bluuebunny/crossref_metadata_2025_split huggingface dataset:
Glaciological Problems Set by the Control of Dangerous Lakes in Cordillera Blanca, Peru. I. Historical Failures of Morainic Dams, their Causes and Prevention
Authors: Lliboutry Louis , Morales Arnao Benjamín , Pautre André , Schneider Bernard 
Published: September 2017

AbstractThe retreat of glaciers since 1927 in Cordillera Blanca has produced dangerous lakes at the front of many glaciers. All the known data, most of them unpublished, are reviewed. The knownaluvionesare listed, and those of Chavin, Quebrada Los Cedros and Artesoncocha described in full. In these three cases a breach in the front moraine came from big ice falls into the lake. The protective devices made on the outlets are described, as well as the effects of the big earthquake on 31 May 1970. In the case of Laguna Parón, which keeps its level thanks to infiltrations, the fluctuations of the discharge of the springs as related to the level of the lake from 1955 to 1969 are reported. The projects for lowering the level of Laguna Parón and for emptying Safuna Alta are described. The latter partially emptied in fact by piping after the earthquake, allowing a final solution.
An Error in Ice-Temperature Measurement
Authors: Sanderson T. J. O. 
Published: September 2017

AbstractAn analysis is made of the disturbance in conductive heat flow caused by drilling a bore hole in ice in which there is a vertical temperature gradient. The model used is that of a perfectly insulating hole placed in a linear temperature gradient; it is shown that the temperature measured at the bottom of the hole deviates from its value before drilling by an amount of order —0.6aU where a is the bore-holt radius and U is the temperature gradient. The deviation takes effect in a few hours. The error is typically between 0.005 and 0.1 deg and is therefore significant only where very high accuracy is required. It should not be present in temperate glaciers, nor where the thermometer is properly frozen in, nor if temperatures are measured at the bore-hole walls far above the bottom.
A Comparison of the CRREL 500 cm3 Tube and the ILTS 200 and 100 cm3 Box Cutters Used for Determining Snow Densities
Authors: Carroll Tom 
Published: September 2017

AbstractThe study indicates that no significant difference in snow densities is found when using either the CRREL tube or the ILTS box cutters. However, inexperienced workers tend to overestimate snow densities in light snow and depth hoar by 6 and 4% respectively.
Radio-Echo Sounding: Reflections From Internal Layers In Ice Sheets
Authors: Clough John W. 
Published: September 2017

AbstractThe origin and nature of radio-echo internal reflections is the subject of much debate. Calculations of single- and multiple-layer reflection coefficients for dielectric changes in the ice sheet indicate that the observed reflection strength may result from reflections from many thin layers but the zone of thin layers may best be approximated by replacing the zone with a single thicker layer with average dielectric properties. Calculation of reflections from density changes, dust and dirt bands and anisotropy of ϵ indicate density variations as the most likely cause of the internal layering in the uppermost kilometer of ice sheets. Comparison of the depth of internal reflections at “Byrd” station, Antarctica, with the physical properties of the ice measured in a deep core hole at that location support this conclusion.
Electrical Resistivity Measurements On The Ross Ice Shelf
Authors: Bentley Charles R. 
Published: September 2017

