bluuebunny/crossref_metadata_2025_split huggingface dataset:
Microwave emission from density-stratified Antarctic firn at 6 cm wavelength
Authors: West Richard D. , Winebrenner Dale P. , Tsang Leung , Rott Helmut 
Published: September 2017

AbstractPrevious observations have shown spatial covariances between microwave emission from Antarctic firn at 6 cm wavelength, physical firn temperature and firn-density stratification. Such observations motivate us to understand the physics underlying such covariances and, based on that understanding, to develop estimation methods for firn in which density, and therefore dielectric permittivity, varies randomly in discrete layers with mean thicknesses on the order of centimeters. The model accounts for depth profiles of the physical temperature, mean density and variance of random density fluctuations from layer to layer. We also present a procedure to estimate emission-model input parameters objectively from in situ density-profile observations, as well as uncertainties in the input parameters and corresponding uncertainties in theoretical brightness-temperature predictions. We compare emission-model predictions with ground-based observations at four diverse sites in Antarctica which span a range of accumulation rates and other parameters. We use coincident characterization data to estimate model inputs. At two sites, layered-medium emission-model predictions based on the most probable input parameters (i.e. with no model tuning) agree with observations to within 3.5% for incidence angles≤50°. Corresponding figures for the other two sites are 7.5% and 10%. However, uncertainties in the input parameters are substantial due to the limited length and depth resolution of the characterization data. Uncertainties in brightness-temperature predictions are correspondingly substantial. Thus brightness-temperature predictions for the last-mentioned sites based on only slightly less probable input parameters are also in close agreement with observations. The significance of agreements and discrepancies could be clarified using characterization measurements with finer depth resolution.
Internal and basal ice changes near the grounding line derived from radio-echo sounding
Authors: Uratsuka Seiho , Nishio Fumihiko , Mae Shinji 
Published: September 2017

AbstractEvidence of changing basal and internal ice properties near the grounding line was derived from airborne radio-echo-sounder observations of the ice sheet around the Sør Rondane Mountains, Antarctica. From the trailing figure of the bottom-echo signal, the roughness of the ice bottom near the grounding line was inferred. Results show that the specular components of scattering begin to appear on the ice-shelf side of the grounding line. Furthermore, double-trip echoes were observed with a strong scattering in the shelf area, and their boundary of occurrence was very close to the grounding line. This is evidence of interaction between ice and sea water at the bottom of the ice shelf. We also examined the occurrence of internal layered echoes. In most of the area around the mountains, internal echoes were observed continously, but they were not found at or close to the ice shelf. The boundary between the appearance and disappearance of internal-layer echoes is distinct, and occurs 20–30 km inland from the grounding line. These results suggest that some major change may occur in the internal ice on the inland side of the grounding line.
Quiescent-phase evolution of a surge-type glacier: Black Rapids Glacier, Alaska, U.S.A.
Authors: Heinrichs T.A. , Mayo L.R. , Echelmeyer K.A. , Harrison W.D. 
Published: September 2017

AbstractBlack Rapids Glacier, a surge-type glacier in the Alaska Range, most recently surged in 1936–37 and is currently in its quiescent phase. Mass balance, ice velocity and thickness change have been measured at three to ten sites from 1972 to 1994. The annual speed has undergone cyclical fluctuations of as much as 45% about the mean speed. Ice thickness and surface slope did not change enough to cause the speed fluctuations through changes in ice deformation, which indicates that they are being drinven by changes in basal motion. The behavior of Black Rapids Glacier during this quiescent phase is significantly different from that of Variegated Glacier, another well-studied surge-type glacier in Alaska. The present medial-moraine configuration of Black Rapids Glacier indicates that a surge could occur at any time. However, ice velocity data indicate that the next surge may not be imminent. We belive that there is little chance that the next surge will cross and dam the Delta River.
Surface morphology and backscattering of ice-ridge sails in the Baltic Sea
Authors: Manninen A. T. 
Published: September 2017

