bluuebunny/crossref_metadata_2025 huggingface dataset:
Climatic Inferences from Former Glaciers in the South-East Grampian Highlands,
Scotland
Authors: Sissons J. B. , Sutherland D. G.
Published: September 2017

Altitudes, lengths, areas, maximum thicknesses and volumes of 27 glaciers that built up
in a small area of the Scottish Highlands during the Loch Lomond (Younger Dryas) stadial are
given. The influence of direct radiation on the glaciers is calculated taking into account
transmissivity of the atmosphere, glacier aspect and surface gradient, and the albedos of ice
and snow. Equilibrium firn lines for the glaciers are determined. The computed regional firn
line, incorporating the influence of direct radiation had a gradient of 14.5 m/km. Former
precipitation values are based on an equation for average annual mass balances of the glaciers
during the stadial that incorporates glacier altitude, regional ablation gradient, direct
radiation, the influence of avalanching and blowing of snow, and final glacier volume. Average
July and January sea-level temperatures of 6°C and at least — 8°C, respectively, are inferred.
Snowfall was principally associated with south-east winds and was similar in total to present
day but rather differently distributed. Cloud amounts, at least in summer, were greater than
now. A more vigorous atmospheric circulation with many depressions moving along more southerly
tracks than now may have been related to the junction of polar water and North Atlantic Drift
water in the immediate vicinity of the British Isles.
Automated Seismic Monitoring System for Lake Michigan Ice Studies
Authors: Taylor R.W. , Kovach J.P. , Lasca N.P.
Published: September 2017

A simple, relatively inexpensive system for signal recovery in retrospect was designed
to record lake-ice seismic events. The system is broad-band, D.C. to 100 Hz, light-weight and
may be added to any existing data-acquisition equipment. The system may be used ( 1 ) to
initiate high-speed paper recordings in the field, (2) to store transient events on magnetic
tape while in the field, or (3) for the unattended laboratory-recovery of transient events
from a continuous field recording. Continuous, high-resolution, broad-band recordings of
seismic events occurring in lake ice over a period of weeks may be stored on a single reel of
magnetic tape. The initial cost of the device is rapidly equaled by the savings in tape cost
and man hours expended in signal recovery.
Phase Relationships in Sea Ice as a Function of Temperature
Authors: Richardson C.
Published: September 2017

Quantitative measurements of the liquid water phase in a sample of sea ice were made with a nuclear magnetic resonance spectrometer. The measurements are used to compute the phase relationships in sea ice as a function of temperature. A model for sea-water based upon a mixture of seven binary salts is used for these computations. The n.m.r. measurements are related to the solvation water which is associated with each binary salt. This solvation water is bound to the salt in a pseudo-crystalline structure, with the amount of water determined by the eutectic concentration of the salt. The results are given in tabular form and differ somewhat from previously published tables. Two controversial hydrated salts were added to the table, based on the n.m.r. data.
Radio-Echo Power Profiling
Authors: Neal C. S.
Published: September 2017

A method of continuously recording the r.f. power returned from a sub-glacial ice/rock or ice/water interface is described. Illustrations of the records produced are given and their relevance to the reconstruction of the small scale roughness of a reflecting surface is discussed.
Origin of Foliation in Glaciers
Authors: Leb. Hooke Roger , Hudleston Peter J.
Published: September 2017

Laboratory studies suggest that neither bubbles nor dirt particles migrate rapidly enough in glacier ice to be responsible for the alternating layers of bubbly and clear ice or dirty and clean ice which constitute foliation. We therefore suggest that these variations in bubble or dirt content are inherited from primary inhomogeneities such as may occur in sedimentary stratification in the accumulation region, in crevasse fillings, or during debris entrainment at the base of the glacier: the appearance of these inhomo-geneities is later modified by strain during flow to produce foliation. We consider six types of inhomogeneity, or components of foliation, and show that, at the very large total strains expected in glaciers, all are eventually flattened, stretched out, and rotated to form a layered structure roughly perpendicular to the direction of maximum total shortening. Most characteristics of observed foliation can be explained by this hypothesis. For example, in the marginal zones of polar ice sheets the rapid decrease in dip of foliation with depth and with distance up-glacier from the margin can he explained by a model in which the foliation is assumed to be nearly parallel to the base of the glacier some distance from the margin, and is deformed passively with the ice thereafter. However, some observations of cross-cutting foliations may require localized inhomogeneous shear parallel to the "new" foliation.
Dielectric Behaviour of Disperse Ice Microcrystals in The Frequency Range 105 to 10-2 Hz
Authors: Lafargue C. , Bourgeois C. , Evrard G.
Published: September 2017

Dielectric properties of ice microcrystals have been studied in the frequency range 3 x 105 to 10-2 Hz. Two separated dispersions are revealed : the Debye dispersion of ice and another dispersion at very low frequencies. Both dispersions present an ageing effect, with decreasing activation energy for the Debye dispersion and with increasing activation energy for the second one. It is shown in this paper that the sum of these activation energies retains a constant value of (1.05±0.02) eV.
Former Ice Shelves in the Canadian High Arctic
Authors: England John , Bradley R. S. , Miller G. H.
Published: September 2017