AbstractElectrical resistivity measurements were made along two perpendicular profiles on the Ross Ice Shelf, Antarctica, in 1973–74. Apparent resistivities are generally well determined at electrode separations from 10 m out to 600 m, where the effect of the highly conducting sea-water beneath the shelf becomes strongly fell. Schlumberger and equatorial-dipole data are in excellent agreement on each profile; apparent resistivities on the two profiles, however, differ by about 12% at separations greater than about 30 m. This apparent anisotropy is attributed to a presumed inhomogeneity at a few tens of meters depth, rather than to true anisotropy in the bulk resistivity.A computer program has been developed to calculate apparent resistivities on an ice shelf in which the density and temperature, and thus the resistivity, vary continuously with depth. Temperatures have been calculated according to the analysis of Crary (1961 [b]) for a steady-state ice shelf; densities have been calculated from seismic velocity data. Several different models of the dependence of resistivity on density have been tested—one appears to fit the observations very closely, but it must be accepted only with great caution because the assumptions on which it is based are violated in the ice shelf.The activation energy and the rate of bottom melting or freezing upon which the temperature-depth variations depend have been treated as variable parameters in the modeling. The most satisfactory model corresponds to a melt/freeze rate close to zero, and an activation energy, 0.25 eV (24 kJ mol−1), in agreement with laboratory measurements on Antarctic ice samples, although less than that suggested by previous field measurements. However, since the actual temperatures in the ice shelf are unknown, models that combine a substantial melt rate with a higher activation energy, or a substantial freeze rate with a lower activation energy, cannot be ruled out at present. Future measurements in places where the temperature profile is known should resolve this uncertainty.The actual resistivity in the solid ice at a depth of about 100 m (temperature about —23°C), lies within ±10% of 70000 Ω m, thus once again confirming the very low resistivities typical of polar glacial ice. The resistivity is, in fact, only about half that found near Roosevelt Island to the north and “Byrd” station to the east. That difference is believed to be real, but its cause is not known and probably will not be known until the basic cause for the generally low resistivity of polar ice is better understood.
Statistical Forecasting Of Snow Avalanches, San Juan Mountains, Southern Colorado, U.S.A.
Authors: Bovis Michael J. 
Published: September 2017

AbstractMeteorological and snow pack variables are measured on chronologically ordered sequences of avalanche and avalanche-free days. Discriminant analysis is used to define a subset of variables which produce an optimal separation of the two multivariate group means. Two seasons are identified in each of the years considered corresponding to periods of dry- and wet-snow avalanches, and form the basic stratification of avalanche days in the analysis. Days are stratified further within each season on the basis of magnitude and number or releases. Weather and snow parameters are integrated over variable time steps prior to each avalanche or avalanche-free day. This introduces a recursive element into the forecast method. Preliminary testing of the method points to its potential in real-time snow avalanche forecasting on a regional basis.
Relocation Of Buried Markers
Authors: Mathews W.H. 
Published: September 2017

AbstractSuccess has been achieved in relocating wire netting, which was subsequently covered by a year’s net accumulation of snow on Berendon Glacier. A signal produced by a wire loop tuned to respond to a 15 kHz electromagnetic output was readily detected by a hand-held battery-powered electromagnetic detector. Sextant readings on fixed landmarks around the glacier aided in locating the search area.
Chemical Sorting Effect at the Base of an Alpine Glacier
Authors: Souchez R. A. , Lorrain R. D. 
Published: September 2017

AbstractA frozen mud layer plastered at the base of the Glacier d’Argentière in the Western Alps acts as an ion-exchange membrane for the interstitial water passing through it, causing electrolyte filtration and relative retardation of cations. This interstitial water, which is forced under a pressure gradient of about 3 bar cm−1, refreezes in the form of ice accretions.A comparison of the chemical composition of these ice accretions and water held at their surface (corresponding to the situation after the forcing) and the water in contact with the mud layer (corresponding to the situation before the forcing) shows a desalinating effect, a monovalent-divalent cation species separation, and a sorting effect between the alkalies as well as between the alkaline-earths. This phenomenon has to be taken into account in the study of the chemical composition of stratified ice containing interbedded mud layers which occurs in the basal part of several glaciers.
The Permittivity and Attenuation in Polycrystalline and Single-Crystal Ice Ih at 35 and 60 MHz
Authors: Johari G. P. , Charette P. A. 
Published: September 2017

