bluuebunny/crossref_metadata_2025 huggingface dataset:
Radio Echo-Sounding of Svalbard Glaciers
Authors: Macheret Yu. Ya. , Zhuravlev A. B.
Published: September 2017

Peculiarities of radio echo-sounding of mountain glaciers and ice fields between nunataks from terrestrial vehicles and from helicopters are considered in this paper. The possibility of using comparatively high frequencies (of up to 865 MHz) for sounding such glaciers is demonstrated on the basis of experimental data. Results of airborne radio echo-sounding of Svalbard glaciers of various types, dimensions, and regime obtained with the help of the 620 MHz airborne equipment of high resolution are shown. Returns from the glacier bed have been obtained on the majority of glaciers under investigation. The firn regions of ice fields with temperate regimes flowing between nunataks are, mostly, an exception. Depression in the glacier bed with the ice thickness up to 540 m, as well as internal reflecting boundaries have been detected in some glaciers. Ice volumes of glaciers have been determined from the airborne radio echo-sounding data with the use of a parabolic approximation to the cross-section glacier profiles. Good correlational dependence between ice volume and surface area of glaciers has been established and is used to estimate the ice and water resources in Svalbard glaciers.
Estimate of Glacier Ablation under a Debris Layer from Surface Temperature and Meteorological Variables
Authors: Nakawo M. , Young G.J.
Published: September 2017

A simple model suggests that the ablation under a debris layer could be estimated from meteorological variables if the surface temperature data of the layer are available. This method was tested by analyzing the data obtained from experiments with artificial debris layers. Fairly good agreement was obtained between the estimated and the experimental data.
Effects Of Bed Inclination And Topography On Steady Isothermal Ice Sheets
Authors: Morland L. W. , Johnson I. R.
Published: September 2017

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.
Naled Ice in Front of Some Spitsbergen Glaciers
Authors: Baranowski Stanisław
Published: September 2017

Ice of naled type, in the form of sheets up to 4 m thick and covering areas of 0.5–2.5 km2, is a frequent feature in front of some of the large Spitsbergen glaciers. Observations from the marginal outwash plain of Werenskioldbreen and the extra–marginal outwash plain of Gåsbreen are presented. The morphological role of this type of ice, on which forms similar to glacial eskers and kames may develop, is indicated.

Glace de type “naled” devant quelques glaciers du Spitsbergen. De la glace de type “naled” (glace de regel de l’eau de fusion) en forme de feuilles allant jusqu’à 4 m d’épaisseur, couvrant des surlaces de 0,5 à 2,5 km2, se rencontre assez fréquemment à l’avant de quelques grands glaciers du Spitsbergen. Quelques observations provenant de la plaine de lavage marginale du Werenskioldbreen et de la plaine de lavage extra–marginale du Gåsbreen sont présentées. Le rôle morphologique de ce type de glace, dans lequel peuvent se développer des formes analogues à des “eskers” ou à des “kames” glaciaires, est mis en évidence.

Festeis vor einigen Gletschern Spitsbergens. Festeis in Schollen von bis zu 4 m Dicke und einer Ausdehnung von 0,5 bis 2,5 km2 ist eine häufige Erscheinung vor einigen grossen Gletschern Spitsbergens. Beobachtungen im Gebiet der randlichen Auswaschungsebene des Werenskioldbreen und der Auswaschungsebene ausserhalb des Randes des Gåsbreen werden wiedergegeben. Die morphologische Bedeutung dieser Eisart. auf der sich Formen ähnlich den glazialen Eskern und Kames entwickeln könnten, wird herausgestellt.
Comparison of Experimental and Computer Modeling of Snow-Block Impact on Structures
Authors: Mead Lorraine B. , Nakamura Hideomi , Lang Theodore E. , Dent Jimmie D.
Published: September 2017

Data from experimental tests of snow-block impact against vertical barriers are used to establish values of parameters in order to computer-model the impact mechanics. The results show that total impulse, impact force, and duration of impact can be modeled by accurate specification of the kinematic viscosity in the fluid representation. In modeling the highly transient impact, kinematic viscosity of the material is determined to vary linearly with the impact velocity. This non-physical condition is attributed to lack of accountability of compressibility effects in the computer model, and reduces modeling to an empirical approach. A biviscous modeling of the impact process is in near correspondence to linear viscous modeling, due to dominant importance of block momentum on impact rather than fluidity of material in the impact region.
Isotropic Points on Glaciers
Authors: Nye J. F.
Published: September 2017

Two isotropic points measured by Meier and others (1985) on Columbia Glacier, Alaska, are examined. The pattern classification of the upper one is on the borderline between monstar and lemon, and this is traced to the fact that the variation of strain-rate in the longitudinal direction is approximately equal to that in the transverse direction, contrary to the assumption made in Nye (1983). The conditions for the lower isotropic point to have the star pattern, as observed, are believed to be typical for a glacier that ends in an ice cliff, like this one, which calves icebergs. Where, as in this case, there is only a small transverse velocity, the isotropic points on a glacier must nearly coincide with stationary points for the speed, and these are almost always either maxima or saddles, alternating. The maxima correspond to lemon or monstar patterns, and the saddles to star patterns.
Ice Conditions of an Arctic Polynya: North Water in Winter
Authors: Steffen Konrad
Published: September 2017

