bluuebunny/crossref_metadata_2025_split huggingface dataset:
Airborne-radar studies: Ice Streams A, B and C, West Antarctica
Authors: Retzlaff R. , Lord N. , Bentley C.R. 
Published: September 2017

AbstractDigital airborne-radar data were collected during the 1988–89 Antarctic field season in six gridded blocks covering the upstream parts of Ice Streams A, Β and C. An automated processing procedure was developed for picking onset times, converting travel times, interpolating missing data, converting pressure-transducer readings, correcting navigational drift, performing cross-over analysis and zeroing remanent cross-over errors. Cross-over analysis was used to remove the effects of temporal variations in atmospheric pressure and to estimate errors. Interpolation between flight lines was carried out using the Kriging method. Surface elevation was referred to the Rapp Set A geoid by tying the gridded surface to satellite-surveyed ground stations, using a planar-model fit.Maps of surface elevation, ice thickness and bottom topography with standard-error estimates of 4–9 m for surface elevation and 30–60 m for ice thickness and bottom topography were produced. These maps show that the locations of the ice streams are not clearly reflected in either the surface or basal topography, so are presumably controled by basal or internal conditions, that there is no clearly demarcated transition zone between sheet flow and streaming flow, that there is no clear cut evidence for the capture of the catchment of Ice Stream C by Ice Stream B, but that Ice Stream Β does drain virtually the entire region between the lateral boundaries of Ice Streams A and C.
Historic retreat of Grand Pacific and Melbern Glaciers Saint Elias Mountains, Canada: an analogue for decay of the Cordilleran ice sheet at the end of the Pleistocene?
Authors: Clague John J. , Evans S. G. 
Published: September 2017

AbstractGrand Pacific and Melbern Glaciers, two of the largest valley glaciers in British Columbia, have decreased over 50% in volume in the last few hundred years (total ice loss = 250–300 km3). Melbern Glacier has thinned 300–600 m and retreated 15 km during this period; about 7 km of this retreat occurred between the mid-1970s and 1987, accompanied by the formation of one of the largest, presently existing, ice-dammed lakes on Earth. Grand Pacific Glacier, which terminates in Tarr Inlet at the British Columbia-Alaska boundary, retreated 24 km between 1879 and 1912. This rapid deglaciation has destabilized adjacent mountain slopes and produced spectacular ice-marginal land forms. The sediments and land forms produced by historic deglaciation in Melbern–Grand Pacific valley are comparable, both in style and scale, to those associated with the decay of the Cordilleran ice sheet at the end of the Pleistocene (c. 14–10 ka BP). Rates of historic and terminal Pleistocene deglaciation also may be comparable.
Identification of subglacial lakes using ERS-1 radar altimeter
Authors: Ridley Jeff K. , Cudlip Wyn , Laxon Seymour W. 
Published: September 2017

AbstractRadar-altimeter data from ERS-1 allow detailed topographic mapping of Antarctica to 82° S to be carried out, revealing several notable surface features. Among these is the large subglacial lake near Vostok which is mapped here in detail. The central part of the lake is found to have an exceptionally smooth surface with r.m.s. elevation variations of less than 0.2 m. A search for other large Antarctic lakes in the data is made based on the smoothness and low gradient of the surface. A number of other flat areas are identified with lake locations previously determined from radio-echo sounding observations. However, radar-altimeter observations show that a minimum lake size of 20 km is required for a surface above a lake to become flat. Numerous bowl-like features can be seen in the surface topography, and these may be associated with intermediate-sized subglacial lakes. It is determined that high spatial-resolution radar altimetery could be used to identify subglacial lakes greater than 10 km in lateral extent. Flat regions of the ice sheet are particularly useful as they may be used as height-reference surfaces to help fix the orbits of radar-altimeter satellites.
Sensitivity to climate change of the mass balance of glaciers in southern Norway
Authors: Laumann Tron , Reeh Niels 
Published: September 2017

AbstractA degree-day model developed for parameterizing melt rates on the Greenland ice sheet is adapted to the climatic conditions on glaciers in southern Norway. The model is calibrated by means of observed average mass-balance-elevation relationships (1963–90) for three glaciers in a west-east transect in southern Norway and 30 year normals (1961–90) of temperature and precipitation observed at nearby climate stations. The calibration gives a surprisingly small variation of the model parameters (degree-day factors for snow-and ice-melt, and precipitation-elevation gradient) from one glacier to another. The derived values of the parameters are used to estimate the change of the mass-balance-elevation relationship for different climatic scenarios. The study indicates that a low-lying glacier in the maritime, high-precipitation environment near the Atlantic coast is more sensitive to both temperature and precipitation changes than the high elevated glaciers in the dry, more continental climate farther away from the coast. However, all of the glaciers studied will lose mass in a warmer climate, unless the warming is accompanied by a dramatic increase in the precipitation of 25–40% deg−1 warming.
A combined surface-and volume-scattering model for ice-sheet radar altimetry
Authors: Davis Curt H. , Moore Richard K. 
Published: September 2017

