The first successful radar echo soundings through glacier ice in Canada were carried out by the Dominion Observatory in 1965 on an outlet glacier of the Penny Ice Cap in Baffin Island. An unmodified 440 MHz SCR-718 radar altimeter was used, of the type that is readily and inexpensively available on the surplus market. The radar soundings were generally in agreement, within the range of the reading accuracy of the oscilloscope (± 15 m), with depths obtained seismically, gravimetrically, and by the electrical resistivity method. The minimum and maximum recorded depths were 45 m and 550 m, respectively. The pip positions on the standard oscilloscope were recorded visually. This recording method was not satisfactory, but for future use the instrument could easily be modified to incorporate a larger oscilloscope with continuous photographic recording. Use of the relatively high carrier frequency of 440 MHz (compared with the more customary frequency of about 35 MHz) allows the use of smaller antennas and results in better resolution of the bedrock surface.

At lat. 7° S. the fern line was at about 3,500 m. during the Riss glaciation, at 3,650 m. during the Würm maximum and at 3,700 m. during a later stage (Würm II?). The moraines were deposited by equatorial-type glaciers from which there was relatively little melt water.

At lat. 14° S., during the Riss glaciation, an important ice cap covered a 3,900–4,000 m. high plateau, the firn line being at about 3,950 m. The role of melt waters was important in the formation of the moraines, suggesting their deposition from tropical-type glaciers. From the evidence of periglacial gravels it appears that this southern region has not been glaciated since Riss times.

The interaction of point detects in ice has been neglected for a long time. Experimental data obtained from dielectric measurements on HF-doped crystals stimulated a new evaluation of the possibility of an interaction between Bjerrum defects and ions. In a previous paper it has been shown that this leads us to assume the existence of aggregates of Bjerrum defects and ions. In this paper these aggregates and Bjerrum defects are used to explain the dielectric properties of ice, especially the temperature dependence of the product of the high and low frequency conductivity σ0σ∞.

The interaction of Bjerrum defects and impurity molecules leads to a dependence of the concentration of frenkel pairs on Bjerrum-defect concentration. At HF concentrations above the native Bjerrum-defect concentration the formation of a Frenkel pair is enhanced. This leads to the fast out-diffusion which has been studied in highly doped crystals by means of NMR techniques.

During two cruises in 1998 and 1999, we examined drift and ridging characteristics of sea ice in the Ross Sea, Antarctica. Mean ice thickness in the western Ross Sea in autumn was 0.5 m, while higher level-ice thicknesses, greater areal coverages of ridges and higher sails were found in the central and eastern Ross Sea in summer. Near the continent, ice drifted westward near the coast and turned eastward further north. We use a regional sea-ice−mixed-layer−pycnocline model to initiate backward trajectories at the time and location of field observations and examine the dynamic and thermodynamic processes that determine ice thickness along these trajectories. Model results agree with previously published field data to indicate that thermodynamic and dynamic thickening and snow-ice formation each contribute significantly to the ice mass of the summer ice field in the central and eastern Ross Sea. For first-year ice in the western Ross Sea, model results and field data both indicate that thermodynamic thickening is the dominant process that determines ice thickness, with dynamic thickening also contributing 20% to the net ice-thickening rate. However, model results fail to reproduce the prevalence of snow- ice formation that was seen in field data.

The cross-sectional profile of a glacial valley can be obtained with a variational principle in which the friction against the valley walls and the glacier bed is extremized, subject to a Lagrangian constraint. We show that the actual valley profile maximizes the friction, thus settling an old debate.

The orientations of individual crystals within a polycrystalline aggregate subjected to stress have a strong influence on its bulk strain rate and flow behavior. The ability to include the effect of crystal fabric and recrystallization processes in an ice flow law, especially at the bottom of glaciers and ice sheets where temperature is close to the pressure-melting point, is important because the stratigraphy of the ice body may be affected and the paleoclimate reconstruction hampered. We present herein three newly developed deformation apparatuses offering the possibility, from single experiments, of investigating different finite strain stages and their corresponding c-axis fabric and grain texture patterns in various confined, shear flow configurations (simple shear, pure shear and compression/extension bending). The technical set-ups and major advantages compared to classical methods are explained, and results from experiments are discussed in order to illustrate the functioning and purposes of the methods. In all experiments, significant variations in the microstructural development have been observed that reflect the varying orientations of the anisotropy and its relationship to the stress pattern. In monocrystalline ice-bending experiments, the pre-existing c-axis fabric is shown to have a profound influence on the response to stress and possibly to the type of slip system activated.

