bluuebunny/crossref_metadata_2025_split huggingface dataset:
Observations of Ground Avalanches with a Video Tape Recorder (VTR)
Authors: Akitaya Eizi 
Published: September 2017

AbstractA description is given and an analysis is made of successful VTR recordings of the process of natural release of eight full-depth avalanches. The observations were made over 7 years on a slope, where avalanches took place. The VTR was capable of taking a visual daytime record of an avalanche in motion for a 12 h sequence per reel.
Swiss Avalanche Hazard Maps
Authors: Frutiger H. 
Published: September 2017

AbstractThis paper describes the various maps concerned with avalanche hazards in Switzerland and gives examples of parts of specimen maps. These include the Wald- und Lawinenkarte der Schweiz (1907) at 1 : 250 000 which marks actual avalanche paths, the Karte der lawinengefährdeten Gebiete (1972) at 1 : 30 0000 which gives a summary view of avalanche hazard, the Gefahrenkarte der Schweiz (1975) at 1 : 100 000 which is intended to give an over-all view of all natural hazards that will influence land use, the Lawinenatlas/Lawinenkarte Uri (1978) at 1 : 25 000 which contains all identifiable avalanche paths in the Canton, the Kombinierte geomorphologische Gefahrenkarte 1: 10 000 von Grindelwald (1977), a Pilot study of mapping natural hazards in a mountain area, and the Lawinengefahrenkarten des Eidg. Institutes für Schnee- und Lawinenforschung at 1 : 10 000 included in 26 advisory reports on 561 individual avalanche paths, and which can act as pilot studies to assist cantons in preparing their own maps.This paper is being published in full in German in Interpraevent 1980, Bd. 3, as part of the proceedings of the symposium held at Bad Ischl, Austria, 8-12 September 1980.
Gear-Type Glide-Meter as an Instrument For Forecasting Full-Depth Avalanches
Authors: Yamada Yutaka 
Published: September 2017

AbstractThis paper is concerned with the variation of snow glide and its predictability in full-depth avalanches. From field measurements of snow glide using a newly developed gear-type glide-meter which is fixed to the ground and which measures the amount of glide as the angle of rotation of a gear, the following characteristics are deduced: (1) the variation of gliding rate is composed of both short-term and long-term variations, and (2) the existence of correlation between the short-term variation and the relative frequency of avalanches is recognized.
Recent variations of Ghiacciaio del Calderone, Abruzzi, Italy
Authors: Gellatly A. F. , Smiraglia C. , Grove J.M. , Latham R. 
Published: September 2017

AbstractResults of a detailed topographic survey of Ghiacciaio del Calderone, Italy, the southernmost in Europe, are described and compared with those of surveys made in earlier years. Recession and thinning, much affected by micro-climate, have been the predominant state of health during the 20th century. Between 1916 and 1990, volume is estimated to have been reduced by about 90% and area by about 68%.
Shear-wave detection of asymmetric c-axis fabrics in the GISP2 ice core, Greenland
Authors: Anandakrishnan S. , Fltzpatrick J.J. , Alley R.B. , Gow A.J. , Meese D.A. 
Published: September 2017

Abstractc-axis fabrics of the GISP2 ice core from central Greenland have been measured rapidly and accurately in the field, using both compressional and shear waves generated by an inexpensive, commercially available, “idiot-proof” device. Compressional-wave data were collected at 10 m intervals for the upper 2250 m of the ice sheet and show progressive clustering of c axes toward the vertical with increasing depth but no large steps at climatic boundaries in the core. The degree of clustering measured by ultrasound agrees closely with that measured using traditional optical techniques but the ultrasound technique is easier and faster than optical methods. A slight asymmetry in the c-axis clustering is revealed by the shear-wave data and increases with increasing depth, indicating that deformation is not symmetric about the vertical at the site.
In-situ measurement of the strength of deforming subglacial till
Authors: Iverson Neal R. , Jansson Peter , Hooke Roger Leb. 
Published: September 2017