AbstractOver the last 15 years, satellite-altimeter data have been used to produce surface-elevation maps of the Greenland and Antarctic ice sheets with a 2 m accuracy. Analysis of Seasat and Geosat cross-over points showed that satellite altimeters can measure changes in the mass balance of the ice sheets. The retracking algorithm used to extract surface elevations from Seasat and Geosat return wave forms is based upon a modified form of the Brown surface-scattering model. Recent work has shown that altimeter wave forms over higher-altitude regions of the ice sheets are affected by sub-surface volume-scattering. Here, we develop a theoretical model for altimeter return wave forms over the ice sheets that is based on a combination of surface-and volume-scattering. By approximating the altimeter’s antenna pattern and transmitted pulse shape with Gaussian functions, we derive a closed-form analytical solution for the return-power volume-scattered from beneath the ice-sheet surface. We then combine the volume-scattering model with the Brown model and apply it to average wave forms from the Greenland and Antarctic ice sheets. The results show that the combined model accurately describes variations in altimeter wave-form shapes that are produced by differing contributions of surface-and volume-scattering to the received power. The combined model is then used to simulate return wave forms from a dual-frequency altimeter. The simulation shows that a two-frequency system can provide quantitative estimates of the absorption and scattering coefficients for near-surface snow.
Engineering Properties of Snow
Authors: Mellor Malcolm 
Published: September 2017

AbstractThe general properties of snow are described with a view to engineering applications of data. Following an introduction and a short note on the origins of snow, data are given for fall velocities of snow particles, and for mass flux and particle concentrations in falling snow and blowing snow. Notes on the structural properties of deposited snow cover grain size, grain bonds, bulk density, overburden pressure, and permeability. A section on impurities deals with stable and radioactive isotopes, chemical impurities, insoluble particles, living organisms, acidity, and gases. Mechanical properties are treated only selectively, and the reader is referred to another paper for comprehensive coverage. The selective treatment deals with stress waves and strain waves, compressibility, effects of volumetric strain on deviatoric strain, and specific energy for comminution. The section on thermal properties covers heat capacity, latent heat, conductivity, diffusivity, heat transfer by vapor diffusion, heat transfer and vapor transport with forced convection, and thermal strain. The section on electrical properties opens with a brief discussion on dielectric properties of ice, and proceeds to a summary of the dielectric properties of snow, including dielectric dispersion, permittivity, dielectric loss, and d.c. conductivity. There are also notes on the thermoelectric effect and on electrical charges in falling and blowing snow. The section on optical properties deals with transmission and attenuation of visible radiation, with spectral reflectance, and with long-wave emissivity. The review concludes with some comments on engineering problems that involve snow, and the requirements for research and development.
Mechanisms and Theory of Indentation of Ice Plates
Authors: Michel B. , Toussaint N. 
Published: September 2017

AbstractThis study gives the results and interpretation of tests made in a cold room on ice plates held vertically in a press and indented at various speeds with a rectangular indentor. These plates, 81 cm square, were held and frozen solid to a steel frame to represent semi-infinite ice sheets. The tests were carried out at — 10°C with indentation speeds varying from 6 × 10 -5 cm/s to 3 cm/s.It was found that the nominal pressure of indentation varies as a function of loading rates in a manner similar to that of the strength of S2 ice in uniaxial compression. The pressure increases rapidly with loading rates up to its maximum value at a strain-rate of 5 × 10-4 S-1. From there on, the pressure decreases. In the ductile range and up to the point of maximum pressure, a theoretical model was proposed where the theory of Hill (1950) of indentation of an ideal plastic body can be applied to predict an indentation pressure close to three times that of the uniaxial crushing strength.The tests did not show any so-called “ratio effect” caused by the ratio of the indentor width to the plane thickness. This effect could be explained by the influence of the geometry of the indentor on the strain-rate.
A Model Study of Powder-Snow Avalanches
Authors: Hopfinger E. J. , Tochon-Danguy J.-C. 
Published: September 2017