Moraines deposited by the outermost ice advance across Judge Daly Promontory, northeastern Ellesmere Island, reflect thin, topographically controlled ice lobes extending to sea-level. The termini of two ice lobes were investigated and both produced ice shelves where they flowed into isostatically depressed embayments along western Kennedy Channel. Morphological evidence for these ice shelves occurs at the entrance to these valleys where steeply descending lateral moraines become abruptly horizontal for 2 km. In addition, both the horizontal moraines and associated pro-glacial terraces are fossiliferous down-valley from the apparent grounding line. Based on the differences in elevation between the horizontal moraines and the valley bottoms, the two ice shelves had estimated thicknesses ofc. 110 and 150 m. A proglacial outwash terrace at 175 m a.s.l. is considered to represent the approximate relative sea-level during the formation and break-up of the ice shelves. This relative sea-level is consistent with the water depths required to float the calculated ice thicknesses in both valleys. Associated with these ice margins are finite14C dates of 28 000-30 000 B.P. and amino-acid age estimates of >35 000 B.P. The importance and likelihood of additional past ice shelves in the Canadian High Arctic is discussed.
An Investigation into the use of Strain Rosettes for the Measurement of Propagating Cyclic Strains
Authors: Squire Vernon A.
Published: September 2017

An investigation into the feasibility of using a strain rosette to measure the principal strains and to locate the principal axes for a propagating strain wave is carried out for the particular application of a flexural-gravity wave in sea ice. It is found that the separation of the instruments in the rosette is extremely critical and, for a physically realizable rosette, errors are unavoidable if strain is to be monitored continuously. An alternative approach is proposed employing frequency-domain analysis and in particular a running-power spectral density. The method is demonstrated with data obtained from strainmeters on fast ice in Notre Dame Bay, Newfoundland. Two distinct wave components are found to be present of period 6 s and 13s. and it is shown with 99.9% confidence that they are propagating in different directions.
Accumulation, Ablation, and Oxygen Isotope Variations on the Queen Elizabeth Islands Ice Caps, Canada
Authors: Koerner R. M.
Published: September 2017

Measurements made on traverses over ice caps in the Queen Elizabeth Islands show that there is a region of very high accumulation (>40 g cm–2 year–1) on the slopes facing Baffin Bay and one of low accumulation (<15 g cm–2 year–1) in the interior parts of northern Ellesmere Island. Ablation rates in summer show much less regional variation over the same ice caps except for lower rates along the north-west edge of the islands and possibly on the Baffin Bay slopes as well. However, there is a stronger relationship between ablation and elevation which is exponential below the firn line. From the fractional 18O content of the snow it is shown that Baffin Bay contributes significant amounts of moisture (>20% of the total) to the Baffin Bay slopes. In addition the Arctic Ocean is seen as another, but much less significant, moisture source. The δ18O data show two effects on the condensation processes—an orographic one (i.e. adiabatic cooling) and a distance-from-source effect (isobaric cooling) where the source is somewhere to the south-east of the islands.
The Formation of Medial Moraines on Alpine Glaciers
Authors: Small R. J. , Clark M. J. , Cawse T. J. P.
Published: September 2017

Field investigation of six medial moraines on glaciers near Arolla, Valais, Switzerland, has revealed that all are nourished by englacial till. This is probably derived from supraglacial point-sources on the accumulation zones of the glaciers, and is released in increasing quantities on the ablation zones, where it emerges diffusely or by way of clearly defined transverse or longitudinal debris bands. Possible mechanisms of formation of these debris bands are reviewed, and it is proposed that the transverse bands originated as crevasse fillings on the accumulation zones. Morphologically all six moraines display waxing sections (of increasing height and breadth), related to development of a protective till cover and resultant differential ablation of the glacier surface. Two only display waning sections (of decreasing height), resulting from lateral sliding of till and “inverted” differential ablation resulting from extreme attenuation of till cover. Four “moraine-types” (related to nature of debris supply and detailed morphology) are identified in the Arolla area. It is believed that these may form the basis for a classification of medial moraines.
Using Linear Discriminant Analysis to Classify Snowfall Situations into Avalanching and Non-Avalanching Ones
Authors: Drozdovskaya N.F.
Published: September 2017

The existing methods of predicting avalanche danger often do not meet users’ demands because of the empiric character of the insufficient volume of information used. In such forecasts the contribution of each individual parameter into the prognostic information is unknown, and this is very important when studying such an event as avalanche formation, which is conditioned by a complex interaction of numerous factors, including snow accumulation, snow thickness, and the conditions of its development. It is obvious that such problems can be successfully solved by statistical methods, and that explains the growing interest in numerical methods of avalanche forecasting. Problems of multi-dimensional observations arises in many scientific fields. The method suited for this problem is discriminant analysis, the purpose of which is to divide a multi-dimensional observation vector into predetermined classes.

This study considers the prognostic (diagnostic) problems of fresh-snow avalanches released during snowfall or in the two days after it has ceased. The theoretical basis is a complex of statistical methods: correlation and dispersion analysis, “sifting” for the choice of predictors’ informative groups, construction of linear parametric discriminant functions, predictions based on training sample, and verification of discriminant functions based on independent material.