The surface condition of the North Water was investigated during two winters (i.e. the three polynyas: Smith Sound polynya, Lady Ann Strait polynya, and Barrow Strait polynya). Since no detailed information was available on ice conditions and the extent of open water during winter, radiometric temperature measurements of the sea surface had to be taken along a flight line of 2650 km from an altitude of 300 m. From November to March 1978-79 and 1980-81, 14 remote-sensing flights were carried out. On the basis of the radiometric measurements, the following ice types were identified: ice-free, dark nilas, light nilas, grey ice, grey-white ice, and white ice. A comparison between the thermal and the visual ice classification (the latter being based on grey tones of the aerial images) showed a deviation of 3%. The analysis showed that in November, December, and January more than 50% of the Smith Sound polynya was covered by young ice, nilas, and ice-free, whereas in February and March white ice was dominant. Moreover, it was found that the two polynyas in Smith Sound and Lady Ann Strait were much smaller than previously believed. In Barrow Strait, a semi-permanent polynya was observed in the winter of 1980-81. The occurrence of polynyas in Barrow Strait seems to be connected with the location of the fast-ice edge. On the basis of the calculated ice-type distribution and heat-flux rates for different ice types, an energy loss of 178 W m-2 was found on the surface of the Smith Sound polynya due to open water and thin ice for the winter months November to March. Compared with other ice-covered sea surfaces in the Arctic, the heat release by the sea-water in the Smith Sound polynya is about 100 W m-2 larger.
Experiments on Freeze-Bonding Between Ice Blocks in Floating Ice rubble
Authors: Ettema R. , Schaefer J.A.
Published: September 2017

Series of experiments were conducted with the aim of determining the influences of the following factors on freeze-bonding between contacting ice blocks in floating ice rubble: pressure normal to the contact plane, period and area of contact, and salinity of the water in which freeze-bonding occurred. Freeze-bonding between ice blocks in air was also investigated. The experiments were conducted with water and air temperatures of about 0°C and normal pressures, between ice blocks, up to 4 kPa. This range of normal pressures may occur hydrostatically between ice blocks in layers of floating ice rubble up to about 10 m thick, or in 2-3 m thick layers which are in a passive Rankine state of pressure. The experiments show that stronger freeze-bonds develop between ice blocks in distilled water, tap water, and water from the Iowa River than develop between ice blocks contacting in air at 0°C. However, stronger freeze-bonds developed in air at 0°C than developed between ice blocks in 0°C saline (NaCl) solutions with salinities in excess of 12.5% by weight. The strength of freeze-bonding increased linearly with contact period for ice blocks in distilled, tap, and river waters, but did not increase with contact period for ice blocks contacting in saline solutions or in air. The results of the experiments are useful contributions to explanations of the shear-strength behavior of a layer of floating ice rubble. For example, thicker layers of ice rubble may show greater cohesive behavior, because normal pressures and thus freeze-bond strengths increase with layer thickness.
Accumulation distribution in terre adélie, antarctica: effect of meteorological parameters
Authors: Pettre P. , Pinglot J.F. , Pourchet M. , Reynaud L.
Published: September 2017

Along the 1040 km extending from Cape Prud’homme (lat. 66°41’S., long. 139°55’ E.), near Dumont d’Urville station, to Dome C (lat. 74°39’S., long. 124°10’E.), the variations in annual accumulation can be analysed by a division of the entire data set into three sub-sets depending on the types of measurements and the character of the spatial distribution. Along the first 33 km, from the coast to stake E40, annual measurements show considerable inter-annual variability, 52% of which can be explained by the spatio-temporal homogeneity of the balance distribution. However, we obtain a better result (64%) for the fluctuation homogeneity standardized using the standard deviation. This means that there is a strong space-time dis-tribution structure, characterized by an equal variation of the balance around the mean value specific to each location. This is so in spite of the existence of considerable surface roughness (sastrugi), the influence of which should be reduced by averaging values around each stake. From stake E40 to stake R60, a distance of 170 km, the almost periodic oscillations in the accumulation with a wavelength close to 40 km can be explained by the formation of a gravity-inertia wave, disturbing the geostrophic equilibrium, occurring at the break in slope 200 km from the coast. The very low values of accumulation for stakes D55 and D58S show that the oscillations were almost stationary during the study period (about 25 years). Finally, along the 840 km from stake R60 to Dome C we can observe a decrease in accumulation resulting from the decrease in mean temperature.
On the Special Rheological Properties of Ancient Microparticle-Laden Northern Hemisphere Ice as Derived from Bore-Hole and Core Measurements
Authors: Fisher D.A. , Koerner R.M.
Published: September 2017

