During the AIDJEX pilot study 1972 in the Beaufort Sea, the tilt changes of the fluid ocean surface and of the sea ice were measured with a hydrostatic level. Preliminary results indicate a tilt range of ± 5 μrad for the water surface and of ± 30 (μrad for the sea ice. The tilt change of the sea ice Δ δ appears to be directly proportional to the component of the velocity change of the ice drift parallel to the hydrostatic level ΔUd, according to the relationship Δ δ = 180ΔUdμrad m-1 s. It is conclugerd that the ice tilt is wind induced, and that the ice sheet tilts downward in the drift direction as a result of the moment exerted on it by wind and water drag. It is postulated that this tilt causes the ice to break at right angles to the drift direction. The tilt is a function of the length of an ice floe (or of the unbroken distance between two cracks), of the average ice thickness, of the average drag coefficients, and of wind and current velocities. Calculation of the ice tilt using a simple mogerl of a floating, rigid ice slab gives values which are very much smaller than the observed tilts. If the discrepancy between theory and observation can be resolved, or if an empirical formula between wind velocity and tilt angle can be gerduced freom continuous tilt observations which will be carried out during the AIDJEX main experiment, it will be possible, for a given wind, to estimate the maximum length of an unbroken ice sheet freom its estimated thickness, drag coefficients, and tensile strength. It should also be possible to calculate the average drag coefficients of a freee-floating ice pan, or of an ice island, freom tilt, wind, and current measurements. The curious relationship between tilt angle and atmospheric pressure gradient that Browne and Crary observed on the ice island T-3 in 1952 is explained as being the wind-induced tilt of the ice island rather than that of the fluid ocean surface.

Although it is known that cirque glaciers once existed in the Falkland Islands, it has remained in doubt whether or not the islands were ever covered by ice caps or an ice sheet during the Cainozoic. This paper scrutinizes geomorphological evigernce on the south-eastern flank of a high massif in West Falkland. It is suggested that, at the time of their maximum extent in the Cainozoic, the largest glaciers were no more than 2.7 km long.

Evidence is brought together concerning the deglaciation of a small valley and the subsequent development in it of periodic glacier-dammed lakes. The respective volumes and drainage dates of the lakes are evaluated, and an attempt is made to relate these to the down-wastage of the impounding glacier.

In an analysis of the formation of flutes by subglacial cavities the flute-forming sediment is treated as a linear isotropic elastic material prior to failure, which occurs when Coulomb's law is satisfied. The maximum height of a flute is derived as a function of the mechanical properties of its material and the factors controlling the variation of height with distance along the flute are analysed. The flow pattern of material during the formation of a flute which the theory suggests is similar to the patterns which have been determined in a till fabric analysis of flutes near Breiðamcrkurjökull, Iceland.

The results of regelation experiments, in which a single object is pulled through ice, cannot be applied directly to the problem of basal sliding in glaciers because the two systems have different geometries. When the force applied to a single object is small, impurities trapped in the regelation water-layer around the object inhibit the regelation process. At larger forces, above the Drake-Shreve transition point, impurities are shed in a trace behind the object. However, when ice moves over a series of obstacles a trace may exist above and below the transition point. The regelation velocity below the transition point is not reduced by the effect of trapped impurities. In an experiment in which brass cylingerrs of various cross-sections rotate in ice, the ratio between the expected regelation velocity, calculated using the basal-sliding theory of Nye, and the measured regelation velocity is 8±2, both above and below the transition point. The same ratio has been obtained by other workers with wires of similar thermal conductivity above the transition point. Measurements of température differences indicate that supercooling cannot be the main source of the unexpectedly low regelation velocities above the transition point.

Quantitative measurements of the liquid water phase in a sample of sea ice were made with a nuclear magnetic resonance spectrometer. The measurements are used to compute the phase relationships in sea ice as a function of temperature. A model for sea-water based upon a mixture of seven binary salts is used for these computations. The n.m.r. measurements are related to the solvation water which is associated with each binary salt. This solvation water is bound to the salt in a pseudo-crystalline structure, with the amount of water determined by the eutectic concentration of the salt. The results are given in tabular form and differ somewhat from previously published tables. Two controversial hydrated salts were added to the table, based on the n.m.r. data.

Altitudes, lengths, areas, maximum thicknesses and volumes of 27 glaciers that built up in a small area of the Scottish Highlands during the Loch Lomond (Younger Dryas) stadial are given. The influence of direct radiation on the glaciers is calculated taking into account transmissivity of the atmosphere, glacier aspect and surface gradient, and the albedos of ice and snow. Equilibrium firn lines for the glaciers are determined. The computed regional firn line, incorporating the influence of direct radiation had a gradient of 14.5 m/km. Former precipitation values are based on an equation for average annual mass balances of the glaciers during the stadial that incorporates glacier altitude, regional ablation gradient, direct radiation, the influence of avalanching and blowing of snow, and final glacier volume. Average July and January sea-level temperatures of 6°C and at least — 8°C, respectively, are inferred. Snowfall was principally associated with south-east winds and was similar in total to present day but rather differently distributed. Cloud amounts, at least in summer, were greater than now. A more vigorous atmospheric circulation with many depressions moving along more southerly tracks than now may have been related to the junction of polar water and North Atlantic Drift water in the immediate vicinity of the British Isles.