The archive used in the study consisted of 500 avalanching cases and 1 300 non-avalanching ones. All situations were grouped according to geomorphological characteristics. Each situation is described by eight meteorological characteristics. The results of classification of snowfall situations into avalanching and non-avalanching ones are as follows: reliability of p is from 75% to 91%, H from 0.15 to 0.51; based on independent material the reliability of p is from 63% to 85%, H from 0. 10 to 0.56.
Fracture Toughness of Fresh-Water Ice
Authors: Liu H. W. , Miller K. J.
Published: September 2017

The plane-strain fracture toughness of fresh-water ice was measured at various loading rates and temperatures. The fracture toughness of ice decreases as loading rate increases and as the test temperature approaches the melting point. The presence of liquid water seems to reduce the fracture toughness. The fracture toughness for crack arrest is slightly lower than the static fracture toughness.
Dielectric Behaviour of Ice Microcrystals: A Study Versus Temperature
Authors: Boned Christian , Lagourette Bernard , Clausse Marc
Published: September 2017

Dispersions of ice microcrystals were obtained from the breakdown of supercooling of water-in-oil type emulsions whose disperse phase was either resin-exchanged water or aqueous solutions of NH4Cl. Their complex permittivity ε⋆ = ε´–jε˝ was studied versus temperature T, up to the melting point of ice microcrystals, by means of an automatically balancing admittance bridge (General Radio 1680 A) working at 400 Hz and 1 kHz, The plots ε´(T), ε˝(T) and ε˝(ε´) reveal that these systems exhibit two distinct dielectric relaxations located on either side of a temperature Tm which was found to be equal to about — 20°C in the case of water and lower than — 20°C in the case of aqueous solutions of NH4Cl. The relaxation located in the lower temperature range arises from the Debye dipolar absorption of ice while the other one could be related to structural changes occurring within the lattice of ice as T approaches its melting point. These results are consistent with those obtained by investigating versus frequency the dielectric behaviour of ice monocrystals at discrete sub-zero temperatures close to their melting point.
Enthalpy Relaxation Phenomenon of Heavy Ice
Authors: Haida Osamu , Suga Hiroshi , Seki Syūzō
Published: September 2017

The heat capacities of quenched and annealed heavy ice Ih were measured in the temperature range 14 to 300 K by an adiabatic calorimeter. A relaxational thermal anomaly was found at around 115K and this phenomenon was ascribed to the onset of deuteron ordering in the crystal. The average activation enthalpy of the relaxational process was determined to be (26±5) kJ mol–1. Residual entropies of the crystal were recalculated on the basis of the present heat-capacity data combined with the revised values for enthalpy of vapourization, saturated vapour pressure, and spectroscopic entropy. They are (3.47±0.41) J K–1 mol–1 for the quenched crystal and (3.44±0.41) J K–1 mol–1 for the crystal annealed at 102–106 K for 264 h. The characteristics and the origin of the anomaly are discussed in comparison with that of ordinary ice.
Determination of a-Axis Orientations of Polycrystalline Ice
Authors: Matsuda Masuyoshi
Published: September 2017

Two new methods have been devised for measurement of crystallographic lattice orientations of individual crystals in polycrystalline ice. The first uses edge-length ratios of etch pits. The second uses a combination of optical measurement on a thin section and etch-pit technique. Although the second method does not work for crystals with their c-axis oriented parallel to the thin section, it is much simpler and more practical than the first method. When used on polycrystalline glacier ice, this method gave the three a-axes orientations as well as c-axis orientation for each crystal with an accuracy of 5°.
Acoustic Emission as an Indication of Stability Decrease in Fracture Zones of Avalanches
Authors: Gubler H.
Published: September 2017

Measurements of the event rate of natural, small-amplitude displacement accelerations in potential fracture zones of avalanches prove to be good indications for decrease of stability.
Evaluation of Jet-Roof Geometry for Snow-Cornice Control
Authors: Dawson K. L. , Lang T. E.
Published: September 2017

Numerical hydrodynamic simulation of the jet-roof geometry for control of snow deposition to prevent cornice formation at mountain ridges is reported. Different jet-roof geometries are evaluated based upon the extent and size of the ground-surface stagnation region and the recirculation region to the lee of the roof. Results show that jet-roof length should be of the same order as nominal height of the roof from the ground surface. Efficient placement of the roof is shown to be that with the leading edge directly above the mountain ridge, and roof angle approximately equal to lee slope angle. In numerical simulation of flow-field start-up, near steady-state flow is approached in less than 1.0 s real time, indicating short transient-flow duration.
Time-Series Modelling of Avalanche Activity from Meteorological Data
Authors: Salway A. A.
Published: September 2017

Avalanche-hazard evaluation by field analysts is largely achieved along causal intuitive lines, depending for its success upon the experience of the analyst in his particular area. Several attempts have been made in the past to quantify such procedures by means of statistical models based upon meteorological measurements. Modified forms of a multivariate technique known as linear discriminant analysis have been tried with only partial success. Intercorrelated variables and autocorrelated data, omission of time-lagged terms, insufficient variation in the dependent variable, and sampling difficulties may have combined to weaken the discriminant approach. These problems and the nature of the phenomenon suggest that a stochastic transfer-function time-series approach may be a useful alternative method.