In the Northern Hemisphere, ice layers which have high microparticle concentrations (in particular late Wisconsin) are “softer” than modern or Holocene ice. Such ice deforms more readily in bore-hole tilt and closure measurements. This enhancement in flow, which is shownnotto be related toc-axis concentration, has a maximum of three for late Wisconsin ice. The closure and tilt of a bore hole in the Agassiz Ice Cap, Ellesmere Island, drilled in 1977, has been followed every year since its drilling and the flow enhancement observed has been compared to the following quantities measured in the cores: concentration, δ(18O), crystal size,c-axis, Ca, Na, conductivity, and density. Flow enhancement of the ice age and bottom ice was found to be unrelated toc-axis concentration and density. Enhancement of flow is best related to microparticle (or Ca) concentration which in turn seems to be inversely related to crystal size. The latter relationship also seems to hold for the Devon Island Ice Cap and Greenland. In future, modellers of northern ice ages should use model ice that is three times softer than modern or Holocene ice.
Rate of Short-Term ablation of Exposed Ground Ice, Banks Island, Northwest Territories, Canada
Authors: Lewkowicz Antoni G.
Published: September 2017

Energy fluxes and resultant short-term ablation rates were measured at a ground-ice slump on south-west Banks Island. Net radiation, as a proportion of the ablation flux, is greatest on days with high incident solar radiation, whereas on overcast days, sensible- and latent-heat inputs may supply more than half the necessary energy. A multiple regression equation using net radiation and a turbulent-energy term as independent variables explains 79% of the variation in the measured ablation fluxes. Overall, at least 60% of the energy used for ablation at the slump is derived from net radiation.
Recent Fluctuations of Rakhiot Glacier, Nanga Parbat, Punjab Himalaya, Pakistan
Authors: Gardner James S.
Published: September 2017

A 1985 survey at Rakhiot Glacier, Nanga Parbat, Punjab Himalaya, indicates that the glacier terminus is advanced about 200 m from its 1954 position. Between 1930 and 1954, the dates of previous surveys, the glacier terminus had thinned and back-wasted 450 m. The recession prior to the 1960s, followed by advance into the 1970s and perhaps 1980s, parallels patterns of glacier fluctuation found in the adjacent western and central Karakorum.
A Field Test to Assess Snow-Slope Stability
Authors: Conway H. , Abrahamson J. , Young R.
Published: September 2017

A simple field test of snow-slope stability is proposed, which allows decisions about a number of factors recently described by Conway and Abrahamson (1984). These include spatial variation of snow strength along a slope, and progression of failure from a localized initial failure. Strength within the snow slab is considered as well as that at its base. A snow saw is required for the test and, because a number of tests can be made in a few minutes, much information on the state of the slope can be obtained in a practical time.
Short Notes: Note on the “Arikaree Stade” of the Rocky Mountains Neoglacial
Authors: Mahaney William
Published: September 2017

Neoglacial deposits in the Indian Peaks section of the Colorado Front Range have been dated lichenometrically by recourse to a growth-rate curve developed for Rhizocarpon geographicum and three glacial fluctuations of the Temple Lake (4500–2700 B.P. ), “Arikaree” (1900–1000 B.P.) and Gannett Peak (300–50 B.P.) have been recognized and identified by Benedict (1968). Recent soil investigations on neoglacial deposits suggest the need to define an alternative type “Arikaree” in the Indian Peaks.
Note On Correlation Coefficients Derived from Cumulative Distributions with Reference to Glaciological Studies
Authors: Andrews J.T. , Faiiey B.D. , Alford D.
Published: September 2017

In many areas of glaciology, cumulative degree days, either positive or negative, are regressed against another cumulative value, such as ablation or lake-ice growth. Very strong functional relationships are frequently found with high correlation coefficients. This note shows that, if pairs of random numbers are cumulated, the resulting correlation coefficients are extremely high with a Fisher transformed mean of r = 0.986 and standard error of ±0.001 (based on 50 individual computations of r which in turn were based on 20 cumulated pairs of random numbers between 0 and 99). These results indicate that caution must be exercised in the physical interpretation of data of this kind.
Corrective Terms in the Glaciological Balance
Authors: Lliboutry L.
Published: September 2017

Two corrective terms in the mass balance between two cross-sections are computed. The first results from the fact that balances are measured at moving stakes. The second correction arises since the discharges are calculated through summer cross-sections which are smaller than their mean values during the whole year.
Ice-Cored Moraines in South-Western Ellesmere Island, N.W.T., Canada
Authors: Souchez R. A.
Published: September 2017

The north-west margin of the main ice cap in south-western Ellesmere Island is fringed by ice-cored moraines. The formation of these moraines seems to be more complex than simple upwarping of the foliation bands at the margin of the ice cap. At one locality, where outer and inner zones can be distinguished on the basis of lithological composition, debris in the outer zone is composed of material from farther back under the ice cap than debris in the inner zone. In another locality, localized ridges cross each other independently of the trend of the main ridge.

