bluuebunny/crossref_metadata_2025 huggingface dataset:
A Model Investigation of Interannual Sea-Ice Variability in the Beaufort Sea
Authors: Ross Becky
Published: September 2017

Model-generated ice-thickness fields for the period 1961–80 are examined in the context of summertime sea-ice predictability in the Beaufort Sea. The correspondence between the modeled and observed fluctuations of ice-covered area is found to be quite good. Lag correlation coefficients based on departures from 20 year “normals” of the ice thicknesses show that the ice anomalies are persistent throughout the August–May period. However, because the thickness anomalies undergo large fluctuations during July and August, only a small amount of summertime predictability can be derived from the thickness data. The findings are consistent with the observational results of Rogers (1978), who found that summertime temperatures and wind directions accounted for much of the variability of Beaufort Sea ice during August and September.
A Field Study of Rough Shore-Fast Sea Ice
Authors: O’D Thomas , Hanley S.J.
Published: September 2017

During December 1973 the initial smooth ice cover on the Chukchi Sea near Barrow, Alaska, broke away from the shore during a period of strong wind and was replaced by a cover of broken, rafted ice which remained for the rest of the winter. Cores pulled from this cover were examined visually, and the salinity and density of sections of the cores were measured. Temperatures at several depths in the ice were recorded continuously, and these are presented near the date when the temperature gradient changed sign. Despite large deviations probably due to the irregularity of the ice cover, thickness and salinity followed the patterns seen by other observers.
The Pico Lightweight Coring Auger
Authors: Koci Bruce R. , Kuivinen Karl C.
Published: September 2017

A new lightweight hand-operated coring auger for use in firn or ice is described. Extensive use of glass-epoxy composites contributes to a drill weight of approximately 1 kg/m in 20 m and 50 m configurations.
Rates of Deposition on Lateral Moraine Embankments, Glacier De Tsidjiore Nouve, Valais, Switzerland
Authors: Small R. J. , Beecroft I. R. , Stirling D. M.
Published: September 2017

In the last decade deposition on lateral moraine embankments of glacier de Tsidjiore Nouve has been re-activated on a large scale. An attempt has been made to reconstruct, from the dimensions of the embankments, average rates of debris accumulation on the moraines during the Neoglacial period. These are compared with rates of deposition over the period 1977–82, calculated from detailed changes in moraine profiles (surveyed by ground- and air-based photogrammetry) and measured rates of ice-margin ablation. At present total output of sediment, by marginal deposition and transport by melt-water streams, from glacier de Tsidjiore Nouve is in the order of 6400–9500m3/a; this suggests the possibility of a high average erosion rate within the glacier catchment of 1.55–2.29 mm/a.
Analyzing the Spatial Distribution of Drumlins: A Two-Phase Mosaic Approach
Authors: Boots B. N. , Burns R. K.
Published: September 2017

Researchers have analyzed various properties of drumlins within individual drumlin fields in order to provide evidence to help in identifying the processes involved in drumlin formation. One property which has been examined is the spatial distribution of drumlins within a field. Traditionally, in such endeavours the individual drumlins have been represented as points and their distribution examined using techniques of point-pattern analysis. We suggest that not only is such a representation inappropriate at this scale, it also introduces statistical bias which makes the results of such analyses questionable. Consequently, we propose an alternative approach which involves representing individual drumlins as areal phenomena and considering their pattern as a two-phase mosaic. The advantages of such an approach are discussed and it is illustrated by applying it to two different drumlin fields.
A New Dry Extraction System for Gases in Ice
Authors: Moor Ernst , Stauffer Bernhard
Published: September 2017

A new extraction system has been designed and constructed which allows the extraction of gases from air bubbles in ice without melting it. The ice sample of about 500 g is crushed an evacuated container by a milling cutter, and the gas escaping from the opened bubbles is collected by condensation at 15K. Results of CO2 analyses of extracted gases are discussed with respect to possible contamination risks by the system.
On the Isotopic Composition in δD and δ18O of Water and Ice During Freezing
Authors: Souchez R. A. , Jouzel J.
Published: September 2017

Experiments on progressive unidirectional freezing are conducted to determine the evolution inδD andδ18O of successive water samples and ice layers taken during the course of freezing. Results indicate that this evolution takes place, in aδD–δ18O diagram, along a straight line with a characteristic slope. This slope, different from that due to the precipitation effect, gives a finger-print of the occurrence of a freezing or of a melting–refreezing process in the studied reservoir.
A Reconsideration of the Mass Balance of a Portion of the Ross Ice Shelf, Antarctica
Authors: Jezek Kenneth C. , Bentley Charles R.
Published: September 2017

The identification of a small region of grounded ice in the north-western sector of the Ross Ice Shelf has forced a re-evaluation of the mass-balance calculations carried out by Thomas and Bentley (1978). Those authors concluded that the Ross Ice Shelf up-stream of Crary Ice Rise was thickening, but they did not take into account the effects on the velocity field of grounded ice (of which they were unaware), which is located near the input gate to their volume element. Reasonable estimates of the degree to which the ice velocity just up-stream of the grounded ice is diminished indicate that it is no longer possible to conclude that the ice shelf is thickening using Thomas and Bentley’s original flow band. Therefore, a new flow band was chosen which was grid east of Thomas and Bentley’s band and unaffected by any nearby grounded areas. The mass balance in this flow band was found to be zero within experimental error; a difference exceeding about 0.2 m a−1 in magnitude between the thickening and bottom freeze-on rates is unlikely.
Audibility within and Outside Deposited Snow
Authors: Johnson Jerome B.
Published: September 2017