A numerical weighting scheme has been devised for the representation of avalanche activity for the Rogers Pass area of British Columbia in terms of terminus, size, and moisture-content codes for each event. From various types of correlation analysis performed on data for the period 1965–73, models were developed using the “best” weighting scheme for avalanche activity representation and the most promising meteorological variables, as indicated by the results of the correlation analysis.

These relatively simple models demonstrate a good fit to the actual data, in both a descriptive and a simulated-forecasting situation.
Forces on Structures Impacted and Enveloped by Avalanches
Authors: Pedersen R. R. , Dent J. D. , Lang T. E.
Published: September 2017

A computer code is reported that models two-dimensional flow of a snow-avalanche cross-section over a down-slope structure of arbitrary cross-sectional shape. Impact forces and pressure are predicted, and the flow pattern past the structure may be arrayed pictorially. The model is applied to the prediction of forces on rectangular obstacles which are of fractional height to the nominal avalanche flow depth for avalanche flow speeds up to 20 m/s. The program is applied to modeling an experiment by Salm of impact of snow blocks upon a slope-normal wall in order to demonstrate the accuracy of the code in comparison to impact-force histories measured by Salm. Difference between the experimental results and the computer simulation is less than 21%, and supporting discussion is given on factors that may account for the difference.
Radiation measurement at Lewis Glacier, Mount Kenya, Kenya
Authors: Hastenrath Stefan , Patnaik J. K.
Published: September 2017

Short- and long-wave radiation on variously oriented vertical surfaces, direct solar radiation, global radiation, and long–wave radiation on a horizontal surface were measured on Lewis Glacier, Mount Kenya, at 4800 m. For the orientation of vertical surfaces, the following azimuths were selected: 45°, facing the steep slope of the upper glacier; 135°, facing a rock ridge and some glacier surface in the foreground; 225°, facing down–glacier towards the Teleki valley with open sky occupying much of the view; and 315°, directed towards the steep south-east face of the Nelion peak.

The horizontal components of diffuse short-wave radiation reach a magnitude comparable to those of direct radiation. As a result of contrastingly different albedos of natural surfaces, the horizontal component of diffuse short–wave radiation is particularly large from the direction of the upper glacier, with values around 330–500 W m−2, and smallest from the direction of the rock face of Nelion peak, where values are around 150–330 W m−2. Long–wave radiation seems enhanced from the direction of the Nelion face, and reduced from the azimuth of the upper glacier, thus apparently reflecting differences in emissivity and temperature.
Laboratory Studies of the Optical Properties of Young Sea Ice
Authors: Perovich Donald K. , Grenfell Thomas C.
Published: September 2017

Laboratory experiments were performed to determine the optical properties of young salt ice and to examine correlations between the optical properties and the state of the ice. Ice was grown at different temperatures (–10, –20, –30, and –37°C) from water of different salinities (0, 16, and 31‰). The experiments were conducted in a cylindrical tank 1 m in diameter designed to approximate natural ice growth and to permit in situ optical measurements. Observed incident, reflected, and transmitted irradiances were used in conjunction with a modified Dunkle and Bevans photometric model to determine spectral albedos and extinction coefficients. Cold ice only 0.25 m thick had albedos which were comparable to the values for 2 to 3 m multi-year ice examined by previous researchers during the summer melt season; extinction coefficients were 1.5 to 15 times greater. As the ice temperature and hence brine volume decreased, both albedo and extinction coefficient increased; when the ice temperature dropped below the eutectic point, they increased sharply. In addition, ice grown at lower air temperatures had greater albedos and extinction coefficients even when ice temperatures were the same. Variations in the optical properties of the ice are determined by changes in the amount of brine and its distribution; thus the optical properties of salt ice depend not only on ice temperature but on initial growth rate. Variations in ice salinity over the range 4‰ to 14‰ produced no detectable changes in the optical properties.
Neoglacial to Recent Glacier Fluctuations on the Volcano Popocatépetl, Mexico
Authors: White Sidney E.
Published: September 2017

Neoglacial to historic and recent fluctuations of the firn field and one glacier on Popocatépetl, Mexico, include advance prior to 1519 to possible mid-Neoglaciation stadial position on gentle, north flanks at 4 150 m, then retreat up-valley to 4 335 m by 1906, and to 4 435 m by 1920 at 7 m/year. After volcanic eruptions and melting to about 4 800 m in 1921, growth of firn field and advance of a thin ice lobe before 1949 to 4 573 m by 1950, then retreat in next eight years at about 34 m/year, re-advance of the firn edge as an ice bulge to about 4 700 m by 1968, and as a thick double-lobed glacier to about 4 600 m by 1978 and 1979. A 37 year crevasse study shows continuous active firn-field movement on the north-west side of the cone.
Theory and Laboratory Observations of Naled Ice Growth
Authors: Schohl G. A. , Ettema R.
Published: September 2017

Based on observations of naleds (also called aufeis or icings) grown in a refrigerated laboratory flume, a detailed, composite description of the processes associated with naled ice growth is presented. A spread length is derived that represents a mass balance between the water supplied to a naled’s surface and the ice that freezes on to the surface. Herein, this spread length is termed an equilibrium length. Guided by this concept of equilibrium length and the laboratory data, length- and time-scales applicable to the growth of two-dimensional naleds are proposed. These scales proved useful for normalizing the times and streamwise lengths that correspond to distinct phases of naled ice growth. It is observed that, even in a laboratory flume, naleds spread and thicken in a complex, layer-by-layer manner.