Stable isotope ratios and salinities of ice samples obtained from a submarine ice cliff at Explorers Cove demonstrate that the upper parts of the ice cliff have frozen directly from sea-water and are an underwater expression of permafrost, whereas the lower parts appear to be partially glacial in origin. These results indicate that there may be ice cores in the moraines of Explorers Cove, in which case the coastline of McMurdo Sound is more extensively ice-cored than previously known.

In November and December 1965 accumulation measurements were made at 3 km. intervals and at networks of poles at six photogrammetric arrays on an oversnow traverse from Mount Chapman to “Byrd” station. The results at the photogrammetric arrays, which yield a mean accumulation of 16.4 g. cm.−2 yr.−1 for 1963–65, are compared with values determined from stratigraphic investigations in 1958–59 and in 1962–63, which gave 12.2 g. cm.−2 yr.−1 and 13.2 g. cm.−2 yr.−1, respectively.

Forty years ago, Ahlmann considered the thermo-physical character of ice masses as a basis for differentiating glaciers into two broad geophysical groups: (1) polar and (2) temperate. About the same time, Lagally sub-divided glaciers into corresponding thermodynamic categories: (1) kalt and (2) warmen. By this it was understood that the temperature of a polar, or “cold”, glacier was perennially sub-freezing throughout, except for a shallow surface zone which might be warmed for a few centimeters each year by seasonal atmospheric variations. Conversely, in a temperate, or “warm”, glacier, the temperature below a recurring winter chill layer was consistently at the pressure melting point. As these terms are thermodynamic in connotation, glaciers of the polar type may exist at relatively low altitudes if their elevations are sufficiently great. Temperate glaciers may be found even above the Arctic Circle at elevations low enough that chilling conditions are not induced by the lapse rate.

In these distinctions, it is implied that regardless of geographical location a glacier’s mean internal temperature represents an identifiable characteristic which can be shown critically to affect the mass and liquid balance of ice masses and significantly to relate climatic influences to glacier regimes. The importance of these implications, and the fact that they are based on a gross, sometimes changing, and always difficult to measure, thermo-physical characteristic, makes some explicit terminology desirable.

To some extent Ahlmann addressed this problem by introducing a subordinate classification, sub-polar glaciers. In these, the penetration of seasonal warmth involved only a shallow surface layer at 0°C, but still to a depth substantially greater than the superficial warming experienced in summer on polar glaciers. Lagally also recognized an intermediate type which he called “transitional”, characterized by a relatively deep penetration of 0°C englacial conditions during the summer. These pioneering efforts reflect Ahlmann’s experience with glaciers in the high Arctic and Lagally’s with the Alpine glaciers of southern Europe. Although some confusion has resulted from alternate application of these different terms, both definitions can be useful. Further to refine the classification, a modified terminology is suggested by the writer. This involves introducing a fourth category, substituting the term sub-temperate for Lagally's “transitional” type on the basis that it is etymologically more consistent with the Ahlmann terminology which has remained most commonly in use. Thus, two distinct transitional categories are identified. These categories, sub-polar and sub-temperate, typify ice sheets during changes from fully polar to fully temperate englacial conditions—a situation pertaining during the waning and waxing stages of deglaciation and reglaciation,

A review of the literature reveals further problems. Flint and others have considered geophysically temperate glaciers as most typical of the inland glaciation which covered much of Europe, northern North America and Siberia during the expanded phases of the Pleistocene, whereas others including Ahlmann have suggested that the massive continental glaciers of the Pleistocene were geophysically polar. Thus, the latter advocates consider that present-day Antarctic and Greenland ice sheets represent conditions comparable to those which pertained in the Laurentide and Cordilleran ice sheets. New insights have developed, however, through deep drilling and englacial temperature measurements carried out in a number of different geographical locations in recent years. Such research has shown that each of the geophysical categories can pertain in a glacier system if there is sufficient range of latitude, area and elevation for the requisite climatological factors to pertain.