AbstractThe shear strength of deforming till beneath Storglaciären, Sweden, was continuously measured with a new instrument, a “dragometer”. A cylinder with conical ends, roughened with till from the glacier bed, was dragged through the till, and the force on the cylinder was recorded. Consistent with studies of cone penetration in soils, it was assumed that the till behaves as a Coulomb plastic material. This allows the residual strength of the till to be calculated from the measured force. Results from laboratory experiments confirm the validity of the analytical procedure.The average residual strength of the till was ∼55 kPa. A source of error is the potential generation of pore pressure in excess of hydrostatic ahead of the cylinder, which could significantly weaken the till. Calculations indicate that excess pore pressure did not develop during the experiment, but could develop during similar experiments beneath rapidly sliding glaciers with less permeable basal till layers.
Ductile saline ice
Authors: Kuehn G. A. , Schulson E. M. 
Published: September 2017

AbstractExperiments have shown that tensile ductility of about 5% or more can be imparted to columnar, saline ice by pre-compressing the material by about 3.5%. This effect is similar to that observed in granular, fresh-water ice and is attributed to the operation of both dislocation creep and diffusion creep within that part of the matrix which recrystallized during the pre-compressive deformation.
Instruments and Methods: Direct measurement of sliding at the glacier bed
Authors: Blake W. , Fischer Urs H. , Bentley C.R. , Clarke Garry K. G. 
Published: September 2017

AbstractSliding at the base of Trapridge Glacier, Yukon Territory, Canada, was measured using a “drag spool”. We describe this simple and inexpensive instrument as well as its installation and operation. From 1990 to 1992 seven sites were instrumented with drag spools. At six of the sites basal sliding, during the period of observation, accounted for 50-70% of the total flow observed at the glacier surface. The contribution from ice creep is known to be small, so most of the remaining surface motion must be attributed to subglacial sediment deformation. For the seventh site the observed sliding rate was ~ 90% of the total flow, an indication that the sliding contribution varies spatially across the bed. Diurnal variations in the response of one of our instruments appear to be correlated to subglacial water-pressure fluctuations and are interpreted in terms of changes in sliding velocity rather than the opening and closing of basal cavities.
The Effect of Crystal Size and Dispersed-Solid Inclusions on the Activation Energy for Creep of Ice
Authors: Baker Robert W. , Gerberich William W. 
Published: September 2017

AbstractSteady-state creep-rates of polycrystalline ice were investigated as a function of temperature, grain-size, and inclusion concentration through uniaxial compression in the laboratory. Samples were run at a constant load with the temperature systematically varied between about —5°C and —40°C. The presence of inclusions inhibits dynamic recrystallization and grain growth; the average crystal size produced by recrystallization is inversely proportional to the inclusion concentration. At temperatures above —8°C, creep-rate is enhanced by about a factor of two. This appears to be the result of the combined effects of recrystallization with accompanying grain growth and grain-boundary sliding. Over the temperature range —10°C to —40°C, the apparent activation energy for creep increases with increasing volume fraction of inclusions. This is apparently due to a thermally activated process which is modified by internal stresses created by the inclusions.
Formation, Flow, and Disintegration Of Ice Shelves
Authors: Robin G. De Q. 
Published: September 2017

AbstractIce shelves may develop either by continued thickening of sea ice that is held fast to the shore, or by the seaward extension of inland ice. For both processes, as well as for an understanding of ablation and of accumulation at the bottom surface of ice shelves, we need to understand melting and freezing processes in relation to salinity, temperature, and pressure. Consideration of these factors shows that basal melting beneath the thicker parts of ice shelves is much greater than is generally appreciated. This could be sufficient to bring the estimated mass balance of Antarctica into approximate equilibrium. It appears that most Antarctic ice shelves are dependent on the supply of inland ice for their continued existence. However the thick layer of sea ice beneath the Amery Ice Shelf is readily explained in terms of sub-ice water circulation.Transport of heat and mass by water motion beneath ice shelves has the potential to change ice thicknesses by similar amounts to that caused by internal deformation of the ice shelf. Bottom freezing due to thermal conduction throughout the ice shelf is of minor importance.While attention is drawn to the basic equations for flow of ice shelves, it is pointed out that they have yet to be applied satisfactorily to the problem of iceberg calving. This appears from field observations to be due primarily to creep failure of spreading ice shelves, possibly aided by impact from floating icebergs. Recent observations show the effectiveness and likely quantitative importance of this “big bang” theory of iceberg formation in Antarctica.A brief discussion of the effects of climatic change on the disintegration of ice shelves is presented.
Lateral Density Differences from Seismic Measurements at a Site on the Ross Ice Shelf, Antarctica
Authors: Kirchner Joseph F. , Bentley Charles R. , Robertson James D. 
Published: September 2017

