bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the Occurrence of Ice Domes and Permanently Snow-Covered Summits
Authors: Manley Gordon 
Published: December 2010

AbstractThe occurrence of isolated ice- or snow-covered summits is reviewed. Their existence appears in the first place to be a function of their breadth in relation to the altitude of the firn line on adjacent glaciers; other factors remain to be discussed. Light may thus be thrown on questions of past glaciation of rounded summits in critical areas, and notably on the amount of precipitation then prevailing.
Contributions to the Glaciology of the Antarctic
Authors: Loewe F. 
Published: December 2010

AbstractDuring a winter in Terre Adélie in 1951 (Antarctica) certain glaciological studies were made. These were strongly hampered by the extraordinary strength and persistence of the blizzards from the ice cap. Near the coast the wind dominates the distribution of snow completely. The firn limit on the open ice cap is at a height of 450 m. (1500 ft.). The deposited snow is very tightly packed with a density of 0.4–0.5 gm./cm.3. On the ice cap the mean annual accumulation is 20–30 cm. water. At the coast and particularly on the ice cap measurements and calculations of the radiation balance show a strong loss for most of the time owing to the high albedo of the snow. The snow surface is almost continuously colder then the snow below and the air above. The radiation loss is mainly replaced by the influx of warmer air into the continent. The density of the drifting snow was measured. On a day with heavy blizzard the snow transport across each m. of the coast line is 2.5–3 kg. /m.sec. In a year at least 20 million tons pass each km. (30 million tons per mile). In Terre Adélie the drifting snow is an important item in the mass economy of the ice cap.
Notes on the Glacier Fluctuations in Bünsow Land, Central Vestspitsbergen
Authors: Sweeting Marjorie , Groom Gillian 
Published: December 2010

AbstractThese notes are based on observations made in 1953 on the nature and state of the glaciers in Bünsow Land while the writers were members of the Cambridge Spitsbergen (Physiological) Expedition. Changes in the glacierization of the area, since the compilation of W. B. Harland’s map in 1949, are indicated. These changes illustrate some of the ways in which the thinning and decay of the Spitsbergen glaciers have been brought about.
Glacial Activity in the Western United States
Authors: Harrison A. E. 
Published: December 2010

AbstractFour coordinated reports on recent trends in glacial activity in the State of Washington, U.S.A., have been prepared by three authors and three of these appear in this issue of the Journal of Glaciology. The fourth report will appear in a later number. Other reports regarding the condition of glaciers in this state and in other regions of the western United States have appeared in various mountaineering journals. It is the purpose of this paper to serve as a reference to the bibliography in this field and show how the detailed story included in the companion papers is part of a widespread change in trend. Results reported by other observers are reviewed briefly. In addition, some data on observations by the author in the Sierra Nevada are included in order to compare the magnitude of the activity in California and Washington.
Design and Operation of a Portable, Digital Impulse Radar
Authors: Jones F.H.M. , Narod B.B. , Clarke G.K.C. 
Published: December 2010

AbstractWe have constructed a back-portable, impulse radar instrument that weighs roughly 12 kg, can be powered by dry cells, and records and stores data digitally. The radar is controlled by an on-board, purpose-built microcomputer that ensures simple field operation, facilitates modifications, and allows unattended operation when investigating time-varying targets. The transmitting unit is triggered from the receiver via an optical link and generates an electromagnetic wavelet by discharging two high-voltage capacitors through back-to-back silicon-controlled rectifiers into a resistively loaded dipole antenna. Successful field operations carried out during the summers of 1986 and 1987 include depth profiling, as well as studies of englacial and subglacial targets, on several temperate and sub-polar glaciers.
The Medial Moraines of Ghiacciaio Dei Forni, Valtellina, Italy: Morphology and Sedimentology
Authors: Smiraglia C. 
Published: December 2010

AbstractTwo distinct medial moraines are located on the tongue of Ghiacciaio dei Forni (Rhaetian Alps, Italy); they are formed by the confluence of three ice streams. The two ice-cored medial moraines originate from rock outcrops situated below the snow line. The moraines, which on the surface comprise angular clasts, extend for approximately 2 km and reach a maximum height of 10 m. Nourishment of the moraines seems to be due primarily to the supraglacial debris derived from the rock walls. Measurements made in the late summer of 1985 provided evidence of the role played by differential ablation in the development of these moraines. Sedimentological analysis further confirmed the mainly supraglacial origin of the debris comprising the moraines.
Force Budget: II. Application to Two-Dimensional Flow along Byrd Station Strain Network, Antarctica
Authors: Van Der Veen C.J. , Whillans I.M. 
Published: December 2010

