The small slope magnitude ε. or aspect ratio. of an ice sheet in steady plane motion under gravity user a horizontal plane bed, subject to balancing surface accumulation and ablation. and basal drainage. is determined by the aceunualation magnitude, maximum depth. and the viscous properties of the ice. Horizontal coordinate scaling by a factor ε allows. series expansions in ε for which the leading-order solution is valid ecenschee under some weak restrictions on the ice law and sliding faw. This procedure is now extended to the plane flow problem when the mean bed line is inclined at angle χ to the horizontal and the bed is not flat. The lead order problems for χ of order unity and χ of order t: are distinct. and both are treated, fiir an isothermal sheet. The present analysis is valid only for a maximum bed slope relative to the mean line of order ε or less. The amplitude of it bed profile is ill, wavelength that of’ the ice sheet may therefore be of the same site as the ice sheet depth, which allows treatment of a typical isostatic bed shape.

Measurements at various epochs in the course of the twentieth century indicate a slowing down of surface ice flow velocity. This is consistent with the numerical modeling of the secular glacier recession, which furthermore shows a gradual upward shift of the regions of highest velocity and mass flux. Crevasse orientation is transverse above, and longitudinal below, the velocity maximum. The secular change in the longitudinal velocity profile seems to affect the crevasse pattern. Net balance in the next five years is a major factor in future changes of the glacier. With this reservation, model calculations for a possible extreme scenario indicate a drastic overall velocity decrease, and a moderate further displacement of the velocity and mass-flux maxima up-glacier, by the mid 1980’s.

Surface and core samples of Neh–nar Glacier in the Kashmir Valley have been analysed for the radionuclides 32Si. 210Pb, 40K, and 137Cs. The lateral and vertical profiles (at an altitude of about 4 140 m) reveal:

(1)32Si activity decreasing slowly from the accumulation zone to 4 050 m altitude and then abruptly towards the snout.

(2)Five zones of alternating high and low 210Pb activity in the surface samples.

(3)An horizon at between 2 and 3 m depth containing 210Pb activity above natural levels. This horizon is also associated with 137Cs and a maximum in total ß activity.

The ice samples have been dated on the basis of a simplified two–component model, the “fresh“contribution determined by 2l0Pb and the old component by 32Si. The following conclusions can be drawn from these observations:

(1)The model age of the snout ice is c. 850 years.

(2)The average rate of ice movement in the lower glacier is about 2 m/year, which compares well with the annual movement rate of 2.65 m/year observed since 1974.

The Gor Garung group of glaciers constitute an ice cover of over 4 km2 in a basin of 27 km2 area, lying in the Sutlej River catchment of the north–western Himalaya. This paper, the first record of these glaciers, their moraines and lakes observed in this area, is the result of mapping the glaciers and the pro–glacial field.

An attempt has been made to utilize lichenometry for establishing relative antiquity of various terminal moraine ridges generated by these glaciers, and six groups have been determined.

A four stream discrete-ordinates photometric model including both anisotropic scattering and refraction at the boundaries is presented which treats the case of a floating ice slab. The effects of refraction and reflection on the redistribution of the incident radiation field as it enters the ice are examined in detail. Using one- and two-layer models, theoretical albedos and transmittances are compared to values measured in the laboratory for thin salt ice. With an experimentally determined three-parameter Henyey–Greenstein phase function, comparisons at 650 nm yield single-scattering albedos ranging from 0.95 to 0.9997. The models are then used to compare the effects of diffuse and direct-beam incident radiation, to investigate the dependence of spectral albedo and transmittance on ice thickness, and to determine the influence of very cold and melted surface layers.

Ice temperature data collected from the area of continental–type glaciers in China since 1959 are analysed. Formulae for the temperature stratification of the active layer and for annual mean temperature profiles are suggested. The temperature in continental–type glaciers in China is quite low, rising rapidly with depth. A major part of the bottom of most glaciers reaches the pressure–melting point, with basal sliding. The extreme huge valley glacier will change from a cold glacier into a temperate one when it descends to the district where the climate is temperate. The ice temperature of the lower bound of the active layer at the altitude of the equilibrium line is 1.8–3.7 deg higher than the annual mean air temperature at the same level. The western section of Ch’i–licn Shan (Qilian Shan) may be the place where the temperature of alpine glaciers is the lowest of the middle and low latitudes. The infiltration zone is warmed significantly by the infiltration and recongelation process. A scheme showing how the lower bound temperature of the active layer changes with glacial zones is drawn.

