bluuebunny/crossref_metadata_2025 huggingface dataset:
Design, Development, Field Observations, and Preliminary Results of the Coherent Antarctic Radar Depth Sounder (CARDS) of the University of Kansas, U.S.A.
Authors: Raju G. , Xin W. , Moore R.K.
Published: September 2017

A modern coherent Antarctic radar depth sounder for probing the ice sheets of Antarctica and Greenland has been designed and developed by the University of Kansas. It was successfully tested during the austral summers of 1987 and 1988 at Downstream Β and Upstream B, Antarctica. Ground-based measurements were made with the radar in a mobile hut hauled by a Sno-cat in 1987 and in a Spryte vehicle in 1988.

The coherent Antarctic radar depth sounder (CARDS) is an unfocussed synthetic-aperture chirp radar where the along-track resolution is improved by extensive coherent integration. Surface acoustic wave (SAW) devices are used to implement pulse expansion and compression. A common stable oscillator for the transmitter and the receiver establishes coherency. The system signal-to-noise ratio is enhanced by pulse compression and coherent integration. Antennas for the ground-based measurements are configured with an array of eight dipole elements, four active and four passive, the latter acting as reflectors. The aircraft antennas also consist of four active elements hung underneath the two wings. The wings serve as reflectors. A PC facilitates system control and data recording on a high-density recorder. Α-scope plots of selected records allow frequent field checks on system performance. More descriptive display facilities have been incorporated in the latest version of the system.

The radar transmits 60 ns, 20 W peak power at 150 MHz. The number of coherent integrations is selectable up to 64 k. The system is capable of 5 m range resolution and 5 km range in ice. A programmable sensitivity time control (STC) increases the receiver dynamic range. System parameters such as pulse-repetition frequency, number of integrations, and display modes can be chosen during field operations by user-friendly software.

This paper describes the design and field operations of the system. Some results of the 1987 operations at Downstream Β are presented.
On the pulling power of ice streams
Authors: Hughes T.
Published: September 2017

Gravity wants to pull an ice sheet to the center of the Earth, but cannot because the Earth’s crust is in the way, so ice is pushed out sideways instead. Or is it? The ice sheet “sees” nothing preventing it from spreading out except air, which is much less massive than ice. Therefore, does not ice rush forward to fill this relative vacuum; does not the relative vacuum suck ice into it, because Nature abhors a vacuum? If so, the ice sheet is not only pulled downward by gravity, it is also pulled outward by the relative vacuum. This pulling outward will be most rapid where the ice sheet encounters least resistance. The least resistance exists along the bed of ice streams, where ice-bed coupling is reduced by a basal water layer, especially if the ice stream becomes afloat and the floating part is relatively unconfined around its perimeter and unpinned to the sea floor. Ice streams are therefore fast currents of ice that develop near the margins of an ice sheet where these conditions exist. Because of these conditions, ice streams pull ice out of ice sheets and have pulling power equal to the longitudinal gravitational pulling force multiplied by the ice-stream velocity. These boundary conditions beneath and beyond ice streams can be quantified by a basal buoyancy factor that provides a life-cycle classification of ice streams into inception, growth, mature, declining and terminal stages, during which ice streams disintegrate the ice sheet. Surface profiles of ice streams are diagnostic of the stage in a life cycle and, hence, of the vitality of the ice sheet.
Application of a general sliding law to simulating flow in a glacier cross-section
Authors: Harbor Jonathan M.
Published: September 2017

Observations at Athabasca Glacier and elsewhere suggest that basal sliding can account for a very significant part of total glacier motion, and that sliding rates vary significantly across a glacier section. The ability to model such spatial variations in basal velocities is important in understanding flow in valley glaciers, as well as in predicting spatial patterns of glacial erosion that drive land-form development models. With a sliding law in which the basal velocity is dependent on the basal shear stress and inversely dependent on the effective pressure at the bed, it is possible to predict an overall flow pattern that is consistent with the empirical data, if it is assumed that friction increases close to the margin of a glacier.
Steady Motion of Ice Sheets
Authors: Morland L. W. , Johnson I. R.
Published: September 2017

Steady plane flow under gravity of a symmetric ice sheet resting on a horizontal rigid bed, subject to surface accumulation and ablation, basal drainage, and basal sliding according to a shear-traction-velocity power law, is treated. The surface accumulation is taken to depend on height, and the drainage and sliding coefficient also depend on the height of overlying ice. The ice is described as a general non-linearly viscous incompressible fluid, with illustrations presented for Glen’s power law, the polynomial law of Colbeck and Evans, and a Newtonian fluid. Uniform temperature is assumed so that effects of a realistic temperature distribution on the ice response are not taken into account. In dimensionless variables a small paramter ν occurs, but the ν = 0 solution corresponds to an unbounded sheet of uniform depth. To obtain a bounded sheet, a horizontal coordinate scaling by a small factor ε(ν) is required, so that the aspect ratio ε of a steady ice sheet is determined by the ice properties, accumulation magnitude, and the magnitude of the central thickness. A perturbation expansion in ε gives simple leading-order terms for the stress and velocity components, and generates a first order non-linear differential equation for the free-surface slope, which is then integrated to determine the profile. The non-linear differential equation can be solved explicitly for a linear sliding law in the Newtonian case. For the general law it is shown that the leading-order approximation is valid both at the margin and in the central zone provided that the power and coefficient in the sliding law satisfy certain restrictions.
The Nature of the Ice-Rock Interface: The Results of Investigation on 20000m2 of the Rock Bed of Temperate Glaciers
Authors: Vivian Robert
Published: September 2017