AbstractResistive stresses and velocities at depth are calculated along the Byrd Station Strain Network, Antarctica, using field data. There are found to be large longitudinal variations in basal drag and this result is little affected by errors in the input data or by uncertainties in the constitutive relation for ice. Basal drag varies by a factor of about 2 along the strain network, and is usually equal to the driving stress to within 10–20%. Sites of high drag are not always correlated with basal topographic highs, indicating that some process such as basal water drainage is involved in controlling the friction at the bed. Basal sliding velocities are very sensitive to errors in measured surface velocities and the rate factor in Glen’s flow law. As a result, calculated sliding velocities are much less reliable than deep stresses, and need to be interpreted with caution.
A Map-plane Finite-element Model: Three Modeling Experiments
Authors: Fastook James L. , Chapman Judith E.. 
Published: December 2010

AbstractPreliminary results are presented on a solution of the two-dimensional time-dependent continuity equation for mass conservation governing ice-sheet dynamics. The equation is solved using a column-averaged velocity to define the horizontal flux in a finite-element formulation. This yields a map-plane model where flow directions, velocities, and surface elevations are defined by bedrock topography, the accumulation/ablation pattern, and in the time-dependent case by the initial surface configuration. This alleviates the flow-band model limitation that the direction of flow be defined and fixed over the course of the modeling experiment. The ability of the finite-element method to accept elements of different dimensions allows detail to be finely modeled in regions of steep gradients, such as ice streams, while relatively uniform areas, such as areas of sheet flow, can be economically accommodated with much larger elements. Other advantages of the finite-element method include the ability to modify the sliding and/or flow-law relationships without materially affecting the method of solution.Modeling experiments described include a steady-state reconstruction showing flow around a three-dimensional obstacle, as well as a time-dependent simulation demonstrating the response of an ice sheet to a localized decoupling of the bed. The latter experiment simulates the initiation and development of an ice stream in a region originally dominated by sheet flow. Finally, a simulation of the effects of a changing mass-balance pattern, such as might be anticipated from the expected carbon dioxide warming, is described. Potential applications for such a model are also discussed.SYMBOLS USEDa(x,y) Accumulation/ablation rate.A Flow-law parameter.B Sliding-law parameter.CijC Global capacitance matrix.f Fraction of the bed melted.Fij,F Global load vector.g Acceleration of gravity.hj,h Ice-surface elevation.H Ice thickness.k(x,y) Constitutive equation constant of proportionality.kij Global stiffness matrix.m Sliding-law exponent.n Flow-law exponent.ρ Density of ice.σ(x,y) Ice flux.t Time.U Column-average ice velocity.UF Column-average deformation (flow) velocity.US Sliding velocity.v Variational trial function.x,y Map-plane coordinates.
Stable-isotope (18O/16O) Tracing of Fresh, Brackish, and Sea Ice in Multi-year Land-fast Sea Ice, Ellesmere Island,Canada
Authors: Jeffries Martin O. , Roy krouse H. , Sckinger William M. , Serson Harold V. 
Published: December 2010

