bluuebunny/crossref_metadata_2025 huggingface dataset:
Interpretation of borehole-inclinometer data: a general theory applied to a new instrument
Authors: Blake Erik W. , Clarke Garry K. C.
Published: September 2017

Borehole inclinometers are standard equipment for field glaciologists and are commonly used for investigating the flow law of ice and for measuring the spatial position of englacial and sub-surface sensors. The recent development, at the University of British Columbia (UBC), of a prototype inclinometer that employs a three-component fluxgate magentometer to obtain a compass bearing has stimulated our interest in borehole inclinometry. Following a review of various approaches to glacier inclinometry, we present a unified theory of data interpretation that can be applied to all inclinometers, discuss the application of the theory to the UBC inclinometer, and discuss the sensitivity of the theory to error in the data.
Analysis of Multiple-Angle Microwave Observations of Snow and Ice Using Cluster-Analysis Techniques
Authors: Rotman Stanley R. , Fisher Arthur D. , Staelin David H.
Published: September 2017

The Nimbus-6 satellite carries the Scanning Microwave Spectrometer experiment (SCAMS) which continuously maps the Earth’s surface at two frequencies (22.235 and 31.65 GHz) and at six angles besides nadir. Cluster analysis was applied to these observations to determine the influence of various geophysical parameters on the radiometric brightness temperatures.

Characteristic microwave signatures for a variety of terrain were obtained by this method; discrete clusters were distinguished for sea ice (with sub-classes for ice age and fractional ice cover) and firn (with accumulation-rate sub-classes). The availability of the angular data greatly facilitated separate determinations of the extent of continuous sea ice and mixtures of sea ice and water.
Creep and Fabrics of Polycrystalline Ice Under Shear and Compression
Authors: Duval Paul
Published: September 2017

Creep tests were performed in torsion and torsion–compression on polycrystalline ice at temperatures near the melting point. Syntectonic recrystallization occurs at strains of the order of 2–3%, leading to a rapid increase in strain-rate. It is shown that the increase of creep-rate during tertiary creep arises from the development of fabrics favouring the glide on basal planes but also from the softening processes associated with recrystallization. The c-axis fabric of recrystallized ice developed in simple shear consists of two-maxima, one at the pole of the permanent shear plane and the other between the normal of the second plane of maximum shearing stress and the principal direction of compression. In torsion–compression, a three- or four-maximum fabric is formed according to the intensity of different components of the stress tensor. The maxima are clustered around the principal direction of compression. Processes of fabric formation are discussed. The experimentally developed fabrics are probably produced by the strain-induced recrystallization, for which the driving force is provided by differences in stored plastic strain energy. However the degree of preferred orientation of ice c-axes must be a function of the total strain when syntectonic recrystallization becomes less important. In this case, fabrics are principally formed by plastic flow and a steady state is obtained for very high strains.
Preliminary Experiments on the Formation of Elongated Air Bubbles in Glacier Ice by Stress
Authors: Nakawo Masayoshi , Wakahama Gorow
Published: September 2017

Biaxial compression tests on glacier ice with bubbles revealed that elongated air bubbles were developed with long axes in the direction of free expansion. The elongated bubbles were not only derived from spherical bubbles but also created by the healing of cracks that were developed during compression. Formation of elongated bubbles and foliations in natural glacier ice are discussed here in the light of results obtained experimentally.
The Effect of the Subglacial Water Pressure on the Sliding Velocity of a Glacier in an Idealized Numerical Model
Authors: Iken Almut
Published: September 2017

In order to interpret observed short-term variations of the sliding velocity of a glacier the effect of a variable subglacial water pressure on the sliding velocity has been studied using an idealized numerical model. In particular the transient stages of growing or shrinking water-filled cavities at the ice-bedrock interface were analysed. It was found that the sliding velocity was larger when cavities were growing than when they had reached the steady-state size for a given water pressure. The smallest sliding velocities occurred while cavities were shrinking. When cavitation is substantial a small drop of water pressure below the steady-state value (e.g. by 0.5 bar) can temporarily cause backward sliding. A limiting water pressure at which sliding becomes unstable is derived. The consequences of more realistic assumptions than those of the model are discussed.
Bottom Melting under George VI Ice Shelf, Antarctica
Authors: Bishop J. F. , Walton J. L. W.
Published: September 2017

Bottom melting rates have been calculated for a large number of sites on George VI Ice Shelf from measurements of its kinematic behaviour. No simple explanation for the melt-rate pattern was found in terms of ice-shelf parameters, assuming steady-state conditions. Values of apparent melt rates varied from 1 to 8 m a−1 of ice. Along different flow lines the melt rate would sometimes increase with distance from the grounding line and sometimes the melt rate would decrease with distance. Large melt rates were found both where ice flowed off Palmer Land and where the ice shelf butted against Alexander Island. Although oceanographic conditions probably control bottom melting rates the complex pattern with large spatial variation seems to indicate that some areas of ice shelf are changing in thickness.
Tracing Particle Paths in the Antarctic Ice Sheet
Authors: Doake C. S. M.
Published: September 2017