AbstractThe relative permittivity ∊’ and attenuation α in laboratory-grown, polycrystalline and single-crystal ice Ih are reported at 35 and 60 MHz in the temperature range —25°C to — 0.2 ° C. The ∊’ and α at 35 MHz and — 1° C are 3.208±0.010 and 6.2±0.1 dB/100 m, respectively. From a comparison between the respective ∊’ and α of the polycrystalline and single-crystal ice measured perpendicular to the c-axis, it is concluded that any anisotropy of polarization at these frequencies is so small as to be undetectable. Amongst several factors that may contribute to anisotropy in ice, electronic polarization contributes 0.0037 to the difference between the relative permittivity measured parallel and perpendicular to the c-axis at — 1° C and at frequencies less than 500 THz.Experiments have shown that the plastic deformation resulting from a uniaxial compressive stress of up to 100 bar does not influence the ∊’ and α of ice at 35 and 60 MHz.
Observations on Ice-Dammed Summit Lake, British Columbia, Canada
Authors: Gilbert R. 
Published: September 2017

AbstractTesting of a water-balance equation for the Summit Lake basin in July and August 1968 indicated that, 2½ months before its fourth known draining, there existed a leak through or under the damming glacier that may have been as large as 3–5 m3/s. Lake temperatures recorded during the same period indicate water at 0.5–0.8°C near the ice dam and up to 2.6°C 4–5 km from the dam. These observations support the proposal of Liestøl (1956) and Mathews (in press) of tunnel enlargement by melting. It is calculated that lake water temperatures of 0.25, 0.9 and 0.15°C are required to account for the November 1965, September 1967 and November 1968 drainings, respectively.
Instruments and Methods: A New Version of a Steam-Operated Ice Drill
Authors: Hodge Steven M. 
Published: September 2017

AbstractA further development of the Howorka steam-operated ice drill is given. It is mounted on a pack frame for easy transportation in rugged terrain. A propane flame is used to vaporize water in a single-pass fire-tube boiler. The steam is delivered to the ice through a double-walled flexible hose and a straight guide tube with an exchangeable nozzle at the end. One hole, 25 mm in diameter and 8 m deep, can be drilled in 15 min; four such holes can be drilled with one tank of water and 10 with one tank of propane. Holes deeper than 16 m are impractical as heat losses in the hose become too large. Sturdy construction has been used and the drill has been tested and found to work satisfactorily under both temperate and arctic conditions.
Electronic Measurement of Ice Velocity
Authors: Harrison A. E. , Lee David 
Published: September 2017

AbstractA light-weight solid-state electronic distance meter was used to measure short-term ice velocities during a two-day interval on the Coleman Glacier at Mt Baker, Washington, U.S.A. The velocities fluctuated rapidly from zero or almost zero to a large fraction of a meter per day. There was little or no correlation between the movement at different stations and the fluctuations masked any diurnal variation if such existed. The ease of obtaining the results demonstrates the utility of the new equipment for extending the possibilities of glaciological research.
Movement of Water in Glaciers
Authors: Shreve R. L. 
Published: September 2017

AbstractA network of passages situated along three-grain intersections enables water to percolate through temperate glacier ice. The deformability of the ice allows the passages to expand and contract in response to changes in pressure, and melting of the passage walls by heat generated by viscous dissipation and carried by above-freezing water causes the larger passages gradually to increase in size at the expense of the smaller ones. Thus, the behavior of the passages is primarily the result of three basic characteristics: (1) the capacity of the system continually adjusts, though not instantly, to fluctuations in the supply of melt water; (2) the direction of movement of the water is determined mainly by the ambient pressure in the ice, which in turn is governed primarily by the slope of the ice surface and secondarily by the local topography of the glacier bed; and, most important, (3) the network of passages tends in time to become arborescent, with a superglacial part much like an ordinary river system in a karst region, an englacial part comprised of tree-like systems of passages penetrating the ice from bed to surface, and a subglacial part consisting of tunnels in the ice carrying water and sediment along the glacier bed. These characteristics indicate that a sheet-like basal water layer under a glacier would normally be unstable, the stable form being tunnels; and they explain, among other things, why ice-marginal melt-water streams and lakes are so common, why eskers, which are generally considered to have formed in subglacial passages, trend in the general direction of ice flow with a tendency to follow valley floors and to cross divides at their lowest points, why they are typically discontinuous where they cross ridge crests, why they sometimes contain fragments from bedrock outcrops near the esker but not actually crossed by it, and why they seem to be formed mostly during the later stages of glaciation.
A Model of a Surging Glacier
Authors: Brückl E. 
Published: September 2017

