bluuebunny/crossref_metadata_2025_split huggingface dataset:
Determination of the Three-Dimensional Velocity Field in a Glacier
Authors: Raymond C.F. 
Published: September 2017

AbstractA method for the determination of the three-dimensional velocity field in a glacier is described, Measurements in three or more bore holes arranged in an appropriate array are needed for its application. Surface motion measured by triangulation and tape measure, bore-hole profiles given by inclinometry, and the geometry of the bed are all considered simultaneously in order to determine the velocity field. The basic assumption is that velocity between the bore holes can be represented by suitable interpolation based on the measurements in the holes. Ice displacement parallel to bore holes is calculated indirectly from incompressibility and the constraint that velocity normal to the bed be zero. As an example, the method is applied to an array of 9 bore holes in Athabasca Glacier.
Basement Ice, Ward Hunt Ice Shelf, Ellesmere Island, Canada
Authors: Lyons J.B. , Savin S.M. , Tamburi A.J. 
Published: September 2017

AbstractOxygen-isotope and chlorinity determinations, as well as petrographie observations, indicate that the basement we of the Ward Hunt Ice Shelf is largely composed of a unique brackish ice, which interdigitates with sea ice. Some iced firn occurs near the top of the Basement Ice, below an unconformity.stratification in brackish and sea ice represents annual increments to the bottom of the ice shelf The c-axis vertical orientation and small-angle grain-boundary relations in brackish ice are explained by nucleation and floating of ice dendrites from the undercooled brackish water zone to the bottom of the ice shelf, where they attach themselves sub-parallel to the plane of the undersurface.Ice island T-3 did not come from a break-up of the main part of the Ward Hunt Ice Shelf, but probably originated in a nearby area to the west.
Albedo of Melting Sea Ice in the Southern Beaufort Sea
Authors: Langleben M.P. 
Published: September 2017

AbstractTwo Kipp hemispherical radiometers mounted back to back and suspended by an 18 m cable from a helicopter flying at an altitude of about 90 m were used to make measurements of incident and reflected short-wave radiation. The helicopter was brought to a hovering position at the instant of measurement to ensure that the radiometers were in the proper attitude and a photograph of the ice cover was taken at the same time. The observations were made in 1969 during 16 flights out of Tuktoyaktuk, Northwest Territories (lat. 69° 26’N., long. 133° 02’W.) over the fast ice extending 80 km north of Tuktoyaktuk. Values of albedo of the ice cover were found to decrease during the melting period according to the equation A = 0.59 —0.32P where P is the degree of puddling of the surface.
Instruments and Methods: A New Bore-Hole Inclinometer
Authors: Raymond C.F. 
Published: September 2017

AbstractA newly developed bore-hole inclinometer permits the determination of bore-hole configurations with greater accuracy and efficiency in comparison with earlier systems of inclinometry. Instrument orientation is given to within 0.1° in magnitude of tilt and 10° in azimuth of tilt by an electrical output which can be read remotely from the surface.
An Improved Method for Determining Ice Fabrics
Authors: Hill J.R. , Lasca N.P. 
Published: September 2017

AbstractIn ice-fabric studies, use of an accessory plate is necessary in conjunction with the Rigsby universal stage to discriminate between the a- and c-axes of an ice crystal when the orientation of the c-axis is parallel or nearly parallel to the stage. The techniques described permit orientation of the c-axis regardless of its orientation.
A Hot-wire Engine to Produce Periodic Grooves on an Ice Surface
Authors: Tobin T.M. , Itagaki K. 
Published: September 2017

AbstractA strain-tree grooving method has been developed for surface self-diffusion studies of ice. This method utilizes a hot-wire grooving engine and is capable of obtaining a uniform spacing between grooves ranging from 15.9 μm to 159 μm in increments of 15.9 μm.
Stress Variations with Ice Flow Over Undulations
Authors: Budd W.F. 
Published: September 2017

