bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Use of Hypsometry to Indicate Long-Term Stability and Response of Valley Glaciers to Changes in Mass Transfer
Authors: Furbish D.J , Andrews J.T. 
Published: September 2017

AbstractA simple equation is derived relating the net mass-balance and hypsometric curves of a steady-state valley glacier. It is used to examine how valley shape is linked to disparate extents and responses of glaciers subjected to similar climatic conditions. Examples are given which show that area-based indices (e.g. AAR) for estimating the equilibrium line altitude (ELA) may be subject to a substantial built-in variance because they implicitly rely upon similarity of glacier shape and regimen over a region. If accurate topographic maps are available, the equation may be used to infer the regimen of modern glaciers in the form of a dimensionless ratio of net mass-balance gradients. Alternatively, if similar information is available concerning regional glacier regimen, disparate extents and responses may be collectively utilized to estimate values of ELA or to infer climatic influence, taking glacier hypsometry into account.
Rates and Mechanisms of Iceberg Ablation in the D’Urville Sea, Southern Ocean
Authors: Keys J. R. , Williams K. L. 
Published: September 2017

AbstractWave action causes ablation in a narrow zone around an iceberg’s waterline, at up to 0.3 m per day, in water of −1°C with waves up to 0.4 m high. Subsequent subaerial calving of ice from iceberg sides takes place up to a similar rate. Submarine melting is an order of magnitude slower than wave action but acts over the largest part of an iceberg. Ablation rates derived theoretically or statistically elsewhere for comparable environmental conditions, are in reasonable agreement with those measured here. Drifting icebergs trail a plume of mixed, slightly cooled and diluted sea-water in their wake.
Shock-Wave Studies Of Ice Under Uniaxial Strain Conditions
Authors: Larson Donald B. 
Published: September 2017

AbstractShock-wave studies of ice under uniaxial strain conditions have been conducted at stress levels up to 3.6 GPa. A light-gas gun accelerated the flat-faced projectile used to impact the ice-containing targets. The ice samples were initially at ambient pressure and at temperatures of –10 ± 2° C. Gages were implaced at different distances in the ice along the path of the shock wave to measure particle velocity time histories inside the ice samples. The recorded time histories of particle velocity show a precursor wave with an average wave velocity of 3.7 km/s and an average particle velocity amplitude of 0.06 km/s. This wave is travelling at a wave velocity approximately 10% greater than longitudinal sound speed and is believed to originate because of the onset of melting of ice I.The particle velocity data from these experiments were converted to stresses and volumes using Lagrangian gage analysis and the assumption of a simple non-steady wave. This conversion provides a complete compression cycle (which includes both loading and unloading paths) for comparison with static measurements. All experiments show the onset of melting at 0.15 to 0.2 GPa. Experiments with maximum stress states between 0.2 and 0.5 GPa yield results which suggest that a mixed phase of ice I and liquid water exists at these conditions. For maximum loading stresses between 0.6 and 1.7 GPa the experimental results suggest that the final state is predominately ice VI. In these experiments the specific volume upon compression is changed from 1.09 m3/Mg to approximately 0.76 m3/Mg, which represents compaction of approximately 30%. The unloading paths determined from these experiments indicate that ice VI remains in a “frozen” or metastable state during most of the unloading process. This hysteresis in the compression cycle gives rise to a large “loss” of shock-wave energy to the transformation process. At stress levels above 2.2 GPa, ice VII should be the stable form for water according to static compression measurements. Experimental data at 2.4 and 3.6 GPa suggest that ice VII may be formed but these results indicate a mixed phase of ice VI and ice VII rather than complete transformation to ice VII.
Ice On Planets of the Solar System
Authors: Krass M.S. 
Published: September 2017