AbstractA powder-snow avalanche is a particular type of turbulent gravity current which it is proposed to treat using methods developed in contexts where the Boussinesq approximation is valid. Hence, it is assumed that the air entrainment rate E primarily depends on the internal Froude number (Tochon-Danguy and Hopfinger, [1975]) and that the large density variation in an avalanche reduces only the drag resulting from the air entrainment. In order for this drag to dominate over the wall stress it is necessary that the slope angle be greater than a certain minimum value which depends on the density ratio of the flow. For a low-density flow, for example, a minimum slope angle of about 5° is necessary. The more unusual aspect is that an avalanche may also entrain snow along its path which increases its mass and can produce in certain cases an accelerating flow. This aspect is included in the theoretical treatment. Experiments have been carried out in an inclined water channel using brine as dense fluid. Visual observations as well as measurements of the velocity and density profiles have been made. Various states of flow are proposed depending on whether the avalanche is “long" (having the structure of a usual gravity current) or “short" (having the structure of a thermal) or whether snow is entrained. The practical consequences which can be drawn from these results are discussed, in particular in the context of the design of defence structures, and flow visualizations of a gravity current impinging on an obstacle give an idea of the protected region.
Engineering Properties of Sea Ice
Authors: Schwarz J. , Weeks W. F. 
Published: September 2017

AbstractAs the continental shelves of the Arctic become important as source areas for the oil and minerals required by human society, sea ice becomes an increasing challenge to engineers. The present paper starts with a consideration of the different fields of engineering which require information on sea ice with the tasks ranging from the design of ice-breaking ships to Arctic drilling platforms and man-made ice islands. Then the structure of sea ice is described as it influences the observed variations in physical properties. Next the status of our knowledge of the physical properties important to engineering is reviewed. Properties discussed include mechanical properties (compressive, tensile, shear and flexural strengths; dynamic and static elastic moduli; Poisson’s ratio), friction and adhesion, thermal properties (specific and latent heats, thermal conductivity and diffusivity, density) and finally electromagnetic properties (dielectric permittivity and loss, resistivity). Particular attention is given to parameters such as temperature, strain-rate, brine volume, and loading direction as they affect property variations. Gaps, contradictions in the data, and inadequacies in testing techniques are pointed out. Finally suggestions are made for future research, especially for more basic laboratory studies designed to provide the data base upon which further theoretical developments as well as field studies can be built.
Areal and Temporal Variation of Percolation of Water Through a Snow-Pack
Authors: Langham E. J. 
Published: September 2017

AbstractSnow melt water that is uniformly generated over the upper surface of the snow-pack does not percolate homogeneously through the snow. Consequently, the rate of arrival of melt water at a single collector at the lower surface does not give a true measure of the melt rate. The experiment described here measures the spatial variability of flow rate and the temporal variation of this two-dimensional pattern. Data are collected from an array of 64 sensors under control of a microprocessor. The microprocessor checks the consistency of the data, calculates the flow rate for each sensor and transfers the results to a recorder. These mean flow rates are calculated at regular intervals for the duration of the experiment. In this way the temporal and spatial variations of flow rate may be related to variations in meteorological conditions and the evolution of the structure snow-pack as the melting progresses.
Movement Studies on a Hanging Glacier in Relation with an Ice Avalanche
Authors: Flotron André 
Published: September 2017

AbstractIn 1972 the state of a hanging glacier on the Weisshorn gave cause for alarm, as part of it seemed to be accelerating and a repetition of an earlier avalanche of ice seemed possible (see Röthlisberger, previous abstract). For this reason movement surveys were undertaken. The various surveying methods applied on the Weisshorn are outlined and the accuracy of the measurements is given. By least-square analysis different types of curves have been fitted to the data for velocity versus time. The best fit obtained so-far has been with hyperbolae. The confidence of extrapolations from such curves is discussed in relation to forecasts. By evaluating repeated photographs taken by an automatic camera from a single position, using a stereo plotter, the flow pattern has been established at the surface, part of the front, and one of the lateral faces of the ice mass. Changes with time caused by the deformation of the ice mass, the formation of crevasses and the crumbling away of the ice at the edge have been observed.
Abstracts of Papers Accepted for the Symposium but not Presented: An Automatic Snow-Depth Meter using Infrared Beam Reflection from a Snow Surface for the Measurement of the Snow Depth on the Road
Authors: Kimura Tadashi 
Published: September 2017

AbstractIn order to measure the snow depth on a road, a new type of snow-depth meter based on trigonometry with an infrared beam source, beam reflection points on the snow surface and a detector of the reflected beam, was developed using a gallium-arsenide infrared-emission diode and a silicon infrared-detection dual diode. The prototype of this meter operated successfully from 1 February to 31 March 1975 at Nagaoka, Japan.In the prototype, an infrared beam source, with 10 mW output power, and a detector were fixed 4 m above the ground facing each other at a distance of 5 m. These two photoelectric elements were set in small light-weight cases. Each has a small window (4 cm × 10 cm) to emit or receive the infrared beam. To avoid catching snow or rain in the windows, air was ejected through them. The visual field of the detector was 4.8° and the dip angle of its centre line was fixed at 45°. On the other hand the beam source emitted with 1.4° divergence and varied its dip angle from 90° to 20° with a period of 4 min in the vertical plane which contains the centre line of the visual field of the detector. This beam was reflected by the snow surface and received by the detector in its visual field. When the detection system of the meter detected the beam centre, the dip angle of the scanning beam was measured by a potentiometer connected mechanically to the infrared source scanner. Output voltages of the potentiometer indicated the measurement of snow depth within an accuracy of ±5 mm for the flat plate or snow surface from 0 to 1.5 m above the ground.In addition, a phase-sensitive detection circuit with equivalent band-width of 0.4 Hz and driven by a synchronous signal of 1 kHz from the modulation circuit of the beam source was adopted in order to eliminate noise such as occurs due to sunshine, heavy snow-storms or traffic. As a result very reliable movements were obtained under conditions of heavy snowstorms with horizontal visibility less than 30 m at eye level in daytime.
Calculation and Prediction of the Total Glacial Melting in Watersheds of Central Asia
Authors: Konovalov V.G. 
Published: September 2017