Because of the foregoing considerations, it is probable that polar, sub-polar, sub-temperate and temperate thermal conditions coexisted in different parts of continental glaciers during the Pleistocene maxima. At times of greatest extension, the ice sheet’s peripheries could have been thermo-physically polar and sub-polar, as on the margins of today’s Greenland icc sheet. But in their most regressive phases, the lower latitude margins were more than likely temperate, with only high interior sectors remaining “cold”. Such combined conditions characterize a fifth thermo-physical category, which in the geophysical sense may be termed polythermal. To some extent all glaciers are poly thermal, except in the final wasting temperate phase when they are fully isothermal.

To elucidate the characteristics of each of these five categories and to identify prototypes with suggested thermal parameters, selected held studies on existing glaciers are discussed and thermal measurements and characteristics illustrated. From the sampled data, arbitrary englacial temperature limits are suggested: for the main body of polar glaciers (—10 to — 70°C); for sub-polar glaciers (—2 to —10°C); for sub-temperate glaciers (-0.1 to —2°C); for temperate glaciers (in summer, 0°C throughout); and for polythermal glaciers (a range across at least two of the foregoing temperature zones). The significance of thermal anomalies, temperature sandwich structures, diagenetic ice zones, and measured shifts in thermodynamic characteristics over a number of years are considered as they aid in the interpretation of ice morphology, glacier regimes, and climatic change.

Type thermo-physical examples are briefly compared from the following areas: the Antarctic and Greenland ice sheets (polar and polythermal), the Nepal Himalaya, Svalbard (polar to sub-polar), Lapland (sub-polar), sub-Arctic Norway (sub-temperate), the Alps (polythermal to temperate), the Canadian Rockies (sub-temperate), the Juneau Icefield, Alaska (sub-temperate to temperate), the Alaskan-British Columbian coast (temperate), glacier systems on Mount Rainier, Washington State (polythermal), and icefields in the St Elias Mountains, Yukon Territory (temperate to polythermal).

The relationship of thermal anomalies is clarified and illustrated within (he defined framework of each category. It is noted how these are manifest by deformation irregularities, differing salinities, and varying heat capacities within the ice. Also discussed is the relationship of changes in thermo-physical characteristics to the sensitivity of ice flow, revealed by changes in entropy and negentropy of glacier systems and by observable shifts from parabolic to rectilinear to surging flow. Finally considered is the long-term implication of secular changes in climate and their influences on englacial thermal regimes which affect the hydrological capacity and fluvial discharge of glaciers as well as their terminal fluctuations. The strong interdependence of all these factors and the total systems analysis which they represent underscore the mandate for a rational thermo-physical classification of glaciers.

In metamorphic rocks a sharp distinction between planar structures (e g. in schiste) and layered structures (e.g. in banded gneisses) is generally made. This same distinction has not been maintained in descriptions of analogous structures in glacial ice. At least part of the problem lies with the use of the term foliation, which, unfortunately, has been applied to both types of structures. On historical and etymological grounds, as well as on the basis of widespread acceptance by petrologists and structural geologists, it is argued that foliation should apply to planar structures in both rocks and glacial ice.

The seasonal precipitation of Ruwenzori is examined and the height of the climatic snowline determined. Two distinct periods of surplus accumulation and two ablation seasons can be recognized and give rise to a somewhat complex stratification. Precipitation diminishes with altitude above about 10,000 feet (3,050 m.). The water equivalent of the annual accumulation on the highest peak is thought to lie between 25 and 30 inches (635–762 mm.). Twelve months’ synoptic charts have been analysed and an attempt is made to relate the seasonal variations of accumulation and ablation to the meteorological factors accompanying the oscillations of the Inter-Tropical Convergence Zone.