AbstractThe analysis of steady-state flow over bedrock perturbations of Budd(1970[a]) is extended to evaluate the stress variations associated with the flow. In particular the four separate terms of the fundamental one-dimensional (longitudinal) stress equation (Budd,1968) are examined to show explicitly how the longitudinal stress gradient G, the base stress τ, the surface slope stress s, and the integrated second derivative of the shear stress T all vary over-a given wave.The result shows an error of a factor of 2 in some earlier studies relating longitudinal stress variations to the slope. This error resulted from the erroneous assumption that remains constant at its regional value. In fact the basal stress varies over the undulations in a similar way to the longitudinal stress gradient, and this is the same as the surface slope stress for long waves, but for short waves or less) requires the addition of the fourth term T, which then becomes dominant.
Small-Scale Strain Measurements on a Glacier Surface
Authors: Colbeck S. C. , Evans R. J. 
Published: September 2017

AbstractSurface deformations in the neighborhood of a crevasse field were measured over short (3 m) gage lengths in order to study flow conditions associated with crevasse formation. The results obtained were unusual in that they were inconsistent with large-scale results found by previous workers. It was concluded that the presence of small-scale surface effects, such as fractures, pot-holes and healed crevasses give rise to small-scale deformation fields with large spatial and temporal variations and that there is a lower limit of gage length below which deformation measurements pertinent to regional (low phenomena cannot be made. This lower limit is apparently an order of magnitude greater than the spacing of the features which give rise to localized effects.
Chloride Segregation Along Grain Boundaries in Ice
Authors: Prodi F. , Nagamoto C.T. 
Published: September 2017

AbstractA new technique for precisely detecting chlorides in ice has been developed. It is based on a microchemical contact reaction which takes place when a thin surface layer of ice melts through a membrane filter previously soaked in a concentrated solution of silver nitrate and dried. The silver chloride thus formed is reduced to metallic silver under ultra-violet light. The results on natural hailstones and laboratory doped ice show that foreign molecules are mainly segregated along the grain boundaries rather than being captured in the ice lattice.The technique, which makes quantitative evaluations possible, appears promising in all experimental studies on natural ice (hailstones and sea ice) and on ice artificially grown in the laboratory (by accretion or by freezing of solutions).
Oxygen-Isotope Measurements on 1700 ± 300 Year Old Antarctic Ice
Authors: Hamilton Wayne L. 
Published: September 2017

AbstractValues of δ18OSMOW measured on ice from 250 m depth at old “Byrd station”. Antarctica, averaged about A monotonie trend in values through the 16 cm long core piece suggested that part of an annual layer was represented. Snow accumulation in excess of 14.4 g cm-2 year-1 ca 1 700 years B.P. is indicated.
A First Simple Model for Periodically Self-Surging Glaciers
Authors: Budd W. F. 
Published: September 2017

A two-dimensional model of glacier flow is presented which includes periodical surging as a natural phenomenon for a certain class of glaciers. The input consists of the bedrock and balance profiles along the glacier, together with the ice flow properties and a frictional lubrication factor. The basal stress is determined from the condition of gross equilibrium for the whole glacier, together with the distribution of the frictional lubrication from energy dissipation along the glacier.The difference between the basal stress and the down-slope stress of the glaciers produces longitudinal strain-rates which determine the basal sliding velocity. Since the velocity is also involved in the frictional lubrication, feed-back develops between the basal stress and sliding velocity.For a given lubrication factor, a critical stage can be reached for which the velocity becomes sufficiently high to lower the basal stress, enough to cause very high velocities to develop. The model thus gives rise to three classes of glaciers with two modes of flow.“Ordinary” glaciers do not have sufficient mass flux, for the given bedrock profile, to go beyond the “slow mode” in which the basal stress and velocity increase together as the glacier builds up to steady state.“Fast” glaciers have sufficient flux to remain continuously in the “fast mode” with high velocities and relatively low basal stress.“Surging” glaciers have sufficient flux to reach the fast mode but not sufficient to maintain it, and thus develop a periodically oscillating state between the fast and slow modes with gradual build up and rapid drainage.Sample results are presented for models of a typical large valley surging glacier and for a very high-speed surging glacier.
Radio Echo Sounding On Temperate Glaciers
Authors: Goodman R. H. 
Published: September 2017

