Ice-marginal features in South Georgia include minor moraine ridges running approximately parallel to the ice margin and developed as superficial forms in various depths of till. It is suggested that these developed as ice-contact landforms, some being created by the interaction of the ice edge and abutting marginal snow bank, whilst the glacier is advancing. This advance is essentially short-term, being part of a seasonal variation in the position of the ice margin. “Snow-bank push” is the term proposed to describe this mechanism of ridge formation.

Several theories exist on the origin of kettle-holes in pro-glacial outwash deposits. The most widely accepted origin involves the melting of buried ice. The author carried out some experiments in which ice blocks were placed on or in outwash sediments in a tank in order to determine which mechanisms of ice melt would be most likely to give rise to kettle-hole features. The largest kettle-holes were produced by the melting of buried ice blocks; smaller transient depressions were formed from ice blocks melting in streams of flowing water; while, rather than depressions, ridges resembling pingos and moraines were created by ice blocks melting on a dry or saturated gravel surface.

Measurements of light transmission and reflection were carried out on first-year sea ice near Point Barrow, Alaska, and on multi-year ice near Fletcher’s Ice Island in the Beaufort Sea (lat. 84° N., long. 77°W.). Spectral albedos (400-1 000 nm) and extinction coefficients (400-800 nm) were determined for melt ponds, snow, and various types of bare ice. Albedos were largest in the 400-600 nm range, decreasing toward longer wavelengths at a rate which appeared to be related to the liquid-water content of the near-surface layers. Extinction coefficients remained nearly constant between 400 and 550 nm, but increased rapidly above 600 nm. At 500 nm, albedos ranged from 0.25 over mature melt ponds to 0.93 over dense dry snow, while the corresponding extinction coefficients ranged from 0.6 to 16 m-1. Intensity profiles taken in the upper 50 cm of the ice indicated that the extinction coefficient at a particular wavelength was nearly constant with depth below 15 cm, although the bulk extinction coefficient decreased with depth because of the strong attenuation in the red. Near the surface it was found that multi-year ice absorbed slightly more energy than did first-year blue ice, but at depths below 10 cm the flux divergence in the first-year ice was three to four times larger than that in the multi-year ice. A simple procedure is described for estimating light transmission and absorption within the ice under clear or cloudy skies from total flux measurements at the surface. Methods by which satellite data could be used to estimate regional albedos, melt-pond fraction, and lead area are also presented.

Meteorological and snow pack variables are measured on chronologically ordered sequences of avalanche and avalanche-free days. Discriminant analysis is used to define a subset of variables which produce an optimal separation of the two multivariate group means. Two seasons are identified in each of the years considered corresponding to periods of dry- and wet-snow avalanches, and form the basic stratification of avalanche days in the analysis. Days are stratified further within each season on the basis of magnitude and number or releases. Weather and snow parameters are integrated over variable time steps prior to each avalanche or avalanche-free day. This introduces a recursive element into the forecast method. Preliminary testing of the method points to its potential in real-time snow avalanche forecasting on a regional basis.

The Laurentide and Fennoscandian ice sheets had three major glaciation maxima during the Last Ice Age. All data from the southern margins of the ice sheets indicate that these maxima, as well as minor fluctuations, were synchronous. The same synchroneity is supposed to apply also for correlations between fluctuations on the north and south margins, which reveal a continuously southward displacement of the distribution of glaciation during the Last Ice Age. This southward displacement explains the saw-tooth pattern of 18O records from deep-sea cores in which the first glaciation maximum is under-represented due to its distribution more towards the north. The synchroneity is consistent with a global climatic control of the stadial/interstadial changes and with the recorded global eustatic changes. The southward displacement of glaciation seems to be a general rule also applicable to earlier Pleistocene glaciations.

Deuterium, tritium, and gross β activity measurements have been performed to a depth of 16 m on a snow core taken on Mont Blanc (French Alps) to establish a chronology of its formation and then deduce the annual accumulation. These three independent methods show that the core was formed over a three-year period. This corresponds to a mean annual accumulation of 2.8 m water equivalent In addition, the isotopic measurements indicate the existence of an altitude effect in the distribution of deuterium and tritium in the precipitation in the Mont Blanc area.