Factors which control the audibility within and outside deposited snow are described and applied to explain the preferential detection of sound by persons buried under avalanche debris as compared to persons on the overlying snow surface. Strong attenuation of acoustic waves in snow and the small acoustic impedance differences between snow and air are responsible for the strong absorption and transmission-loss characteristics that are observed for snow. The absorption and transmission-loss characteristics are independent of the direction of propagation of acoustic signals through the snow. The preferential detection of sound by a person buried under snow can be explained by the relatively higher level of background acoustic noise that exists for persons above the snow surface as compared to an avalanche burial victim. This noise masks sound transmitted to persons on the snow surface, causing a reduction of hearing senstitivity as compared to the burial victim. Additionally, the listening concentration of a buried individual is generally greater than for persons working on the snow surface, increasing their subjective awareness of sound.
Changes in Texture and Fabric of Particles in Glacial Traction with Distance from Source, Mỳrdalsjökull, Iceland
Authors: Humlum Ole
Published: September 2017

Evolution of sedimentological characteristics for traction debris is investigated along a transport path down-glacier from a subglacial point source at the northern rim of the ice cap MỲrdalsjökull, Iceland. Losses and gains from this path are discussed. Close to mature characteristics as to particle size, shape, roundness, and fabric are developed after only short basal transport, about 500 m, while further transport only results in minor changes. This development is interpreted as the result of selective subglacial lodgement of large particles and/or particles with longitudinal α-axis orientation, while particles of median size and/or oblique orientation tend to stay in basal transport. Implications for basal sliding and subglacial sedimentation patterns are discussed.
Measurement of the Fracture Toughness of Glacier Ice
Authors: Andrews R.M.
Published: September 2017

Fracture-toughness testing of both fresh-water and sea ice has used specimen geometries designed for metals. These designs are too large and difficult to manufacture for testing material cored from a glacier. This paper presents an alternative specimen, a radially cracked ring fractured by internal pressure. Tests using this specimen on the Bersærkerbræ, a valley glacier in the Stauning Alper, north-east Greenland, gave a mean fracture toughness of 58 . This is half the value typically obtained by other workers in laboratory tests. The results are compared with other data and the reasons for the disagreement discussed.
Cylindrical Flow in and Over Channels of Irregular Shape
Authors: Shoemaker E. M.
Published: September 2017

Earlier work by Nye (1965), who obtained numerical solutions for axial independent flow of a non-linear Glen material in channels of rectangular, elliptic, and parabolic cross-sections with a null-slip basal condition, is extended by using an inverse technique. Exact analytical solutions are obtained for flow in irregular-shaped channels (subject to symmetry restrictions) for both a Newtonian and an n = 3 Glen material. The cross-sections are regulated by multi-parameters. Solutions are obtained for two types of channel: (a) those whose side walls meet the free ice surface vertically, and (b) periodic channel arrays whose basal profiles do not intersect the free ice surface, i.e. overfilled channels. Solutions for the second type have not been presented previously. The solutions for the n = 3 Glen material employ a small parameter which limits the geometry variation to perturbations on semicircular or uniform-depth channels. Basal slip conditions can be incorporated although results are not presented here.
A Reconstruction of Snow-Avalanche Characteristics in Montana, U.S.A., Using Vegetative Indicators
Authors: Butler David R. , Malanson George P.
Published: September 2017

Widespread wet-snow avalanches were observed on the southern boundary of Glacier National Park, Montana, in February 1979. Severe tilting, scarring, and breakage of trees were observed along a transverse trim-line of one path, 70 m from a wet-snow deposit. Tree-ring data were used to establish the date of occurrence, and the nature of damage was used to characterize the avalanche event. The event probably included a previously unrecognized dry-snow avalanche and associated wind blast. Such events present different problems for natural-hazard planning. The nature of vegetative damage along the margins of avalanche paths is shown to be a useful indicator of the characteristics of past unobserved avalanche events.
Examination of Selected Microparticles from the Sentik Glacier Core, Ladakh Himalaya, India
Authors: Goss Emily , Mayewski Paul A. , Lyons William Berry
Published: September 2017

Several characteristics and interpretative comments are reported for microparticles from selected samples in the Sentik Glacier core. Four basic morphologic groups are defined: platy, angular, biogenic, and anomalous.
Icing on a Non-Rotating Cylinder Under Conditions of High Liquid Water Content in the Air: II. Heat Transfer and Rate of Ice Growth
Authors: Launiainen Jouko , Lyyra Markku
Published: September 2017

