bluuebunny/crossref_metadata_2025_split huggingface dataset:
Recent Progress in North American Avalanche Forecasting and Control
Authors: LaChapelle E. R. 
Published: September 2017

AbstractThe techniques of avalanche forecasting and control have found increasingly wide adoption in North America in the past decade. Numerous government and private agencies are now engaged in work to protect ski areas, highways, railroads and power lines. Practical control measures such as artillery fire have been developed to a high degree of effectiveness, but the construction of permanent defense structures other than snow sheds is still in its infancy. Experimental work on instrumentation, forecasting, defense structures and the use of explosives, artillery and jet aircraft is currently in progress.
Quaternary Glaciations in Southern Victoria Land, Antarctica
Authors: Bull C. , McKelvey B. C. , Webb P. N. 
Published: September 2017

AbstractIn the coastal mountain chain of southern Victoria Land approximately 4,000 km.2 of glacier-cut valleys and dividing ranges are almost completely ice-free, while the surrounding areas are fully glacierized.In the ice-free Wright Valley and Victoria Valley systems evidence of four glaciations is recognized. The earliest two glaciations were the most extensive; glaciers flowed eastwards from the ice plateau through the coastal ranges and cut broad valleys extending to McMurdo Sound and the Ross Sea. The moraines of these glaciations are thin and highly weathered. The third glaciation was less extensive, consisting of advances by smaller glaciers derived from the inland ice plateau, the Wilson Piedmont Glacier and névé fields in the dividing ranges. The surfaces of moraines of this glaciation are now partly covered by saline lakes, evaporite deposits and extensive areas of desert pavements strewn with ventifacts. The fourth and youngest glaciation comprised small advances by remnants of the plateau-fed valley glaciers. Thick boulder moraines of this glaciation overlie earlier deposits.During each glaciation the greatest volume of ice was derived from the inland ice plateau. The volume of ice entering the valleys was dependent on the difference in altitude between the plateau surface and subglacial rock thresholds at the valley heads. Decrease in the surface level of the inland ice plateau caused the rock thresholds to increasingly hinder the eastward flow of plateau ice until practically no ice could flow down into the valleys, thereby terminating the glaciation. Such a condition exists at the present time.
Origin of Debris-Covered Icebergs and Mode of Flow of Ice Into “Miller Lake”, Martin River Glacier, Alaska
Authors: Reid John R. , Callender Edward 
Published: September 2017

AbstractDuring the summer of 1963. a drift-veneered mass of ice suddenly emerged at the surface of “Miller Lake”, art ice-walled lake at the terminus of the Martin River Glacier, Alaska. Subsequent fathometer traverses, together with the fact that the ice was not at the pressure melting point, revealed that it had been derived from a hole approximately 40 m. below the surface of the lake. There are numerous large debris-covered icebergs in the lake and presumably at least some are formed in this manner. Others are derived through differential ablation of projections of the glacier into the lake. Only the small icebergs are formed through calving. The interpretation of the mechanism of release of ice from the bottom of the lake, and the observation and interpretation of a rising ice-cored island in the same lake suggest that the ice on the bottom is deforming plastically and that it is undergoing compressive flow. Much of the movement may be along shear planes actually found in icebergs derived from the bottom of the lake.
A Numerical Method of Inferring the Budget History of a Glacier from its Advance and Retreat
Authors: Nye J. F. 
Published: September 2017

AbstractThe paper considers how to calculate the budget history of a glacier from the historical record of its advance and retreat. The linearized differential equations developed in previous papers are used to compute a series of coefficients g(n). The g(n) operate directly on a record of annually spaced observations of the position of the glacier terminus, to give the time variation of net budget. The g(n) are calculated for South Cascade Glacier, Washington, U.S.A. and for Storglaciären, Kebnekaise, Sweden, and are applied to the terminus records of these two glaciers. The results indicate that the figures for the retreat during individual years are not sufficiently reliable to deduce annual net budget changes with confidence. But the coarser features of the terminus records give net budget figures that agree well with the 9 yr. or 10 yr. means of recent observations. The theory extends the generalized budget record of Storglaciären back by several decades. and shows an increase in net budget in the 1930’s that is not immediately apparent in the terminus record.
The Flow of a Glacier in a Channel of Rectangular, Elliptic or Parabolic Cross-Section
Authors: Nye J. F. 
Published: September 2017