AbstractSeveral aspects of space glaciology are considered in the paper. Estimates of the water content of the Earth, Mars, and the Galilean moons of Jupiter are corrected. A considerable proportion of the total amount of water in the solar system is localized near Jupiter; part of this water is contained as ice in glaciations, glacial caps, and ice crust on the planets. Ice is one of the main components of the surface of some planets. The major amount of ice on Mars is contained in a permafrost layer of mean thickness about 3 km. The model of an ice crust floating on a water mantle is considered for Jupiter’s moon Europa. It is shown that for definite values of certain parameters this crust may be subject to destruction due to the instability of its proper oscillations, which explains the numerous systems of fractures and cracks observed on Europa’s surface. The stress-strain state of such an ice crust is calculated within the framework of a non-linear thermo-elasticity model. The role of short-period temperature variations at Europa’s surface is estimated and the peculiarities of relief observed on this planet are analysed.
Electrical Resistivity of Ice from the Antarctic Peninsula, Antarctica
Authors: Reynolds John M. , Paren J. G. 
Published: September 2017

AbstractGeoresistivity soundings have been carried out at four sites in the Antarctic Peninsula. The objective of the work was to investigate the electrical behaviour of ice from an area where substantial melting occurs in summer and from contrasting thermal regimes. Electrical measurements made at three sites along a flow line within George VI Ice Shelf reveal that:
(a)the resistivity of deep ice is similar to that of other Antarctic ice shelves,(b)the resistivity of the ice-shelf surface, which is affected by the percolation and refreezing of melt water, is similar to that of deep ice and hence the ice is polar in character.A compilation of published resistivities of deep ice from polar regions shows that the range of resistivities is very narrow (0.4 –2.0) x 105 Ω m between –2 and – 29°C, irrespective of the physical setting and history of the ice. Typically, resistivity is within a factor of two of 80 kΩ m at –20° C with an activation energy of 0.22 eV. In contrast, the resistivity of surface ice at Wormald Ice Piedmont, where the ice is at 0°C throughout, is two orders of magnitude higher and falls at the lower end of the range of resistivities for temperate ice.
A Mathematical Model for Perched Block Formation
Authors: Patterson E. A. 
Published: September 2017

AbstractA mathematical model for the formation of perched blocks on glaciers due to differential ablation is developed by considering energy balances. The model is applied to naturally positioned rocks on Bersærkerbræ, Greenland. The model predicts correctly whether a rock will perch or sink in eleven out of twelve cases. For artificially positioned small rocks of mean dimension 0.2 m, the model has a 53% success rate. The reduced performance is probably due to the thicknesses of the rocks being of similar magnitude to the range of relief of the glacier surface.
Avalanche Tarns
Authors: Fitzharris B. B. , Owens I. F. 
Published: September 2017

AbstractAvalanche tarns are a particular morphological form of avalanche impact and sixteen of these features are described from the Fiordland region of New Zealand. Average area of the tarns is 11000 m2. Profiles are given for eight of the avalanche paths where such tarns occur. All are found at the base of very steep avalanche tracks (slopes 38–59°), where there are no fans, so that there is an abrupt change of slope with the valley floor. The plunging avalanches which cause the tarns may have a mass of up to 300000 tonnes and impact pressures of more than 600 kN/m2, although no direct measurements are available.
The Natural Oscillations of an Ice-Covered Channel
Authors: Green Theodore 
Published: September 2017

AbstractThe natural modes of oscillation of an infinitely long, ice covered channel are considered, using the hydrostatic approximation, and assuming the ice to behave elastically. The dispersion relation, mode shape, and associated force on the channel wall are found for the lowest three modes. Special attention is paid to the limitations associated with the hydrostatic and elastic approximations.
The Shear Strength Characteristics of Frozen Coarse Granular Debris
Authors: Nickling W.G. , Bennett L. 
Published: September 2017