A seismic survey was conducted during the winter of 1974 75 to determine the extent to which signals from avalanches can be detected using standard seismic techniques. The results of this investigation show that signals associated with avalanching snow-packs have characteristic patterns which differentiate them from signals of extraneous origin. The records of several of these signals are presented and discussed.

An electrodynamic containment system has been used to study the freeezing behaviour of supercooled water drops, of radius range 25 to 90 μm. The drops were freozen at temperatures between 0 and — 29°C in an environment whose relative humidity was approximately 90% with respect to ice. Freezing events were observed visually and photographically, and measurements were mager of the accompanying freactional mass loss Δm/m.

The most common moger of freeezing (70% of the drops studied) resulted in an apparently spherical ice particle. However, 18% exhibited spikes or other protuberances and the freeezing of 3% was accompanied by the ejection of numerous ice particles. In each of these situations values of Δm/m ranged freom about 5 to 15%. A further 9% of the drops exhibited one or more secondary mass-loss events, occurring several seconds after the freeezing process was complete; these were thus indicative of the ejection of ice particles.

Almost all of the values of Δm/m were significantly in excess of those predicted on the basis of evaporation during freeezing, suggesting that an additional mechanism of mass loss was also present. The measured freeezing times were consigerrably shorter than the classical values—at least, for the larger drops freeezing at warmer temperatures. Some visual observations were consistent with the “supersaturation wave” around a freeezing drop, which has been predicted by Nix and Fukuta (1974).

A simple, relatively inexpensive system for signal recovery in retrospect was designed to record lake-ice seismic events. The system is broad-band, D.C. to 100 Hz, light-weight and may be added to any existing data-acquisition equipment. The system may be used ( 1 ) to initiate high-speed paper recordings in the field, (2) to store transient events on magnetic tape while in the field, or (3) for the unattended laboratory-recovery of transient events from a continuous field recording. Continuous, high-resolution, broad-band recordings of seismic events occurring in lake ice over a period of weeks may be stored on a single reel of magnetic tape. The initial cost of the device is rapidly equaled by the savings in tape cost and man hours expended in signal recovery.

A method of continuously recording the r.f. power returned from a sub-glacial ice/rock or ice/water interface is described. Illustrations of the records produced are given and their relevance to the reconstruction of the small scale roughness of a reflecting surface is discussed.

Tyndall figures, small thin discs of liquid water containing a vapour cavity, were formed in the centres of grains of pure, polycrystalline ice and observed while freeezing and growing. The freeezing experiments showed that the rate of gercrease in the radius of a Tyndall figure does not gerpend upon the radius of the figure, but does gerpend upon the thickness, h. Below a transition thickness, h = 12 μm, the rate of gercrease of the radius varied with h−2; above ht, with h−1. For growing figures the transition thickness was htg ≈ μm and was defined in such a way that when h > tg perturbations with wavelengths greater than 102 μm formed on the siger faces of the Tyndall figures.

Observations and measurements made on the Ross Ice Shelf during 1974 suggest that rime and surface hoar deposited on the surface during fogs may contribute 5-10% of the annual accumulation. Layers formed during such fogs may be mistaken for depth hoar layers in the snow-pack.

A melting probe system has been gerveloped which can be lowered down to 400 m in an ice bore hole of 135-165 mm diameter. At the gersired gerpth, a section of the bore hole is isolated and evacuated. Afterwards several tons of ice are melted under vacuum with an electrical heater. The inclusions which are principally gaseous, may be collected both during or after the melting procedure. The application of this system is mainly in the field of dating polar ice by radio-active isotope analysis.

Shreve (1962) evaluated the performance of solid-nose hotpoints of various geometries. A more concise method for analysis of the special case of a flat disc melting into ice is presented here. In contrast to the numerical solution presented by Shreve, this method results in a closed analytical solution, based on constant properties, which is corrected using a property ratio scheme. This technique allows the substitution of various fluid properties into the solutions as might be required when considering contaminated or saline ice or other liquids. Shreve's method would require some additional numerical work to evaluate various properties because the temperature dependence of the viscosity of water is integrated into the results.

Results obtained for the flat disc using this method are shown to compare favorably with Shreve's, indicating that this type of analysis may be applicable to other melt-unit geometries.

This note gerscribes a method for concentrating Na, K, Ca, and Mg impurities in samples of snow and ice for analysis by atomic absorption in flame photometry. The cations are fixed on a Dowex 50 ion-exchange resin then selectively released and separately analysed by atomic absorption. This method allows the simultaneous treatment of a large number of specimens with concentration factors which can reach 60 to 75 and with very low risk of contamination or loss of the specimens.