The rate of ice growth and heat transfer during a stationary wet-growth icing was studied, based on wind-tunnel experiments of Reynolds numbers of I04 to 105, and air temperatures of 0°C to –13°C. The convective heat-transfer coefficient, a quantity of primary importance entering the heat-balance equation of a freezing surface, was found to depend strongly on the liquid water content in the air (or rather, on the impinging water flow on the surface). The convective heat-transfer coefficient was considered theoretically and the dependence is thought to be caused by an increase in the surface roughness and, especially, by an effect of the impinging water droplets on viscous sub-layers and on turbulent heat transfer near the icing boundary. The above evaluation allows us to calculate an accretion efficiency for each icing condition.
Subglacial Hydrology for an Ice Sheet Resting on a Deformable Aquifer
Authors: Shoemaker E. M.
Published: September 2017

Subglacial hydrology is investigated for an ice sheet where the substrate consists of a deformable aquifer resting on an aquitard. If sliding velocities are low or absent, subglacial melt-water drainage is dominated by drainage through the aquifer to water channels. Drainage along the bed is negligible. Efficient melt-water drainage requires that a system of subglacial water channels exists; otherwise, pore-water pressures will exceed the overburden pressure. In general, aquifer deformation near (away from) the terminus is most likely to occur during the winter (summer). The effect of short-term high channel pressures is, in general, not critical to aquifer deformation because the pressure pulse does not propagate far into the aquifer. (For aquifers of high permeability, short periods of high channel pressures constitute the most critical condition.) Aquifer deformation at the terminus is very likely to occur if the terminus ice slope exceeds tan ϕ, where ϕ is the Coulomb friction angle of the aquifer material. Upwelling of basal melt water near the terminus will normally cause soil dilation if the aquifer has a low permeability (e.g. till). Maximal profiles are computed corresponding to various aquifer materials using channel spacings which provide efficient drainage. (A maximal profile is the highest ice profile which the aquifer can sustain without deformation.) In general, maximal profiles lie well above observed profiles (such as h(x) = 3x1/2 (m)) except near the terminus. However, if channel spacings are sufficiently large, pore-water pressures are increased and maximal profiles can lie well below h(x) = 3x1/2.
Glacial Erosion of a High Arctic Valley
Authors: England John
Published: September 2017

A large valley, ideally suited for “selective linear erosion” by ice, extends from the Kreiger Mountains to Tanquary Fiord, north–central Ellesmere Island. During the last glaciation, the outlet glacier at the head of the valley advanced 18 km and was at least 250 m thick where it contacted the sea in the lower valley. Erosion of bedrock inside the last ice limit is recorded by an abraded diabase dike, and by crag–and–tail features developed in limestone. During deglaciation (7800 B.P.), melt–water streams along the ice margin incised a large alluvial fan that pre–dates the last glaciation. The fan shows little alteration by the over–riding ice and its final erosion by the melt–water streams incised, but did not remove, its original ice–wedge polygons.

The preservation of the fan indicates that the glacier was locally non–erosive and that it probably advanced across the fan by over–riding a protective frontal ice apron. Although it is commonly assumed that such alluvial fans occupying glaciated valleys are of post–glacial age, this need not be the case in permafrost terrain. In fact, at this site, there has been a net increment of alluvium versus glacial erosion or deposition spanning the last glacial cycle. The paper discusses the processes of erosion associated with sub–polar glaciers and questions whether erosion by them or more pervasive ice is responsible for such High Arctic valleys and fiords.
The Formation of Fjord Thresholds
Authors: Shoemaker E. M.
Published: September 2017

The erosion rate of bedrock by glacier action is analyzed under conditions of constant-state radial convergent and divergent flow, assuming that the quarrying rate increases with increasing sliding velocity, and assuming a conventional power-function sliding law. Ice is modeled as a non-linear Glen material. Deviatoric stresses are computed but are shown to be negligible compared to the basal shear stress, provided that suitable restraints are placed on the ratio of channel radius of curvature to ice thickness. If the ice is sufficiently thick, radial divergent flow results in erosion rates which decrease in the down-stream direction This provides an explanation for the formation of the largest class of fjord thresholds which occur at channel widenings. In contrast, increased erosion rates are predicted at narrows which can explain the presence of deep troughs at gradual narrows. It is argued that the presence of pronounced thresholds in abrupt narrows can be explained by low quarryability or locally high roughness which reduces the sliding velocity. The origin of till overlying thresholds is explained as a natural consequence of a threshold being a position of relative stability for the terminus of a retreating tide-water glacier.
The Effects of Basal Melting on the Present Flow of the Ross Ice Shelf, Antarctica
Authors: MacAyeal D.R. , Thomas R.H.
Published: September 2017