This paper reviews the results of 10 years study of the only four subglacial sites which are permanently accessible due to activity by hydro-electrical companies. All the sites occur beneath temperate ice. The first part is devoted to the study of the ice-rock interface as a glaciological phenomenon, and emphasizes the dynamic conditions for separation of the ice from the rock bed. This glaciological cavitation phenomenon occurs when tan α > Vi/Hi. Another phenomenon, “regressive cavitation” refers to the existence up-stream of the large permanent cavities, of a series of small cavities which although they are not permanent are fundamentally important because they control the subglacial water drainage allowing the water to penetrate new routes. The second part analyses the sliding movement of the ice on the rock bed. The deformation of the cavities depends mainly on variations in the velocity of the glacier. The sliding velocity measured at the interface accounts for 60 to 80% of the surface movement of the glacier; 80 to 90% of the surface velocity movement is attained a few metres above the glacier-bed interface. The third part describes the characteristics of subglacial drainage which are necessary to understand the nature of the ice-rock interface. The fourth part is devoted to the precise description of the different types of interface as they appeared in the subglacial sites.
The Chemical Stratigraphy of Polar Ice Sheets — A Method of Dating Ice Cores
Authors: Wilson A. T. , Hendy C. H.
Published: September 2017

Studies of the chemical stratigraphy in the snow near Vostok station, which is near the centre of the East Antarctic ice sheet, show that sodium exhibits annual concentration differences of up to a factor of ten. Similar work on the 952 m Vostok ice core enabled accumulation rates along selected parts of the core to be determined. This in turn enables the core to be dated. The accumulation rate in this central region of the East Antarctic ice sheet for the last 50000 years has been determined and is presented. An interesting result is that the accumulation rate during the last glacial period is only half that in post-glacial times. Results from the bottom of the core provide some evidence of a past surge in the East Antarctic ice sheet.
The Altitude Effect on the Isotopic Composition of Snow in High Mountains
Authors: Niewodnizański Jerzy , Grabczak Jerzy , Barański Lesław , Rzepka Jerzy
Published: September 2017

The stable isotopes oxygen-18 and deuterium in snow samples collected in four mountain regions (the South American Andes, the Central Asian Hindu Kush, the Himalaya, and Mounts Kenya and Kilimanjaro in Africa) have been measured. The altitude effect in fresh snow precipitation and in the snow-pack was determined for δ180 as being within the range —0.6‰ to about — 1.0‰ per 100 m of elevation, but this can be altered or even inverted by secondary factors. These factors are connected with conditions of snow-fall and post-depositional changes in the snow, which are strongly dependent on the topography of the sampled mountain slope and on climatic conditions. All these effects are discussed.
Evidence of the Bedrock Beneath the Greenland Ice Sheet Near Camp Century, Greenland
Authors: Fountain John , Usselman Thomas M. , Wooden Joseph , Langway Chester C.
Published: September 2017

Igneous and metamorphic cobbles in sub-ice material recovered from a drill core which penetrated the ice sheet at Camp Century, Greenland, provide a rare look at the geology beneath the ice in the interior of Greenland. The sub-ice material can be correlated, based on petrography, with rocks of the Rinkian mobile belt of the west coast of Greenland; however, preliminary strontium isotopic data suggest such correlation should be made with caution. Chemical analyses and rare-earth element data are given to provide the basis for more rigorous correlations as more data become available on the Rinkian rocks.
Structure Control on Cirque-Like Features in South-East New York State, U.S.A.
Authors: Liebling Richard S. , Scherp Horst S.
Published: September 2017

Cirque-like features, occurring on the western flank of Shawangunk Mountain in south-east New York State, are unique in the area. Though these topographic forms are apparently the product of periglacial and glacial processes, their initiation and subsequent development were dependent to a considerable extent on a specific set of jointing and bedding attitudes and differential lithologies.
Micro-Morphology of the Snow Surface at the Quelccaya Ice Cap, Peru
Authors: Hastenrath Stefan , Koci Bruce
Published: September 2017

During the June-July 1979 expedition a large variety of micro-forms was observed at the surface of the Quelccaya ice cap, their altitudinal distribution being primarily controlled by the heat budget. At 5200–5300 m penitentes are best developed, with azimuth orientation and inclination of features conforming to the insolation geometry around local noon. At a westward-facing slope in 5360–5380 m a set of penitentes striking parallel to the contours is superimposed on the pattern dominating at the lower elevations. The ablation forms of penitentes give way to various deposition features above a transition zone around 5400 m in broad agreement with the larger net all-wave radiation and greater importance of melting at lower elevations. The succession of forms with an upward change from surface-parallel plates to elaborate dendritic forms appears to be controlled by the temperature conditions. The conspicuous development of forms encountered during the 1979 expedition appears characteristic of prolonged absence of fresh snow-fall subsequent to a season with abundant precipitation.
Interaction Among Controls of Cirque Development: Sangre de Cristo Mountains, Colorado, U.S.A.
Authors: Olyphant Greg A.
Published: September 2017