Le régime des températures dans les glaciers de type continental en Chine. On analyse les températures de la glace recueillies sur glaciers de type continental en Chine depuis 1959. On a suggéré des formules pour rendre compte de la stratification des températures du niveau actif, et pour le profil de température moyenne annuelle. La température dans les glaciers de type continental en Chine est très basse, s’élevant rapidement en profondeur. La plus grande partie du fond, dans la plupart des glaciers atteint le point de fusion correspondant à la pression, avec glissement sur le fond. Un très grand glacier de vallée se transforme de glacier froid en glacier tempéré lorsqu’il aborde une région où le climat est tempéré. La température de la glace à la limite inférieure du niveau actif, à l’altitude de la ligne d’équilibre est de 1,8 à 3,7 deg supérieure à la température moyenne annuelle de l’air à la même altitude. La section occidentale du Ch’i–lien Shan (Qilian Shan) est peut être l’endroit où la température d’un glacier alpin est la plus basse dans les latitudes moyennes et basses. La zone d’infiltration est, de manière significative, réchauffée par un processus d’infiltration et de regel. On a dressé un schéma montrant les variations de la température de la limite inférieure du niveau actif avec les zones de glaciations.

Über den Wärmehaushalt der kontinentalen Gletscher in China. Die Beobachtungen der Eistemperaturen aus dem Gebiet der kontinentalen Gletscher in China seit 1959 werden analysiert. Formeln fūr die Temperaturschichtung im aktiven Eis und fūr ein Profil der Jahresmitteltemperalur werden vorgelegt. Hie Temperatur in den kontinentalen Gletschern Chinas ist sehr niedrig, steigt jedoch schnell mit der Tiefe. Ein Grossteil der Grundschicht in den meisten Gletschern befindet sich auf dem Druckschmelzpunkt und gleitet am Untergrund. Extrem mächtige Talgletschcr wandeln sich von kalten zu temperierten Gletschern, wenn sie in den Bereich temperierten Klimas herabfliessen. An der unleren Grenze des aktiven Schichts in Höhe der Gleichgewichtslinie ist die Temperatur 1.8-3.7 deg höher als die Jahresmitteltemperatur in derselben Höhe. Der Westteil des Ch’i-lien Shan (QMian Shan) dūrfte der Ort sein, wo alpine Gletscher der mittleren und niedrigen Breiten ihre tiefste Temperatur erreichen. Die Sickerzone wird durch das Sickerwasser und die Wiedergerrierwärme beträchtlich erwärmt. Eine schematisch Darstellung zeigt die Veränderung der Temperatur der Untergrenzc des aktiven Schichts innerhalb der vergletscherten Zonen.

The influence of snow structure on the liquid water distribution is recorded by measuring the high-frequency relative permittivity. The structure is characterized by the size and the shape of the ice grains, which are derived by analyzing the static dielectric constant and by analyzing photographs of the surface of the snow samples. The liquid distribution is very sensitive to the liquid saturation and to the shape of the ice grains; it is unaffectcd by the grain size. A transition from the pendular into the funicular mode of liquid distribution occurs in the range of 7 to 18% saturation. This transitional zone is very sensitive to the structure of snow; it decreases from approximately 13 to 18% liquid saturation for new snow to 7 to 12% saturation for old, coarse-grained snow.

Sediment deposition on to snow overlying glacier ice occurs in a marginal zone extending 200–300 m up-glacier from the terminus of Sylgjujökull. Debris on ice above the marginal snow zone comes from debris-rich layers, and 85% of this debris falls between 1 and 4ϕ, the characteristic grain-size of volcanic ash within Icelandic glaciers. The ash is transported down-glacier as suspended load in melt-water streams at concentrations between 61 and 430 mg l−1, and loads from 0.2 to 32.7 g s−1. A diurnal hysteretic loop is present in the relationship between suspended sediment and discharge for one stream.

Supraglacial streams flow from relatively impermeable ice on to more permeable snow near the glacier terminus. As they move across the snow, stream discharge (up to 0.1 m3 s−1 on ice) is reduced and debris is re-sedimented as linear debris trains 1–3 cm thick and orientated orthogonal to the glacier margin. Since sediment deposition reduces the permeability of the snow substrate, the debris trains are successively extended across the snow cover at rates of up to 36.5 m d−1. If the debris is then let down on to glacier ice, linear dirt-cone assemblages may be produced. Re-sedimented debris trains are of little stratigraphic significance if deposited pro-glacially.

Movement of pack ice in Smith Sound in northern Baffin Bay was observed for April 1975 using the satellite imagery obtained by Landsat. Mean velocity was found to be directed to the south with a magnitude of 4 km d−1. The influence of the wind is discussed and the amount of ice transported from Smith Sound evaluated. The findings show that on a daily average 600 km2 of pack ice was carried out of the area.