The time required to obtain the quantity of debris forming the moraine at the ice surface is estimated to be between 65 and 300 years.
The Effect of Impurities on the Surface Structure of Evaporating Ice
Authors: Cross J.D.
Published: September 2017

Micrographs of the surface of evaporating polycrystalline ice containing impurities are presented. The micrographs show that impurities that enter the ice lattice substitutionally enhance the fine structure on the surface, but impurities rejected by the lattice suppress the fine structure. It is concluded that the observed fine structure is not an artifact of the machine but a real property of evaporating ice dependent upon the defects at the surface.
Short Notes: New Data on the Thermal Conductivity of Natural Snow
Authors: Weller Gunter E. , Schwkkdtfecjer Peter
Published: September 2017

The thermal conductivity and diffusivity of natural snow computed from Fourier-type analyses of annual snow temperature variations are shown to be strongly temperature dependent. The computed temperature coefficients of-0.007 and -0.012 deg-1 respectively, agree well with older laboratory experiments carried out on polycrystalline ice.
The Crystallization Pressure of Ice—A Simple Experiment
Authors: Connell D.C. , Tombs J.M.C.
Published: September 2017

Polycrystalline ice, growing from the melt, can exert a pressure against an extended obstacle, even though it is free to grow in other directions. Pressures of over 0.2 bar (20kN m-2) have been measured with simple apparatus. This phenomenon may be important in explaining the frost-shattering of rocks.
Deducing Thickness Changes Of An Ice Sheet From Radio-Echo And Other Measurements
Authors: Nye J. F. , Wills H. H.
Published: September 2017

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.
Quaternary Glaciations in the Andes of North-Central Chile
Authors: Caviedes Cesar N. , Paskoff Roland
Published: September 2017

The extension of the Quaternary glaciations has been studied in the semi-arid Andes of north-central Chile, where the glacial modelling is striking. In the Elqui valley (lat. 30°S.), two glacial advances were identified reaching down to 3 100 m (Laguna glaciation) and 2 500 m (Tapado glaciation). In the Aconcagua valley (lat. 33°S.), moraines from three major glacial advances were found, at 2 800 m (Portillo glaciation), 1 600 m (Guardia Vieja glaciation) and 1 300 m (Salto del Soldado glaciation).

The Quaternary glaciations were linked with a decrease of temperature, but more significantly with a marked increase of precipitation probably related to an equatorward shift of 5–6 degrees of the austral polar front. The results obtained in the semi-arid Chilean Andes are correlated with those recently reported from other sectors of the southern Andes.
Snow Pressure on Rigid Obstacles
Authors: McClung David
Published: September 2017

In this paper a continuum mechanical formulation of snow pressure is given. The snow
pressure against retaining structures on slopes is considered in two separate parts: (1) the
static component due to the regression of transverse expansion as discussed by Haefeli, and
(2) the dynamic component due to the interruption of the creep (internal deformation) and
glide (slip of the entire snow cover over the ground). Snow-pressure calculations made using
the non-linear viscous constitutive equations given by McClung (in press) are given for the
plane strain-rate problem of a rigid barrier on a snow-covered slope. These calculations are
compared with the previous formulation of snow pressure given by Haefeli for the expected
range of boundary conditions for the structure and for the snow-earth interface. The results
show that the original formulation by Haefeli gives a dynamic component of similar magnitude
to the present calculations. Substantial differences are apparent when the up-slope distances
for interruption of the creep and glide processes are compared.
Temperature-Gradient Induced Mass-Instability Theory of Glacier Surge
Authors: Shoemaker E. M.
Published: September 2017

A theory is proposed that glacier surges are the result of a time-independent but positionally-dependent temperature distribution in which the mean effective temperature increases down slope. The theory is modeled by a slab analogy in which plane motion on a plane slope consists of uniform shear in a sub-region called the reservoir region. Assuming the usual power function relationship between stress and strain-rate, a thickening of the glacier in excess of its constant-state condition tends to induce instability; i.e. as the reservoir region thickens the oscillation of the region (up and down the slope) becomes unstable. Assuming an accumulation rate which increases linearly with elevation, this oscillation is represented by a non-linear ordinary differential equation. Numerical results are considered and reasonable assumptions, where data does not exist, render surge cycle times in close agreement with observation. The theory does not require basal sliding but this can be included.
Glacier Sliding Down an Inclined Wavy Bed With Friction
Authors: Morland L. W.
Published: September 2017

The effects of frictional tangential traction combined with regelation on the basal sliding of a temperate glacier down an inclined wavy bed are examined. Two friction models are treated. First, a Coulomb law model having the assumptions that sliding occurs everywhere and that the tangential traction is proportional to the normal pressure. Secondly, a velocity power law in which the tangential traction is proportional to a power of the slip velocity. The ice motion is approximated by steady slow Newtonian flow and the bed undulation about a mean bed-line has a maximum slope ∊ ≪I. Flow solutions are constructed as perturbations (in powers off ∈) of the plane laminar flow corresponding to non-slip on the mean bed-line assuming that the ice remains everywhere in contact with the bed; that is, no cavitation takes place. If the normal traction is predicted to be tensile over part of the bed, implying that cavitation has occurred, then a new solution is needed in which the ice base over cavities is traction-free. Since the cavity sections and profile of the free ice base are then part of the overall solution, an intricate mixed boundary-value problem is set up for the flow and the present analysis is inadequate.