AbstractThe triangular shape of an ice-ridge sail in the Baltic Sea was studied statistically. The dimensions and orientation of individual ice blocks were measured in several ridges. All measurements were carried out from the standpoint of backscattering research. The results confirm that given geometrical properties of the two sides of ice ridges are in general not equal. A slight negative correlation was found between the slope angle and width of the sail. All three orientations and all three size parameters of ice blocks on both sides of the ridges studied can be considered as normally distributed. A log-normal distribution, however, fits slightly better the dimensions of the orientationally best rectangular approximations of the polygonal main facets of flat ice blocks. Three-dimensional modelling of ice ridges is essential, since the total side-facet area visible is typically at least as large as the total main-facet area. Calculated incidence-angle distrubutions show that the broad distributions of orientations and dimensions make different redges appear very similar on radar images.
Observations of pressure effects on the creep of ice single crystals
Authors: Cole David M. 
Published: September 2017

AbstractExperiments performed on ice single crystals oriented for basal slip indicate that the steady-state creep rate is only marginally affected by confining pressure up to 19 MPa, at a constant absolute temperature of 263 K. The observations Contradict earlier work at similar pressures and the disparity is examined in terms of experimental errors.
Sampling-rate effects on the properties of dye breakthrough curves from glaciers
Authors: Nienow Peter W. , Sharp Martin , Willis Ian С. 
Published: September 2017

AbstractDye-tracer techniques are widely used in infer the character of subglacial drainage systems. Quantitative analysis of dye breakthrough curves focuses on the determination of the water through flow velocity (u), the dispersion coefficient (D) and the dispersivity parameter (d = D/u). Together, these parameters describe the rate of passage of tracer through the drainage system and the extent to which the dye cloud becomes spread out during passage. They have been used to infer the nature of flow conditions within a drainage system and temporal changes in system morphology. Estimates of all three parameters, however, are dependent upon the sampling interval at which measurements of dye concentration used to define breakthrough curves are made. For a given breakthrough curve, the dispersion coefficient increases with the sampling interval, while the through flow velocity shows no systematic variation. As a result, the dispersivity also tends to increase with the sampling interval. Investigations of the sensitivity of parameter estimates to the sampling interval reveal that reliable estimates can be obtained only if the sampling interval is less than 1/16 of the time from dye injection to peak dye concentration. As a general guide, we Suggest that, ideally, quantitative analyses of dye breakthrough curves should therefore be conducted only when this criterion can be met.
A Further Comparison of Glacier Velocities Measured by Radio-echo and Survey Methods
Authors: Doake C. S. M. , Gorman M. , Paterson W. S. B. 
Published: September 2017

AbstractA comparison has been mager between ice velocities that were measured by the radio-echo technique and by a survey method on the Devon Island ice cap, Arctic Canada (lat. 75° 23' N., long. 82° 23'W.). Results were 2.58±0.11 ma1 by radar and 2.17±0.20 m a–1 by survey. The discrepancy between the two measurements is within the limits of statistical significance, and the methods are consigerred to give comparable results.
Ice and Ocean Tilt Measurements in the Beaufort Sea
Authors: Weber J.R. , Erdelyi M. 
Published: September 2017

AbstractDuring the AIDJEX pilot study 1972 in the Beaufort Sea, the tilt changes of the fluid ocean surface and of the sea ice were measured with a hydrostatic level. Preliminary results indicate a tilt range of ± 5 μrad for the water surface and of ± 30 (μrad for the sea ice. The tilt change of the sea ice Δ δ appears to be directly proportional to the component of the velocity change of the ice drift parallel to the hydrostatic level ΔUd, according to the relationship Δ δ = 180ΔUdμrad m-1 s. It is conclugerd that the ice tilt is wind induced, and that the ice sheet tilts downward in the drift direction as a result of the moment exerted on it by wind and water drag. It is postulated that this tilt causes the ice to break at right angles to the drift direction. The tilt is a function of the length of an ice floe (or of the unbroken distance between two cracks), of the average ice thickness, of the average drag coefficients, and of wind and current velocities. Calculation of the ice tilt using a simple mogerl of a floating, rigid ice slab gives values which are very much smaller than the observed tilts. If the discrepancy between theory and observation can be resolved, or if an empirical formula between wind velocity and tilt angle can be gerduced freom continuous tilt observations which will be carried out during the AIDJEX main experiment, it will be possible, for a given wind, to estimate the maximum length of an unbroken ice sheet freom its estimated thickness, drag coefficients, and tensile strength. It should also be possible to calculate the average drag coefficients of a freee-floating ice pan, or of an ice island, freom tilt, wind, and current measurements. The curious relationship between tilt angle and atmospheric pressure gradient that Browne and Crary observed on the ice island T-3 in 1952 is explained as being the wind-induced tilt of the ice island rather than that of the fluid ocean surface.
The Maximum Extent of Glaciers in Part of West Falkland
Authors: Clapperton C. M. , Suggern D. E. 
Published: September 2017