A layer of moraine within the Antarctic ice sheet has been detected in the course of airborne radar ice soundings. The moraine was injected at the margin of the ice and can serve as a tracer to pick out a particle path within the ice. When combined with surface measurements, the ability to trace particle paths should allow detailed modelling of the dynamic behaviour in limited areas.
A Cirque-Glacier Chronology Based on Emergent Lichens and Mosses
Authors: Calkin Parker E. , Ellis James M.
Published: September 2017

Recession of “Golden Eagle” glacier in the central Brooks Range is exposing undisturbed lichen-covered boulders. Radiocarbon analysis of dead moss surrounding these boulders dates a Neoglacial advance across this site at 1120±180 years b.p Measurements of the preserved lichens indicate that a minimum ice-free period of 1500–2500 years preceded this glacial expansion.
Summer Heat and Ice Balances on Hodges Glacier, South Georgia, Falkland Islands Dependencies
Authors: Hogg I. G. G. , Paren J. G. , Timmis R. J.
Published: September 2017

The heat and ice balances of a temperate sub-Antarctic cirque glacier were measured through the 1973–74 melt season at an altitude midway between the climatic firn limit and the snout. The melt calculated from mean daily measurements at a single level of net radiation, wind-speed, temperature, and humidity agreed with that observed at nearby budget stakes. In the central ablation zone, radiation provided (54 ± 6)% and sensible fluxes (46 ± 6)% of the heat income through the summer, which was exceptionally warm and sunny. Latent-heat fluxes made no significant contribution to the heat balance. The calculation by Smith (1960) that the radiative, sensible, and latent heat fluxes contribute about equally to ablation in this zone has not been substantiated by measurement. The measured partition of the glacier’s heat balance suggested that maritime influences on its regime are mitigated by its position in the lee of a major mountain range.
Stability of Sheet Flow of Water Beneath Temperate Glaciers and Implications for Glacier Surging
Authors: Walder Joseph S.
Published: September 2017

A mathematical model is presented for the stability of sheet flow of water beneath a temperate glacier. Enhanced viscous heat dissipation in thick parts of the sheet tends to make sheet flow unstable, the instability increasing as sheet thickness and pressure gradient increase. However, incipient channels may be destroyed as the glacier slides over protuberances on its bed. Quasi-stable sheet flow may be possible for sheets up to several millimeters in thickness, especially beneath glaciers that have relatively gentle surface slopes and slide at moderate to high speeds. Such water sheets may somewhat reduce the effective roughness of glacier beds, but probably not enough to allow surge initiation. Furthermore, the presence of numerous water-filled cavities at the glacier bed will tend to reduce the sheet thickness and lessen the degree of “lubrication” of the glacier bed by the water sheet.
Short-Term Variations in Velocity of South Cascade Glacier, Washington, U.S.A.
Authors: Jacobel Robert W.
Published: September 2017

Displacement of an array of eight stakes was measured at approximately 12 h intervals on South Cascade Glacier, Washington, for a period of 638 h during July and August 1979. The array was located on the glacier center-line and had overall dimensions comparable to the 200 m ice thickness in this part of the glacier. Variations in velocity for individual stakes was typically 100% for periods of 12 h but decreased for longer time intervals in accordance with reports in the literature. The constraint of requiring compatible motion for the entire array reduces the averaged short-term fluctuations to the same order as the variations between stakes for a given 12 h period. This implies that non-uniformity in individual stake motion does not represent true velocity variation of the studied portion of the glacier.
Surging of Fisher Glacier, Eastern Antarctica: Evidence From Geomorphology
Authors: Wellman Peter
Published: September 2017

A study of the geomorphology of the Prince Charles Mountains using colour vertical air photographs shows well–preserved old moraines throughout much of the outcrop area. Along Fisher Glacier, lower Lambert Glacier and the Amery Ice Shelf, within the altitude range 50–2 000 m, the old moraines show that the ice level had risen 150–200 m above the present level at least three times. Old moraines elsewhere show that none of the other glaciers had risen significantly in their upper parts; the rise of their lower parts was caused by the rise of lower Lambert Glacier and the Amery Ice Shelf. The changes in ice level are unlikely to be due to climatic change because this would not repeatedly affect only one glacier draining central Antarctica. It is thought that the changes in ice level are caused by repeated surges of Fisher Glacier.
Ice Movement through Smith Sound in Northern Baffin Bay, Canada, Observed in Satellite Imagery
Authors: Ito Hajime , Müller Fritz
Published: September 2017

Movement of pack ice in Smith Sound in northern Baffin Bay was observed for April 1975 using the satellite imagery obtained by Landsat. Mean velocity was found to be directed to the south with a magnitude of 4 km d−1. The influence of the wind is discussed and the amount of ice transported from Smith Sound evaluated. The findings show that on a daily average 600 km2 of pack ice was carried out of the area.
Fracture Criterion for Ice Using a Dislocation Model
Authors: Parameswaran V.R.
Published: September 2017