Isoglacihypses depicting the configuration of the glaciation threshold (= “glaciation limit”) in Washington broadly parallel the crest of the Cascade Range and curve around the west and south flanks of the Olympic Mountains. In both uplands the glaciation threshold rises inland (eastward) with a mean gradient of 10-12 m/km. However, the gradient in the Cascades is more variable (7-25 m/km) due to five east-trending troughs in the glaciation threshold surface that coincide with topographic depressions along the range crest and that apparently result from greater eastward penetration of moist maritime air.

Mean accumulation-season precipitation correlates strongly (r2 = 0.86) with altitude of the glaciation threshold in the North Cascade Range, but the correlation of glaciation threshold with altitude of the July freezing isotherm, determined from the calculated July lapse rate within the mountains, is much weaker (r2 = 0.40). Multiple regression analysis relating independent climatic variables that affect the height of the glaciation threshold indicates that 90.4% of variance is explained by accumulation-season precipitation and estimated mean annual temperature at the glaciation threshold.

The glaciation threshold during the greatest ice advance of the last (Fraser) glaciation in the southern North Cascade Range (c. 18 000-22 000 years B.P.) was 900 ± 100 m below that of the present. Depression of the glaciation threshold by this amount most likely resulted from a change in accumulation-season precipitation of no more than 30% from present values and a decrease in mean ablation-season temperature of 5-5 ± 1.5 deg.

Three different types of saline ice were cut into sections a few millimeters thick along planes parallel to the surface. The resulting melts were analyzed quantitatively for chloride, sulphate, sodium, potassium, magnesium, and calcium. Two of the specimens were artificial sea ice, grown in the laboratory at ambient temperatures of —30°C and - 15°C, respectively. A portion of the latter exhibited a clear, glassy, fresh-ice structure. The third was natural sea ire. The resulting ion concentration profiles and ion ratios are presented. For sections of widely varying salinity, the various ion ratios assumed values fairly close to those in natural sea-water.

During a field survey in High Semyen, northern Ethiopia, two moraine complexes were mapped, the lower one extending down to around 3 750 m. Glacial morphology is best developed in the north-western and western quadrants. Moraines are deeply weathered and carry abundant vegetation. For Mounts Badda, Cilalo, Cacca and Enguolo in southern Ethiopia, possible moraines are inferred from air photographs; there are indications for more pronounced glaciation in the western quadrant, and moraines seem to extend further down than in High Semyen. Highest moraines at Mount Elgon in northern Kenya/ Uganda were found to below 3 600 m. Major moraine complexes in the mountains of Ethiopia and East Africa suggest some spatial correlation in elevation and appearance, but absolute dates are absent.

Drumlins in parts of central Scotland and east Cumbria form two populations according to their size. In certain cases the small features are superimposed on the large. Drumlins, superimposed drumlins, and megadrumlins are considered to be part of a continuum of glacier bed forms, which is the product of changes in the stress applied by glaciers and the strength of bed material. Glacier behaviour can be inferred on the basis of this interpretation.

Drumlins in parts of central Scotland and east Cumbria form two populations according to their size. In certain cases the small features are superimposed on the large. Drumlins, superimposed drumlins, and megadrumlins are considered to be part of a continuum of glacier bed forms, which is the product of changes in the stress applied by glaciers and the strength of bed material. Glacier behaviour can be inferred on the basis of this interpretation.

Side-looking airborne radar (SLAR) imagery obtained in April-May 1974 from the North Slope of Alaska between Barrow and Harrison Bay indicates that tundra lakes can be separated into two classes based on the strength of the radar returns. Correlations between the areal patterns of the returns, limited ground observations on lake depths and water compositions, and information obtained from LANDSAT imagery strongly suggest that areas of fresh-water lakes giving weak returns are frozen completely to the bottom while areas giving strong returns are not. This is a reasonable interpretation inasmuch as the reflection coefficient associated with the high-dielectric-contrast ice-water interface would be roughly twelve times that associated with the low-contrast ice-soil interface. Brackish lakes also give weak returns even when they are not completely frozen. This is the result of the brine present in the lower portion of the ice cover limiting the penetration of the X-band radiation into the ice. The ability to separate tundra lakes rapidly and easily into these two classes via SLAR should be useful in understanding a wide variety of problems.