AbstractSeismic compressional-wave data from short refraction shooting carried out during the 1974–75 and 1976–77 seasons at J-9, the site of the Ross Ice Shelf Drilling Project, have been compared. Significant dissimilarities were found to exist between the two sets of data. The measurements were made at locations about 2 km apart, with three unreversed profiles 60° apart recorded during the 1976–77 season and one unreversed profile during the 1974–75 season. The resulting velocity–depth profiles, and hence the derived density–depth profiles, differ by as much as 8%, with the 1976–77 results indicating a maximum velocity, corresponding to solid ice, at a shallower depth than the 1974–75 data. Both profiles were subjected to the same analysis, and a comparison of travel-time curves shows the differences to be real. Densities measured on cores from a 100 m bore hole drilled in 1974–75 about 50 m from the center of the 1974–75 profile agree well with densities computed from that profile. The density difference is believed to be due to the passage of the ice through the high-stress system associated with the interaction between Ice Stream B, flowing in from the West Antarctic ice sheet, and the Ross Ice Shelf. A reversed refraction profile carried out at station B.C. about 30 km up-stream, shows evidence of dipping layers that may be similarly caused.
Seismic Short-Refraction Studies on the Ross Ice Shelf, Antarctica
Authors: Kirchner Joseph F. , Bentley Charles R. 
Published: September 2017

AbstractSeismic short-refraction studies were carried out at five stations on the Ross Ice Shelf during the 1976–77 summer season as part of the comprehensive Ross Ice Shelf Geophysical and Glaciological Survey. Measurements of the velocities of compressional waves were made at each location. Compressional wave velocities were measured along more than one azimuth at three sites, and shear wave velocities (both components) at two. Travel-time curves were fitted to an exponential expression by means of a non-linear least-squares regression technique. The errors in the apparent velocities are estimated to be about ±50 m s–1 at short distances, diminishing to about ±10 m s–1 near the ends of the profiles. Compressional-wave velocities show only slight variations with azimuth and only over certain depth intervals, showing that constant-velocity surfaces are essentially horizontal. Shear-wave velocities, however, exhibit large variations according to azimuth and polarization, indicating that transverse isotropy is violated at least in the upper 30–40 m of the ice shelf. It is believed that the anisotropy is caused by structural details in the firn perhaps modified by preferred crystal orientation and that it may arise at least partly from anisotropic stresses in the ice shelf.
Mass-Balance Aspects of Weddell Sea Pack Ice
Authors: Ackley S. F. 
Published: September 2017

AbstractThe Weddell Sea pack ice undergoes several unique advance–retreat characteristics related to the clockwise transport in the Weddell Gyre, the physical setting for the pack ice, and the free boundary with the oceans to the north. From satellite-derived ice charts, the annual cycle of the pack ice advance and retreat is depicted. The Weddell pack advance is characterized by a strong east-moving component as well as the north advance seen in other regions such as East Antarctica.Physical characteristics of the pack ice at the summer minimum ice edge are presented. Indications are that deformation is a significant component of the ice accumulation, deformed ice accounting for c. 15 to 20% of the area covered in the year-round pack. Ablation characteristics are inferred from observations made during field work and from satellite imagery. These observations indicate that surface-melt ablation typically seen on Arctic pack is not seen on the Weddell pack inside the summer edge.Using the physical-property data and transport inferred from ship and iceberg drifts, a new annual ice accumulation η < 3 m is inferred over the continental shelf in the South compared to η < 2 m previously estimated (Gill, 1973). The implication is that salt flux into the ocean over the shelf may be significantly larger, thereby increasing the production of Western Shelf Water, a component of Antarctic Bottom Water.
A Simple Model to Calculate the Compactness of Ice Floes
Authors: Neralla V. R. , Liu W. S. 
Published: September 2017