We use a hybrid finite-element/finite-difference model of ice-shelf flow and heat transfer to investigate the effects of basal melting on the present observed flow of the Ross Ice Shelf, Two hypothetical basal melting scenarios are compared: (i) zero melting everywhere and (ii) melting sufficient to balance any large-scale patterns of ice-shelf thickening that would otherwise occur. As a result of the temperature-dependent flow law (which we idealize as having a constant activation energy of 120 kJ mol−1, a scaling coefficient of 1.3 N m−2 s1/3, and an exponent of 3), simulated ice-shelf velocities for the second scenario are reduced by up to 20% below those of the first. Our results support the hypothesis that melting patterns presently maintain ice thickness in steady state and conform to patterns of oceanic circulation presently thought to ventilate the sub-ice cavity. Differences between the simulated and observed velocities are too large in the extreme south-eastern quarter of the ice shelf to permit verification of either basal melting scenario. These differences highlight the need to improve model boundary conditions at points where ice streams feed the ice shelf and where the ice shelf meets stagnant grounded ice.
On the Mechanics of Surging Glaciers
Authors: McMeeking R. M. , Johnson R. E.
Published: September 2017

Observations of surging glaciers indicate that the flow regime is one dominated by extensional flow. The stress state has substantial longitudinal deviatoric stress. This regime is very different from the conventional model for glacier dynamics which is dominated by shearing flow. In addition, the initiation of surging often involves a compression front which travels down the glacier. The compression front seems to divide an up-stream region of high drag at the base of the glacier from one of low drag which allows the rapid sliding. We develop a framework for the mechanics of glaciers undergoing surging. Relevant issues are the extensional and compression flows, high longitudinal deviatoric stress, and the stress state near the basal discontinuity. We find that some of the down-slope component of glacier weight is borne by longitudinal stress in the rapidly sliding region. This stress thrusts against the slowly moving parts of the glacier. We hypothesize that this effect causes the rapidly sliding part to spread and causes the compression front to travel down the glacier. A criterion for spreading of the rapidly sliding part is developed. The mechanics outlined above are used to develop a highly idealized model for glacier surging. We propose that regions of low drag are relatively common features of glaciers. The surge initiates when conditions are met which allow the surge nucleus to spread. The rapidly sliding region of low drag spreads to a large part of the glacier. Surging ends when the low-drag conditions terminate. Because of the changed state of the glacier, surge nuclei are now stable against spreading. Several years of rebuilding must occur before nuclei are once more unstable. Calculations are performed for the evolution of the shape of Medvezhy Glacier during the surge of 1963. We find a remarkable similarity between the data and our computations.
Waterways, Ice Permeability at Depth, and Water Pressures at Glacier D’Argentière, French Alps
Authors: Hantz Didier , Lliboutry Louis
Published: September 2017

To clear up the changes which had happened at the subglacial catchment of glacier d’Argentière, an extensive study, with 31 borings and a coring down to the bottom (240 m) was performed in 1979/80, just upstream from the catchment, in an overdeepened area. The behaviour of the water level during boring with a hot water jet, and just after, was different from one bore hole to another, mainly because transient leaks appeared in the walls of bore holes. Next, the water level fluctuated slowly, in the same way in most of the deep bore holes, showing that glacier ice below about 100 m deep is slightly pervious. What is so measured is the pore pressure of water in deep ice. The piezometric gradient between bore holes, and the time lag between fluctuations of water level, which increases with distance from the right bank, shows that there is no waterway at the bottom of the overdeepened area, save at its up-stream end. Most of the melt water must flow between ice and rock along the right bank, its free surface rising by about 150 m during the increased discharge in June. No clear-cut correlation between the bottom pore pressure and the air temperature or the discharge at the subglacial catchment down-stream was found.
The Energy-Balance Structure of the Antarctic Ice Sheet/Atmosphere System as an Index of Antarctic Glaciation
Authors: Aver’yanov V. G.
Published: September 2017

Mean multi-year values of the components of external mass and energy exchange in the ice sheet, moisture, radiation, and heat balances in the system Antarctic ice sheet/atmosphere have been estimated by various methods.

The major features of the above-mentioned balances have been determined as absolute and relative values. For the moisture balance, income of advective moisture is equal to 100%; loss due to accumulation of moisture in the ice sheet is 83%, due to sink into the atmosphere is 15%, and sink from the ice sheet surface is 2%. As for the radiation balance it has been found that income due to radiation at the top of the atmosphere and absorbed by the atmosphere long-wave radiation are 57% and 43%, respectively; loss due to reflected short-wave radiation is 35%, atmospheric long-wave radiation is 78%, and net outgoing radiation from the surface is 9%. Heat budget components have been found as follows: income due to absorbed short-wave radiation is 49%, advection of heat is 40%, and latent heat from phase transition of advective moisture is 11%; loss due to outgoing long-wave radiation is 98%, heat from phase transition of atmospheric moisture is 2%.