AbstractIce salinity and 18O/16O ratios were measured on 12 ice cores drilled from thick, multi-year land-fast sea ice (MLSI) off the north coast of Ellesmere Island, Canada. Fresh, brackish, and sea ice were identified in the ice cores using the 18O/16O ratios. Two cases are considered: case 1, which assumes that no isotopic fractionation occurs on freezing; and, case 2, which assumes that a maximum isotopic fractionation factor (a) of 1.003 applies. The amount of each ice type is variable among the cores, but overall the 12 cores comprise 29.6% brackish ice, 70.0% sea ice, and 0.4% fresh ice in case 1, and 42.3% brackish ice, 57.3% sea ice, and 0.4% fresh ice in case 2. The data suggest that time-dependent brackish sea-water stratification below the ice is quite common and is often associated with the inverted bottom topography. However, the stratification is not always confined to small, areally limited under-ice melt pools in inverted depressions, and neither is it a summer-only phenomenon. Brackish ice growth apparently occurs in a brackish water layer that in some instances underlies the ice sheet year-round. For both case 1 and case 2 the salinity distribution in brackish ice is positively skewed, with 50% of salinity values occurring in the range 0–0.49‰. Sea-ice salinity values are more evenly distributed. In case 1, brackish ice has mean salinity and mean δ18O values of 0.66 and –19.9‰, respectively, compared to mean values of 1.88 and –6.5‰ for the sea ice. In case 2, brackish ice has mean salinity and mean S18O values of 0.75 and –18.1% compared to mean values of 2.03 and –5.2‰ for the sea ice. The salinity of brackish ice and sea ice, ice-growth mechanisms, and the inclusion of brine in the sub-structure are discussed briefly.
Water-pressure Coupling of Sliding and Bed Deformation: II. Velocity-Depth Profiles
Authors: Alley R.B. 
Published: December 2010

AbstractBasal motion of a glacier resting on an unconsolidated bed can arise from sliding between ice and bed, ploughing of clasts through the upper layer of the bed, pervasive deformation of the bed, or shearing across discrete planes in the bed. Theoretical analyses and limited observations of soft-bedded glaciers not dominated by supply of channelized melt water from the surface suggest that sliding will be slow if the bed contains abundant clasts in the 1–10 mm size range, and that high velocities by ploughing are unlikely though possible. Pervasive deformation usually will account for 60–100% of the basal velocity, and the strain-rate will be proportional to the basal shear stress and inversely proportional to the square or cube of the effective pressure. These hypotheses are based on results of part I in this series, and allow modeling of Ice Stream B, West Antarctica, in part III of this series.
Snow-crystal Growth with Varying Surface Temperatures and Radiation Penetration
Authors: Colbeck S.C. 
Published: December 2010

AbstractThe temperature field is derived for a sinusoidally varying surface temperature with varying solar radiation penetration. The growth rates of snow crystals are calculated to explain the rapidly growing layers of faceted crystals (i.e. depth hoar) that form just below the surface at high altitudes and in polar snow. The solutions also show that a layer of wet snow can exist just below the surface even on days when the surface temperature remains sub-freezing.
A Synthetic-Aperture Radio-Echo Experiment at Storglaciären, Sweden
Authors: Walford M.E.R. , Kennett M.I. 
Published: December 2010

AbstractA polarization-sensitive aperture-synthesis experiment has been carried out using radio-echo data from Storglaciären, Sweden. Echoes were recorded in each of three antenna configurations over an array of sites on the glacier surface. The echo information was transferred to a mainframe computer and manipulated in order to reveal any major individual targets present. Within a 100 m cube, six major targets were identified, each with its own echoing characteristics. Echo strengths indicate that the targets are probably cavities containing water. It cannot be determined whether they are isolated or parts of a continuous system.
Water-pressure Coupling of Sliding and Bed Deformation: III. Application to Ice Stream B, Antarctica
Authors: Alley R.B. , Blankenship D.D. , Rooney S.T. , Bentley C.R. 
Published: December 2010

AbstractGeophysical studies and glaciological analyses suggest strongly that Ice Stream B, West Antarctica, moves primarily by pervasive deformation of a meters thick subglacial till. Analysis of the longitudinal profile of the ice stream up-stream of the ice plain suggests that basal sliding is slow everywhere, that effective pressure decreases slowly down-stream, and that the strain-rate of pervasive shear is proportional to the basal shear stress and inversely proportional to the square or cube of the effective pressure. Discrete shearing may occur beneath the pervasively deforming zone. These and other hypotheses, which build on the analyses of the first two papers in this series, can be tested in the field.
Modelling Antarctic Fast-Ice Growth
Authors: Crocker G.B. , Wadhams P. 
Published: December 2010

