a constant equal to . The shape factor S is a dimensionless number between 0 and 1 that varies according to the shape of the frontal surface, greater values of S being associated with blunter profiles (thus S = 1.0 for a plane frontal surface perpendicular to the axis). For coring hotpoints the same numerical results are obtained, but the performance number is given by

where 2ϖia is the inside diameter of the hotpoint.

A set of internally consistent mass budget terms is proposed for consideration. Vertically measured, water-equivalent components of accumulation, ablation, and net budget are defined for points on a glacier (specific quantities) or as area-integrated totals for the whole glacier (total quantities). The budget year is defined as the time between two minima of net budget. Additional terms involving specific and total rates of accumulation, ablation, net budget, and various subdivisions of the glacier area are developed. Mass budget quantities can be separated into steady-state and budget imbalance terms. Net budgets can be calculated by simplified means when the variation of budget with altitude is known. It is suggested that the term “firn” be applied to layers which have survived one summer’s ablation season.

On the Ross Ice Shelf near Scott Base the annual surface snow accumulation is about 18 g.cm.−2. The increase of firn density with depth is greater than normal, due to horizontal compaction. Where the bottom of the ice shelf has a density less than 0.8 g.cm.−3 the shelf becomes brine-soaked by vertical infiltration. The bottom of the shelf is melting, at about 44 g.cm.−2 yr.−1 where the bottom is impermeable ice and 73 g.cm.−2 yr.−1 where the bottom is permeable firn. Surface velocities at 40 points within 30 km. of Scott Base vary between 4 and 840 m.yr.−1. From the pattern of velocities, ice thicknesses and surface features, a transition zone is delineated, separating the Ross Ice Shelf from the “McMurdo Ice Shelf”.

An analysis of the iceberg count off Newfoundland for the period 1880–1925 shows that stronger than usual north-westerly winds off the Labrador and Newfoundland coasts and relatively low temperatures over Newfoundland during the months from December to March lead to greater than average berg counts off Newfoundland in the following months, mainly April to June. Conversely, lighter than usual north-westerly winds and relatively high temperatures lead to lower than average berg counts in the following months. The relative strength of winds can be measured by the pressure difference between Belle Isle and Ivigtut. The relationship investigated provides a basis for predicting the berg count each year at the end of March. A comparison of the computed values of the berg count with the actual values on scale 0 to 10 for the following period 1927–61 shows marked agreement.

It is further indicated that a more detailed representation of the winds, temperatures and other elements during the winter and early spring in that general area would lead to a closer relationship with the berg count and a broader basis for its prediction.

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.

A description is given of two tunnels, each 60–70 m. long, one directly above the other, at 4,000 and 4,020 m, a.s.l. excavated through cold firn and ice of the Breithorn in the Alps. The temperature rose from −5.5° C. at the portal to −0.5° C. at the rock interface 70 m, from the portal in the upper tunnel, and from −5.5° C. to 0° C. at a water reservoir 60 m. from the portal in the lower tunnel. In both cases cracks or minute sealed crevasses, cut by the tunnel, operated to cool the ice locally below the temperature to be expected from a smooth curve. Possible. origins of the water reservoir are discussed.

Small amounts of air at a moderate pressure, enclosed in small, sealed cracks and hollows, were punctured between 60 and 70 m. from the portal in the upper tunnel. The pungent odor of the air thus released was identified as ozone (a) by its characteristic odor, (b) by its reaction on rubber, and (c) by potassium iodide starch paper tests. The source of such ozone is suspected to be minute electric sparks resulting from static electric charges built up in cold ice when it is subjected under pressure to cracking or deformation; Photographs taken with exposures of 8 hr. in the upper tunnel at night apparently show such sparks.

A description is given of the appearance of cold ice, frozen to the bedrock, being forcibly tortured into streamers and bands by the movement of the entire ice body at 0.6 m./yr.

Massive calving of the Ward Hunt Ice Shelf, northern Ellesmere Island, occurred between August 1961 and April 1962. An estimated 596 km.2 of ice shelf with a volume of 18 to 24 km.3 became detached to form ice islands, five of which are very large with areas ranging from 70 to 140 km.2. The fracture pattern and the subsequent drift of these ice islands are discussed.

The Vaughan Lewis Glacier is one of the more striking glaciers in the Juneau Icefield Of Alaska. It lies in lat. 58° 50’ N., long. 134° 17’ W., at the head of a great canyon extending 30 miles (48 km.) inland from the northern end of Alaska's “inside passage”, about 36 miles (58 km.) north-north-east of the town of Juneau (Fig. 1 ); the glacier trends generally north westward for approximately 3·5 mil es (5.6 km.) to a nice fall where it joins the Gilkey Glacier.

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.

Investigations of the mass balance of the Hintereisferner are dealt with for the period 1952–61. Ablation of ice was measured with stakes, ten of which per square kilometre were considered as a sufficient number. The area of ice ablation terminates in the “zero-line of ice ablation”. The net accumulation was studied in pits, and by mapping of enduring accumulation patterns. In order to avoid errors it is proposed that the term “firn line” be replaced by the term “old snow line”. This would more clearly emphasize that only the net accumulation of old snow from the current budget year is a gain of mass for the glacier. The term “firn”, in accordance: with Flint’s [1957] definition should be used only for snow more than one year old. Between the old snow line and the zero-line of ice ablation in some years an appreciable firn ablation takes place. The mass balance reveals a large variation between +0 77×106m.3 of water in the most favourable budget year 1954–55, and −9.83×106m.3 of water in the most unfavourable budget year 1957–58. The average annual mass balance was −3.60×106m3 of water, with an estimated maximum possible error of about ±0.54×106m3 of water.