AbstractNumerical solutions are found for the steady rectilinear flow of ice, obeying Glen’s non-linear flow law, down uniform cylindrical channels of rectangular, semi-elliptic and parabolic cross-section. The results are also directly applicable to the pumping of a non-Newtonian fluid down a pipe. There is assumed to be no slip of the ice on the channel surface. Certain results on the centre-line velocity in symmetrical channels may be derived purely from dimensional and symmetry principles. An analytical solution due to Dr. W. Chester is given for a semi-elliptic channel section which departs only slightly from a semi-circle. Contrary to a view sometimes held, the maximum shear stress at the ice surface in a parabolic channel and in some elliptical channels does not always occur at the edge. With the flow law, strain-rate proportional to (stress)3, the velocity averaged across the ice surface, which is easily measured with a line of stakes, is close to the average velocity over the whole section for a wide range of parabolic sections; the hydrological importance of this result is that the discharge may be inferred without the need to measure the velocity at depth. Arguments are given to show that the result still holds when there is slipping on the bed and when the power in the flow law differs somewhat from 3, Depending on the amount of bed slip and the shape of the channel section, the kinematic wave velocity for a range of parabolic channels is between 2.0 and 2.3 times the centre-line velocity of the ice, and between 2.0 and 3.5 times the mean surface velocity of the ice.
Experimental Study of Non-Basal Dislocations in Ice Crystals
Authors: Levi L. , de Achaval E. M. , Suraski E. 
Published: September 2017

AbstractStructures produced by chemical etching on the basal plane of ice crystals have been studied and are discussed in terms of non-basal glide features. Slip bands, revealed by parallel rows of etch pits, generally result from a rapidly applied stress. Etch channels were observed relatively rarely in these experiments; they can be interpreted as trails of dislocations moving slowly under the action of local stresses, sometimes to stresses produced during the etching process. Features of the channels indicate that the dislocations emerging on the basal plane are screw dislocations; their Burgers vector was considered by previous authors to be in the direction <1123>, gliding on {1122}and {101o} slip planes. This assumption is inconsistent with the changes of channel direction we observed, for which the {0111}and {2421}slip planes would have to be considered. As a simpler hypothesis the glide system 〈0001〉, {101o} and 〈0001〉, {1120}is proposed.
Snow Surface Elevation in the Filchner Ice Shelf Area, Antarctica
Authors: Behrendt John. C. 
Published: September 2017

AbstractAltimeter observations made on flights during the austral summer 1963–64 in the vicinity of the Filchner Ice Shelf have allowed the construction of a new topographic map of the snow surface in that area. The ice stream flowing into the ice shelf from the polar plateau is more clearly defined. A previously shown connection from Berkner Island to the grounded ice to the west-south-west appears not to exist. The mass flux from the drainage basin on the polar plateau can be accounted for by a reasonable ice-shelf flow rate. The area of the ice shelf shown on the map is 0.43×106 km.2.
Velocity Fluctuations of the Bersækerbræ, East Greenland
Authors: Friese-Greene T. W. , Pert G. J. 
Published: September 2017

AbstractThe results of measurements of surface flow and ablation on the glacier Bersækerbræ, in the Staunings Alper, East Greenland, are presented. A correlation is shown between the rate of flow and rate of ablation, as suggested by current theory.
New Light on the Mode of Uplift of the Fish and Fossiliferous Moraines of the Mcmurdo Ice Shelf, Antarctica
Authors: Gow A. J. , Weeks W. F. , Hendrickson G. , Rowland R. 
Published: September 2017