AbstractAlthough it is known that cirque glaciers once existed in the Falkland Islands, it has remained in doubt whether or not the islands were ever covered by ice caps or an ice sheet during the Cainozoic. This paper scrutinizes geomorphological evigernce on the south-eastern flank of a high massif in West Falkland. It is suggested that, at the time of their maximum extent in the Cainozoic, the largest glaciers were no more than 2.7 km long.
The Freeezing behaviour of Supercooled Water Drops
Authors: Gay M. J. , Latham J. 
Published: September 2017

AbstractAn electrodynamic containment system has been used to study the freeezing behaviour of supercooled water drops, of radius range 25 to 90 μm. The drops were freozen at temperatures between 0 and — 29°C in an environment whose relative humidity was approximately 90% with respect to ice. Freezing events were observed visually and photographically, and measurements were mager of the accompanying freactional mass loss Δm/m.The most common moger of freeezing (70% of the drops studied) resulted in an apparently spherical ice particle. However, 18% exhibited spikes or other protuberances and the freeezing of 3% was accompanied by the ejection of numerous ice particles. In each of these situations values of Δm/m ranged freom about 5 to 15%. A further 9% of the drops exhibited one or more secondary mass-loss events, occurring several seconds after the freeezing process was complete; these were thus indicative of the ejection of ice particles.Almost all of the values of Δm/m were significantly in excess of those predicted on the basis of evaporation during freeezing, suggesting that an additional mechanism of mass loss was also present. The measured freeezing times were consigerrably shorter than the classical values—at least, for the larger drops freeezing at warmer temperatures. Some visual observations were consistent with the “supersaturation wave” around a freeezing drop, which has been predicted by Nix and Fukuta (1974).
The Freeezing of Small Tyndall Figures in Ice
Authors: Mae Shinji 
Published: September 2017

AbstractTyndall figures, small thin discs of liquid water containing a vapour cavity, were formed in the centres of grains of pure, polycrystalline ice and observed while freeezing and growing. The freeezing experiments showed that the rate of gercrease in the radius of a Tyndall figure does not gerpend upon the radius of the figure, but does gerpend upon the thickness, h. Below a transition thickness, h = 12 μm, the rate of gercrease of the radius varied with h−2; above ht, with h−1. For growing figures the transition thickness was htg ≈ μm and was defined in such a way that when h > tg perturbations with wavelengths greater than 102 μm formed on the siger faces of the Tyndall figures.
Extraction of Trace Components from Large Quantities of Ice in Bore Holes
Authors: Oeschger H. , Stauffer P. , Bucher P. , Moell M. 
Published: September 2017

AbstractA melting probe system has been gerveloped which can be lowered down to 400 m in an ice bore hole of 135-165 mm diameter. At the gersired gerpth, a section of the bore hole is isolated and evacuated. Afterwards several tons of ice are melted under vacuum with an electrical heater. The inclusions which are principally gaseous, may be collected both during or after the melting procedure. The application of this system is mainly in the field of dating polar ice by radio-active isotope analysis.
A Method of Concentrating the Major Impurities Contained in Ice by Ion Exchange
Authors: Ricq-de Bouard M. 
Published: September 2017