The propensity for crack formation on basal and prismatic planes and twin nucleation on two pyramidal planes in hexagonal ice is examined on the basis of fracture theories and anisotropic elastic theories of dislocations. Calculations show that the ease of crack formation is almost the same in the basal and prismatic planes, whereas it is almost impossible to produce mechanical twinning in ice by stress alone.
Preparation of Section Planes in Snow Specimens
Authors: Perla R.
Published: September 2017

Diethyl phthalate, dimethyl phthalate, ethyl anisate, and α-tetralone are examples of liquids that can be used to fill the pore space of snow specimens. After the pore space is filled, the specimen is frozen solid. A section plane is microtomed and polished. Photomicrographic contrast of the section plane is improved by gently rubbing on to the plane a water–insoluble powder, such as carbon powder, or by rubbing on a water–soluble stain such as powder of acid fuchsin. Photomicrographic contrast is also improved by adding a water–insoluble dye such as oil blue N or oil red O to the pore–space filler.
Stress-Gradient Coupling in Glacier Flow:III. Exact Longitudinal Equilibrium Equation
Authors: Kamb Barclay
Published: September 2017

The “vertically” integrated, exact longitudinal stress-equilibrium equation of Budd (1970) is developed further in such a way as to yield an equation that gives explicitly and exactly the contributions to the basal shear stress made by surface and bed slope, surface curvature, longitudinal stress deviators, and longitudinal stress gradients in a glacier flowing in plane strain over a bed of longitudinally varying slope. With this exact equation, questions raised by various approximate forms of the longitudinal equilibrium equation can be answered decisively, and the magnitude of errors in the approximations can be estimated. To first order, in the angle δ that describes fluctuations in the surface slope α from its mean value, the exact equilibrium equation reduces to

where G and T are the well-known stress-deviator-gradient and “variational stress” terms, K is a “longitudinal curvature” term, and B is a “basal drag” term that contributes a resistance to sliding across basal hills and valleys. Except for T, these terms are expressed in simple form and evaluated for practical situations. The bed slope θ (relative to the mean slope) is not assumed to be small, which allows the effects of bedrock topography to be determined, particularly through their appearance in the B term.
Changes in the Salinity and Porosity of Sea-Ice Samples During Shipping and Storage
Authors: Cox G.F.N. , Weeks W.F.
Published: September 2017

A theoretical examination of salinity and porosity changes introduced in sea-ice samples by brine expulsion and gas entrapment caused by thermal cycling during shipping and storage shows that in extreme cases such effects can be significant, resulting in 15% reductions in porosity (n) More representative scenarios give porosity changes of less than 2% which, assuming that ice-property variations scale with n1/2, result in property variations of less than 1%.
A Preliminary Assessment of Glacial Ice Profiling Using Vlf Surface-Impedance Measurements
Authors: Thiel David V.
Published: September 2017

VLF surface-impedance measurements have been used in the past for sub-surface mapping. The application of this technique to glacial ice probing is discussed theoretically and results of measurements on Brewster Glacier, New Zealand, are presented. Results were fitted to a three-layer model and a section profile is given. Dramatic changes in the phase of the surface impedance were observed in the vicinity of crevasses. Results indicate that the technique has potential as a tool for quick, reliable, and non-invasive ice-thickness measurements.
The Larsen Shelf Ice
Authors: Mason Douglas
Published: September 2017

Description of that part of the Larsen Shelf Ice traversed by the author when taking part in a sledging expedition which reached lat. 74° 42′ S., manned jointly by members of the Falkland Islands Dependencies Survey and the Ronne Antarctic Research Expedition 1946–48.
Evidence of Cirque Glaciation in the Falkland Islands
Authors: Clapperton Chalmers M.
Published: September 2017

The presence of 49 cirques on the Falkland Islands indicates that glacial conditions were prevalent during the Pleistocene. Cirque moraines and glacially eroded valleys also occur. There appear to have been three phases: a period of cirque formation, the growth of local ice caps and subsequent cirque development. Periglacial landforms such as stone runs, stone terraces and stone lobes also developed during the Pleistocene and attained very large dimensions because of the lithology, the relatively small scale of glacierization and the presence of rotted bedrock.
An Analysis of the Relation Between the Surface and Bedrock Profiles of Ice Caps
Authors: Budd W.F. , Carter D.B.
Published: September 2017

Results art, presented of spectral analyses of the surface and bedrock profiles along a flow line of the Wilkes ice cap and the surface along the Greenland E.G.I.G. profile. Although the bedrock appears irregular over all was velengths studied, the ice-cap surface is typically characterized by a smooth curve with small-scale surface undulations superimposed on it. The following relations of Budd (1969, 19701 are confirmed. The “damping factor" or ratio of the bedrock amplitude to the surface amplitude is a minimum for wavelengths λ about 3.3 times the ice thickness. The surface lags the bed in the direction of motion by λ/4. The magnitude of the minimum damping factor φm is typically least near the coast, and increases inland depending on the ice thickness Z, the velocity V, and the mean ice viscosity η (which is a function of stress and temperature) according to

where p is the mean ice density and g is the gravitational acceleration. Thus the determination of the damping factors provides a valuable means of estimating the ice flow parameter η.
Movement of the Ward Hunt Ice Shelf, Ellesmere Island, N.W.T., Canada
Authors: Dorrer E.
Published: September 2017