AbstractAs the cause of a surge we assume a sudden improvement of the sliding conditions at the glacier bed. This improvement has the same effect on the behaviour of the glacier as an equivalent variation of the annual balance. We are therefore able to apply Nye’s (1963) theory of the advance and retreat of glaciers to our problem. A simple glacier model discussed in this theory shows as a consequence of an improvement of the sliding conditions, an additional discharge of ice, which can be separated in two phases. The first phase of strong motion yields a transport of ice from the upper to the lower part of the glacier. The ice essentially remains within the previous limits of the glacier. The sequence of motion during this phase corresponds to a surge. The second phase of motion is essentially slower. During this phase the ice accumulated in the lower part of the glacier flows beyond the previous limits, till the whole surface level is lowered.
Periodic Surge Origin of Folded Medial Moraines on Bering Piedmont Glacier, Alaska
Authors: Post Austin 
Published: September 2017

AbstractThe vast Bering piedmont glacier, which has large folds in the medial moraines in its terminal lobe, recently experienced two surges with a combined ice displacement of as much as 13 km. Vertical aerial photographs taken before and after the surges disclose the direction and magnitude of ice flow in various parts of the piedmont lobe. The ice moved toward the terminus and expanded in a normal, radial pattern with no evidence of unusual shearing that would result in the formation of large folds. Many surging glaciers display repeated lateral displacements in their medial moraines which result from periodic surging of the main glacier past non-surging tributaries. Moraines of Bering Glacier display small periodic irregularities of this nature. The large “accordion” folds in the moraines in the piedmont lobe are judged to be due to the combined effects of compressive flow and lateral or transverse expansion of these previously formed irregularities. The initially small pre-existing perturbations in the moraines are simply spread laterally and shortened radially into large folds as the ice spreads out.A very large debris band composed of repeatedly folded medial moraines extends across the center of the Bering Glacier lobe. These remarkable folds are thought to result from the deformation of surge-related irregularities in medial moraines as they pass through the zone of intensive shear near the glacier’s margin.
Survey of the Rusty Glacier Area, Yukon Territory, Canada, 1967–70
Authors: Collins S. G. 
Published: September 2017

AbstractA study of the movement of Rusty Glacier was undertaken and continued through four summers because it is believed to be a surging glacier in the last stages of the inactive phase preceding a surge. The entire glacier is very slow moving, essentially motionless in the lower third and most rapid in an area well above the firn line. Unusually steep flow-line emergence angles and higher than average longitudinal compression rates in the lower–middle part of the glacier indicate gradual thickening of the ice above the stagnant lower tongue. There is no clear correlation between local variations in flow rates and surface or bottom topography. The glacier is mostly colder than 0° C to the bottom, and in the one known area of 0° C bottom temperature, flow rates are not greater than elsewhere. Although the glacier is everywhere very thin, maximum flow rates seem clearly related only to variations in ice thickness. The nearby Trapridge Glacier is also a surging glacier and exhibits a strikingly similar flow pattern.
Electronic Detection of Serac Avalanches and Glacier Noise at Vaughan Lewis Icefall, Alaska
Authors: Pinchak Alfred C. 
Published: September 2017

AbstractDesign details of a portable, light-weight, seismic recording system are presented together with data concerning sensitivity and frequency response. Field procedures and methods are described with emphasis on coupling the hydrophone detector to waves propagating in the glacier ice. Two of the field-recorded signals are reproduced here: the first resulted from a small serac avalanche in the ice fall and the second was produced by an unusual, local source of glacier noise.
The Decay of an Annual Cover of Sea Ice
Authors: Langleben M. P. 
Published: September 2017