AbstractThis paper describes a simple model for predicting compactness over a given area. The model incorporates equations of continuity and momentum. The momentum equation is based on a balance between air-ice stress, water–ice stress, Coriolis force, and internal ice resistance. Since our interest is in short-range small-scale prediction, as a first step we have neglected sources and sinks terms in the continuity equation and assumed ice to be a film of Newtonian highly-viscous fluid. The solution of a simple equilibrium formulation is used as initial conditions.Surface winds over the area of interest are obtained from an available model developed on the basis of similarity theory. The compactness model has been applied for a few real cases in summer 1975 over the Beaufort Sea area. The preliminary results of the model are encouraging. The main advantage of this model is that it can run on mini-computers available at most forecasting centres.
Stability of Glaciers and Ice Sheets Against Flow Perturbations
Authors: Thompson David E. 
Published: September 2017

AbstractA stability equation is derived for a model glacier of initially uniform thickness and of infinite extent transverse to the primary flow flowing without slip down an inclined plane. A stress-dependent power-law viscosity is wholly incorporated into the equations of motion. Stability of the glacier is tested against long-wavelength surface perturbations. Results for this initial formulation indicate that the glacier is stable against infinitesimal amplitude surface perturbations, although for certain variations of model parameters, the decay-rate of the disturbance becomes very slow, approaching neutral stability. Results are presented in terms of decay-rate magnitudes over a large range of perturbation wavelengths for many model glaciers in which bed slope, ice thickness, and ice rheology parameters are varied. For all models, the maximum decay-rate of the perturbation occurs at disturbance wavelengths of roughly three to six times the glacier thickness. Infinite-wavelength perturbations are found to be only neutrally stable. Long-wavelength perturbations propagate at a faster rate down-glacier than do the intermediate- or shorter-wavelength ones which tend to remain fixed on the glacier surface andride down-glacier with the primary flow as they decay.
Ice-Sheet flow in the Vicinity of Southern Victoria Land, Antarctica: Implications for Glacial Chronology
Authors: Drewry David J. 
Published: September 2017

AbstractSystematic radio echo-sounding during three seasons since 1971–72 has produced data on the configuration of the ice sheet in East Antarctica. In the sector extending inland from southern Victoria Land, the ice sheet exhibits a large ridge which drives ice towards David Glacier in the north and Mulock and Byrd Glaciers to the south. Within 100 km of the McMurdo dry-valley region soundings along ten sub-parallel lines (c. 10 km apart) provides detail on ice surface and flow patterns at the ridge tip. A small surface dome lies just inland of Taylor Glacier. The surface drops by 100 m or more before rising to join the major ridge in East Antarctica.
Ice-Sheet Surface Elevation and Changes Observable by Satellite Radar Altimetry
Authors: Zwally H. Jay , Brooks R. L. , Stanley H. Ray , Campbell W. J. 
Published: September 2017

AbstractA major question in ice-sheet dynamics is the state of balance between the net mass input and ice flow. Since an imbalance produces a change in surface elevation, the state of balance can be studied by monitoring the elevation, and this has been accomplished by surface-leveling techniques in a few locations. Due to the requirement for accurate and repetitive measurements over large areas, it is not practical to determine the status of balance of an entire ice sheet or even a major drainage basin by conventional techniques. Now, recent results from satellite-borne radar altimeter measurements over the Greenland ice sheet demonstrate the feasibility of accurately measuring and monitoring the topography of large ice masses. The application of this new technique offers the possibility of making a meaningful mass-balance determination and for detecting actual or potential ice-sheet surges.
Predicting the Motions of Drifting Open Pack Ice
Authors: Feldman Uri , Howarth Philip J. 
Published: September 2017