The movement at a marginal location on the Ward Hunt Ice Shelf, northern Ellesmere Island, was determined by repeated survey measurements with theodolite and geodimeter. The purpose and duration of the field work, and reduction of the observational data are described, and the resulting mean ice velocity of 0.53 m year-1 is discussed. Strain-rates of a 1 km by 1 km deformation figure are determined. The parameters n and B of Glen’s power flow law are determined by using the equations given by Nye and Weertman. The results are compared with experimental data. Computed ice stresses show that the “ridge-and-trough" structure on the ice shelf surface is not originated by internal ice forces. The elevations of all survey markers have been determined from vertical-angle measurements, and the peculiarities of atmospheric refraction in near-surface layers are discussed.
Interference Phenomena in Deformed Single Crystals of Ice
Authors: Readings G. J. , Bartlett J. T.
Published: September 2017

When rectangular single crystals of ice were subjected to uniaxial compression parallel to their Long axes and viewed between crossed polarizers, interference fringes were often observed. Some of these interference bands were associated with grain boundaries formed as a result of “kinking”. These can be explained in terms of the known anisotropic optical properties of ice and the change in the orientation of the optic axis across the boundary. This case has been analysed in detail with the aid of Jones’ calculus and good quantitative agreement exists between the theory and the experimental observations.

Other interference bands were observed parallel to the trace of the basal plane on the surface of some deformed crystals. Alternative hypotheses for the explanation of this phenomenon have been considered and it seems probable that these bands are a result of slight random misorientations between adjacent slip lamellae. Applying Jones’ calculus to a simple model of such a deformed crystal indicates that the required misorientations are of the order of 1º If this explanation is correct, it implies that dislocations with non-basal Burgers vectors (probably c[0001]) make an active contribution to the deformation.
Calculation of Grain-Boundary Thickness in Polycrystalline Ice of Low Salinity
Authors: Chatterjee Amiya K. , Jellinek H.H.G.
Published: September 2017

Grain-boundary thickness in polycrystalline ice is a function of time (age), salinity, tempera-turf ·, and mode of sample preparation. It is directly proportional to the salinity of the ice and the number-average grain diameter (spheres) or edge-length (cubes). Practically the total salt content resides in the grain boundary for low salinity ice samples. The gram-boundary thickness S is also directly proportional to growth time of the grains raised to a power n(n = 0.25 to 0.3) and increases exponentially with absolute temperature for constant salinity and age. The energy of activation for growth increases with salinity. The results of the grain-boundary thickness calculations are useful for evaluating grain-boundary diffusion coefficients.
Liquid Brine in Ice Shelves
Authors: Thomas R. H.
Published: September 2017

Holes drilled into thin areas of the Brunt Ice Shelf encounter a layer of liquid brine less than 1 m thick approximately at sea-level. Assuming the brine to be moving horizontally, analysis of its effects on thermal equilibrium gives an estimate of steady-state annual brine flow that is in good agreement with the value deduced from a percolation model. The effect of firn density on percolation rates is such that the slope of an active brine layer increases rapidly as ice thickness increases. However, the heat transport model predicts that brine layers are unlikely to be active in both very thick and very thin ice shelves.
The Origin of Foliation in Glaciers: Evidence from Some Norwegian Examples
Authors: Hambrey M. J.
Published: September 2017

Studies of Norwegian glaciers indicate that foliation is frequently derived from sedimentary stratification. Shearing and accompanying recrystallization of the ice is most likely to occur in the planes of the sedimentary layers, particularly where they are steeply dipping and have a longitudinal trend, Foliation not related to pre-existing layering is uncommon. Steeply dipping transverse layers, often referred to as foliation, are believed to be simply the traces of former crevasses.
Drop Stones Resulting From Snow-Avalanche Deposition On Lake Ice
Authors: Luckman B.H.
Published: September 2017

Dirty snow avalanches have been observed to carry considerable amounts of rock debris on to lake ice at the foot of scree slopes. As ice breaks up in the spring thaw, this material is carried back and forth on ice floes and is gradually deposited in the lake. In some areas this produces typical drop stones of rock debris in predominantly fine-grained deposits. Most avalanche debris is very angular which enables avalanche drop stones to be differentiated from those of glacial or other drift-ice origins. However, where avalanches incorporate glacial debris, such deposits may be indistinguishable from those formed by floating glacier ice.
The Effect of Subglacial Chemical Processes on Glacier Sliding
Authors: Hallet Bernard
Published: September 2017

The glacier sliding theory of Nye is modified to include the effect of solutes in
subglacial regelation waters on the sliding process. Motivation for this development stems
from studies of subglacially formed chemical deposits that appear to be widespread on rock
surfaces recently exposed by retreating temperate glaciers. These deposits indicate clearly
that considerable local concentration of solutes commonly occurs subglacially as a result of
the selective rejection of solutes into the melt during the freezing associated with
regelation sliding. Because solutes accumulate where regelation waters refreeze, they tend to
lower the temperature there and hence inhibit the heat transport away from these areas that is
essential for regelation sliding. For a simple sinusoidal bed and solute distribution in the
regelation water film, the modified theory shows that a maximum excess of solutes of, for
example, several millimoles/1 of dissolved CaCO3 along lee surfaces
relative to stoss surfaces impedes basal sliding significantly, especially if the bed
roughness wavelength does not exceed about one meter.
A Concise Method for Analyzing the Ice-Melting Performance of a Heated Disc
Authors: Lea J.F.
Published: September 2017