For a sinusoidal bed the perfect-slip (zero tangential traction) solution predicts compressive normal traction everywhere on the bed provided that the mean bed-line inclination α (to the horizontal) is less than a critical value αe which is of order ε. For greater values of α including a range of order ∊, the normal traction is tensile on some parts of the bed, and a solution with cavitation is needed. If the tensile sections are relatively small it is expected that the resulting cavitation will not change the overall solution significantly. However, the Coulomb friction solution has extensive zones of tensile traction for all values of α, so that extensive cavitation would occur. In contrast, the velocity-power friction solution has compressive traction everywhere on the bed for α ⩽αe=0(I) provided that the ice depth is not too large, and also for deep glaciers for α ⩽αe=O∊ Furthermore, the predicted basal sliding velocity varies much less with the length scale of the bed undulation than in the perfect-slip solution, and is smaller.
Seismic Signals Associated with Avalanches
Authors: Lawrence William ST. , Williams Thomas R.
Published: September 2017

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.
Thermal Stresses near the Surface of a Glacier
Authors: Sanderson T. J. O.
Published: September 2017

Stresses occur in the uppermost 10 m of a glacier as a result of temperature fluctuations at the surface. A model is set up of a typical year's surface temperature variation, and the progress of temperature waves through the glacier is calculated using Fourier theory of heat conduction. Short-period fluctuations are rapidly attenuated, and at 10 m depth the annual cycle is reduced to 5% of its surface amplitude. As the temperature of the ice varies it undergoes small volume changes; stresses are calculated on the assumption that any tendency of the ice to expand or contract laterally results in the creation of just enough stress to cause the ice to remain unstrained. It is found that in the top 2 or 3 m stresses of thermal origin are generally in excess of those due to gross deformation or overburden pressure. For the case of high-density ice Glen's flow law is used, and conditions are found to be favourable for the formation of surface rumples of wavelength about 10 m. For the case of firm or snow a Newtonian flow law is assumed, and it is found that under cold conditions fracture under tension can occur. Cracks of thermal origin may be responsible for the initial formation of crevasses, and they also provide an explanation for background noise encountered when seismic shooting at low temperatures. Calculations are made of the strain-rate field surrounding a crack and it is found that thermal effects can lead to appreciable Strain-rate anomalies for strain-rate measurements near cracks. The magnitude of the effect is easily sufficient to account for anomalous fluctuating strain-rates found by workers using wire strainmeters on the Barnes Ice Cap.
Early Discoverers XXXII: P. A. Tutkovskiy and the Glacial Theory of Loess Formation
Authors: Smalley I. J.
Published: September 2017

In 1899 P. A. Tutkovskiy published a theory of loess formation which depended on the presence of large continental glaciers. Unfortunately there was no glacial requirement in the theories of Berg and Richthofen and these have survived better than that of Tutkovskiy with the result that the close relationship between glacial action and loess formation is sometimes overlooked.
A Mechanical Test Procedure for Avalanche Snow
Authors: Mccabe S. L. , Smith F. W.
Published: September 2017

The design, construction, and testing of a portable constant strain-rate testing machine for determining the mechanical behavior of avalanche snow is described. The machine is intended for use in determining the stress strain time behavior of low-density natural snows in the field. A technique for making direct measurements of strain in the snow sample is described and stress-strain curves are presented for strain-rates ranging from 0.5 to 5.0 x 10-5 s-1. The densities of the snow samples tested range from 186 to 335 kg m-3 Ultimate-strength data and relaxation curves arc also presented.
Grain Coarsening of Water-Saturated Snow
Authors: Raymond Charles F. , Tusima Katsutosi
Published: September 2017

Experimental measurements were made of changes in grain-size distribution with time in snow saturated with solutions of various impurity contents. Qualitatively, the changes in grain-size distribution occur by shrinkage and eventual disappearance of the relatively small particles and growth of the relatively large particles by a solid mass-exchange process which conserves the total solid mass. The distribution of relative grain size is found to be essentially time independent except for transient effects lasting only several to several tens of hours after the time of initial saturation. Mean grain volume increases at a constant rate, which for solutions of impurity concentration less than about 0.01 mol 1–1 is (5 to 6) X 10–3 mm3 h–1. In pure solutions the smallest particles shrink at a characteristic rate of about 1 x 10–2 mm3 h–1. Once the steady relative-size distribution is established, the rate of volume change of typical grains varies linearly with grain volume from the characteristic negative rate for the smallest particles through zero for particles of mean volume to positive values for particles of larger volume. The basic features of the changes that take place are explained in terms of heat-flow controlled melting and freezing determined by temperature differences associated with the effect of particle surface curvature on melting temperature. The constant rate of increase of mean grain volume is a consequence of conservation of total ice volume. The expectation that particles of intermediate size would be neither shrinking or growing leads to the conclusion that the actual rate of increase in mean grain volume is about one-half the characteristic melting rate of the smallest particles, which fits the observations. The process of grain growth is slowed by impurities in a way which can be predicted from the melting-temperature depression caused by the impurity and its diffusion coefficient. The transport of heat between grain surfaces is largely through the liquid-filled gaps between them, but about 19% is conducted through the solid.
Cryoconite Holes on Sermikavsak, West Greenland
Authors: Gribbon P. W. F.
Published: September 2017