A regression model calibrated on 23 cirques from the Sangre de Cristo Mountains, south-central Colorado, suggests that local-scale climatic controls interact with geologic materials to explain intramountain variation to cirque development. Topoclimatic effects maximize cirque development on ridges that project well above the Pleistocene glaciation limit, and in positions that minimize total radiation receipt. If an optimum topoclimate coincides with densely jointed (erosible) bedrock materials, cirque development will be at a maximum. However, cirque development can be deceptively poor in situations where a favorable topoclimate coincides with massive (sparsely jointed) bedrock materials. The interaction between local-scale climatic–geologic controls subsumes their independent effects. Significant correlation between cirque development and an individual process control may not emerge due to complications produced by one or more other controls.
Supraglacial Re-Sedimentation from Melt-Water Streams on to Snow Overlying Glacier Ice, Sylgjujökull, West Vatnajökull, Iceland
Authors: Dowdeswell Julian A.
Published: September 2017

Sediment deposition on to snow overlying glacier ice occurs in a marginal zone extending 200–300 m up-glacier from the terminus of Sylgjujökull. Debris on ice above the marginal snow zone comes from debris-rich layers, and 85% of this debris falls between 1 and 4ϕ, the characteristic grain-size of volcanic ash within Icelandic glaciers. The ash is transported down-glacier as suspended load in melt-water streams at concentrations between 61 and 430 mg l−1, and loads from 0.2 to 32.7 g s−1. A diurnal hysteretic loop is present in the relationship between suspended sediment and discharge for one stream.

Supraglacial streams flow from relatively impermeable ice on to more permeable snow near the glacier terminus. As they move across the snow, stream discharge (up to 0.1 m3s−1on ice) is reduced and debris is re-sedimented as linear debris trains 1–3 cm thick and orientated orthogonal to the glacier margin. Since sediment deposition reduces the permeability of the snow substrate, the debris trains are successively extended across the snow cover at rates of up to 36.5 m d−1. If the debris is then let down on to glacier ice, linear dirt-cone assemblages may be produced. Re-sedimented debris trains are of little stratigraphic significance if deposited pro-glacially.
Preliminary Observations on Two Rock Glaciers in South Georgia, Falkland Islands Dependencies
Authors: Birnie Richard V. , Thom Gordon
Published: September 2017

Two rock glaciers are described from the maritime sub-Antarctic island of South Georgia. The Cooper Sound rock glacier is a spatulate feature, probably ice-cored, 1.5 km long, and developed below a dissected cirque headwall. The Binary Peaks rock glacier is a lobate feature, possibly ice-cemented, only 175 m long, and contiguous with the talus behind it. Evidence for an ice-cored rock glacier in this maritime environment indicates that the debris supply and receiving glacier areas may be more important factors in determining rock-glacier development than zonal climate.
Geophysical Investigations Of The Tropical Quelccaya Ice Cap, Peru
Authors: Thompson L. G. , Bolzan J. F. , Brecher H. H. , Kruss P. D. , Mosley-Thompson E. , Jezek K. C.
Published: September 2017

During the 1978 and 1979 field seasons, ice thicknesses on the Quelccaya ice cap were determined using a Worden geodetic gravity meter along a west–east traverse and using a mono–pulse ice radar sounder along a north–south traverse. The maximum ice thickness measured was 180 ± 10 m. Based upon the known thickness of the ice cap and the net accumulation, depth–age calculations indicate that an ice core record covering at least the past 600 years and perhaps 1 300 years could be obtained from this tropical ice cap.

A topographic map of the Qori Kalis glacier (the largest outlet glacier from the Quelccaya ice cap) has been compiled at a scale of 1:6 000 from 1963 aerial photography. Terrestrial photography of the glacier was obtained in 1978 and coordinates of the edge of the glacier were determined photogrammetrically. Comparison of these two shows that over this 15 year period the glacier has thinned with the terminus retreating more than 100 m. The retreat measured for the Qori Kalis glacier is consistent with the behavior of other tropical glaciers.
Radiometric Chronology of Neh–nar Glacier, Kashmir
Authors: Nijampurkar V. N. , Bhandari N. , Vohra C. P. , Krishnan V.
Published: September 2017

Surface and core samples of Neh–nar Glacier in the Kashmir Valley have been analysed for the radionuclides 32Si. 210Pb, 40K, and 137Cs. The lateral and vertical profiles (at an altitude of about 4 140 m) reveal:

(1)32Si activity decreasing slowly from the accumulation zone to 4 050 m altitude and then abruptly towards the snout.

(2)Five zones of alternating high and low 210Pb activity in the surface samples.

(3)An horizon at between 2 and 3 m depth containing 210Pb activity above natural levels. This horizon is also associated with 137Cs and a maximum in total ß activity.