Shreve (1962) evaluated the performance of solid-nose hotpoints of various geometries.
A more concise method for analysis of the special case of a flat disc melting into ice is
presented here. In contrast to the numerical solution presented by Shreve, this method results
in a closed analytical solution, based on constant properties, which is corrected using a
property ratio scheme. This technique allows the substitution of various fluid properties into
the solutions as might be required when considering contaminated or saline ice or other
liquids. Shreve's method would require some additional numerical work to evaluate various
properties because the temperature dependence of the viscosity of water is integrated into the
results.

Results obtained for the flat disc using this method are shown to compare favorably
with Shreve's, indicating that this type of analysis may be applicable to other melt-unit
geometries.
Climatological and Photogrammetric Speculations on Mass-balance Changes of McCall, Glacier, Brooks Range, Alaska
Authors: Dorrer Egon , Wendler Gerd
Published: September 2017

The mean mass balance of the McCall Glacier, Brooks Range, Alaska, was estimated for the period 1958 to 1971. The three methods used, photogrammetry, mean height of the equilibrium line, and correlation with the height of the synoptic 500 mbar pressure level, all gave negative values, but the amount depended on the method used. This trend of glacier recession is in agreement with most observations of glaciers in the Brooks Range as well as with the majority of the glaciers in the Northern Hemisphere.
A Study of Glacier-dammed Lakes Over 75 Years Brimkjelen, Southern Norway
Authors: Mottershead D. N. , Collin R. L.
Published: September 2017

Evidence is brought together concerning the deglaciation of a small valley and the subsequent development in it of periodic glacier-dammed lakes. The respective volumes and drainage dates of the lakes are evaluated, and an attempt is made to relate these to the down-wastage of the impounding glacier.
The Spatial Distribution of 10 m Temperatures in the Antarctic Peninsula
Authors: Martin P. J. , Peel D. A.
Published: September 2017

Temperatures from 10 m bore holes have been analysed to determine the spatial variation of mean annual surface temperature over the Antarctic Peninsula. In general there is a decrease in temperature of 0.84 deg per degree latitude southwards combined with an altitude lapse rate of 0.68 deg per 100 m. There is a sharp divide between the continental type climate of the east coast and a maritime climate of the central and western regions. Temperatures are approximately 7 deg lower along the east coast compared with those at sites of a similar altitude and latitude on the west.
An Alternate Statistical Interpretation of the Strength Snow
Authors: Gubler H.
Published: September 2017

The basic features of the statistical models to describe brittle and ductile strength of snow are outlined and discussed. The concept of the "fundamental unit" is introduced. The models are applied to estimate the development of slab stability during heavy snowfalls and to simulate measurements of the tensile strength of snow using the centrifugal method as a function of the load rate. The models developed in this paper are compared with Sommerfeld’s applications of statistical methods to estimate the strength of snow in the starting zone of a slab avalanche.
Glacial Erosion by the Laurentide Ice Sheet
Authors: Sugden D. E.
Published: September 2017

The aim of the paper is to analyse landscapes of glacial erosion associated with the Laurentide ice sheet at its maximum and to relate them lo the three main variables affecting glacial erosion, namely former basal thermal regime of the ice sheet, the topography of the bed, and the geology of the bed. The key to the analysis is the comparison of the distribution of landscape types with the simulated pattern of the basal thermal regime of the former ice sheet.

Landscapes of areal scouring are found to be associated with zones of basal melting and occur beneath much of the former ice-sheet centre and in those places where the topography favoured converging ice flow. The landscape type may also have formed beneath cold-based ice when it was carrying debris inherited from an up-stream zone of regelation. Areas with little or no sign of glacial erosion occur primarily in the north in the Queen Elizabeth Islands but they also occur on uplands associated with diverging ice flow; they coincide with areas calculated to have been covered by cold-based ice devoid of debris. Landscapes of selective linear erosion are common on uplands near the eastern periphery of the ice sheet. In these situations, pre-existing valleys channelled ice flow and created a situation where there was warm-based ice over the valleys and cold-based protective ice over the intervening plateaux. Variations in the permeability of the bedrock base have modified the landscape pattern, mainly in those areas where there was a change from one basal thermal regime to another. In general, permeable rocks tend to have experienced less erosion than impermeable rocks.

Using lake-basin density as an indication of the intensity of glacial erosion, a zone of maximum erosion is identified and this forms a ring between the centre of the former ice sheet and its periphery. This ring coincides with a zone where melt water from the ice-sheet centre is calculated to have frozen on to the bottom of the ice sheet. This regelation incorporated basal debris into the ice, forming a basal layer 20-50 m thick and afforded an efficient means of debris evacuation.