The Antarctic ice sheet is a vast area of heat sink. Constant negative surface radiation balance and low temperature of the ice sheet suggest that the latter will exist at any small amount of precipitation and, therefore, current glaciation of Antarctica is rather stable.
Accumulation Characteristics on a Cold, High-Alpine Firn Saddle from a Snow-Pit Study on Colle Gnifetti, Monte Rosa, Swiss Alps
Authors: Haeberli W. , Schotterer U. , Wagenbach D. , Schwitter H. Haeberli , Bortenschlager S.
Published: September 2017

In a snow pit, incorporating about 2.5 a of accumulation, on the 4 450 m high Colle Gnifetti, Monte Rosa, various snow characteristics, isotopes (δ18O,3H), electrical conductivity, dust, trace elements, and pollen were investigated. The aim of this study was to develop a key for the stratigraphic interpretation of cores from cold, high-alpine firn areas. It appears that the strong influence of wind results in mixing and re-sedimentation processes in the surface layers. Nevertheless, by interpreting several parameters in a combined way, it is possible to classify a large number of the layers according to their season and sometimes to their place of origin. Apart from the melt layers, which only appear in early summer to summer layers, other prominent features are the (Saharan) dust falls, characterized by dust and conductivity peaks.
Spectral Reflectances of Snow and Fresh-Water Ice from 340 Through 1 100 nm
Authors: Bolsenga S. J.
Published: September 2017

Measured spectral reflectances of new and moderately metamorphosed snow were generally >80% from 340–950 nm. From 950–1 100 nm a characteristic dip and rise of spectral reflectances occurred. One spectroradiometer scan over a deteriorated snow patch showed much lower spectral reflectances than fresh snow, but the shape of the curve remained similar to that of fresher snow. Spectral reflectances for clear ice contrasted sharply with those for snow. In general, values were <10% and the curves lacked distinctive shape. Higher spectral reflectances, due to “lighter”-appearing ice in the measurement area, were measured at some sites. Refrozen slush, pancake, brash, and slush curd ice revealed spectral reflectance curves similar in form to each other, but which varied significantly in the range of spectral reflectances for each ice type. Generally, reflectances rose slowly from 340 nm to a peak near 550 nm. From 550–775 nm reflectances decreased slowly but significantly. A slight dip and rise in reflectances occured from 775–850 nm after which values again dipped significantly (850–900 nm). From 950–1 100 nm, a dip and rise in reflectances similar to that for snow was observed. The amount of slush included seems to control the reflectances of these ice types. All measurements were acquired with a pair of scanning spectroradiometers having picowatt accuracy, adapted to obtain, automatically, simultaneous readings of incident and reflected radiation from 340–1 100 nm. The spectroradiometers were field-calibrated using Sun-plus-sky radiation as a calibration source.
Inter-Relations between the Arctic Sea Ice and the General Circulation of the Atmosphere
Authors: Wendler G. , Nagashima Y.
Published: September 2017

Satellite imagery has substantially improved the quality of sea-ice observation over the last decades. Therefore, for a 25 year period, a statistical study based on the monthly Arctic sea-ice data and the monthly mean 700 mbar maps of the Northern Hemisphere was carried out to establish the relationships between sea-ice conditions and the general circulation of the atmosphere. It was found that sea-ice conditions have two opposing effects on the zonal circulation intensity, depending on the season. Heavier than normal ice in winter causes stronger than normal zonal circulation in the subsequent months, whereas heavier than normal ice in the summer-fall causes weaker zonal circulation in the subsequent months. Analyzing the two sectors, the Atlantic and Pacific ones separately, a negative correlation was found, which means a heavy ice year in the Atlantic Ocean is normally associated with a light one in the Pacific Ocean and vice versa.
Steady-State Three-Dimensional Ice Flow over an Undulating Base: First-Order Theory with Linear Ice Rheology
Authors: Reeh Niels
Published: September 2017

The problem of ice flow over threedimensional basal irregularities is studied by considering the steady motion of a fluid with a linear constitutive equation over sine-shaped basal undulations. The undisturbed flow is simple shear flow with constant depth. Using the ratio of the amplitude of the basal undulations to the ice thickness as perturbation parameter, equations to the first order for the velocity and pressure perturbations are set up and solved.

The study shows that when the widths of the basal undulations are larger than 2–3 times their lengths, the finite width of the undulations has only a minor influence on the flow, which to a good approximation may be considered two-dimensional. However, as the ratio between the longitudinal and the transverse wavelength L/W increases, the three-dimensional flow effects becomes substantial. If, for example, the ratio of L to W exceeds 3, surface amplitudes are reduced by more than one order of magnitude as compared to the two-dimensional case. The L/W ratio also influences the depth variation of the amplitudes of internal layers and the depth variation of perturbation velocities and strain-rates. With increasing L/W ratio, the changes of these quantities are concentrated in a near-bottom layer of decreasing thickness. Furthermore, it is shown, that the azimuth of the velocity vector may change by up to 10° between the surface and the base of the ice sheet, and that significant transverse flow may occur at depth without manifesting itself at the surface to any significant degree.
Force, Mass, and Energy Budgets of the Crary Ice Rise Complex, Antarctica
Authors: Macayeal D.R. , Bindschadler R.A. , Shabtaie S. , Stephenson S. , Bentley C.R.
Published: September 2017