The ice samples have been dated on the basis of a simplified two–component model, the “fresh“contribution determined by 2l0Pb and the old component by 32Si. The following conclusions can be drawn from these observations:

(1)The model age of the snout ice is c. 850 years.

(2)The average rate of ice movement in the lower glacier is about 2 m/year, which compares well with the annual movement rate of 2.65 m/year observed since 1974.
The Confined Compressive Strength of Polycrystalline Ice
Authors: Jones Stephen J.
Published: September 2017

Triaxial tests were carried out on randomly oriented, laboratory-made, polycrystalline ice, between strain-rates of 10–7and 10–1s–1and with confining pressures from 0.1 to 85 MN m–2, at –11 ± 1°C. Below strain-rates of about 10–5s–1the confining pressure has little effect, but at higher strain-rates the confining pressure prevents cracking which allows the compressive strength to rise to a value greater than the unconfined compressive strength. At 1.4 ×10–2s–1, the unconfined strength of 12 MN m–2rises to 26 MN m–2with a confining pressure of 25 MN m–2, before dropping slowly with greater confining pressures. Above 10–2s–1the unconfined strength decreases rapidly with increasing strain-rate, but the confined strength continues to increase. The dependence of strain rate on the maximum compressive stress is discussed.
Chemical Fractionation of Brine in the McMurdo Ice Shelf, Antarctica
Authors: Cragin James H. , Gow Anthony J. , Kovacs Austin
Published: September 2017

During the austral summers of 1976–77 and 1978–79, several ice cores were taken from the McMurdo Ice Shelf brine zone to investigate its thermal, physical, and chemical properties. This brine zone consists of a series of superimposed brine layers (waves) that originate at the seaward edge of the ice shelf and migrate at various rates, depending on their age and position in the ice shelf. The brine in these layers becomes increasingly concentrated as the waves migrate inland through the permeable ice-shelf firn. Chemical analyses of brine samples from the youngest (uppermost) brine wave show that, except for the advancing front, it contains sea salts in normal sea-water proportions. Further inland, deeper and older brine layers, though highly saline (S > 200°/00), are severely depleted in SO42-, with the SO42-/Na+ ratio being an order of magnitude less than that of normal sea-water. Consideration of the solubility of alternative salts, together with analyses of Na+, K+, Ca2+, Mg2+, SO42-, and Cl- concentrations, shows that the sulfate depletion is probably due to selective precipitation of mirabilite, Na2SO4·10H2O. The location of the inland boundary of brine penetration is closely related to the depth at which the brine encounters the firn/ice transition. However, a small but measureable migration of brine is still occurring in otherwise impermeable ice; this is attributed to eutectic dissolution of the ice by concentrated brine as it moves into deeper and warmer parts of the McMurdo Ice Shelf.
Explosive Growth of Shear-Heating Instabilities in the Down-Slope Creep of Ice Sheets
Authors: Yuen David A. , Saari Marc R. , Schubert Gerald
Published: September 2017

The time-scale for the onset of the explosive growth of a finite-amplitude shear-heating instability in the down-slope creep of a thick ice sheet is determined by integrating the equation for the temporal evolution of the temperature-depth profile subsequent to a sudden change in ice thickness. All instabilities eventually grow explosively after a prolonged period of simmering or relatively slow monotonic growth. Though times for explosive growth depend on initial and final ice thicknesses, surface temperature, accumulation rate, basal heat flux, and ice rheological parameters, the explosion times are extremely sensitive to the activation energy and the pre-exponential constant of the ice-creep law. Sudden increases in ice-sheet thickness of 1–2 km due to a rapid climatic deterioration can lead to explosive instability and melting of the basal shear layer in only thousands of years if ice-creep activation energies are lower than about 60 kJ mol-1.
Wave Ogives
Authors: Waddington E.D.
Published: September 2017

Wave ogives arise in a solution of the continuity equation by the method of characteristics. Steady ice flow is assumed. Ice velocity, channel width, and mass-balance functions combine to form a wave-excitation potential that yields the forcing function for wave ogives. This linear-systems formulation extends the ogive theory of Nye. Convolution of the temporal cumulative mass balance and spatial forcing functions gives the total wave pattern below an ice fall. Many ice falls do not generate ogives because the wave amplitude is modulated by a factor related to ice-fall length. The wave ogives at Austerdalsbreen, Norway, are due almost entirely to ice acceleration at the top of the ice-fall, i.e. the same zone that King and Lewis showed was responsible for forming Forbes bands.
Isotopic Fractionation at the Base of Polar and Sub-Polar Glaciers
Authors: Boulton G.S. , Spring U.
Published: September 2017

The melting of ice and the subsequent production of regelation ice from the melt water in a large-scale closed system beneath sub-polar and polar glaciers produces progressive fractionation between the melt water and the regelation ice derived from it. A theory is developed which predicts the change of isotopic composition in regelation ice in a subglacial zone of freezing and in the water from which it is derived. The theory is tested against data from the Byrd Station bore hole in West Antarctica, and applied to explain features of the isotopic composition in several other glaciers where thick sequences of regelation ice have formed.