AbstractAn existing thermodynamic ice-growth model (Semtner, 1976) has been tested for its ability to predict the growth of fast ice in McMurdo Sound, Antarctica. Significant discrepancies between observed and predicted ice thicknesses were found to occur, primarily due to the presence of sub-ice platelets and the formation of a snow-ice layer. Although these ice-growth processes are not well enough understood to permit rigorous physical modelling, it is shown that fairly simple modifications to the model greatly improve the accuracy of the thickness predictions, and serve to highlight the importance of these processes in the Antarctic fast-ice environment. Surface flooding and snow-ice formation are assumed to occur immediately upon the establishment of a positive hydrostatic water level, and a surface temperature in excess of a critical value, above which interconnecting channels in the ice matrix permit the flow of water to the surface. The presence of the sub-ice platelet layer is assumed to increase columnar ice growth at a rate proportional to the volume fraction of ice in the platelet layer, a simple technique but one that permits estimates of platelet-enhanced growth without detailed knowledge of oceanographic conditions. The resulting model predictions are in close agreement with measurements of fast-ice growth and decay in McMurdo Sound; however, data suitable for testing the model over a complete range of conditions and over multi-year cycles are not available at the present time.
Laboratory Simulations Of Glacial Abrasion: Comparison With Theory
Authors: Iverson Neal R. 
Published: December 2010

AbstractGlacial abrasion was simulated in experiments in which a small artificial glacier bed was pushed beneath a fixed ice block under pressure. The experiments provide a means of testing theoretical models of abrasion, particularly those factors that govern the magnitude of stress concentrations beneath abrading rock fragments. In preliminary experiments, vertical ice flow around a sphere mounted on the bed was studied. In subsequent experiments, marble tablets were pushed beneath granitic rock fragments frozen into the base of the ice block. Unlike previous abrasion experiments, the sliding velocity was realistic (25 mm d−1), and ice near the bed was at the pressure-melting temperature. Resultant striations closely resemble those observed on glaciated bedrock.As predicted by Hallet (1979), the component of the ice velocity towards the bed strongly influenced stresses beneath fragments, and classical regelation and creep theory provided an approximate estimate of the downward drag force on fragments. Half of the rock fragments rotated significantly, accounting for 10–50% of their motion relative to the bed and influencing abrasion rates and the shear stress supported along the ice-bed interface. Striation patterns indirectly suggest that fragment rotations were inhibited by increases in ice pressure, which presumably increased the drag on roughness elements on fragment surfaces. This may have resulted from a reduction in the thickness of the water film around fragments, facilitated by leakage of water from the bed.
Boudinage: A Source Of Stratigraphic Disturbance In Glacial Ice In Central Greenland
Authors: Cunningham J. , Waddington E.D. 
Published: December 2010

AbstractA hydrodynamic model of interface stability in a stratified fluid is reviewed. The model predicts that irregularities on the boundaries of a stiff layer, embedded in a soft matrix, are unstable in pure shearing flow, when compression is normal to the layer. Perturbations on such a layer can grow to form symmetric pinch-and-swell structures called boudins. The model predicts initial perturbation growth rates on the boundaries of an interglacial period ice layer. We find that, beneath an ice divide, irregularities on the Sangamon layer boundaries will not kinematically decay, as the layer thins. Finite-element modelling is used to determine the strain history of Sangamon ice beneath the divide at Summit, Greenland. That history suggests boundary irregularities have grown, relative to layer thickness, at least 26 fold over the past 90000 years. The result may be severe distortion or severing of the layer. Core holes penetrating the layer may recover anomalously thick or thin columns of ice resulting in erroneous environmental and climatic interpretations. Radio echo-sounding may be useful in searching for zones of boudinage, which should be avoided when coring. Initial perturbations might arise from mass-balance spatial variations or from transient flow fields.
A Modern Pollen Spectrum From Dye 3, South Greenland Ice Sheet
Authors: Bourgeois Jocelyne C. 
Published: December 2010

AbstractResults of pollen analysis of a large firn sample from Dye 3, southern Greenland, are reported. The sample was divided into three sections: all dominated by pine, birch, and ragweed pollen. Pollen concentration for the entire sample is 15 pollen grains per litre and the annual pollen deposition rate has been estimated at approximately 0.73 grains cm−2 year−1 (7300 grains m−2 a−1). Although these values are slightly lower than expected, considering the relatively southern latitude of the site, they are within the range of values obtained from other Arctic ice caps.
Flow Laws For Glacier Ice: Comparison Of Numerical Predictions And Field Measurements
Authors: Van Der Veen C.J. , Whillans I.M. 
Published: December 2010