A conceptual model is developed and hangs round the following postulates:

(1)

Landscapes of glacial erosion are related primarily to the basal thermal regime of the ice sheet.

(2)

Landscapes of glacial erosion are equilibrium forms related to maximum glacial conditions. This implies that at some stage in the Pleistocene the Laurentide ice sheet was in a stable maximum condition for a long period of time.

(3)

Mechanisms allowing evacuation of debris rather than those of abrasion or fracture may be the most important in influencing the amount of erosion achieved by an ice sheet.

(4)

Cold-based ice may accomplish erosion if it contains debris.
Application of Numerical Transient Fluid Dynamics to Snow Avalanche Flow. Part II. Avalanche Modeling and Parameter Error Evaluation
Authors: Lang T. E. , Martinelli M.
Published: September 2017

Under evaluation is the range of the parameters of internal viscosity and surface friction of flowing avalanches in order to represent the flow numerically by computer program AVALNCH. Nominal values of these parameters are determined to be in the range 0.4 to 0.6 for, snow flowing on snow, with values as high as 0.8 to 0.9 for snow flowing on rough ground. Using a nominal avalanche path, the basic parameters: (1) depth of initial release slab, (2) viscosity and friction, (3) adverse grade, and (4) flow spreading are determined to be in the order listed as regards their relative effect on avalanche runout distance. Program AVALNCH, which permits treatment of flow parameters separately from geometric parameters, provides a versatile tool for the prediction of avalanche runout, as well as for related studies of avalanche dynamics.
A Recommendation for the Application of the Roch Index for Slab Avalanche Release
Authors: Sommerfeld R. A. , King R. M.
Published: September 2017

Detailed measurements on several avalanches verify that a Daniels’ (1945) type statistical correction to Roch’s (1966) stability index would accurately predict snow-slope instability. It is recommended that one-half the median of at least 50 shear-strength measurements be used as a measure of the strength of a weak layer.
Snow–Avalanche Impact on Structures
Authors: Lang Theodore E. , Brown Robert L.
Published: September 2017

Two–dimensional hydrodynamic equations for laminar, viscous flow, and admitting a frictional slip-plane lower boundary are applied to the modeling of snow-avalanche impact on rigid wall structures. Predicted maximum pressures and pressures versus time are compared with published experimental results, and general correspondence is established. Impact pressure versus time is found to depend upon the shape of the avalanche leading edge, for which general information is lacking. Computer modeling of more complex structural configurations is feasible using the methodology reported.
Instruments and Methods: Radio-Echo Equipment for Depth Sounding of Temperate Glaciers
Authors: Sverrisson Marteinn , Jóhannesson Ævar , Björnsson Helgi
Published: September 2017

Radio echo-sounding equipment has been designed, and used for depth sounding on temperate glaciers in Iceland. Two devices have been built. Mark I operates in the frequency band 2 to 5 MHz. The overall range is 100 to 1000 m. The arrival of the echo can be timed with an accuracy which corresponds to 20 m resolution. The equipment has been used for routine soundings on Mýrdalsjökull and Vatnajökull for the last two years. Mark II operates at 2 to 10 MHz. The range is from 30 to 400 m and the range resolution is 8 m. The equipment has been used for successful soundings on valley glaciers.

The power consumption of the whole system is 18 W plus 72 W for the oscilloscope (Tektronix Model 465). The voltage is supplied from 12 V car batteries. The total weight of the equipment is about 35 kg plus the weight of batteries. The antennae are contained in 16 mm plastic tubes. The equipment is placed on two sledges and towed behind a snowmobile or a skidoo. A continuous sounding record is photographed from the oscilloscope.
“Global Dynamics” of a Temperate Valley Glacier, Mer De Glace, and Past Velocities Deduced from Forbes’ Bands
Authors: Lliboutry Louis , Reynaud Louis
Published: September 2017

Transverse profiles and velocities which have been measured on the ablation zone of Mer de Glace more or less continuously since 1891 contradict the Weertman–Nye theory of glacier kinematic waves. Faint broad waves, which undoubtedly result from fluctuations in the balance, travel down the glacier faster than this theory predicts. (This theory having first been completed by taking changes in width with time and with distance down the glacier into account.) On the other hand, velocity fluctuations are synchronous and more or less the same over the entire length studied (6 km).

These discrepancies result from bottom friction being of the solid type, i.e. independent of sliding velocity. Friction should also be almost insensitive to discharge in subglacial waterways, since in the steady state energy for keeping them open, not entirely flooded, and at atmospheric pressure, is superabundant. The sliding velocities at all cross-profiles are thus controlled by some areas where the body of the glacier suffers strong deformation because the valley shape is far from cylindrical. One such controlling zone exists on Mer de Glace owing to the existence of a subglacial transverse shoulder. A new perturbation equation and a new rough expression for wave velocity are given.