The principal conclusions are:

1. Basal isotopic profiles can be used to reconstruct important features of a glacier’s hydrological system.

2. Isotopic profiles in basal regelation ice do not simply reflect isotopic characteristics of ancient atmospheres but also, by using the theory, some of the isotopic characteristics of the normal glacier ice which was destroyed by melting and subsequently produced regelation ice can be reconstructed. Basal regelation ice at Byrd Station reflects an original ice source isotopically colder than the overlying normal ice, and may have formed during the penultimate glacial period, equivalent to stage 6 of the oceanic record.

3. The subglacially derived debris typically found in basal regelation ice gives a complex strain response to a changing pattern of stresses produced by flow over an irregular subjacent bed. Thus, complex tectonic structures in this ice produce highly variable isotopic profiles. However, its gross isotopic characteristics can still be used to reconstruct some of its history. A sharp change in isotopic values tends to occur at the upper limit of basal regelation ice, the nature of which depends on the style and thickness of tectonic disturbance.

4. Isotopic profiles in basal ice can be used to distinguish normal glacier ice from regelation ice, and give strong support to the view that regelation is the major process by which debris is incorporated into the base of a glacier.
Method of Measuring Liquid Water Mass Fraction of Snow by Alcohol Solution
Authors: Fisk D.
Published: September 2017

a method of making field measurements of the liquid water fraction of snow has been developed in which a snow sample is dissolved in methanol to produce a temperature depression. The depression is linearly related to the liquid water content of the snow sample. a single operator can perform four to five measurements per hour with a maximum absolute error of 1.0%.
Some Comments on Glacier Flow
Authors: Finsterwalder Richard
Published: September 2017

Drs. Orowan and Perutz have shown that glacier ice does not behave as a viscous fluid but is plastic like all crystalline materials. The present author discusses two observed types of ice flow:—(1) the normal, regular streaming flow in slow-moving glaciers; (2) Block-Schollen movement in swiftly flowing ice. Mention is made of the shear plane or laminar flow theory of Philipp. lt appears that Orowan s thesis is also applicable to Block-Schollen flow. The author agrees with Orowan on the fundamental point that when ice is subjected to shear stress a critical value of the shear stress exists beyond which the ice alters its consistency. But the author disagrees with Orowan in that he believes that below this critical value ice behaves as a viscous material, and he supports this view by reference to many phenomena, measurements and calculations.
The Significance of air Bubbles in Glacier Ice
Authors: Bader Henri
Published: September 2017

The study of air bubbles in glacier ice can give valuable information on the evolution of the ice. An analysis of the relation between an air bubble and the water associated with it shows that it may be possible to determine the maximum depth from which the ice containing the bubble has emerged. The shapes of the cavities containing water and air bubbles are described. They are found to reflect the anisotropism of ice crystals and reveal that the main crystallographic axis is polar. The question of the mechanism of elimination of air bubbles from glacier ice is raised. The investigations were made on the very old and coarse-grained ice from the foot of the Malaspina Piedmont Glacier in Alaska, which is a temperate glacier.
The Possible Future Behaviour of Berendon Glacier, Canada—A Further Study
Authors: Fisher David A. , Jones Stephen J.
Published: September 2017

Untersteincr and Nye (1968) calculated the possible future movement of Berendon Glacier, B.C. These calculations are repeated using much improved data and a slightly different method for computing the datum state. The predictions that result are very similar to those found in the earlier work. It is concluded, however, from mass-balance data, that the chance of the glacier rising sufficiently in the next 25 years to be a danger to the mining installations situated near the snout of the glacier is much greater than was previously considered. The sensitivity of the theory to changes in input data is discussed.
Permafrost Occurrence in the Front Range, Colorado Rocky Mountains, U.S.A.
Authors: Ives Jack D. , Fahey Barry D.
Published: September 2017

In contrast to the extensive and rapidly growing body of knowledge on permafrost in the Eurasian and North American Arctic and sub-Arctic, little is known about permafrost occurrence in the high mountain regions of the world. Preliminary results of permafrost studies from the Colorado Rocky Mountains are presented.

Above tree line (about 3 500 m) in the Front Range, scattered patches of permafrost begin to occur under wet sites blown free of snow in winter with a mean annual air temperature of about — 1.0°C. At greater elevations, with correspondingly lower mean annual air temperatures (extreme case — 9.0°C and 4400 m), permafrost becomes more extensive and probably exceeds 60 m in thickness. These initial results are derived from a skeleton ground-temperature observation program supplemented by indirect evidence and by data gathered from engineering and mining operations in the high country. It is probable that under the higher summits and ridge crests the alpine equivalent of the continuous zone of Arctic permafrost can be anticipated.
River-ice Fabrics: Preliminary Results
Authors: Lasca N.P.
Published: September 2017

Preliminary data indicate that fabric is developed in river ice. Crystal orientations are usually sub-parallel to the ice surface, and develop partly in response to stress generated by stream flow.
The Formation of Brine Drainage Features in Young Sea Ice
Authors: Ingolf Eide Lars , Martin Seelye
Published: September 2017