AbstractIce flow along the 20 km long strain network up-stream of the Dye 3 bore hole in Greenland is studied in detail. By solving the force-balance equations and using selected flow laws, stresses and strain-rates are calculated throughout the section of the ice sheet. The validity of the results is evaluated by comparison with the velocity profile derived from bore-hole-tilting measurements, and with observed surface strain-rates. A number of constitutive relations are tried and most predict a velocity profile at the bore-hole site that is in good agreement with that observed, if appropriate enhancement factors are used. However, there are major discrepancies between modelled and measured surface strain-rates. Use of Nye’s generalization of Glen’s flow law, or an anisotropic constitutive relation, requires unrealistically large along-flow variations in the enhancement factor. Inclusion of normal stress effects can lead to much better agreement, but it is possible that other processes, such as dynamic recrystallization or primary creep, should be included in the constitutive relation of polar ice.
Sur la critique des données démographiques en Afrique
Authors: Stengers Jean 
Published: December 2010

The use of demographic data on Africa can be difficults, il not extremely hazardous, without a critical approach. In order to avoid errors and traps, it is advisable to analyse the data via four critical questions :
- what is the type of operation which is the source of the figures ? (estimate, count, census or demographic survey, suspicion of the authorities, of the vocabulary, of the series data, of the registration);
- what are the abilities of the team that led the operation ? (competence of the census taker faced with constraints of time, distances and methods);
- how far were the people surveyed able to answer the questions ?
- what were the intentions of the surveying team in terms of their objectives, assuming that the intention of the survey may not solely be aimed at discovering the truth ? (temptation to increase or reduce the figures according to financial or political interests).
Esprits sans patrie : une analyse de la « religion du voyage » dans les îles du Cap-Vert
Authors: Laurent Pierre-Joseph , Plaideau Charlotte 
Published: December 2010

À la découverte des îles au XV e siècle, la spiritualité capverdienne se construit sur un double mouvement où la conversion forcée des esclaves africains au catholicisme va de pair avec une familiarisation des Européens aux systèmes de pensées de l’Afrique. Au fil des siècles, ce métissage fait naître un imaginaire catholique populaire où l’esprit du défunt ( finado ) s’établit comme l’un des ciments de la société ; par sa mainmise symbolique sur le sort de ces familles de migrants tourmentées entre ici et là-bas, l’esprit « apatride » devient le commun dénominateur entre le natif et le migrant, le jeune et le vieux, le populaire et l’érudit, le catholique et le protestant, le continental et l’insulaire, l’Africain et l’Européen. Qu’il soit « errant » – inférieur – ou « de lumière » – supérieur –, l’esprit du défunt est également l’entité convoquée par le rationalisme chrétien pour (re)créer du lien. Ce n’est pas un hasard puisque cette doctrine spiritualiste née au Brésil en 1910 s’est répandue à l’étranger en accompagnant la diaspora capverdienne. Ses « irradiations » et séances de « dédoublement et nettoyage psychique » dirigées vers le monde entier, en font une spiritualité délocalisée, permettant de relier les destins humains par-delà les frontières géopolitiques.
Le culte de Maximón.
Authors: Pédron-Colombani Sylvie 
Published: December 2010

Au Guatemala, Maximón est un personnage aux multiples facettes issu de la rencontre entre deux univers de sens – maya et catholique. Son culte, identifié il y a seulement quelques décennies à un territoire, une culture, voire un groupe ethnique, est aujourd’hui pris dans un processus de translocalisation. Il s’est répandu sous diverses formes dans l’ensemble du pays – y compris parmi les couches métisses urbaines –, mais également au Mexique et aux Etats-Unis, au gré des flux migratoires des guatémaltèques. Cet article propose une réflexion conjointe sur les dynamiques nationales et internationales du culte, sur les transformations et re-significations du culte, ainsi que sur les revendications identitaires sous-jacentes. À partir d’un travail de terrain mené dans la ville de Los Angeles, nous verrons notamment comment le culte a pris une dimension individuelle et syncrétique, s’éloigne du monde maya et devient porteur d’un ensemble de significations collectives propres au monde des migrants latino-américains.