AbstractThe effect of ice content and normal load on the shear strength characteristics of a frozen coarse granular debris was investigated. 31 shear tests were carried out in a modified shearbox allowing a sample temperature of (–1.0 ± 0.2)° C and a load rate of 9.63 × 10−4cm/min. The tests showed that as the ice content of the frozen debris was increased from 0% (under-saturated) to 25% (saturated), sample shear strength was markedly increased. In contrast, sample shear strength was reduced as ice content was increased from 25% (saturated) to 100% (supersaturated). The changes in shear strength with increasing ice content were attributed directly to changes in internal friction and the cohesive effects of the pore ice. The shear tests also indicate that shear strength increases with increasing normal load up to a critical limit. Above this limit, dilatancy is suppressed causing the shear strength to decrease or remain relatively constant with increased normal load.The stress-strain curves of the 31 tests indicated that samples with higher ice contents tended to reach peak strength (τP) with less displacement during shear. Moreover, the difference between τpand τr(residual strength) was lowest for pure polycrystalline ice and highest for ice-saturated samples. The Mohr-Coulomb failure envelopes displayed very distinctive parabolic curvilinearity. The degree of curvature is thought to be a function of ice creep at low normal loads and particle fracture and crushing at high normal loads.
Snow Wetness Measurement by Fluorescent Dye Dilution
Authors: Davis Robert E. , Dozier Jeff 
Published: September 2017

AbstractThe fluorescent dye dilution method for determining the liquid-water content in snow is based on measuring the concentration change of a solution when it is mixed with snow. Samples for analysis can be obtained rapidly and reliably, and, unlike calorimetric or equilibrium-temperature methods, field use requires no on-site data analysis.
Electrical Resistivity Soundings of Glacier Beds: A Test Study on Grubengletscher, Wallis, Swiss Alps
Authors: Haeberli Wilfried , Fisch Werner 
Published: September 2017

AbstractElectrical resistivity sounding, using electrodes which are lowered directly to the ice–rock interface in bore holes, is proposed as a technique for studying the exact position of glacier beds, as well as their lithological characteristics. A test study is described on Grubengletscher, a partially cold Alpine glacier in Switzerland. Results of soundings along a 400m long profile indicate that previous depth determinations, based on radio echo-soundings, were in general accurate to within less than 5% of the actual ice thickness. The results also show that the glacier rests on non-consolidated sediments of considerable thickness. The proposed method could add substantial information about glacier sliding and glacier erosion, if applied alongside conventional deep drilling projects.
Accelerating Flow of the Brunt Ice Shelf, Antarctica
Authors: Simmons D. A. , Rouse J. R. 
Published: September 2017

AbstractPosition fixes made at the British Antarctic Survey station, Halley, on the Brunt Ice Shelf are considered for the period 1968–82. These show an initial westward velocity of approximately 400 ma−1 rising to over 700 m a−1 by the end of the period. The data are well fitted by two straight lines. The first for 1968–71 has a slope 430 m a−1 in agreement with that found by Thomas (1973) for the period up to 1968. The second for 1972–83 has a slope 740 ma −1, a large increase sustained for up to 10 years.
Spatial and Temporal Variations in Electrical Conductivity in a Pro-Glacial Stream System
Authors: gurnell A. M. , Fenn C. R. 
Published: September 2017

AbstractSpatial and temporal observations of electrical conductivity during the summers of 1978 and 1981 on the pro-glacial stream sytem of glacier de Tsidjiore Nouve, Valais, Switzerland, are described. Three space–time scales of electrical conductivity variations are considered: single-site, hourly monitoring for a two-month period; multiple-site sampling over 12 h periods using a 1 h sampling interval, and multiple-site sampling over monthly periods using a 24 h and 48 h sampling interval. Detailed analysis of the information from the three scales shows that the sampling strategies employed can reliably be used to investigate space–time patterns in the data. The results demonstrate that there are diurnal cycles in both electrical conductivity and discharge which are slightly different in form and which are out of phase with one another at the same site. Simultaneous multiple-site sampling of electrical conductivity shows that the tributary streams draining the glacier snout exhibit complementary shifts in electrical conductivity between ablation seasons, between days, and within days. The significance of these complementary shifts in tributary electrical conductivity are discussed in the light of possible source areas, storage, and routing fluctuations of melt water draining from the glacier.
Normal Stress Effects in the Creep of Ice
Authors: McTigue David F. , Passman Stephen L. , Jones Stephen J. 
Published: September 2017