Intervals between Forbes’ bands were plotted on seven aerial surveys between 1939 and 1979. Progressive tilting of the slices of blue, dusty ice from the position from which these dark bands proceed and progressive lowering of their exposed edge must be taken into account. This analysis confirms the validity of our simple model for velocity fluctuations and allows us to estimate the entire series since the year 1888.
Mass Balance of “Vesper” Glacier, Washington, U.S.A.
Authors: Dethier David P. , Frederick Jan E.
Published: September 2017

During 1974–75 glaciologic and geologic studies were conducted on a small (0.17 km2) avalanche-nourished glacier in the North Cascade Range of Washington. The approximate equilibrium-line altitude (ELA) for this ice body, informally called “Vesper” glacier, lies at 1475 m, some 300 m below the regional ELA value. Estimated annual accumulation was 6 100±675 mm during the two years of study; 15 to 30% of this flux resulted from avalanche and wind–transported snow. Average annual ablation during the period was 5 350 mm, giving a total net balance of + 1 600 mm for the two-year study period. “Vesper” glacier persists well below the regional snow-line because of excessive local precipitation, substantial avalanche contributions, and a favourable north-facing aspect.

Neoglacial moraines indicate that maximum ELA lowering in this period was approximately 165 m and occurred prior to a.d. 1670. Minor re-advances occurred during the nineteenth century. These reconnaissance measurements are consistent with the sparse geologic data reported from other glaciers in the Cascade Range. While the relationship between regional lowering of snow-line and avalanche activity is uncertain at present, these data suggest that avalanche-nourished glaciers provide a useful record of climatic fluctuations.
A Method for Growing Large Single Crystals of Sea Ice
Authors: Kawamura Toshiyuki
Published: September 2017

A simple technique is presented for growing large single crystals of sea ice. Using this technique, crystals with dimensions of 20 cm × 20 cm × 10 cm or more can be readily obtained within an orientational accuracy of 3°. Such crystals can then be used to investigate the physical properties of sea ice.
Thermo-mechanically coupled ice-sheet response — cold, polythermal, temperate
Authors: Hutter Kolumban
Published: September 2017

Classical mixture concepts are the appropriate vehicle for describing the dynamics of ice masses containing some water. We review and derive, respectively, the theoretical formulations of cold, polythermal and temperate ice masses, emphasize the peculiarities of the model equations and point to difficulties that were encountered with the proposed models. The focus is both on the adequate physical motivation of the models and the consistency of their mathematical representation. The paper also has a tutorial character.

As usual, cold ice is treated as a single-component incompressible heat-conducting viscous fluid, while two different models are presented for temperate ice. When it arises in a polythermal ice mass, the water content is small and a simple diffusive model for the moisture content suffices. This diffusive model is further simplified by taking its appropriate limit, when the moisture diffusivity tends to zero. Temperate ice in a wholly temperate — Alpine — glacier is treated as a two-phase flow problem, i.e. the momentum-balance laws of both constituents ice and water are properly accounted for. Such Darcy-type models are suggested because the water arises in a greater proportion; so its dynamic role can no longer be ignored.

The constituent ice is treated as an incompressible non-linearly viscous isotropic body with constitutive properties similar to those of cold ice. The interstitial water is a density-preserving ideal or perfect fluid. The two interact with an interaction force that is proportional to the “porosity” and the seepage velocity. Internal melting that arises will lead to a generalization of the familiar Darcy law.

When water is present, the boundary and transition conditions across internal singular surfaces take special, more complicated forms and involve statements on drainage to the base. These conditions are also discussed in detail.
Analysis of synthetic aperture radar Data collected over the southwestern Greenland ice sheet
Authors: Jezek K. C. , Drinkwater M. R. , Crawford J. P. , Bindschadler R. , Kwok R.
Published: September 2017

Analyses of the first aircraft multi-frequency, Polarimetric synthetic aperture radar (SAR) data acquired over the southwestern Greenland ice sheet are presented. Data were collected on 31 August 1989 by the Jet Propulsion Laboratory SAR using the NASA DC-8 aircraft. Along with curvilinear patterns associated with large-scale morphologic features such as crevasses, lakes and streams, frequency and polarization dependencies are observed in the P-, L-and C-band image products. Model calculations that include firn grain-size and volumetric water content suggest that tonal variations in and between the images are attributable to large-scale variations in the snow-and ice-surface characteristics, especially snow wetness. In particular, systematic trends in back-scatter strength observed at C-band across regions of changing snow wetness are suggestive of a capability to delineate boundaries between snow facies. Ice lenses and ice pipes are the speculated cause for similar trends in P-band back-scatter. Finally, comparison between SEASAT SAR data collected in 1978 and these airborne data collected in 1989 indicate a remarkable stability of surface patterns associated with the locations of supraglacial lake and stream systems.
Steady flow of a viscous ice stream across a no-slip/free-slip transition at the bed
Authors: Barcilon Victor , MacAyeal Douglas R.
Published: September 2017

An exact, analytic description of the steady, downhill flow of a viscous ice stream across a no-slip to free-slip transition in basal boundary condition suggests ways in which such transitions might be detected by observations of ice-stream surface properties. We find that the best expression of this transition is in the free-surface profile, which dips over the point of transition and becomes horizontal far downstream. The streamwise velocity at the surface shows a gradual change across the transition, and this is in disagreement with previous studies which suggest a marked change. Basal shear stress and basal pressure exhibit singularities at the point of transition. As concluded in previous study, the former singularity is a likely point of strong basal erosion. The latter singularity is problematical, however, because it violates the assumptions which make the exact solution possible. It is not clear how this problem can be overcome without appealing to thermodynamics, non-Newtonian material properties, cavitation or wake separation.
How many reservoirs? An analysis of flow recessions from a glacier basin
Authors: Gurnell Angela M.
Published: September 2017