Inverse theory is applied to relative sea-level data to reconstruct a glacial history that is consistent with the emergence data near Glacier Bay, Alaska over the past half century. A comparison between the predicted glacial thinning and observed thinning indicates that a combination of elastic uplift of the ground and a fall in the geoid defining the ocean surface, causes 25% to 35% of the observed emergence of the coast line. Because of errors in the sea-level data, inverse theory cannot provide a unique solution in terms of glacier response, and, in fact, the least-squares fit is very inaccurate. However, by considering (1) the error of fit to the data, (2) the accuracy of the model, (3) the variation in the model, and (4) the model resolution, a physically realistic glacial history can be deduced. The advantage of inverse calculations is not only in its efficient means of finding a model that fits the data, but more importantly, it provides a means of assessing the reliability of the model by indicating the accuracy of the model and the range of other glacial histories that also fit the data. This approach also allows an estimate of the extent to which each data point constrains the model, independent of the actual data values. From this information, the most useful areas for additional data collection may be delimited.

A microtoming and replicating technique has been developed for examining the micro-structure of sea ice optically and by scanning electron microscope. This dual observation method is useful for studying the grain and sub-grain structure of sea ice, the nature of the brine pockets, and the precipitation pattern of the salt crystals at low temperatures.

The study of subglacial movements taking place in regions of cavitation beneath the Glacier d’Argentière, has demonstrated the necessity for using several cavitometers. The very unusual conditions in which such apparatus is installed to measure simultaneously the velocity and the position of the ice vault have led us to design and produce a prototype of a portable cavitometer which records the data on magnetic tape (cassettes).

Evidence from aerial photographs, maps, and field checks indicates that 319 glaciers lie in cirques of the Rocky Mountains, south of the United States-Canadian border. On a subcontinental scale, the distribution of glaciers is highly clustered, with larger and denser clusters located in the northern Rocky Mountains. Lesser concentrations of small glaciers occur in the southern Rocky Mountains. The total area of glaciers in the Rocky Mountains of the U.S.A. is 78.9 km2.

An ice cover impinging on a long straight structure is assumed to be under a condition of plane strain. A technique is described for performing plane-strain compression tests, and results are presented for the strain-rate dependence of strength. The plane-strain compressive strength of ice having anisotropic structure (columnar-grained ice) is at least two and a half times the uniaxial compressive strength, whereas the plane-strain compressive strength of ice having an isotropic structure (granular-snow ice) is at most 25% greater than the uniaxial case. The greater plane-strain compressive strength of columnar grained ice when the loading and confining directions are in the plane of the ice cover, can be attributed to its anisotropic structure, which leads to a different failure mechanism for the plane-strain case.

A diamond wire saw was modified for cutting thin sections of frozen soil and suitable operating conditions were determined experimentally. It was found that a lubricated wire, 0.34 mm in diameter, operaied at cutting velocities of 100-300 mm s-1 and cutting forces 0.02-0.1 kg produced smooth cut surfaces un thin sections 0.4-0.5 mm in thickness. The; temperature and wire size were not critical operating parameters and the wire tensions recommended by the manufacturer were satisfactory. A method of mounting the thin sections is also described.

A preliminary assessment of the daily variation of ice albedo in the 285-2 800 nm range was made using field data collected over snow ice and refrozen slush. Significant diurnal variations could be attributed to changing low solar altitude under clear skies or to decay of the ice surface. Changes in albedo due to changes in cloud cover were observed for the most part to be slight. The measurements provide a base for a program of wider scope which would consider other types of ice under a variety of natural conditions.

An analysis is made of the disturbance in conductive heat flow caused by drilling a bore hole in ice in which there is a vertical temperature gradient. The model used is that of a perfectly insulating hole placed in a linear temperature gradient; it is shown that the temperature measured at the bottom of the hole deviates from its value before drilling by an amount of order —0.6aU where a is the bore-holt radius and U is the temperature gradient. The deviation takes effect in a few hours. The error is typically between 0.005 and 0.1 deg and is therefore significant only where very high accuracy is required. It should not be present in temperate glaciers, nor where the thermometer is properly frozen in, nor if temperatures are measured at the bore-hole walls far above the bottom.

The study indicates that no significant difference in snow densities is found when using either the CRREL tube or the ILTS box cutters. However, inexperienced workers tend to overestimate snow densities in light snow and depth hoar by 6 and 4% respectively.