To the best of the authors’ knowledge, this is the first reported laboratory study on naled ice growth. The descriptions and concepts presented herein should be useful to engineers concerned with the effects of naleds on engineering works, and of interest to those who are planning experiments on naleds.
Refraction Correction for Radio Echo-Sounding of Ice Overlain by Firn
Authors: Rasmussen L. A.
Published: September 2017

Radio-echo signals travel faster in firn than in ice, which affects the analysis of ice-mass thickness. If this effect is neglected, then the calculated thickness of an ice mass may be in error by an amount of the order of one-tenth of the firn thickness. An exact formulation is derived for the path of the signal through the firn and the ice. Explicit solutions are given for constant, linear, and quadratic profiles of the refractive index in the firn layer.
Discharges of Turbid Water during Mini-Surges of Variegated Glacier, Alaska, U.S.A.
Authors: Humphrey Neil , Raymond Charles , Harrison Will
Published: September 2017

Discharges of water, sediment, and dissolved impurities from Variegated Glacier, Alaska, were monitored in the early summers of 1980 and 1981 during the occurrence of mini-surges. Seasonal trends, weather-related events, and diurnal variations similar to behavior of other temperate glacier streams were found. The principal effect in the stream associated with mini-surge occurrence was a brief discharge of extremely turbid water. The turbidity is assumed to be introduced into the basal hydraulic system by initiation of the fast motion of a mini-surge at a time and location on the upper glacier known from other measurements. The mean water velocity in the hydraulic system over the intervening distance is thereby determined (0.3 ms−1). The mean water velocity, together with the water discharge (≈16 m3 s−1 at the terminus), places constraints on the distribution of water velocity u and total cross-sectional area AT of the flow paths along the glacier base. This leads to the conclusion that within the zone of mini-surge occurrence in its unperturbed state: u is about 0.1 ms−1 or possibly less; AT is about 102 m 2 or possibly more, and it must be divided into a very large number of small passageways, be blocked by constrictions, or both. The total water cross-section corresponds to a layer 0.1–0.2 m thick when spread uniformly over the glacier width. The water velocity is close to or less than the propagation velocity of the mini-surges. Between the zone affected by mini-surges and the stream, a dynamically less active lower section of the glacier is probably underlain by a small number of conduits, in which the water velocity may be very high (≥ 2 m s−1). Water discharge following the mini-surges puts an upper limit on water-storage changes associated with the anomalous ice motion.
Determination of Particle Paths using the Finite-Element Method
Authors: Stolle D. F. E. , Killeavy M. S.
Published: September 2017

Large ice masses contain a wealth of information regarding past climates and atmospheric chemistry. To interpret properly information from ice cores obtained from glaciers, a time-scale for the ice core must be established. A procedure based on the finite-element method, using velocity-pressure and stream-function formulations to establish particle paths and hence isochrones, is outlined. Examples are presented which demonstrate the ability of the procedure to predict particle paths and isochrones which can be used to determine the time-scale or to confirm dates established by other methods, of ice cores obtained from large ice masses.
Flow of the Brunt Ice Shelf, Antarctica, Derived from Landsat Images, 1974–85
Authors: Simmons D.A.
Published: September 2017

Satellite images recorded in 1973, 1974, and 1985 of the Brunt Ice Shelf are compared. There are sufficient identifiable features moving with the ice shelf to show flow patterns over an area of ~10 000 km2. Velocities vary from 500 m a−1 in the west, near the Dawson-Lambton Ice Stream, to 1300 m a−1 in the east, within the Stancomb-Wills Ice Stream.
A topological approach to the strain-rate pattern of ice sheets
Authors: Nye J. F.
Published: September 2017

The pattern of horizontal strain rate in an ice sheet is discussed from a topological point of view. In a circularly symmetric ice sheet, the isotropic point for strain rate at its centre is degenerate and structurally unstable. On perturbation the degenerate point splits into two elementary isotropic points, each of which has the lemon pattern for the trajectories of principal strain rate. Contour maps of principal strain-rate values are presented which show the details of the splitting.
Mechanisms of fast flow in Jakobshavns Isbræ, West Greenland: Part I. Measurements of temperature and water level in deep boreholes
Authors: Iken A. , Echelmeyer Κ. , Harrison W. , Funk M.
Published: September 2017

Several holes were drilled to depths of 1500–1630 m along a profile across Jakobshavns Isbræ, 50 km upstream from the calving front. Drilling was by hot water and required approximately 20 h. The holes were rapidly closed by refreezing, but it was possible to instrument them with thermistors and tilt sensors before this occurred.