Analysis of hydrograph-recession curves from temperate catchments has frequently been directed towards identifying a linear-storage element with mean residence time Κ which characterizes the delayed-flow component. This paper presents the results of applying such an analysis to recession curves from 11 years of discharge records from a glacier basin. Four reservoirs are identified but their estimated recession coefficients (K values) are found to vary with discharge and with time in the ablation season. This implies that the reservoirs are non-linear. Whilst it may be helpful for the interpretation of glacier-hydrological processes to identify several reservoirs, it appears that a single non-linear reservoir may provide an adequate representation of the glacier for operational forecasting purposes.
Niche Glaciers in Bünsow Land, Vestspitsbergen
Authors: Groom G. E.
Published: September 2017

Small glaciers lying in funnel-shaped hollows on steep slopes have been variously described as wall-sided glaciers, cascade glaciers, cliff glaciers and niche glaciers. This type of glacier and the landforms associated with them in Bünsow Land, central Vestspitsbergen are described and their possible mode of origin is discussed. The theory that they were formed by an overspill of plateau ice and that they are thereby genetically related to hanging glaciers is rejected. It is suggested that they are formed by an accumulation of snow in an initially water-worn gully and that as the small glacier develops the original form of the gully is modified by nivation to a rounded, funnel-shaped hollow. Niche glaciers may thus be considered as glacier types genetically related to cirque glaciers, forming an early stage in corrie development.
Errors in Ablation Measurements from Settlement and Sub-Surface Melting
Authors: LaChapelle E.
Published: September 2017

Both long and short-term snow ablation measurements usually contain errors when made with a simple ablation stake. Ablations measured over long periods for glacier regimen studies are subject to a settlement error in even dense snow, corrections for which may be made by simultaneous measurements with stakes of different lengths. For observation periods in the order of twenty-four hours or less, both mass loss and ice melt are often poorly represented by the simple product of mean bulk density and change in surface level. These quantities may be measured directly by successive determinations of bulk density and ice density profiles in the surface snow layer. Under certain favorable conditions, they may also be derived by observing directly the total and ice mass changes in a sampled area of the snow surface.
The Motion of Ice Sheets and Glaciers
Authors: Nye J. F.
Published: September 2017

The distribution of velocity along a vertical line in Greenland is calculated. Almost all the relative shear motion is concentrated at and very near to the bottom, and this result is thought to apply generally in Greenland and Antarctica. It is due to the relatively high temperature of the lowest layers and the strong dependence of creep rate on temperature. The outward velocity being thus almost constant with depth, it is assumed proportional to themth power of the shear stress on the bed; the results previously obtained by the approximation of perfect plasticity then correspond tom→∞. Steady-state solutions for finitemare derived, and non-steady states are discussed by use of Weertman’s perturbation method. The steady-state height of an ice sheet is found to be very insensitive to the rate of accumulation. Surface waves in Antarctica are attributed to mountains buried beneath the ice, and it is shown how the height and form of a buried mountain ridge may be calculated from the associated surface disturbance.

The application of a law of sliding to glaciers leads to an expression for the longitudinal strain-rate, hitherto an undetermined parameter.
Particle-Size Distribution of Pulverized Snow
Authors: Jellinek H. H. G. , Schlueter Warren A.
Published: September 2017

A microscopic method for the determination of particle-size distribution of pulverized snow was worked out. The method gives satisfactory distribution curves, presenting the number of particles as a function of their cross-sectional “areas”. The measurements were made by means of a filar micrometer eyepiece, the snow particles being placed on a ruled glass slide, which was submerged in silicone oil to prevent evaporation. The time for the determination of a distribution can be appreciably shortened by estimating the size of the particles instead of measuring them, though the accuracy is not so high in this case.
Temperature Distribution Near a Crevasse
Authors: Pings C. J.
Published: September 2017

During the summer of 1955, 53 thermocouples were installed in the ice mass near a crevasse in a glacier in the ice sheet of northern Greenland. Temperatures were observed in 1955 and 1956. The accumulated data were sufficient to prepare a description of the transient thermal behavior of the ice body adjacent to the crevasse. The isotherm maps have provided a base for the computation of heat flux vectors.
Glacier Problems in South Georgia
Authors: Smith Jeremy
Published: September 2017

This paper is a synopsis of Falkland Islands Dependencies Survey Scientific Report No. 29. Glaciological and climatic investigations carried out in South Georgia during the International Geophysical Year are described. The budgets of the Hodges and Hamberg Glaciers for 1957–58 are given and discussed in relation to climatic factors. Temperature measurements indicate that the Hodges Glacier, and probably all ice in South Georgia below an altitude of 1,000 m., is geophysically temperate. The fluctuations of South Georgian glaciers during relatively recent times are briefly discussed.