AbstractMethods based on remotely-sensed data are needed to predict motions of drifting open pack ice and to determine sea-ice parameters associated with these motions. The method presented here is able:
(a)to predict the motions of groups of wind-driven detached ice floes over periods of 12, 36, and 60 h;(b)to determine sea-ice thickness and the surface and sub-surface drag coefficients associated with these motions.
Longitudinal Stress Gradients and Basal Shear Stress of a Temperate Valley Glacier
Authors: Bindschadler Robert 
Published: September 2017

AbstractFor the first time field data from a temperate valley glacier, the Variegated Glacier, are used to investigate the behavior of longitudinal stress gradients predicted by the relation
1
where
H is the local depth, and ys and yb are the surface and bed elevations respectively. This equation is similar to one derived by Budd (1970) for plane strain-rate, to evaluate the importance of longitudinal stress gradients, but a shape factor f is included to account approximately for lateral strain-rate gradients. Predictive numerical models of valley glaciers require the local base shear stress to be known as accurately as possible. It has been argued on theoretical grounds that when T is averaged over distances of more than five to ten times the depth, this term is negligible. At larger averaging scales, 2G can then be considered a correction to the simple geometric expression of base stress due to the presence of longitudinal stress gradients. Field data of velocity and geometry are used to evaluate the terms of Equation (1), where τb and 2G are estimated as

and

at intervals of 100 m, Us is the measured surface center-line velocity, A and n are the flow-law parameters, and is the surface longitudinal strain-rate. The expression for 2G is an approximation proposed by Budd (1970).
The Mass Budget of the Lambert Glacier Drainage Basin, Antarctica
Authors: Allison Ian 
Published: September 2017

AbstractEstimates have been made of the mass budget of the total drainage basin of Lambert Glacier. These show a small but significant positive state of balance for the interior basin (the accumulation area up-stream of the major ice streams) and strongly suggest a positive balance for the Lambert Glacier system (the region of major ice streams, between the Amery Ice Shelf and the interior basin). The total mass flux into the interior basin is estimated as 60 Gt a–1. Results are presented from a number of ice movement stations established between 1972 and 1974 around the perimeter of thesouthern Prince Charles Mountains. These results, together with ice thicknesses from radio echo-sounding in the area, give a total mass outflux through the 2000 m contour of 30 Gt a–1, implying a budget excess of a further 30 Gt a–1 over the whole interior basin. Results from velocity and ice-thickness measurements give a mass discharge through a section near the junction of Lambert Glacier and the Amery Ice Shelf of 11 Gt a–1. Losses within the Lambert Glacier system proper account for a further 7 Gt a–1 and an overall mass excess of 12 Gt a–1 is estimated for the Lambert Glacier system. This present positive state of balance contrasts with geomorphological evidence from the southern Prince Charles Mountains of a large drop in ice level in recent geological time, and the ice surface in the area may now be building up after a major recession.This paper has been published in full in Journal of Glaciology, Vol. 22, No. 87,1979, p. 223—35.
Determining the extent of pressurized flow beneath Storglaciären, Sweden, using results of tracer experiments and measurements of input and output discharge
Authors: Kohler Jack 
Published: September 2017

AbstractTwo experiments were conducted on the drainage system beneath the Lower part of the ablation zone of Storglaciären, a small valley glacier in northern Sweden. In the first experiment, over 70 tracer tests were performed in a cluster of moulins during a 1 month period, at sub-daily intervals. In the second experiment, input- and output-discharge signals were measured on the supraglacial melt stream emptying into a moulin and on the proglacial stream to which the moulin drains. The data from these two experiments are used in an idealized model of the subglacial drainage system to calculate the percentage of the system flowing as an open channel. Results from the tracer experiment suggest that the system is pressurized to within 60-340 m of the snout, while analysis of the discharge data indicates pressurized ronduits to within 0-415 m of the snout.