Resistive force exerted by the Crary Ice Rise on its ice-shelf/ice-stream environment and back-pressure force transmitted across the grounding lines of Ice Streams A and B are calculated from airborne radio echo-sounding data and measurements of surface strain-rates. Resistance generated by the ice rise ranges in magnitude between 45 and 51% of the back-pressure force on the ice streams (depending on the flow law). The mechanical-energy budget of the ice rise is computed by considering work done against frictional forces at the perimeter of the ice rise and gravitational potential energy fluxes associated with changing mass distribution in the ice/ocean system. Energy dissipated by flow surrounding the ice rise is balanced by potential energy released within Ice Streams A and B, and accounts for between 15 and 49% of the work done by the ice streams against ice-shelf back pressure at their grounding lines. Mass balance of the ice rise, and the discharge of Ice Streams A and B, are calculated from surface-velocity and snow-accumulation measurements. The ice rise and its immediate environment gain mass by advection and snowfall at a rate equivalent to an area-averaged thickening rate of 0.44 ± 0.06 m/year. This mass gain may be balanced by regional basal melting (which we do not measure), or could contribute to ice-rise expansion through regional thickening and ice-shelf grounding. Approximately 1/4 to 1/2 of the excess volume discharged by Ice Streams A and B above snow accumulation in their catchment areas is deposited in the vicinity of the ice rise (or melted from the bottom of the ice shelf). This suggests that the ice rise may have formed as a consequence of recent ice-stream acceleration, and that its continued growth may eventually reverse this trend of ice-stream discharge.
Electrochaude: A Self-Flushing Hot-Water Drilling Apparatus for Glaciers With Debris
Authors: Rado Claude , Girard Claude , Perrin Jacky
Published: September 2017

In order to avoid problems stemming from the accumulation of rock fragments at the bottom of the hole during conventional thermal drilling in ice, a new type of probe has been developed. In this system, the water is warmed electrically inside the probe itself and propelled by a micro-pump. In this way, the hot water sprayed towards the ice scatters the insulating layer of debris and drilling continues normally, as shown by tests on several glaciers over the past 4 years.
Strain-Rate and Grain‒Size Effects in Ice
Authors: Cole David M.
Published: September 2017

This paper presents and discusses the results of constant deformation-rate tests on laboratory-prepared polycrystalline ice. Strain-rates ranged from 10−7 to 10−1s−1, grain–size ranged from 1.5 to 5.8 mm, and the test temperature was −5°C.

At strain-rates between 10−7 and 10−3 s−1, the stress-strain-rate relationship followed a power law with an exponent of n = 4.3 calculated without regard to grain-size. However, a reversal in the grain-size effect was observed: below a transition point near 4 × 10−6 s−1 the peak stress increased with increasing grain-size, while above the transition point the peak stress decreased with increasing grain-size. This latter trend persisted to the highest strain-rates observed. At strain-rates above 10−3 s−1 the peak stress became independent of strain-rate.

The unusual trends exhibited at the lower strain-rates are attributed to the influence of the grain-size on the balance of the operative deformation mechanisms. Dynamic recrystallization appears to intervene in the case of the finer-grained material and serves to lower the peak stress. At comparable strain-rates, however, the large-grained material still experiences internal micro-fracturing, and thin sections reveal extensive deformation in the grain-boundary regions that is quite unlike the appearance of the strain-induced boundary migration characteristic of the fine-grained material.
Observations on a Debris-Covered Polar Glacier “Whisky Glacier”, James Ross Island, Antarctic Peninsula, Antarctica
Authors: Chinn T.J.H. , Dillon A.
Published: September 2017

“Whisky Glacier” on James Ross Island, Antarctic Peninsula, comprises a névé and clean ice trunk surrounded by an extensive area of debris-covered ice resembling a rock glacier. The debris-free trunk of the glacier abuts abruptly against the broad, totally debris-covered tongue at a number of concentric zones where debris-laden beds crop out at the surface in a manner similar to the “inner moraine” formations of many polar glaciers.

Ice structures and foliation suggest that “Whisky Glacier” is a polythermal glacier which is wet-based under the debris-free zone, and dry-based under the debris-covered zone. It is surmised that the glacier sole crosses the freezing front close to where the basal debris beds are upwarped towards the surface. Here, basal water is confined, and freezes to the under side of the glacier in thick beds of regelation ice which are uplifted to the surface along with the debris-laden beds. Ablation losses effectively cease beneath the blanket of debris covering the tongue.

The transition from wet-based to dry-based conditions at the glacier sole is a powerful mechanism for entraining debris into a glacier and, in the case of “Whisky Glacier”, for lifting debris to the surface. It is suggested that this may be a mechanism for forming some polar rock glaciers.
Some Observations on a Recent Surge of Peters Glacier, Alaska, U.S.A.
Authors: Echelmeyer Keith , Butterfield Robert , Cuillard Doug
Published: September 2017

A spectacular surge occurred on Peters Glacier, Alaska, in 1986 and 1987. Several observations on the glacier were made during the course of its surge. These observations are compared with those on other surging glaciers and then interpreted in terms of the ideas on surge mechanisms and dynamics as originally postulated by Post (unpublished) and further developed during the surge of Variegated Glacier by Kamb and others (1985) and Raymond and Harrison (1986, in press). It is shown that the concepts of rapid basal motion due to high water pressure at the glacier bed and the initiation of a surge during the winter due to a pressurization of the limited supply of basal water are well supported by these observations on the surge of Peters Glacier. An extremely high suspended sediment load rich in very fine material was observed, which also supports ideas on basal processes expected during this type of surge.