Near the margins of the ice stream the holes reached the bed and connected with the subglacial drainage system. Water-level changes recorded in these holes are discussed in terms of the basal hydraulic system. The temperature measurements show that the glacier is temperate-based. Moreover, extrapolation of a measured temperature profile and its curvature suggests that a temperate layer of substantial thickness may exist at the bed near the center of the ice stream. There is a striking difference in the shapes of temperature profiles measured at different locations: beneath the center line the temperature minimum is at a considerably smaller relative depth than near the margins, but it is nearly the same in magnitude (−22.1°C). This may indicate a disproportionately large vertical stretching of the basal ice in the center of the ice stream. Since the basal ice is warmer and much less viscous than the ice above, a thickening of that layer would cause a corresponding increase of surface velocity. We presume that this mechanism contributes to the fast flow of Jakobshavns Isbræ.
Consolidation of sediments by glaciers: relations between sediment geotechnics, soft-bed glacier dynamics and subglacial ground-water flow
Authors: Boulton G. S. , Dobbie K. E.
Published: September 2017

A theory of subglacial consolidation is developed which shows how the meltwater flux beneath a glacier leaves a consolidation signature from which many important glacier-dynamic properties can be inferred. Conditions under which water is discharged through channels or in a thin film at the ice—bed interface or by ground-water flow are discussed, and it is concluded that glaciers flowing over aquifers of high transmissibility can induce deep circulation patterns quite different from non-glacial circulation. Examples of glacial pre-consolidation profiles in sediments from The Netherlands and England are used to illustrate how basal melting rates, subglacial ground-water flow patterns, ice overburden, basal shear stress, ice-surface profile and the amount of sediment removed by erosion can be inferred.
Glaciation and deglaciation mechanisms in a coupled two-dimensional climate—ice-sheet model
Authors: Berger André , Gallée Hubert , Tricot Christian
Published: September 2017

A two-dimensional model which links the atmosphere, the mixed layer of the ocean, the sea ice, the continents, the ice sheets and their underlying bedrock has been used to test the Milankovitch theory over the last glacial—interglacial cycle. It was found that the orbital variations alone can induce, in such a system, feed-backs sufficient to generate the low-frequency part of the climatic variations over the last 122 kyear. These simulated variations at the astronomical time-scale are broadly in agreement with ice volume and sea-level reconstructions independently obtained from geological data. Imperfections in the simulated climate were the insufficient southward extent of the ice sheets and the too small hemispheric cooling during the last glacial maximum. These deficiencies were partly remedied in a further experiment (Gallée and others, in press) by using the time-dependent CO2 atmospheric concentration given by the Vostok ice core in addition to the astronomical forcing. For this second experiment, the main mechanisms and feedbacks responsible for the glaciation and the deglaciation in the model are discussed here.
Statistics of firn closure: a simulation study
Authors: Enting I. G.
Published: September 2017

The trapping of bubbles of air in polar ice has provided a unique record of past atmospheric composition. However, the interpretation of measured concentrations depends on the statistics of the trapping process. Measurements of trace atmospheric constituents whose concentrations are changing steadily can be interpreted in terms of an “effective age” of the gas which differs from the age of the ice by a delay which corresponds to the mean trapping time. The statistics of bubble trapping can be modelled as a percolation model which is one of a class of models whose transitions are characterized by large critical fluctuations. These critical fluctuations cause an intrinsic sample-to-sample variability in the delay time and thus in the effective age. Monte Carlo simulations using a lattice model of the firn are presented, showing the effect of finite sample size on the age distribution of trapped gas. For samples containing more than about 103–104 bubbles, the simulations indicate that the range of variability is small compared to the average duration of the trapping process.
Geometry and flow conditions of subglacial water at South Cascade Glacier, Washington State, U.S.A.; an analysis of tracer injections
Authors: Fountain Andrew G.
Published: September 2017

Tracers were injected into South Cascade Glacier to determine the flow condition and geometry of the subglacial water system. Results indicate that two distinct drainage basins on the glacier feed the two main streams flowing from the glacier. In the largest basin, two parallel drainage networks exist, one englacial and the other subglacial. The englacial system is an arboresecent network of conduits, whereas the subglacial system is a distributed flow system. Both systems connect to a single subglacial conduit which appears as a stream at the glacier’s terminus. The comparison between the travel time of the tracers and stream discharge indicated that the single conduit was pressurized in July and partly filled in August and September.

To estimate the flow geometry (e.g. path length, flow depth and velocity), the advection-diffusion equation was formulated to express the water velocity as a function of water depth. Longitudinal dispersion of the tracer was calculated from the shear in longitudinal water velocity. Results indicate that the flow is very wide compared to its depth and that the path is sinuous. The estimated flow speed in the conduits is an order of magnitude larger than the measured speed through the glacier, indicating that other flow processes, probably englacial, route the water much more slowly.