Laboratory experiments on the growth of sea ice in a very thin plastic tank filled with salt water, cooled from above and insulated with thermopane, clearly show the formation and development of brine drainage channels. The sea-water freezing cell is 0.3 cm thick by 35 cm wide by 50 cm deep; the thermopane insulation permits the ice interior to be photographed. Experimentally, we observe that vertical channels with diameters of 1 to 3 mm and associated smaller feeder channels extend throughout the ice sheet. Close examination of the brine channels show that their diameter at the ice-water interface is much narrower than higher up in the ice, so that the channel has a “neck” at the interface. Further, oscillations occur in the brine channels, in that brine flows out of the channel followed by a flow of sea-water up into the channel. Theoretically, a qualitative theory based on the difference in pressure head between the brine inside the ice and the sea-water provides a consistent explanation for the formation of the channels, and the onset of a convective instability explains the existence of the neck. Finally, an analysis based on the presence of the brine-channel neck provides an explanation for the observed oscillations.
Steam, Hot-Water and Electrical Thermal Drills for Temperate Glaciers
Authors: Gillet F.
Published: September 2017

The study of temperate glaciers has led to the development of three drilling processes. The steam drill used for ablation stakes is easily portable and its speed is 30–40 m/h for the first 10 m. With the hot-water drill we can drill a fairly large but irregular hole; and reach 100 m depth in less than 5 h. The electro-thermal drill, usable to great depths, is particularly suitable for rapid drilling (15m/h and more) of small diameter holes (25 min) with easily portable equipment.
The Origin of Glacially Fluted Surfaces-Observations and Theory
Authors: Boulton G. S.
Published: September 2017

Studies of fluted surfaces beyond the margins of glaciers in Spitsbergen, Iceland,
Norway and the Alps show that almost all emanate from rigid obstructions, commonly boulders in
till. Field relations of flutes are described and it is shown that a relationship exists
between flute height and the height of the initiating obstruction. Subglacial observations
indicate that flutes form when till is intruded into tunnels which tend to open up in the lee
of obstacles. The pattern of strain implied by this process is shown to be reflected by micro-
and macrofabrics in the till. The commonly found occurrence of an average spacing between
flutes does not arise because of some rhythmic or periodic mechanism in the glacier, but is
produced by the random seeding of boulders which themselves generate flutes.

It is suggested that the term flute be used as a genetic rather than a descriptive
term, and be restricted to long parallel-sided ridges which reflect accurately the direction
of ice movement and which form when deformable subglacial materials are intruded into tunnels
which tend to open up on the lee sides of single rigid obstructions on the glacier
bed.
Deuterium, Tritium and Gross-Beta-Activity Investigations on Alpine Glaciers (Ötztal Alps)
Authors: Ambach W. , Eisner H. , Elsässer M. , Löschhorn U. , Moser H. , Rauert W. , Stichler W.
Published: September 2017

By measuring the deuterium contents of stream water, spring water and melt water, as well as ice and snow samples, the mean contributions to melt water in the run-off from Hintereisferner have been estimated: that of melt water being 60% and that of spring water being 40% in the months of July to September. Spring water is characterized by very low deuterium contents, whereas ice-melt water and snow-melt water in the summer were found to have about the same, rather high deuterium content. The deuterium content in the run-off was subjected to considerable seasonal fluctuations owing to the changing shares in melt water and spring water. The deuterium contents in individual glacier run-offs show similar seasonal fluctuations and are furthermore characterized by a parallel shift of the deuterium concentrations, because of the different altitudes of catchment areas. Differences in the mean altitudes of catchment areas were estimated for the winter and summer discharges on the basis of the isotope altitude effect.

The seasonal fluctuations of the tritium contents in glacier discharges are caused mainly by the melt water from glacier ice, which contains practically no tritium. Minimum values of tritium content in the runoff were thus found during the period of maximum ice ablation. The mean residence time of the base-flow in the ground-water system of a catchment area was roughly estimated to be a few years on account of the tritium content in the winter run-off and in the precipitations of past years.

Profiles of the gross beta activity in firn cores, despite a reduced atmospheric fall-out during the past years, clearly show activity peaks in summer horizons that are suitable for net accumulation analyses. A characteristic peak in the profile of the tritium content which may be attributed to the net accumulation of 1962/63 is well suited for use as a reference horizon.
Mathematical Model of a Three-Dimensional Non-Isothermal Glacier
Authors: Grigoryan S. S. , Krass M. S. , Shumskiy P. A.
Published: September 2017

A mathematical model is constructed for land glaciers with the thickness much less than the horizontal dimensions and radii of curvature of large bottom irregularities by means of the method of a thin boundary layer in dimensionless orthogonal coordinates. The dynamics are described by a statically determinate system of equations, so the solution for stresses is found. For the general non-isothermal case the interrelated velocity and temperature distributions are calculated by means of the iteration of solutions for velocity and for temperature. Temperature distribution is determined by a parabolic equation with a small parameter at the senior derivative. Its solution is reduced to the solution of a system of recurrent non-uniform differential equations of the first order by means of a series expansion of the small parameter. A relatively thin conducting boundary layer adjoins the upper and lower surfaces of a glacier, playing the role of a temperature damper in the ablation area. For ice divides, the statically indeterminate problem is solved, so the result for stresses depends on the temperature distribution.
Mathematical Models of Ice Shelves
Authors: Shumskiy P. A. , Krass M. S.
Published: September 2017

For flat external ice shelves, expanding freely in all directions, the problem of thermodynamics is one-dimensional. In the affine dimensionless system of coordinates, equations of the dynamics together with the rheological equation lead to the non-linear integro-differential equation involving the reduced temperature. In the quasi-steady case the boundary problem for this equation is solved by means of the method of combining asymptotic expansions. It is shown that if ice is coming from the upper and lower surfaces in the opposite directions the regime is unsteady because of the internal heat accumulation.