The depths and diameters of 158 cryoconite holes were measured at ten positions in the ablation zone of Sermikavsak, West Greenland. It was found that the depths increased on going up the glacier in agreement with other measurements made earlier on polar glaciers. There was no significant correlation of depth with diameter. The relative importance of the combined short- and long-wavelength radiation balances and the transfer of heat by convectional mixing in water-filled holes is discussed. The variations in depth are attributed to changes in the albedo and the bulk extinction coefficient of the surface ice layers on the glacier.
Equilibrium Profile of Ice Shelves
Authors: Sanderson T. J. O.
Published: September 2017

Using expressions for ice-shelf creep derived by Weertman (1957) and Thomas (1973[b]) a general method is developed for calculating equilibrium thickness profiles, velocities, and strain-rates for any ice shelf. This is done first for an unconfined glacier tongue and the result agrees well with data for Erebus Glacier tongue (Holdsworth, 1974). Anomalies occur within the first 3 km after the hinge zone and these are too great to be the result of local bottom freezing; they are probably due to disturbance of the velocity field. Secondly, profiles are calculated for bay ice shelves. Thickness gradients are largely independent of melt-rate or flow parameters but are inversely proportional to the width of the bay. Data from Antarctic ice shelves agree with this result both qualitatively and quantitatively. The theory is readily extended to ice shelves in diverging and converging bays. An ice shelf in a diverging bay can only remain intact if it is thick enough and slow enough to creep sufficiently rapidly in the transverse direction. If it cannot, it will develop major rifts or will come adrift from the bay walls. It is then likely to break up. The presence of ice rises or areas of grounding towards the seaward margin can radically alter the size of the ice shelf which can form. The theory could be used as a starting point to study non-equilibrium behaviour.
“Saw-Tooth” Moraines in Front of Bødalsbreen, Southern Norway
Authors: Matthews John A. , Cornish Roger , Shakesby Richard A.
Published: September 2017

A series of end moraines, with a remarkable saw-tooth pattern, is reported from the glacier foreland of Bødalsbreen, a northern outlet of the ice cap Jostedalsbreen. The three-dimensional morphology of the moraines is described and analysed. Historical records and lichenometric measurements indicate that they were deposited after the “Little Ice Age” glacier maximum of the mid-eighteenth century. It is inferred that the local topography of Bødalen was conducive to the formation of a heavily crevassed pecten at the snout of Bødalsbreen, which produced the end moraines by a push mechanism during minor glacier advances. The observations suggest that pushing may be an underestimated mechanism in moraine ridge formation generally.
Performance of V.H.F. Aerials Close to a Snow Surface
Authors: Doake C. S. M. , Gorman M.
Published: September 2017

Measurements of aerial admittance as a function of height above a snow surface show that when the surface temperature is below freezing, the aerial performance is insensitive to slight surface irregularities.
An Analysis Of Ice Profiles Obtained By Submarine Sonar In The Beaufort Sea
Authors: Wadhams P. , Horne R. J.
Published: September 2017

A profile of the ice cover in the southern Beaufort Sea was obtained by the submarine U.S.S. Gurnard in April 1976, using a narrow-beam upward-looking sonar. The 1 400 km profile consisted of three legs, of which the long south-north and east-west legs intersected near the Caribou camp of the AIDJEX experiment. A statistical analysis was carried out over contiguous 50 km sections to yield probability-density functions of the drafts of ice and of level ice, the distributions of keel spacings and drafts, and the frequencies and widths of leads. Two distinct types of ice cover were found in the profile. The first, nearest the coast in the south and west of the experimental area, consisted of heavily ridged ice with mean drafts of up to 5.1 m. The rest of the track (1 200 km) consisted of a homogeneous ice cover with a mean draft of 3.7 m. The percentage of thin ice varied greatly from section to section, with a range of 0.4 to 12.3% for ice of 0–1 m draft. Level ice, defined as ice with a local gradient of less than 1 in 40, made up 56% of the homogeneous cover, with a preferred draft of 2.7 to 2.9 m. Keel spacings obeyed a negative exponential distribution, with a deficit at small spacings due to a keel shadowing effect and a surfeit at very large spacings due to the contribution of polynyas. The draft distribution of keels was a negative exponential of form , with B and b as parameters. This differs from the distribution of Hibler and others (1972), probably because the narrow beam records a complex structure for every keel. The homogeneous cover had a lower keel frequency and mean draft than the ice nearest the coast. Maximum keel draft was 31.12 m. The average separation of leads was 212 m, with almost all leads being less than 50 m in width.
Applications of Satellite Thermal Infrared Images for Monitoring North Water during the Periods of Polar Darkness
Authors: Dey B.
Published: September 2017