AbstractMost non-linear fluids for which the appropriate measurements have been made exhibit non-zero and unequal normal stress differences in shearing flows. Power-law models such as Glen’s law cannot represent this phenomenon. The simplest constitutive equation that does embody normal stress effects defines the second-order fluid. An exact analytical solution for biaxial creep of such a fluid is fit to data from four tests on polycrystalline ice. The model gives an excellent representation of both primary and secondary creep. The fits provide values for the three material constants. These coefficients indicate positive first and second normal stress differences. One consequence is the prediction that a steady open-channel flow will exhibit a longitudinal free-surface depression of up to several meters for sufficiently thick ice on steep slopes. In addition, the compressive principal stress at the channel margin is decreased and the tensile principal stress is increased in magnitude over those predicted by models without normal stresses. The normal stresses thus favor the formation of crevasses. Furthermore, the angle these crevasses form with the channel margin is decreased.
Mass Balance of the Greenland Ice Sheet at Dye 3
Authors: Reeh Niels , Gundestrup Niels S. 
Published: September 2017

AbstractThe mass balance of the Greenland ice sheet at Dye 3 is estimated on the basis of observations of ice thickness, accumulation rate, surface velocities, and surface strain-rates. The calculations indicate a rate of increase of surface elevation of 3 cm/year, with 95% confidence limits of −3 cm/year and +9 cm/year. Previous estimates of the mass balance of the Greenland ice sheet by the same method reported large imbalances; these are most probably due to lack of precise data and the use of quantities measured at the surface as representative of depth-averaged quantities. The most reliable observations indicate that the interior regions of the Greenland ice sheet are at present thickening at a rate of a few centimetres per year; a contributing cause for this may be the slow thinning of a bottom layer of relatively soft Wisconsin ice.
Icing on a Non-Rotating Cylinder Under Conditions of High Liquid Water Content in the Air: I. Form and Size of Ice Deposits
Authors: Launiainen Jouko , Lyyra Markku 
Published: September 2017

AbstractIce accretion on a non-rotating cylinder was studied under icing conditions involving a wet-growth (glaze) process. Experiments were performed in an outdoor wind tunnel designed for icing studies. In this paper, the experimental method is introduced and the characteristics of form, size, and time development of deposits are given. In terms of freezing conditions, these characteristics were found to be very complex, in which all the external effects: air temperature, wind conditions, liquid water content in the air, and accretion time, are of the same order of importance. In a wet-growth process there exists above the icing surface a water film, the behaviour and dynamics of which are affected by various variables. The water film seems to play an important role in the wet-growth icing.
Drainage-Basin Characteristics of Nordaustlandet Ice Caps, Svalbard
Authors: Dowdeswell Julian A. 
Published: September 2017

AbstractRecent mapping of ice-surface and bedrock topography from airborne radio-echo sounding has shown that the ice caps of Nordaustlandet, Svalbard, are divided into a series of well-defined drainage basins. Three lines of evidence indicate that several distinctive modes of ice-flow regime characterize these basins: (1) comparison between observed and theoretical ice-surface profiles; (2) analysis of driving stresses; and (3) observations of ice-surface features on satellite imagery and air photographs. The drainage basins are inferred to behave in the following ways. First, basins with low driving stresses and surface profiles, some of them clearly stagnant, are associated with the quiescent phase between glacier surges. Secondly, the ice streams draining southern Vestfonna have low surface profiles, relatively low driving stresses, and marked shear zones at their margins. They are interpreted to be flowing continuously at a relatively faster rate than the ridges between them. Basal melting, perhaps combined with substrate deformation, is probably responsible for the regime of these glaciers. Thirdly, the remaining basins studied on Nordaustlandet have relatively high marginal driving stresses and high surface profiles. They are interpreted to be frozen to their beds, at least near their margins. Some of these basins may also surge, particularly those where a part of the basin is below sea-level, and therefore is probably underlain by considerable thicknesses of deformable sediments.
Assessment of mass-balance variations within a sparse stake network, qamanârssûp sermia, west greenland
Authors: Braithwaite Roger J. 
Published: September 2017