One interesting (and puzzling) feature of this surge cycle is that the termination of the surge occurred in late winter 1987, when surface melt water was at a minimum. This is in direct contrast to the termination of the surge on Variegated Glacier, which occurred during the period of peak ablation.
Mass Balance of Rhonegletscher During 1882/83–1986/87
Authors: Chen Jiyang , Funk Martin
Published: September 2017

The glaciological investigations on Rhonegletscher were started in 1874. The mass-balance data measured during 1884/85–1908/09 and during 1979/80–1981/82 are presented. Two methods are used for estimating the mass changes. During 1882/83–1968/69, the cumulative specific net balance is −24 ± 6 m w.e. at the 90% confidence level by the regression model of annual mass balance, annual precipitation, and summer air temperature (the PT model), while the thickness change revealed by the maps is −23 ± 5 m w.e. The cumulative specific net balance during 1882/83–1986/87 is −26 ± 6 m w.e. at the 90% confidence level.

The study shows that Rhonegletscher generally experienced mass loss, especially during the periods from the late 1920s through the early 1960s with some short periods of positive balance. The glacier tongue retreated by 970 m during 1882–1986, that is, from 1780 ma.s.l. (1882) to 2130 ma.s.1. (1986). During 1882–1969, the ice-covered area decreased by 4.37 km2 and the volume by 4.71 × 108 m3.

The PT models of Rhonegletscher and other alpine glaciers suggest that the contribution of the temperature changes to the mass balance is of more importance than that of the precipitation changes. The great mass loss reflects the climatic warming after the end of the Little Ice Age, with the warmest period occurring around the 1940s in this region.
Accumulation and flow rates of ice on Chhota Shigri glacier, central Himalaya, using radio-active and stable isotopes
Authors: Nijampurkar V. N. , Rao D. K.
Published: September 2017

Systematic isotopic studies based on natural and artificial radio-isotopes (32Si,137Cs), stable isotopes (δ18O) and total β activity measurements have been carried out on Chhota Shigri glacier, Himachal Pradesh, central Himalaya, to study the dynamics of the ice, meltwater composition and to identify the deposition of the Chernobyl fall-out in the Himalayan region.

Using32Si concentrations, the snout ice has been dated at ~ 250 years, based on which the past average surface ice-flow rate has been estimated as ~ 28 m year−1. Based on δ18O variations, in a shallow ice core, the accumulation rate of the ice has been estimated at ~520kgm−2year−1.32Si measurements of snout ice and englacial meltwaters indicate that at least 55% of the snow meltwater mixed with 45% of the old ice-melt water that emerged from englacial streams in the month of August 1987. Deposition of the artificial radionuclide (137Cs) and the very high total β activity observed in snow samples on Chhota Shigri glacier give the first evidence of Chernobyl fall-out deposition in the Indian Himalaya.
Subglacial water flow inferred from stream measurements at South Cascade Glacier, Washington, U.S.A.
Authors: Fountain Andrew G.
Published: September 2017

The subglacial drainage system of South Cascade Glacier is inferred by examining how discharges of water, solutes and artificial tracers in streams draining the glacier respond to meltwater and precipitation on the glacier surface. Results indicate that the glacier is divided into three (two large and one small) drainage basins, each drained by a single stream. The positions of drainage divides on the glacier surface do not always lie directly over those at the base of the glacier. Comparisons of water discharge and cation load in each of the two main streams indicate that subglacial hydraulic processes differ between drainage basins. One stream drains from a conduit that is isolated in its lower reach from the surrounding subglacial region and receives water routed englacially from the surface. The upper reach of the conduit also receives water routed englacially from the surface as well as from a distributed subglacial flow system. The other main stream drains from a conduit coupled to a debris layer beneath the glacier. Observations of the layer in natural ice tunnels indicate that the water may flow within a thin layer of debris. A one-dimensional model of flow through the debris layer can explain both the base-flow and diurnal variations of the second main stream.
Mass balance of Himalayan glaciers using AAR and ELA methods
Authors: Kulkarni Anil V.
Published: September 2017

The accumulation area ratio (AAR) for Himalayan glaciers representing zero mass balance is substantially lower than for North America and Europe. Regression analysis suggests 0.44 for the AAR representing zero mass balance in the western Himalaya. A good correlation was observed when this method was applied to individual glaciers such as Gara and Gor-Garang in Himachal Pradesh, India. The correlation coefficients (r), using 6 and 7 years of data, respectively, were 0.88 and 0.96 for Gara and Gor-Garang Glaciers, respectively. However, when data from six western Himalayan glaciers were correlated, the correlation was 0.74. The AAR was also estimated by using Landsat images which can be useful in obtaining a trend in mass balance for a large number of Himalayan glaciers for which very little information exists.

