The continuity relationship that is often used in the study of ice sheets and ice shelves is developed by integrating the equation of continuity through the ice thickness. This equation is then integrated again with respect to horizontal distance from an ice divide, showing that the difference between the true ice velocity and the balance velocity, which is defined, is a measure of the time chance of the mass of a column through the ice thickness.

The relationship is applied using data from along the “Byrd” station strain network, Antarctica. This region is found to be thinning slowly (0.03 m a−1 of ice of mean density) and uniformly, but it is still close to steady-state. The calculations would show a larger thinning rate if bottom sliding contributed more to the ice movement and integral shear contributed less, but the “Byrd” station bore-hole tilting results of Garfield and Ueda (1975, 1976), together with surface velocity measurements at “Byrd” station, indicate that most of the ice flow is by deformation within the ice mass. This large amount of internal deformation is more than that predicted by most “flow laws”, probably because of the strongly oriented ice-crystal fabric in the ice sheet. The cause of ice thinning is probably decreased surface mass balance beginning before A.D. 1550.

The consistent relationship between measured velocity and balance velocity indicates that the ice flow is simple and that flow lines are in the same direction at depth as at the surface when considered smoothed over a distance of 10 km. Because the ice sheet is at present thinning, the balance velocity, calculated only from flow line and surface mass-balance data, and the somewhat mistaken assumption of steady-state is 15% less than the true ice velocity. This rather small difference confirms the use of balance-velocity estimates where velocity measurements are not available.

A three-dimensional model of the temperature and velocity distribution within any arbitrary-shaped ice mass is described. There is a mutual interaction in the model between the flow of the ice and its thermodynamics, since the flow law used in the model is temperature-dependent.

Ice growth in three dimensions is governed by mass accumulation through precipitation, by mass depletion through loss of ice over the ocean, and by continuity requirements. Phase changes at the base of the ice are accounted for. The model has been applied in art exploratory manner to the Greenland ice sheet. Changes in the ice shape and temperature are presented and discussed. The basic shortcoming of the model as here presented appears primarily due to the coarse finite-difference mesh used, and to an unsophisticated approach to modelling the boundary ice.

Thermal drilling and deep ice-temperature measurements along a flow line in a surge area of the Barnes Ice Cap, Baffin Island, N.W.T., Canada revealed a layer of basal temperate ice 30 m thick. Marginal areas were determined to be frozen to bedrock and geothermal heat flow estimated to be 1.02 μcal/cm2s (42 mW/m2).

Three glaciers in Switzerland, Griesgletscher, Oberaargletscher and Vadrec da l’Albigna, terminate in lakes recently impounded for hydro-electricity generation. Calving at their snouts has produced excellent cross-sections which enable one to study the structures along almost complete vertical profiles when the lakes are empty. Each of the glacier cliffs displays a shallow synclinal structure which, by comparison with surface structures, is interpreted as the vertical expression of an arcuate foliation, originating in or below an ice fall or an area of transverse crevassing. Extensive minor folding of an earlier layering is associated with this foliation. Well-developed longitudinal foliation exposed at the surface is sometimes visible in these vertical sections, indicating that the structure can form at depth.

The Gara Glacier, a north-facing valley glacier situated in the western Himalaya, was selected to be part of the study undertaken by India in connection with the International Hydrological Decade. This paper deals with the procedure adopted and the results obtained for mass-balance assessment over a period of one year between September 1974 and September 1975. The glacier has recorded a positive net balance of the order of 2.48 X 106 m3 in terms of water equivalent.

The results of an experiment to examine the glacier boundary layer over melting ice are described. They show that the boundary layer, as defined by the applicability of the log—linear profile, is approximately 1 m thick. The boundary layer is a frequent, but not a dominant feature of the air close to the ice. The frequency of occurrence is relatively high in cases where wind speeds are mainly controlled by katabatic forces.

Warm waste water, at 30°C, has been discharged from a copper concentrater on to the active terminal ice of Berendon Glacier, British Columbia, since 1970. As a result, rapid basal ice melt causes the formation of caverns and subsequent collapse features referred to as glacier thermokarst. A review of the literature reveals that such features have been described elsewhere from active ice, and the usual conditions assumed for the development of glacier thermokarst (stagnant, heavily debris-covered ice) should be redefined to include these examples.

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.

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.

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.

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.

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 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.