AbstractThe McMurdo Ice Shelf and associated faunal remains were examined in the vicinity of the easternmost Dailey Island. Stratigraphic, petrographic, and chemical composition studies of cores from two holes drilled through the ice shelf show that at these locations the shelf is composed only of fresh-water ice. Although cores from the deeper hole possessed typically glacial textures throughout, much of the ice from this part of the McMurdo Ice Shelf may have been formed from the freezing of a layer of fresh water found sandwiched between shelf bottom and the underlying sea-water. The existence of fresh water under the ice shelf can most probably be attributed to drainage of surface melt water during the ablation season. There was no evidence to indicate that this part of the McMurdo Ice Shelf is being nourished by the growth of sea ice onto its lower surface. The fish remains found on the ice surface were confined to a narrow zone along the tide crack and are believed to have been left in this vicinity by deep diving seals. The marine invertebrate remains on top of the ice are associated with morainal material and are believed to have been incorporated into the ice at the time of formation of the moraines.
Observations on the Quaternary Firn Line in Peru
Authors: Tricart J. 
Published: September 2017

AbstractAt 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.
A Theoretical Consideration of the Strength of Snow
Authors: Ballard G. E. H. , Feldt E. D. 
Published: September 2017

AbstractA consideration of possible expressions for the number and size of bonds intersected by a potential failure surface leads to the following expression for the strength of snow, σf, which is age-hardening at a constant porosity n:
where σi is the strength of ice, tf is the time at failure, α is a parameter specifically related to the mechanism of bonding, and ω is a temperature-dependent parameter. Allowing tf to become infinite provides the envelope of maximum strength for fully age-hardened snow at any porosity n.
Light Scattering and Particle Aggregation in Snow-Storms
Authors: Mellor Malcolm 
Published: September 2017

AbstractAttenuation of visible radiation by falling snow was studied by a method based on brightness contrast between topographic features and the adjacent sky. Extinction coefficient and visual range are related to bulk snow density, and are compared with data for Antarctic blizzards. Since attenuation depends more on the size and concentration of discrete particles than on the mass density of suspended snow, the process of particle aggregation and snow-flake formation during fall is considered by collision theory, and an expression describing aggregation effects is developed. This offers an explanation for the relative constancy of particle concentration observed at ground level during snowfalls of varying intensity. Since there is no strong justification for relating extinction coefficient to snow density, an empirical correlation between extinction coefficient and precipitation rate is given for practical use. It is shown that visual range estimated by eye in hilly terrain may be less than the true value, since sky brightness is locally reduced over broad hill-tops with low albedo.
The Adhesion of Ice Spheres in Electric Fields
Authors: Latham J. , Saunders C. P. R. 
Published: September 2017

AbstractThe force F required to separate two ice spheres was measured as a function of environmental temperature T, relative humidity H and the strength E of the external electric field in which the spheres were situated. It was found that over the entire attainable range of T and H, F increased rapidly with increasing E. The increased adhesion was not accompanied by an increase in the rate of growth of the ice bridge between the two spheres and is explicable in terms of Davis’s (1964) calculations of the purely electrostatic forces between two spheres situated in an electric field. The experiments indicate that the rate of growth of snowflakes in a cloud by means of ice crystal aggregation will be markedly enhanced if the cloud is highly electrified.
Pleistocene Periglacial Topography in Southern Africa
Authors: Sparrow G. W. A. 
Published: September 2017

AbstractStudies in the south-eastern part of the Drakensberg mountains and the Basutoland uplands, above the 6,000 ft. (1,830 m.) level, of Southern Africa have yielded evidence for a periglacial regime during the Pleistocene. The limited earlier work in Southern Africa suggested that the Pleistocene climate was too dry for glaciation to have occurred, but the existence of oversteepened slopes, solifluction slumps and cirques is indicative of a periglacial environment. There is some correlation between the respective altitudes and latitudes of these periglacial features.
Planar and Layered Structures in Glacial Ice
Authors: Ragan Donal M. 
Published: September 2017