AbstractThis note gerscribes a method for concentrating Na, K, Ca, and Mg impurities in samples of snow and ice for analysis by atomic absorption in flame photometry. The cations are fixed on a Dowex 50 ion-exchange resin then selectively released and separately analysed by atomic absorption. This method allows the simultaneous treatment of a large number of specimens with concentration factors which can reach 60 to 75 and with very low risk of contamination or loss of the specimens.
The Quantity of Melt Water in the Marble Point–Gneiss Point Area McMurdo Sound, Antarctica
Authors: Davis John R. , Nichols Robert L. 
Published: September 2017

Among the important factors in the formation of melt water are: (1) The air and soil temperatures. (2) The presence or absence of debris on snow and ice. (3) The surface gradients of the glaciers. These gradients determine the areas of snow and ice in the zone where melting can occur as well as the amount of insolation. (4.) The orientation of snow and ice slopes. In general, in the Southern Hemisphere north-facing slopes receive more insolation than south-facing slopes.The main source of the melt water is Wilson Piedmont Glacier, and the snowdrift-ice slabs are next in importance. The seasonal snowfall is not an important source, nor is the ice in the active zone. As no rain has ever been reported, all run-off is melt water.The seasonal discharge of the Surko and Scheuren Rivers was roughly measured in 1957–58. It was found to be approximately 13 m3 s−1 d for the Surko River and approximately 19 m3 s−1 d for the Scheuren River, and it seems likely that the total seasonal discharge of all streams in the area was not far from 50 m3 s−1 d.
Ice-Fabric Study of the Mawson Region, East Antarctica
Authors: Kizaki K. 
Published: September 2017

Attempts are made to test the relation predicted by Brace (1960) between strain-rates and the ice-fabric patterns obtained at Mawson station, east Antarctica. These orientation fabrics not only are hardly related to the prediction by Brace (1960) or Kamb (1959) but also change easily within a strain grid with 100m diagonals.Stable patterns of two- and three-maximum fabrics are confirmed. The latter is common and stable in the coarse ice at the surface of the ice sheet. It is apparent that the fabric patterns are generally related to the grain-size. The single-maximum fabric always occurs in fine-grained ice, then more maxima are formed in the course of grain growth.It appears that syntectonic-secondary recrystallization is effective in producing the orientation fabrics with two, three and multiple maxima. Also, the maxima always shift away from the pole of foliation as grain-size increases and there are several stable positions of maximum such as 0°, 17°, 23° and 30°. It is expected that further stable angles would occur with coarser crystals as found in temperate glaciers.
On the Use of Asymptotic Solutions to Plane Ice—Water Problems
Authors: Lock G. S. H. 
Published: September 2017

The paper considers one-dimensional freezing and thawing of ice–water systems for the conditions first examined by Stefan. An order-of-magnitude analysis applied to the governing equations and boundary conditions quantifies the error resulting from the neglect of various factors. Principal among these are density difference, initial superheat and variable properties.Asymptotic solutions for the temperature distribution and interface history are developed for a wide range of boundary conditions: prescribed temperature or heat flux, prescribed convection and prescribed radiation. Comparison with known results reveals the general adequacy of the asymptotic solutions and an estimate of the error incurred.
Radio Echo Sounding of Horizontal Layers in Ice
Authors: Harrison C. H. 
Published: September 2017

Radio echo-sounding surveys of Antarctica and Greenland have revealed extensive layering within the ice. Formulae for the effective reflection coefficient, when viewed by a pulsed radar, are derived for isolated or multiple randomly spaced layers. In the latter case the variation in dielectric constant with depth is described by a vertical autocorrelation function and a standard deviation. Some measurements of the reflection coefficient of layers, and the dielectric absorption of ice are given. The significance of the fading of layer echoes and the possible causes of variations in the dielectric constant are considered and some further investigations are suggested.It is concluded that the echo strengths found in the Antarctic may be explained by multiple layering, and that the necessary fractional change in the dielectric constant may be as small as 10−4. It is suggested that this change in dielectric constant may be due to differences in orientation of anisotropic ice crystals.
Subglacial Cavitation Phenomena Under the Glacier D’Argentière, Mont Blanc, France
Authors: Vivian Robert , Bocquet Gerard 
Published: September 2017