The integro-differential equation for the temperature in the case of thinning internal ice shelves is more complicated, but it can be solved by a method analogous to the one mentioned above.
Surface Mass-Balance Variability Near “Byrd” Station, Antarctica, and its Importance to Ice Core Stratigraphy
Authors: Whillans I. M.
Published: September 2017

The local variability in surface mass balance (net snow accumulation) up-glacier from "Byrd" station, Antarctica, is due to the combined effects of year-to-year "climate" variations and of the surface microrelief clue to snow drifts and sastrugi. These variabilities are consistent with the variability in surface mass balance obtained from core stratigraphy (Gow, 1968), and are used in a discussion of the difficulties encountered with the deep "Byrd" station core in detecting annual layering by the stable oxygen-isotope ratio and the microparticle concentration techniques. The recognition of annual layers by these techniques requires that the snows of certain seasons be present in the measured section, but near "Byrd" station the microrclief is such that summer snow layers are not horizontally continuous and may be absent from a given section. At other sites on ice sheets, where the microrelief is less (less wind activity) or where the surface mass balance is larger, or both, less difficulty is anticipated in using the stable oxygen-isotope ratio and micro-particle-concentration techniques to identify annual layers.
Recording Wire Strainmeters on the Barnes Ice Cap, Baffin Island, Canada
Authors: Evans K. , Goodman D.J. , Holdsworth G.
Published: September 2017

The report describes an experiment to evaluate the use of geophysical (Cambridge-type) wire strainmeters for the rapid acquisition of strain-rate data and to compare strains on a large ice mass over gauge distances of 5 m, 50 m, and 1 km.

Three continuously recording wire strainmeters were installed at the centre of two separate arrays of strain poles 10.6 km and 19.5 km from the ice divide on the Barnes Ice Cap. Data was collected between 24 April and 15 May 1976. The 1 km strain arrays had previously been measured in 1974 and 1975. The results show good agreement between the strainmeter data and the larger strain arrays at the 10.6 km site but differ at the 19.5 km site. When the daily means are calculated for the strainmeters at the 19.5 km site, the strain-rates show a possible periodic variation with an apparent period ofabout 11 d. Since there appears to be no direct correlation between the strainmeter signal and either temperature or pressure, the result is assumed to represent real varying strain within the ice.
Direct Measurement of Stress at the Base of a Glacier
Authors: Boulton G. S. , Morris E. M. , Armstrong A. A. , Thomas A.
Published: September 2017

Contact stress transducers were placed in subglacial bedrock and used to monitor continuously shear stress and normal pressure changes at the contact with the overriding glacier sole 100 m beneath the surface of the Glacier d’Argentière during periods in summer 1973 and spring 1975. The measured fluctuations in normal pressure and shear stress do not appear to be related to changes in sliding velocity. Analysis of the data reveals short-term fluctuations in normal pressure and shear stress which appear to be related to the passage of individual large debris particles or groups of particles over the transducer. The shear stress appears to be a function of the volume concentration of debris in the ice. The volume concentration at any point appears to be partially dependent on a “streaming” process by which basal debris-rich ice tends to flow around the lateral flanks of hummocks on the glacier bed. Where sub-glacial cavities occur, this streaming effect appears to be dependent on the extent of cavitation and thus on ice overburden pressure and velocity. It is suggested that this process can account for an apparent lag between changes in normal pressure and shear stress.

The maximum ratio between shear and normal stress averaged over a period of 10 min was 0.44. This is equivalent to a spatial average over 0.3 cm. Debris concentrations in basal ice of up to 43% by volume occurred. It is suggested that concentrations of this order are common at the base of temperate glaciers and thus that a significant part of the drag at the base of a glacier may be contributed by frictional interactions between the basal-debris load and the bed.
Pattern of Ice Surface Lowering for Rennick Glacier, Northern Victoria Land, Antarctica
Authors: Mayewski Paul A. , Attig John W. , Drewry David J.
Published: September 2017

Rennick Glacier is one of the major ice drainages in northern Victoria Land. Unlike glaciers farther south along the Transantarctic Mountains, Rennick Glacier does not drain into the Ross Ice Shelf but flows directly into a seasonally ice-covered ocean. Therefore, current fluctuations of this glacier are unhampered by the dampening effects of the Ross Ice Shelf. The primary controls on the activity of this glacier and others in this region are mass balance and sea-level.