AbstractA computer method for calculating the total melting from May to October has been developed both for a single glacier and for a glacial area. In the second case (which is the more interesting and important for hydrology and glaciology) it is necessary to calculate some characteristics of an “average" glacier of the region using morphometric characteristics included in the Catalogue of the U.S.S.R. glaciers. These are: glacier area; average area of moraine on the glacier; weighted average of heights of upper and lower ends of a glacier and weighted average of mean height of firn line. It is also necessary to obtain data on glacier area distribution by height, precipitation data, and data on air temperature and cloudiness at meteorological stations.In addition to defining typical glacial regions within the limits of the glacial area considered and determination of the “average" glacier characteristics listed above, preparation of the computer programme includes (a) definition of precipitation dependence on orography height and calculation of appropriate parameters, (b) reduction (if necessary) of data obtained from the meteorological station nearest to glacial area to a more prolonged range, (c) calculation of a special balance index of accumulation and melting of seasonal precipitation which makes it possible to define maximum excess of seasonal snow line over the “average" glacier terminus in separate years, and (d) computation of total solar radiation occuring in clear days during May to October.In the course of computation on computer the following operations are realized: (a) determination of an average value of total radiation arriving during months of May to October period given the real cloudiness conditions, (b) calculation of the height of the snow line on the glacier, (c) calculation of quantity and duration of solid atmospheric precipitation which melts between May and October on the glacier surface, (d) estimation of absorbed solar radiation taking account of the differing albedo of glacial surfaces situated above and below the seasonal snow line, (e) calculation of the total melting of glaciers belonging to the given mountain watershed.Checking of the calculational method has been performed using data from Lednik Tsentralnyy Tuyuksu and Lednik Ayutor-2 where numerous ablation stakes were installed. Values of measured and calculated melting agree satisfactorily.
Icing Rate on Stationary Structures Under Marine Conditions
Authors: Itagaki K. 
Published: September 2017

AbstractIcing on stationary structures is an increasingly serious problem as off-shore drilling operations in the sub-polar regions becomes more popular. Since this problem is less complicated than icing on a ship, an attempt was made to calculate accretion rate using existing data.The rate of ice accumulation R can be calculated from R = CfCcF where F is the mass flux of the water drops and Cf and Cc are the proportions of spray frozen on the surface and coefficient of capture of drops, respectively. Cc can be close to unity for larger drops such as sea spray. Although many other factors may contribute, Cf seems to be a strong function of the air temperature.Mass flux can be written as Vr3 dr where n(r) is the number of drops of radius r in unit volume, V is the wind velocity, ρ is the density of water; n(r) is a function of wind velocity and height of observation. For a stationary structure, the mass flux is primarily dependent upon the wind speed.The ice accretion rate R, calculated using published data on the size distribution of sea spray and using a capture efficiency Cc of I agrees surprisingly well with the diagrams given by previous authors for icing on ships.
Characteristics of The Seasonal Sea Ice of East Antarctica and Comparisons with Satellite Observations
Authors: Jacka T.H. , Allison I. , Thwaites R. , Wilson J.C. 
Published: September 2017

A cruise to Antarctic waters from late October to mid December 1985 provided the opportunity to study characteristics of the seasonal sea ice from a time close to that of maximum extent through early spring decay. The area covered by the observations extends from the northern ice limit to the Antarctic coast between long. 50 °E and 80 E. Shipboard observations included ice extent, type and thickness, and snow depth. Ice cores were drilled at several sites, providing data on salinity and structure.The observations verify the highly dynamic and divergent nature of the Antarctic seasonal sea-ice 2one. Floe size and thickness varied greatly at all locations, although generally increasing from north to south. A high percentage of the total ice mass exhibited a frazil crystal structure, indicative of the existence of open water in the vicinity.The ground based observations are compared with observations from satellite sensors. The remote sensing data include the visual channel imagery from NOAA 6, NOAA 9, and Meteor 11. Comparisons are made with the operational ice charts produced (mainly from satellite data) by the Joint Ice Center, and with the analyses available by facsimile from Molodezhnaya.