The study reported here illustrates the unique value of NOAA thermal infrared (TIR) images for monitoring the North Water area in Smith Sound and northern Baffin Bay during the periods of polar darkness. Wintertime satellite images reveal that, during the months of December through February, open water and thin ice occur in a few leads and polynyas. However, in March, the areas of open water and thin ice decrease to a minimum with a consequent higher concentration of ice. Two ice dams, in northern Kennedy Channel and in northern Smith Sound, regulate the flow of ice into northern Baffin Bay and also determine the areal variations of open water and thin ice in Smith Sound.
Growth Rate and Salinity Profile of First-Year Sea Ice in the High Arctic
Authors: Nakawo M. , Sinha N. K
Published: September 2017

This paper describes the growth of sea ice and the salinity profiles observed in Eclipse Sound near Pond Inlet, Baffin Island, Canada, during the winter of 1977–78. A numerical method of calculation has been developed to incorporate the variations in snow conditions and physical properties of ice and snow during the growth season. It is shown that the growth rate can be predicted reasonably well. It is also shown that the vertical salinity profile in the ice towards the end of the season, provides a record of previous climatological conditions. A dependence has been shown between the predicted growth rate and the measured salinity.
A Numerical Study of Plane Ice-Sheet Flow
Authors: Hutter K. , Yakowitz S. , Szidarovszky F.
Published: September 2017

The plane steady flow of a grounded ice sheet is numerically analysed using the approximate model of Morland or Hutter. In this, the ice behaves as a non-linear viscous fluid with a strongly temperature-dependent rate factor, and ice sheets are assumed to be long and shallow. The climate is assumed to be prescribed via the accumulation/ablation distribution and the surface temperature, both of which are functions of position and unknown height. The rigid base exerts external forcings via the normal heat flow, the geothermal heat, and a given basal sliding condition connecting the tangential velocity, tangential traction, and normal traction. The functional relations are those of Morland (1984) or motivated by his work. We use equations in his notation.

The governing equations and boundary conditions in dimensionless form are briefly stated and dimensionless variables are related to their physical counterparts. The thermo-mechanical parabolic boundary-value problem, found to depend on physical scales, constitutive properties, and external forcing functions, has been numerically solved. For reasons of stability, the numerical integration must proceed from the ice divide towards the margin, which requires a special analysis of the ice divide. We present this analysis and then describe the versatility and limitations of the constructed computer code.

Results of extensive computations are shown. In particular, we prove that the Morland–Hutter model for ice sheets is only applicable when sliding is sufficiently large (satisfying inequality (30)). In the range of the validity of this inequality, it is then demonstrated that of all physical scaling parameters only a single π-product influences the geometry and the flow within the ice sheet. We analyse the role played by advection, diffusion, and dissipation in the temperature distribution, and discuss the significance of the rheological non-linearities. Variations of the external forcings, such as accumulation/ablation conditions, free surface temperature, and geothermal heat, demonstrate the sensitivity of the ice-sheet geometry to accumulation conditions and the robustness of the flow to variations in the thermal state. We end with a summary of results and a critical review of the model.
Some Observations on Subglacial Ground-Water flow
Authors: Smart C. C.
Published: September 2017

Conduit and regelation water are inferred to drain as ground water from up to 130 km2 of Columbia Icefield. Subglacial conduits appear to be generally occupied by free surface streams. Ground-water flow will allow exchange between the regelation film and conduits. Present-day discharge from beneath the accumulation zone carries little sediment, and past injections of sediment appear to correspond to ancient interglacials. Transport of sediment through cave passages may be analogous to transport through basal conduits.
A New Instrument for Determining Strength Profiles in Snow Cover
Authors: Dowd Timothy , Brown R. L.
Published: September 2017

The Digital Thermo-Resistograph is a portable microprocessor-based data-probe system for quick and accurate field collection of snow-cover strength. This was accomplished by constructing a probe with a load cell, a small snow platform for probe-position information, and a Z-80 microprocessor-based data acquisition system. A 64 × 240 dot matrix LCD graphic display unit is used to show immediately complete strength profiles in the field. Sufficient memory for the storage of 25 profiles is provided. Temperature and temperature-gradient collection is also planned as a part of the instrument but as yet this work has not been completed.