AbstractVariations of area-averaged annual balance can be calculated from sparse stake networks, if the specific balances satisfy a simple version of the linear model proposed by Lliboutry. The linear model is tested with 4 years of data at 13 stakes on Qamanârssûp sermia, West Greenland, and is satisfied with a model error of ±0.34 m water equivalent. From analyses of data from three stakes a few metres apart, the random error in the measurement of annual balance is estimated to be greater than ±0.23 m water equivalent. The variation in balance for the 4 years is ±0.52 m water equivalent which reflects the year–to–year variation in climate. The shortness of the present data series is admitted and its continuation is recommended.
Combined measurements of Subglacial Water Pressure and Surface Velocity of Findelengletscher, Switzerland: Conclusions about Drainage System and Sliding Mechanism
Authors: Iken Almut , Bindschadler Robert A. 
Published: September 2017

AbstractDuring the snow-melt season of 1982, basal water pressure was recorded in 11 bore holes communicating with the subglacial drainage system. In most of these holes the water levels were at approximately the same depth (around 70 m below surface). The large variations of water pressure, such as diurnal variations, were usually similar at different locations and in phase. In two instances of exceptionally high water pressure, however, systematic phase shifts were observed; a wave of high pressure travelled down-glacier with a velocity of approximately 100 m/h.The glacier-surface velocity was measured at four lines of stakes several times daily. The velocity variations correlated with variations in subglacial water pressure. The functional relationship of water pressure and velocity suggests that fluctuating bed separation was responsible for the velocity variations. The empirical functional relationship is compared to that of sliding over a perfectly lubricated sinusoidal bed. On the basis of the measured velocity-pressure relationship, this model predicts a reasonable value of bed roughness but too high a sliding velocity and unstable sliding at too low a water pressure. The main reason for this disagreement is probably the neglect of friction from debris in the sliding model.The measured water pressure was considerably higher than that predicted by the theory of steady flow through straight cylindrical channels near the glacier bed. Possible reasons are considered. The very large disagreement between measured and predicted pressure suggests that no straight cylindrical channels may have existed.
Changes in microstructure of snow under large deformations
Authors: Edens Michael Q. , Brown Robert L. 
Published: September 2017

AbstractA set of microstructural variables is selected to characterize the behavior of snow. Corresponding mathematical relations from quantitative stereology theory are presented along with relations and techniques required for numerical evaluation. An experimental investigation is carried out to determine changes in these variables for snow subjected to large compressive deformations. The micro-structural variables studied included coordination number, grain-size, bond radius, neck length, pore-size, free surface area and grains/unit volume. Measurements at several stages of deformation are used to evaluate the changes in the microstructure as functions of deformation. Microstructure measurements of six snow samples subjected to confined compression tests are presented for pre-compressed and compressed states, corresponding to final stresses of 0.387, 0.77 and 1.55 MPa. Grain-size and bond radius were found to go through finite changes during compression, although the variation of bond radius was more complicated in nature. The coordination number and number of bonds/unit volume were found to go through large changes during compression, while specific free surface area was found to increase by 100% due to grain- and bond-fracture processes. No discernible patterns of change in neck length could be found in the experiments. A close relationship between some of the microstructural variables and the stress response of the material was observed. These results serve to contribute to the presently available data and understanding of the microstructural behavior of snow.