The displacement of the surface of an ice sheet and of markers set in its top layers can be measured geodetically, and also, it is expected, by radio-echo methods. The paper discusses how such measurements could be interpreted as showing long-term changes in the thickness of the ice sheet; in particular it discusses how one might design an experiment so as to avoid unwanted effects due to short-term changes in rate of accumulation. The analysis is similar to that of Federer and others (1970), but it corrects an error, so that when applied to their results for central Greenland it gives a different result for the lowering of the surface. Federer and others have already concluded that the average accumulation rates during the past 100 years have been below those needed to keep in balance with the velocity of the ice sheet as a whole. Using a particular model, it is found that this has resulted in the surface lowering at a mean rate of 0.050 m a−1 between 1871 and 1968, and a mean rate of 0.140 m a−1 between 1959 and 1968.

Holes drilled into thin areas of the Brunt Ice Shelf encounter a layer of liquid brine less than 1 m thick approximately at sea-level. Assuming the brine to be moving horizontally, analysis of its effects on thermal equilibrium gives an estimate of steady-state annual brine flow that is in good agreement with the value deduced from a percolation model. The effect of firn density on percolation rates is such that the slope of an active brine layer increases rapidly as ice thickness increases. However, the heat transport model predicts that brine layers are unlikely to be active in both very thick and very thin ice shelves.

Parameterizing the incoming longwave radiation L ↓ in terms of the fourth power of the absolute temperature at the reference height is used in glaciology for several purposes. In this paper, the validity of this kind of parameterization is investigated for the Greenland ice sheer, both by observations and by numerical simulation with a meso-scale model, It is found that such a parameterization severely underestimates the increase of L ↓ in response to large-scale warming in an area where surface melting is important. This is explained by the systematic influence that is exerted on the shape of the temperature profiles by surface melting.

The towing of unprotected icebergs from the Antarctic continent (66° S.) to latitude 38° S. has been simulated using an explicit hydrodynamic model and an extended two-dimensional melting model. It was found that nominal towing accelerations in excess of 2 × 10-5 m s-2 were required to deliver ice over this route in most circumstances, and minimum energy consumptions were obtained at accelerations around 10-4 m s-2. Unprotected icebergs could be delivered with about 50% yield to latitude 38° S., but the rate of deterioration in the warm waters indicates that protection would be required for longer journeys. The towing simulation was most sensitive to north-south current components, the total towing distance and the rate of iceberg deterioration. Efforts directed towards locating suitable icebergs in the region 50° S. to 60° S., and towards increasing knowledge of the changing current patterns in the Southern Ocean would be most valuable, as would a knowledge of the mechanisms and rates of deterioration of icebergs in warm seas.

Mountain glaciers have response times that govern retreat due to anthropogenic climate change. We use geometric attributes to estimate individual response times for 383 glaciers in the Cascade mountain range of Washington State, USA. Approximately 90% of estimated response times are between 10 and 60 years, with many large glaciers on the short end of this distribution. A simple model of glacier dynamics shows that this range of response times entails consequential differences in recent and ongoing glacier changes: glaciers with decadal response times have nearly kept pace with anthropogenic warming, but those with multi-decadal response times are far from equilibrium, and their additional committed retreat stands well beyond natural variability. These differences have implications for changes in glacier runoff. A simple calculation highlights that transient peaks in area-integrated melt, either at the onset of forcing or due to variations in forcing, depend on the glacier's response time and degree of disequilibrium. We conclude that differences in individual response times should be considered when assessing the state of a population of glaciers and modeling their future response. These differences in response can arise simply from a range of different glacier geometries, and the same basic principles can be expected in other regions as well.

The Pindari Glacier is situated in the heart of the Kumaon Hills in lat. 30° 17′ N. and long. 80° 0′ E. This glacier was visited by the authors in October 1959 when morphological and other observations were made. On the basis of these observations, it appears that during the last hundred years the rate of retreat of this glacier has been phenomenal, and it may be as much as 132 ft. (40.2 m.)/yr. There is also evidence that in the past the Pindari valley suffered at least two glacial advances.