The other, smaller, basin drains the water from the surface to the subglacial distributed flow system. Based on the travel time of the individual concentration peaks, the water could be flowing through a linked-cavity system or interconnected bands of highly permeable debris separated by zones of less permeability.
Basal ice accretion and debris entrainment within the coastal ice margin, Law Dome, Antarctica
Authors: Goodwin Ian D.
Published: September 2017

Basal ice stratigraphy in coastal ice cliffs at the Law Dome margin has revealed the basal accretion of clean and debris-bearing ice, marine congelation ice and granular marine ice inland of the margin. Co-isotopic analysis of δ18O and δD isotopes together with solute chemistry were applied to determine the modes of accretion and debris entrainment. The marine congelation ice and the granular marine ice were formed from the basal freezing of desalinated sea water and the episodic mixture of basal meltwater and sea water, respectively. Two different debris-entrainment mechanisms were identified. Debris-band ice with debris concentrations of 6.3–33% (by volume) was formed from proglacial raised beach and shallow marine sediment incorporated by an over-riding advance of the margin. Two other debris-bearing ice types, dispersed debris-poor ice with debris concentrations <0.3% (by volume) and laminated debris ice with debris concentrations 0.9–1.9% (by volume) were accreted further inland from the margin by basal regelation processes associated with the Robin (1976) heat-pump effect.
Automated image analysis of ice thin sections — instrumentation, methods and extraction of stereological and textural parameters
Authors: Eicken Hajo
Published: September 2017

Image-analysis procedures have been developed for a simple PC-based system to evaluate the textural features of ice thin sections automatically. The method yields parameters that describe both ice crystals and pores in an objective, reproducible manner. Specimens are recorded in linearly and circularly polarized light (ice grains) as well as in transmitted and incident plain light (pores) under standardized conditions. After preparative filtering, images are segmented through union of two Sobel-filtered images (ice crystals/grain boundaries) or through thresholding (ice crystals/pores). The quantification of texture is based on the evaluation of image contrast as well as on linear analysis and non-linear transforms to obtain information on grain-sizes and their distribution. In the study of ice pores, stereological effects of finite section thickness have to be corrected. The discussion focuses on errors involved in automated textural analysis and the glaciological yield of measured and derived parameters.
Velocity of radio waves in glaciers as an indicator of their hydrothermal state, structure and regime
Authors: Macheret Yu. Ya. , Moskalevsky M. Yu. , Vasilenko E.V.
Published: September 2017

The results of measurements of radio-wave velocities (RWV) by wide-angle reflection (WAR) methods in the temperate Abramov Glacier in the Alai Mountain Ridge and the “two-layered” sub-polar Fridtjovbreen and Hansbreen on Svalbard using a low-frequency (2–13 MHz) radar are considered and discussed. The experimental data obtained and the data from the literature show that the values of RWV could be a good indicator of the hydrothermal state of glaciers. As such, these data enable the identification of cold, temperate and transitional (two-layered) glaciers, and can be used for estimation of the water content in glaciers and changes in the hydrothermal state.
The Shape of Drumlins
Authors: Chorley Richard J.
Published: September 2017

The lemniscate loop, previously employed in the approximate generic description of the shapes of erosional drainage basins, is shown to bear a close genetic relationship to streamlined forms. This is illustrated by comparison with the shape of airfoils, the snowdrift and certain eggs. Drumlins have been recognized as similar streamlined forms and the lemniscate loop is suggested as providing a quantitative genetic description of their shapes.
Snow Crystals Observed at Mauna Loa
Authors: Nakaya Ukichiro
Published: September 2017

The expedition to Mauna Loa in Hawaii was undertaken in the winter of 1956–57 in order to study the nature of snow crystals in the district where the fewest aerosol particles are present. 170 photomicrographs of snow crystals were taken at the summit—13,450 ft. (4000 m.). The varieties of snow crystals were abundant and almost all types hitherto known were observed. The characteristic of the snowfall was the abrupt transition of one type to the other. Many single needles were observed, which were very rare in Hokkaido. Two new types were found; one was a needle composed of many hexagonal columns, and the other an elongated column which is the intermediate state of needle and column. Several photographs were obtained which show the mechanism of formation of ice pellets.
The Deformation of a Glacier Below an Ice Fall
Authors: Nye J. F.
Published: September 2017

Measurements have been made on Austerdalsbreen, Norway, to test the theory that wave ogives at the foot of an ice fall are formed by pressure. The pattern of deformation over the first three waves from the Odinsbre ice fall was studied by measuring the absolute and relative motions of 35 stakes during August 1956. There are large variations of longitudinal compression through the wave pattern, but no simple correlation exists between the compression and the crests; nor are the crests consistently rising with respect to the average surface. We conclude that the waves are not forming by pressure in this area. A detailed quantitative explanation of the observed pattern of deformation is found by improving the existing theory of glacier flow. The deformations taking place are explained as essentially independent of the presence of the waves; they are primarily due (a) to the compression that must occur in the ice as its slope decreases and it becomes thicker, and (b) to the bending and unbending to which the ice is subjected as it passes over a bed of changing curvature. Additional contributions to the deformation arise from the widening of the glacier channel, which is important at the immediate foot of the ice fall, and from the annual ablation.

The theory explains quantitatively the rotation and bending of the tunnel excavated in 1955; it was also used to make a prediction, which was successfully verified in a further experiment on the glacier in July and August 1957.