Two major glacial events are recorded in the upper Rennick Glacier region. The location of erratics and glacially scoured features suggest that during the oldest or Evans glaciation ice covered all but the highest peaks in the region. Following this glaciation a re-advance produced the Rennick glaciation. Drift produced during this glaciation has a surface cover of unweathered clasts and is commonly found in the form of recessional moraines with associated ice-marginal lakes. Rennick Glacier is currently in a recessional phase of the Rennick glaciation. The phase is characterized by physical re-adjustments of local ice masses including progressive inland migration of the Rennick Glacier grounding line. To date the grounding line has migrated up to the mid-point of the glacier. This trend may be expected to continue.
The Formation and Composition of the Gas Content of Sea Ice
Authors: Tsurikov V. L.
Published: September 2017

The different factors contributing to the formation of the gas porosity of sea ice are: (Ia) gases captured during the formation of the initial ice cover, (Ib) gases released from solution during the initial freezing of sea-water, (Ic) the inclusion of gases rising from the sea bottom, (2a) the substitution of gas for brine drained from the ice during times of melting, (2b) the release of gas from the brine within the ice during the course of partial freezing, and (2c) the formation of voids filled with water vapour during the course of internal melting. An analysis is made of each of these processes and it is concluded that processes Ib, 2a, and 2C are important. Process Ic may also be a major effect but it is difficult to evaluate until the rate of gas release from the sea floor is better known. The migration of air pockets into the ice from the overlying snow is shown to be a possible but not a significant effect. Available data on the composition of gas in sea ice are reviewed and it is shown to be significantly different from air. Possible causes for these differences are discussed.

The porosity of sea ice, i.e. the total relative volume of its gas plus its brine inclusions, is one of the factors strongly affecting its strength, as has been shown by Tsurikov (1947) and by Weeks and Assur (1968). In seas with high salinities the effect of the presence of brine within the ice will usually be the dominant factor. However on water bodies with low salinities the effect of the gas included within the ice may be greater than the effect of the brine. Despite its significance there have not been any attempts at a quantitative analysis of the entrapment of gas in sea ice. This paper is an attempt at such a study.
Flexural Wave Studies on the Basis of Single-Sensor Recordings
Authors: Taylor R. W.
Published: September 2017

The method described here provides a means of measuring flexural-wave dispersion and attenuation appropriate to a selected area, on the basis of single-sensor recordings made remote from the area of interest. The measured dispersion may then be inverted in the conventional manner to obtain thickness and elastic properties of the ice within the selected area. The procedure eliminates the need for equipment within the study area and minimizes the need for personnel within the area. As only a single sensor is necessary, the requirements for recording equipment and sensor cabling are also minimized. The method is suited to any study of flexural-wave dispersion from artificial sources and is ideally suited to the study of areas where personnel and equipment safety are a major concern.
Gravitational Stresses in Floating Ice Sheets
Authors: Evans R.J. , Parmerter R. Reid
Published: September 2017

This note is addressed to the determination of the in-plane components of stress in floating ice sheets due to gravity and the hydrostatic pressure in the water. The distribution and magnitude of these stresses are of interest with regard to crack propagation in sea ice. Two cases are considered. In the first, the ice sheet is formed on land by accretion at the top surface and then introduced into the water, such as happens in the Antarctic. In the second, the ice is formed in the water by accretion on the bottom, which is the usual situation in the Arctic pack ice.
An Analysis of the In-Situ Resistivity of Sea Ice in Terms of its Microstructure
Authors: Timco G. W.
Published: September 2017

The results of 66 Schlumberger geoelectric soundings on first-year sea ice are analysed to obtain average values of d.c. electrical resistivity both parallel ρ1 and perpendicular ρp to the long brine cell direction. This analysis yields ρ1 = 104 Ω m, 80 Ω m, 45 Ω m, and ρp = 298 Ω m, 230 Ω m, 129 Ω m for brine volumes νb of 40‰, 67‰, and 82‰ respectively. The observed dependence of ρ1 on νb is used in conjunction with a mixing formula for the electrical resistivity of a two-phase heterogeneous system to arrive at values of “average” brine cell lengths l for relatively warm sea ice. This treatment yields l ≈ 1.7 cm for 40‰ ≤νb≤ 70‰ with a rapid extension of brine cell lengths for brine volumes above c. 70‰.
A Field Study of Brine Drainage and Oil Entrainment in First-Year Sea Ice
Authors: Martin Seelye
Published: September 2017

From field observations this paper describes the growth and development of first-year sea ice and its interaction with petroleum. In particular, when sea ice initially forms, there is an upward salt transport so that the ice surface has a highly saline layer, regardless of whether the initial ice is frazil, columnar, or slush ice. When the ice warms in the spring, because of the eutectic condition, the surface salt liquifies and drains through the ice, leading to the formation of top-to-bottom brine channels and void spaces in the upper part of the ice. If oil is released beneath winter ice, then the oil becomes entrained in thin lenses within the ice. In the spring, this oil flows up to the surface through the newly-opened brine channels and distributes itself within the brine-channel feeder systems, on the ice surface, and in horizontal layers in the upper part of the ice. The paper shows that these layers probably form from the interaction of the brine drainage with the percolation of melt water from surface snow down into the ice and the rise of the oil from below. Finally in the summer, the oil on the surface leads to melt-pond formation. The solar energy absorbed by the oil on the surface of these melt ponds eventually causes the melt pond to melt through the ice, and the oil is again released into the ocean.