AbstractIn 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.
Photogrammetry Applied to Avalanche Studies
Authors: van Wijk M. C. 
Published: September 2017

Stereophotogrammetric techniques were used for a study of snow avalanches. The contour lines of the avalanche slope were mapped from stereo-photographs taken before and after the occurrence of the avalanche. The outline of the avalanche front at certain time intervals and the contours of the snow cloud were also plotted. A relative accuracy for the different maps of 0.7 m. on the terrain was established.The volume of the snow cloud at four different stages of the avalanche was determined from the maps. These volumes were also computed independently from coordinate readings that were made in the stereo models. The standard errors of both methods of volume determination were estimated to be 450 m.3 and 290 m.3 respectively, representing errors of 5 per cent and 3 per cent of the average cloud volume.The photographs were taken with an accurately determined time interval. Therefore, the velocity of the avalanche front could be determined from the photogrammetric measurements.
The Midsummer Heat Balance of an Alaskan Maritime Glacier
Authors: Streten N. A. , Wendler G. 
Published: September 2017

AbstractThe heat balance of an Alaskan mountain glacier located close to the sea is calculated for a period of 16 d in midsummer—a period which is typical of the summer in this region in its high cloudiness and in its temperature and humidity conditions. The radiative and the combined sensible and latent heat components are found to contribute equally to the observed high rate of ice melting.
Microwave Emissivity and Accumulation Rate of Polar Firn
Authors: Jay Zwally H. 
Published: September 2017

AbstractRadiative transfer theory is formulated to permit a meaningful definition of emissivity for bulk emitting media such as snow. The emissivity in the Rayleigh-Jeans approximation is then the microwave brightness temperature TB divided by an effective physical temperature 〈T〉. The 〈T〉 is an average of the physical temperature, T(z), weighted by a radiative transfer function ƒ(z). Similarly, where e(z) is the local emittance. An approximate ƒ(z) is used to determine analytically the effects of various absorption coefficients, of scattering coefficients that vary with depth, and of the seasonal variation of T(z). It is shown that a mean emissivity, which is equal to the mean annual TB divided by the mean annual surface temperature Tm, is a useful quantity for comparing theory and observations. Snow-crystal size measurements, r(z), at seven locations in Greenland and Antarctica are used to determine the Mie/Rayleigh scattering coefficient γs(z) and to calculate the mean emissivities. The observed mean emissivities are determined by a which is the average of 12 monthly Nimbus-5 (1.55 cm) microwave observations, and the Tm measured at the same locations. The calculated emissivities are about one-half of the observed values. The assumption that each snow crystal is an independent and equally effective scatterer, and the use of an approximation to ƒ(z), tend to over-estimate the effect of scattering. Therefore, a parameter multiplying γs(z) is used. The emissivities calculated with a single value of this empirical parameter for all seven locations agree well with the observed emissivities, showing that the microwave emissivity variations of dry polar urn can be characterised as a function of the crystal sizes. One optical depth corresponds to a typical fini depth of 5 m, but significant radiation emanates from up to 30 m. Since r(z) depends on the snow accumulation rate A and Tm. the sensitivity of the emissivity to changes in Tm or A are estimated using this semi-empirical theory. The results show that a one degree change or uncertainty in Tm is approximately equivalent to a 10% change in A, and that such a change will affect the emissivity by 0.003 to 0.014 or the TB by about 0.6 K to 3 K, depending on the location.
Phase-Sensitive Radio-Echo Sounding at the Devon Island Ice Cap, Canada
Authors: Walford M.E.R. , Holdorf P.C. , Oakberg R.G. 
Published: September 2017