Two rock glaciers are described from the maritime sub-Antarctic island of South Georgia. The Cooper Sound rock glacier is a spatulate feature, probably ice-cored, 1.5 km long, and developed below a dissected cirque headwall. The Binary Peaks rock glacier is a lobate feature, possibly ice-cemented, only 175 m long, and contiguous with the talus behind it. Evidence for an ice-cored rock glacier in this maritime environment indicates that the debris supply and receiving glacier areas may be more important factors in determining rock-glacier development than zonal climate.

Specimens of polycrystalline ice were experimentally deformed in plane strain at a temperature of –1°C, under a constant load and with shortening strains varying from 2 to 27%. The random c-axis orientation of the initial ice aggregates changes continuously with increasing strain towards a steady-state, small-circle containing two maxima lying about the shortening direction. The ice microstructure is sequentially transformed from undeformed grains to smaller, irregular, deformed grains containing recrystallized grains. Grain growth then occurs forming a coarse interlocking-grain aggregate. These microstructural changes are attributed to solid-state processes occurring during deformation. The previously deformed specimens were then annealed without a load at –1°C. Annealing resulted in a substantial grain-size coarsening. However, no c-axis preferred-orientation difference developed between annealed and unannealed samples.

The propensity for crack formation on basal and prismatic planes and twin nucleation on two pyramidal planes in hexagonal ice is examined on the basis of fracture theories and anisotropic elastic theories of dislocations. Calculations show that the ease of crack formation is almost the same in the basal and prismatic planes, whereas it is almost impossible to produce mechanical twinning in ice by stress alone.

A new method has been developed for the observation of crystal axes orientation in fine-grained polycrystalline ice (grain-size approximately one millimetre). A two per cent ethylene dichloride solution of polyvinyl formal (Formvar) is applied to the surface of a sample. This solution produces adequate density of small holes in the Formvar coating and subsequently the nucleation sites for hoar crystal growth. The geometrical shape of each hoar crystal reveals both the c-axis and a-axes orientations using an optical microscope.

Triaxial tests were carried out on randomly oriented, laboratory-made, polycrystalline ice, between strain-rates of 10–7 and 10–1 s–1 and with confining pressures from 0.1 to 85 MN m–2, at –11 ± 1°C. Below strain-rates of about 10–5 s–1 the confining pressure has little effect, but at higher strain-rates the confining pressure prevents cracking which allows the compressive strength to rise to a value greater than the unconfined compressive strength. At 1.4 ×10–2 s–1, the unconfined strength of 12 MN m–2 rises to 26 MN m–2 with a confining pressure of 25 MN m–2, before dropping slowly with greater confining pressures. Above 10–2 s–1 the unconfined strength decreases rapidly with increasing strain-rate, but the confined strength continues to increase. The dependence of strain rate on the maximum compressive stress is discussed.

The Nimbus-6 Satellite’s Scanning Microwave Spectrometer (SCAMS) mapped the terrestrial surface continuously for eleven months at 22.2 and 31.6 GHz. A semi-empirical method was devised to process these observations of Greenland and Antarctica and to infer long-term snow accumulation rates; comparison with in situ data suggests the method is generally successful except in certain locations where re-melting is more likely.

Shear tests performed on natural snow exhibited three kinds of behaviour with increasing shear rate: (1) viscous, without failure, (2) brittle of the first kind (cycles of brittle failure), (3) brittle of the second kind (only one brittle failure, and solid friction). These results can be explained by fast metamorphism of the bond system during the tests. When the shear rate is low, bonds can be regenerated after their destruction, and this regeneration is less active as the shear rate increases.

Diethyl phthalate, dimethyl phthalate, ethyl anisate, and α-tetralone are examples of liquids that can be used to fill the pore space of snow specimens. After the pore space is filled, the specimen is frozen solid. A section plane is microtomed and polished. Photomicrographic contrast of the section plane is improved by gently rubbing on to the plane a water–insoluble powder, such as carbon powder, or by rubbing on a water–soluble stain such as powder of acid fuchsin. Photomicrographic contrast is also improved by adding a water–insoluble dye such as oil blue N or oil red O to the pore–space filler.

A correlation between temperature gradient in snow–pack and material strength is found to exist in laboratory studies on temperature gradient metamorphism of snow. These results are in agreement with earlier field investigations and eliminate diurnal solar and temperature variations as reasons for the existence of the maximum temperature gradient in the zone of minimum strength. Also the laboratory studies have indicated that locally dense layers such as ice crusts tend to enhance weakness directly below the crust due to local alteration of the thermal regimen. Further studies are continuing to describe the thermodynamic process of temperature gradient metamorphism more exactly.