AbstractIn his now classic book L’dy Arktiki [Arctic ice], Zubov discussed the melting of sea ice during the Arctic summer by thermal interaction with the surrounding water and derived an expression which indicates that the proportion of open water increases exponentially with time until total ice-free conditions result. His equation predicts that the time required for complete decay of the ice cover after initial break-up is greater than one month and more likely as long as two months for representative values of incident shortwave radiation and initial ice thickness upon break-up. It is unlikely that above-freezing temperatures persist for this length of time.To explain the observed complete disintegration of the annual ice cover in many sheltered areas of the Arctic, a modified model of the thermal decay process has been introduced. This model takes into account the influence of radiation absorbed by the ice which was not included in the Zubov formulation. Considerable reduction in the time required for complete decay, generally by about a factor of 2 if an albedo of 0.4 is assumed for the ice surface, is obtained.
Equation of Isotope Fractionation Between Ice and Water in A Melting Snow Column with Continuous Rain and Percolation
Authors: Búason Thorvaldur 
Published: September 2017

AbstractPartial differential equations are derived to describe isotope fractionation between ice and water phases in temperate snow caps and glaciers. Numerical solutions are obtained and shown to be consistent with laboratory experiments and measurements of deuterium concentrations in temperate glaciers. The process of isotope fractionation as described is manifested by application of the model to tritium fractionation in temperate snow caps.
A Quantitative Assessment of Dirt-Cone Dynamics
Authors: Drewry David J. 
Published: September 2017

AbstractQuantitative investigations have been made of ice-cored dirt cones on Bersaerkerbræ in north-east Greenland. Experiments were also undertaken to evaluate field observations. Measurements included: maximum cone dimensions, sediment thickness and particle size, cone growth rates, slope angles and the temperature distribution within the debris layer and ice core. Particle size, which has not been stressed in previous studies, and related liquid consistency limits, appear as the dominant controls in cone formation, independent of debris thickness within the observed range of 10 mm to 125 mm. A threshold grain-size for dirt-cone inception was found, between 0.2 mm and 0.6 mm. The growth of cones was usually not more than 50% of the ablation over “clean” ice. Temperature measurements within dirt cones has enabled heat-flow studies to be made, evaluating the thermal conductivity of a sediment layer and the heat transfer involved in melting the ice core. A simple model of dirt-cone dynamics is proposed, characterized by negative feedbacks and describing a steady-state system.
A System to Combine Stratigraphic and Annual Mass-Balance Systems: A Contribution to the International Hydrological Decade
Authors: Mayo Lawrence R. , Meier Mark F. , Tangborn Wendell V. 
Published: September 2017

AbstractMass-balance quantities at specific points on a glacier as defined in [IHD] (1970) relate either to annual maxima or minima in ice mass at that point (the stratigraphic system), or to values at the beginning and end of a hydrologic year (the annual or fixed-date system). Most quantities measured in the field relate to summer surfaces, which correspond to the annual minima at the measurement points. When stratigraphic system point values are integrated over a whole glacier, the result may be meaningless because annual maxima and minima and summer surfaces may form at different times at different places.The combined system utilizes several kinds of data to derive meaningful area-average results that can be directly related to other hydrologic and meteorologic information. Measurements to summer surfaces at certain specific times, including the beginning and end of a hydrologic year, are added together with proper recognition of the types of material involved: old firn and ice, snow and superimposed ice of the year under study, new firn formed during that year, and late snow deposited toward the end of the year. Other “balance increment” terms relate values at the beginning and end of a hydrologic year to corresponding area-average balance minima. As a result, two types of “net balance” and many other terms are given precise meaning for a glacier as a whole. The scheme is sufficiently versatile to be used on any glacier, although the terms relating to summer surfaces are not defined on a glacier in which ablation or accumulation is continuous throughout a year.