The works undertaken on the Glacier d’Argentière in order to divert the subglacial stream, have allowed access to several natural cavities which correspond to places where the glacier loses contact with its rock bed. These cavities show a certain number of original phenomena both on the rock bed and also on the ice arch. Studies of the basal ice layer reveal peculiar characteristics which distinguish it from the rest of the ice mass: lamination, interstratification of ice containing sand with pure ice, crystallographic composition, and specific chemical composition.The sliding speeds of the glacier are variable, and an increase in the friction below these cavitations is at the origin of a form of regressive glacial cavitation. The subglacial cavities are grouped together in a network transverse to the direction of glacier flow; they are interconnected by channels which are more or less open which allow proper thermal exchanges to be established and favour sliding.
On the Formation of Small Marginal Lakes on the Juneau Icefield, South-Eastern Alaska, U.S.A.
Authors: Seppälä Matti 
Published: September 2017

AbstractThis paper puts forward an explanation of the origin of small marginal lakes (superglacial or moat lakes) occasionally found on the edges of valley glaciers. The explanation departs from earlier theories. On the basis of observations made on the Juneau Icefield in south-eastern Alaska, I have come to the conclusion that the lake basins are primarily blow-outs formed as a result of wind erosion.
Short-Term Snow Melt and Ablation Derived from Heat- and Mass-Balance Measurements
Authors: Föhn Paul M. B. 
Published: September 2017

AbstractThe daily snow melt calculated from meteorological observations is compared with detailed mass-balance measurements taking into account internal changes in density and free water content in the surface layers of a glacier snow-pack. The energy balance is calculated from measurements obtained by a meteorological station at the experimental site. In addition to the standard ablation measurements the run-off from the melting snow-pack was obtained for a few days. The snow-density profiles were measured with a portable gamma-transmission probe and the liquid-water content of snow was determined by a calorimetric method.Agreement between the melt calculated by the heat-balance method and the mass changes observed in the mass-balance measurements is fair for daily periods. It appears that about 20% of the daily snow melt takes place internally as a result of penetration of solar radiation.
Lichen Growth on an Active Medial Moraine, Jotunheimen, Norway
Authors: Matthews J. A. 
Published: September 2017

AbstractAbundant specimens of lichens, includingRhizocarpon geographicum, are reported from an active medial moraine on Storbreen, southern Norway. The size and distribution of two crustose and two foliose species are described. Inferences are made regarding the age, origin and population dynamics of the lichens. Some implications of the observations for lichenometric dating and use of lichens as indicators of moraine stability are discussed.
Instruments and Methods Comparison of the Snow Resistograph with the Ram Penetrometer
Authors: Lawrence William St. , Bradley Charles C. 
Published: September 2017

AbstractComparative tests of the snow resistograph with the ram penetrometer indicate that there is a high degree of correlation between the two instruments despite fundamental differences in operation. It is probable therefore that the two instruments are measuring essentially the same parameters and may be used interchangeably. The resistograph has a large advantage over the ram penetrometer, in terms of speed and ease of operation, and in its capacity to measure the strength of very weak snow.
A Comparison of the Energy-Balance and Bulk-aerodynamic Approaches for Estimating Glacier Melt
Authors: Hay J. E. , Fitzharris B. B. 
Published: September 2017

AbstractTwo models that estimate glacier ablation from simple meteorological observations are described. Both the energy-balance and bulk-aerodynamic approaches are used to determine the bulk-exchange coefficient for transfer of sensible- and latent-heat energy to the melting ice surface from 17 summer days of measurement on Ivory Glacier, New Zealand. The behaviour of the coefficient is examined over progressively increasing time intervals and as a function of wind speed and gradient, and of atmospheric stability. The models are verified with 36 d of independent data from a different summer on the same glacier. The more accurate short-term estimates of ablation are obtained using the energy-balance approach with empirically but independently derived values of the exchange coefficient.