A higher correlation was observed between equilibrium-line altitude (ELA) and mass balance. The field data from Gara and Gor-Garang Glaciers shows a high correlation coefficient, i.e. −0.92 and −0.94, respectively. The ELA values obtained from the Landsat satellite images combined with topographic maps suggest positive mass balance for the year 1986–87 and negative for 1987–88.
Surficial Glaciology of Jakobshavns Isbræ, West Greenland: Part II. Ablation, accumulation and temperature
Authors: Echelmeyer Κ. , Harrison W. D. , Clarke T. S. , Benson C.
Published: September 2017

Accumulation studies along the lowermost 100 km of Jakobshavns Isbræ show that the local net balance above the equilibrium line (1210 m elevation in 1986) is significantly less than that measured along the EGIG line about 100 km further north. This indicates the presence of a precipitation low in this region which will affect any global mass-balance assessment for the Jakobshavns Isbræ drainage basin. Comparison of the estimated calving and ablation fluxes shows that calving removes about twice as much mass from this drainage basin as does melting. Basal melting over the entire basin accounts for about 20% of the total ice loss by ablation. Temperature measurements at 12 m depth along the same section of the Isbræ show the warming effects of refreezing meltwater and cooling effects of severe crevassing. In addition, there is a significant variation in temperature across the fast-moving ice stream which is probably caused by deformation heating in the shear margins which delineate the ice stream within the ice sheet. This lateral temperature gradient could be important in ice-stream dynamics through its effects on ice rheology. Detailed measurements within the percolation fades show that surface melt can penetrate up to 3 m by piping in cold firn, and, upon refreezing, can cause significant warming at these depths.
Time-Dependent Surface Elevation of an ice Slope
Authors: Hutter Kolumban
Published: September 2017

By introducing a coordinate stretching, the governing field equations of the creep flow of a non-Newtonian viscous medium down a uniform slope are solved to determine the differential equation describing the propagation of long surface waves caused by initial disturbances and/or time-dependent accumulation-rate The differential equation for the surface wave depends on the flow law of the non-Newtonian fluid, the boundary condition at the ice-bedrock interface, the bedrock topography and the thickness–wavelength ratio. For moderately long waves and small elevation above the mean thickness the results agree in their essentials with those of the kinematic wave theory and the forward wave equation with a diffusion term is derived, but when improving this by allowing higher elevations the Burger's equation and even more complex equations are obtained. To derive these results Glen’s flow law must be generalized to avoid infinitely fast changes in stress deviators close to zero Strain-rates, The range of applicability of the various equations is discussed.
An Analysis of Non-Steady Plastic Shock Waves in Snow
Authors: Brown R. L.
Published: September 2017

The propagation of plastic shock waves in snow is analyzed in order to evaluate the effect of wave intensity and frequency content on attenuation. The results show that frequency content is not very significant and that large amplitude pressure waves lose their effectiveness very quickly. These results seem to support the present-day contention that air-induced explosions are a more effective means of controlling avalanches than explosives placed in the snow-pack and that explosive speed is not a particularly important factor in determining explosive effectiveness.
The Inverse Problem for Valley Glacier Flow
Authors: Hantz Didier , Lliboutry Louis
Published: September 2017

We seek to infer the velocities within a cylindrical valley glacier from measured surface velocities. In the Newtonian viscous case, an explicit finite-difference scheme does not fulfil von Neumann’s condition for numerical stability. How this fact does not contradict the existence of Somigliana’s analytical solution is explained. A procedure is given which delays the onset of instability and allows velocities at shallow depths to be determined.
Note on the Morphology of Baspa Glacier, Kinnaur District, Himachal Pradesh, India
Authors: Bassi U. K. , Chopra S. , Tewari A. P.
Published: September 2017

Baspa Glacier occupies an area of about 35 km2 in the south-eastern part of Kinnaur District, Himachal Pradesh, and it is the source of the Baspa River, a major tributary of the Sutlej. It is a longitudinal valley-type glacier with a large cirque area. The field evidence indicates that the glacier has retreated considerably in the recent past.
A Stress-Wave Generator for Snow and Ice Studies
Authors: Bowles D. , Brown R. L.
Published: September 2017

An electromagnetic stress-wave generator which was developed to study shock waves in snow and ice is described. This system works on the principle of generating large electrical currents to produce highly transient loads on the test specimen. In its present configuration, the generator can produce pressures ranging from a few kilopascals to as large as 104 kPa and load frequencies as, high as 150 kHz. The system has been found to have high repeatability and has good turn-round time.
Periglacial Features on the Margins of a Receding Plateau Ice Cap, Lyngen, North Norway
Authors: Whalley W. Brian , Gordon John E. , Thompson David L.
Published: September 2017

Some features around the perimeter of the Balgesvarri plateau ice cap are described. Sorted stone circles were found beneath a slowly retreating ice margin, the basal ice in this area appears to be below the pressure-melting point. No absolute dating of features was possible but a relative chronology is suggested.
Till Texture in Drumlins
Authors: Karrow P. F.
Published: September 2017

Drumlin till has often been described as clay-rich. Drumlins in Ontario are composed of sandy till. Additional examples from north-eastern North America show that sandy till is common in drumlins.

It is suggested that the widely accepted association between drumlins and clay till was fostered by the use of such terms as “boulder clay” and “glacial clay”. Also, because till in drumlins may be finer than other glacial materials in such areas as the Appalachian region, a loose and exaggerated description of such material as being clay-rich arose. More careful description of drumlin till is advocated. It is suggested that grain-size distribution of till may have had a role in drumlin formation.