A high-resolution radio echo sounder operating at a frequency of 620 MHz has been developed for studies of temperate glaciers. Excellent spatial resolution is obtained through the use of a short pulse length (70 ns) and an antenna beam width of 5.2°. Large amounts of high-quality data may be rapidly collected since the sounder incorporates an automatic positioning system and an on-line computer. Real time analysis of the echoes facilitates the understanding of complex reflecting horizons observed in temperate glaciers.Results obtained during field trials of the echo sounder on both the Wapta Icefield and Athabasca Glacier are given. Intraglacial structures which may be due to water levels within the ice have been detected.
Effect Of Inversion Winds On Topographic Detail And Mass Balance On Inland Ice Sheets
Authors: Whillans I. M. 
Published: September 2017

Steady-state gravity flow of air (inversion wind) on sloping snow-covered ice sheets is analyzed for sensitivity to local topography. Topographic features of the order of a few kilometres or less in length are too small to affect the direction and speed of this air flow. Air flow on a longer scale should however conform cosely to topography. Surface roughness on ice sheets is consistent with these results. Features of length shorter than a few kilometers (drifts and sastrugi) are transient, but longer features (surface undulations) remain essentially unaltered for many years. On the longer scale, inversion wind speed and therefore the amount of drifting and blowing snow should vary with the surface slope even where slope changes by as little as 1/10%. Observed variations in surface mass balance (aceumulated snow) in upper Marie Byrd Land, Antarctica, support this hypothesis.Snow drift and inversion winds thus constitute a feed-back mechanism on the form of ice sheets and some of the topographic detail, formerly attributed to ice-flow character alone, may be in large part due to this mechanism.
Water Flow in Glaciers: Jökulhlaups, Tunnels and Veins
Authors: Nye J. F. 
Published: September 2017

AbstractThe physics of water flow within and under glacier ice is examined with special reference to the periodic catastrophic outbursts of water (jökulhlaups) from the subglacial lake Grímsvötn, Vatnajökull, Iceland. The lake is sealed until it reaches a critical level which enables it to lift the glacier, helped by a hydrostatic cantilever effect. The differential equations for non-steady water flow in a subglacial tunnel are derived and applied to the 1972 Grímsvötn outburst. The discharge: time relation observed during the growth stage, and the abrupt ending of the flood, are both very well accounted for by a theory which is insensitive to the details of the subglacial tunnel system. The steady state, in which an intergranular vein or tunnel is simultaneously melted open by frictional heat and closed by plastic deformation, may be stable or unstable according to the conditions imposed at the ends. This explains why the flow of water in a vein does not normally increase unstably as in a jökulhlaup. An ice-dammed lake does not drain away through the vein system because the driving force on the vein-water is towards the lake rather than away from it.
The Application of Fracture Mechanics to the Problem of Crevasse Penetration
Authors: Smith R. A. 
Published: September 2017

AbstractThe elastic stress intensity factor is a parameter used in fracture mechanics to describe stress conditions in the vicinity of the tip of a sharp crack. By superimposing solutions of stress intensity factors for different loading conditions, equations are derived which model crevasses in ice. Solutions are presented for the theoretical depth of isolated crevasses, free from or partially filled with water. Close agreement exists with a previous calculation by Weertman using a different technique. The effect of crevasse spacing is investigated and it is demonstrated that closer spacing always reduces crevasse depth, but over a wide range of spacing the predicted variation in depth is slight.
The Bearing Capacity of Floating Ice Plates Subjected to Static or Quasi-Static Loads*
Authors: Kerr Arnold D. 
Published: September 2017

AbstractThis paper contains a critical survey of the literature on the bearing capacity of floating ice plates. It consists of a discussion of general questions, a critical survey of analytical attempts to determine the bearing capacity of floating ice plates and a survey of field and laboratory tests on floating ice plates and their relation to the analytical results. It concludes with a systematic summary of the results, a discussion of observed shortcomings, and suggestions for needed investigations.
Climatic Inferences from Former Glaciers in the South-East Grampian Highlands,
Scotland
Authors: Sissons J. B. , Sutherland D. G. 
Published: September 2017

Abstract
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

Abstract
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.
Origin of Foliation in Glaciers
Authors: Leb. Hooke Roger , Hudleston Peter J. 
Published: September 2017

AbstractLaboratory 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

AbstractDielectric 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

AbstractMoraines 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

AbstractAn 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

AbstractMeasurements 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

AbstractField 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.