A pressure mechanism of wave formation can be reconciled with the observations if it is supposed that the compression in the lower two-thirds of the ice fall, which was measured photogrammetrically in August 1956, varies significantly with the seasons. However, the positions and amplitudes of the observed waves are fully accounted for by the combined plastic deformation and ablation mechanism recently described in another paper. There is therefore no longer any need for the pressure hypothesis as a primary cause of the waves.
Geothermal Heat and Glacial Growth
Authors: Wexler H.
Published: September 2017

In a 300 m. deep hole drilled in the 3000 m. thick ice at Byrd Station (lat. 80° S. long. 120° W., 1513 m. above sea-level), the temperature was observed to decline with depth below 45 m. This profile was extended to the bottom of the ice with the aid of heat conduction theory under these assumptions:

i.

that as the ice was deposited the climate became warmer at the rate of 045° C. per 1000 years;

ii.

The conduction of geothermal heat is 31.6 cal. cm.−2 yr.−1.

It is estimated that the first 2000 years of geothermal heat conducted to this ice, whose annual accumulation is 30 cm., is dissipated to the atmosphere and space. When the ice becomes thicker, it retains all the geothermal heat given to it for a long time.

An alternative, non-climatic change explanation of the decreasing temperature in the Byrd Station hole is based on colder ice from higher elevations moving under the warmer ice accumulated locally. However, an examination of the topography of the Marie Byrd Land ice does not appear to support this explanation.
Mass Balance Studies in Antarctica
Authors: Mellor Malcolm
Published: September 2017

The general characteristics of the coastal regions between long. 45° E. and long. 80° E. are described. The features and conditions are similar to those found along the coasts of the Australian sector further to the east. Measurements of accumulation, snow transport, ice flow and ablation are described and results are given.

Accumulation, measured from stakes and pits, is 1.0 × 1014 gm./yr. in a 1 km. wide strip running 850 km. inland from the coast of MacRobertson Land. The methods of gauging drifting snow and extrapolating the results are given and a meridional mass transport of 0.16 × 1014 gm./km. yr. is deduced. Iceberg calving rates given in a previous paper are again quoted, although they are now felt to be too low. Net ablation is 0.053 × 1014 gm./km. yr. and additional evaporation above the firn limit accounts for 0.045 x 1014 gm./km. yr. The estimates are compared with old and new observations from other parts of Antarctica and the problem of bottom melting beneath ice shelves is discussed.

A distinction is made between the meteorological water budget for Antarctica and the glaciological mass balance for the ice sheet. Mass budgets for the sector between long. 45° E. and long. 80° E. and for the whole of Antarctica are drawn up. In each case a surplus of accumulation over losses appears, but it is felt that the data are insufficient to claim that the ice sheet is growing at the present time. The drift snow and ablation losses are added to the net accumulation to give a figure of 14 cm. of water as the mean annual precipitation over Antarctica, a value lying between the estimates of Meinardus and Kosack.
Equilibrium Profile of Ice Caps
Authors: Weertman J.
Published: September 2017

Nye’s theory of the equilibrium profile of two-dimensional ice caps is modified to include longitudinal stress and creep rate effects. A more generalized law for the sliding velocity of a glacier over its bed is introduced into the analysis in order to permit the inclusion of these additional complications. It is found that in the case of small ice caps (of the order of 30 km. in width), it is important to include the longitudinal stress. A somewhat “flatter” profile than that calculated by Nye is obtained. For ice sheets of the dimensions of the Greenland or Antarctic Ice Sheets, the additional stress causes essentially no modification in Nye’s theory. Nye’s theory also has been extended to include an isostatic sinking under the weight of the ice of the bedrock below an ice cap.
Mechanism for the Formation of Inner Moraines Found Near the Edge of Cold Ice Caps and Ice sheets
Authors: Weertman J.
Published: September 2017

A new mechanism is described which explains the formation of moraines in the ablation areas of cold ice sheets. The mechanism involves the freezing of water onto the bottom surface of an ice sheet. This water comes from regions of the bottom surface where the combination of the geothermal heat and the heat produced by the sliding of ice over the bed is sufficient to melt ice. A number of criticisms are made of the shear hypothesis, which has been advanced to explain moraines occurring on Baffin Island and near Thule, Greenland. It is concluded that this older hypothesis may be inadequate to account for these moraines.

Although in theory the mechanism proposed in this paper undoubtedly will lead to the formation of moraines, the existing field data are insufficient to prove conclusively that actual moraines have originated by means of this mechanism.
Glaciological Work of the 1959–60 U.S. Victoria Land Traverse
Authors: Stuart A. W. , Heine A. J.
Published: September 2017

Accumulation along the route of the 1959–60 Victoria Land traverse, derived from 19 snow pits, was found to be 16 cm. of water equivalent. Sastrugi, reflecting prevailing surface wind directions, indicate that the surface winds in Victoria Land are katabatic. Movement points on the Ross Ice Shelf show a maximum rate of about 844 m./yr. with Iesser rates obtaining in more marginal areas. Stake measurements of accumulation on the Ross Ice Shelf indicate an average of 20 cm. of water equivalent/yr. A large glacier, about 300 km. long and up to 30 km. wide and draining into Rennick Bay, was discovered.