AbstractA radio-echo sounder has been built with which both the amplitude and phase of radio echoes can be measured. In experiments with this instrument at the Devon Island ice cap, in the Canadian Northern Territories, precise amplitude and phase measurements have been made upon radio echoes from the bed of the ice cap. If these measurements are repeated after a number of years, the results, considered in conjunction with snow accumulation and compaction data, will be interpretable as a long-term change in the thickness of the ice cap. Wave dislocations and bend points have been observed in radio echoes reflected from the bed, It is suggested that amplitude and phase measurements from a network of sites may be synthesized in order to explore the geometry of the reflecting surface on a fine scale.
Glaciological Problems Set by the Control of Dangerous Lakes in Cordillera Blanca, Peru. III. Study of Moraines and Mass Balances at Safuna
Authors: Lliboutry Louis , Arnao Benjamín Morales , Schneider Bernard 
Published: September 2017

AbstractWe explain how preliminary results concerning the internal constitution of the big push moraine at Safuna were obtained in 1967. Cross-sections which were obtained later through electrical and seismic exploration and arduous borings are given. Under the lake Safuna Alta there exists a layer of dead ice which is probably a remnant from an old glacier advance and over which the active glacier slides, but this dead ice does not extend into the push moraine. Since 1950 Safuna Alta has formed, the glacier tongue has lowered by 0.8 m per year on average, and the big push moraine has moved and settled.The annual balance on the glacier tongue was measured in 1968. It increases by 3.9 m of ice per 100 m in altitude. The discharge of ice near the lake and the annual balance further up-valley allow an estimate of the mean annual balance in the accumulation zone (between 4850 and 6020 m) at 2.30 m of water per year. Until now no annual precipitation higher than 1 m/year had been measured in Cordillera Blanca, but this Cordillera includes many meso-climates.Eight successive moraines are found at Safuna. They are tentatively correlated with the eight existing between Huaraz and Laguna Llaca. Clapperton's (1972) “group 4” was not formed during the 20th, but during the 17th century. His “group 3” is not from A.D. 1750-1800, but is rather 5 000 to 7 000 years old, according to the offset of Cordillera Blanca great fault.
Penetration Depth of Closely Spaced Water-free Crevasses
Authors: Weertman J. 
Published: September 2017

AbstractAn approximate, analytic solution is found for the profile of a water-free crevasse in a field of closely spaced crevasses. The depth of penetration of the crevasses into the glacier is found. If the fracture strength of ice is taken to be zero, the penetration depth is equal to the value found by Nye and is independent of the crevasse spacing. This conclusion is in disagreement with results reported recently by R.A. Smith. If the fracture strength of ice is taken to be finite, the penetration depth is reduced if the spacing between crevasses is reduced.The results of the analysis can be applied to other crack problems. In particular, it can be applied to thermal, secondary cracking that it is hoped occurs when cooling fluid flows through the cracks created by hydraulic fracture for the purpose of extracting geothermal heat from hot, dry rock masses.
A Method For Cutting And Preparing Thin-Sections Of Frozen Soil
Authors: Osterkamp T.E. 
Published: September 2017

AbstractA diamond wire saw was modified for cutting thin sections of frozen soil and suitable operating conditions were determined experimentally. It was found that a lubricated wire, 0.34 mm in diameter, operaied at cutting velocities of 100-300 mm s-1 and cutting forces 0.02-0.1 kg produced smooth cut surfaces un thin sections 0.4-0.5 mm in thickness. The; temperature and wire size were not critical operating parameters and the wire tensions recommended by the manufacturer were satisfactory. A method of mounting the thin sections is also described.
Wind Erosion By Snow
Authors: Dietrich R.V. 
Published: September 2017

AbstractCalcite (Mohs hardness 3), fluorite (hardness 4) and periclase (hardness 5 1/2) have been eroded by snow blown at moderate wind velocities, at temperatures between —10 and —25°C. Future interpretations involving ventifacts and apparently wind-blasted rock exposures must take this information into account.