The results of winter 1984 field tests are presented. The Digital Thermo-Resistograph proved to be fast and reliable in collecting snow-strength information. Comparisons with the ram penetrometer are shown and suggestions for future developments are discussed.
Solar-heating rates and temperature profiles in Antarctic snow and ice
Authors: Brandt Richard E. , Warren Stephen G.
Published: September 2017

Observations of temperature maxima at about 10 cm depth in cold Antarctic snow during summer have previously been explained by proposing that solar heating is distributed with depth whereas thermal infrared cooling is localized at the surface (the “solid-state greenhouse”). An increase in temperature from the surface to 10 cm depth (ΔΤ ≈ 4 K) found by Rusin (1961) on the Antarctic Plateau was successfully reproduced by Schlatter (1972) in a combined radiative-transfer and heat-transfer model. However, when we improve the model’s spectral resolution, solving for solar radiative fluxes separately in 118 wavelength bands instead of just one “average” wavelength, ΔΤ shrinks to 0.2 Κ and moves toward the surface, indicating that the solid-state greenhouse is largely an artifact of inadequate spectral resolution. The agreement between Schlatter’s broad-band model and Rusin’s measurement suggests that the measurement is inaccurate, perhaps due to solar heating of the buried thermistors. Similar broad-band models which have been applied to the icy surface of Jupiter’s satellite Europa are also shown to overestimate the solid-state greenhouse by a factor of about 6.

The reason that the solid-state greenhouse effect is insignificant in the case of Antarctic snow is that the wavelengths which do penetrate deeply into snow (visible light) are essentially not absorbed and are scattered back to the surface, whereas the wavelengths that are absorbed by snow (near-infrared) are absorbed in the top few millimeters.

The conditions needed to obtain a significant solid-state greenhouse are examined. The phenomenon becomes important if the scattering coefficient is small (as in blue ice) or if the thermal conductivity is low (as in low-density snow, such as near-surface depth hoar).
Particulate matter in pack ice of the Beaufort Gyre
Authors: Reimnitz Erk , Barnes P.W. , Weber W. S.
Published: September 2017

Ice observations and sediment samples were collected in the Beaufort Gyre in 1988. Fine sediment occurred in very small patches of turbid ice, as thin spotty surface layers, in mud pellets or in old snowdrifts. The latter were widespread south of 74°N, containing an estimated 22 tonnes of silt and clay km−2. Average particle concentration in sea ice (40mg l−1) was much higher than in sea water (0.8 mg l−1) or in new snow, but the sediment load was significantly smaller and of finer texture compared to that observed in a shelfal source area after a major entrainment event. About 30% of the sediment consisted of small pellets. Mud in pellets has similar texture, clay minerals and organic/inorganic carbon content as dispersed mud. Particle sizes <16μm dominate, sand is less than 1%, compared to as much as 8% in four samples obtained in 1971 and 1972. Organic carbon content is about 2%, illite dominates clay minerals (~50%), and diatoms suggest a shelf sediment source. From the prevalence of wind-reworked surficial deposits, the spotty occurrence of only small patches of turbid ice in old clean ice, and the virtual lack of sand-size material, we assume the sediment had drifted at least 2 years since entrainment and was distant from its source. Assuming one-third of the load is released each year, the estimated deposition rate would equal the measured Holocene rate (~2cm 1000year−1). Therefore, modern sea-ice rafting represents a substantial fraction of the total Arctic Ocean sediment budget.
Two-dimensional similarity solutions for finite-mass granular avalanches with coulomb- and viscous-type frictional resistance
Authors: Hutter Kolumban , Greve Ralf
Published: September 2017

This paper is concerned with the motion of an unconfined finite mass of granular material down an inclined plane when released from a rest position in the shape of a circular or elliptical paraboloid. The granular mass is treated as a frictional Coulomb-like continuum with a constant angle of internal friction. The basal friction force is assumed to be composed of a Coulomb-type component with a bed-friction angle that is position-dependent and a viscous Voellmy-type resistive stress that is proportional to the velocity squared. The model equations are those of Hutter and others (in press b) and form a spatially two-dimensional set for the evolution of the avalanche height and the depth averaged in-plane velocity components; they hold for a motion of a granular mass along a plane surface.

Similarity solutions, i.e. solutions which preserve the shape and the structure of the velocity field, are constructed by decomposing the motion into that of the centre of mass and the deformation relative to it. This decomposition is possible provided the effect of the Voellmy drag on the deformation is ignored. With it, the depth and velocities relative to those of the centre of mass of the moving pile can be determined analytically. It is shown that the pile has a parabolic cap shape and contour lines are elliptical. The semi-axes and the position and velocity of the centre of mass are calculated numerically. We explicitly show that

(i)

For two-dimensional spreading, a rigid-body motion does not exist, no matter what be the values of the bed-friction angle and the coefficient of viscous drag.

(ii)

A steady final velocity of the centre of the mass cannot be assumed, but the motion of the centre of mass depends strongly on the value of the Voellmy coefficient.

(iii)

The geometry of the moving pile depends on the variation of the bed-friction angle with position, as well as on the value of the coefficient of viscous drag.