bluuebunny/crossref_metadata_2025 huggingface dataset:
Firn Densification: An Empirical Model
Authors: Herron Michael M. , Langway Chester C.
Published: September 2017

An empirical model of firn densification from the surface to the zone of pore close-off has been constructed. Fundamental rate equations have been derived for the first two stages of densification. In the first stage, for densities less than 0.55 Mg m−3, the densification rate is proportional to the mean annual accumulation times the term (ρi − ρ), where ρ is the density of the snow and ρi is the density of pure ice. The densification rate in the second stage, where 0.55 Mg m −3 < ρ < 0.8 Mg m−3, is proportional to the square root of the accumulation rate and to (ρi− ρ). Depth–density and depth–age calculations from this model are compared with observation. Model accumulation rates are within about 20% of values obtained by other techniques. It is suggested that depth intervals of constant density in some Antarctic cores may represent a synchronous event in the 1880 ’s when ten times the normal accumulation fell within a year or two.
Observations of Sediment–laden Icebergs in Antarctic Waters: Implications to Glacial Erosion and Transport
Authors: Anderson John B. , Domack Eugene W. , Kurtz Dennis D.
Published: September 2017

Sediment-laden icebergs are rarely sighted in Antarctic waters. However, during the recent Deep Freeze 79-USCGC Glacier expedition to the George V Coast and the south-western Ross Sea, nine sediment-laden icebergs and several pieces of pack ice with surficial sediment layers were observed. These observations include basal debris zones, debris slumped on to glaciers and floating ice, and englacial debris believed to have been incorporated along shear zones.

Sediment samples collected from icebergs were texturally and mineralogically variable. Some were unsorted mixtures consisting of a wide variety of angular minerals and rock fragments; others consisted primarily of slate clasts, quartz sand, and rock flour.
Ice–shelf Grounding: Ice and Bedrock Temperature Changes
Authors: MacAyeal Douglas R. , Thomas Robert H.
Published: September 2017

Ice rises form where an ice shelf runs aground on the sea bed. After grounding occurs, basal ice temperatures cool from the sea-water temperature towards an equilibrium temperature appropriate to grounded ice. This cooling can take many thousands of years, and much of the delay is due to the thermal inertia of the bedrock. Here, we calculate transient temperature profiles for an ice rise with a final summit thickness of 520 m that formed by grounding of ice shelf 420 m thick. Seventy-five per cent cooling of the basal ice takes between 7 000 and 11 500 years, depending on the “thermal memory” of the bedrock. This compares with an equivalent time of only 1400 years if we neglect the thermal inertia of the bedrock.

Because the surface slopes of the ice rise are related to the flow properties of the underlying ice, the summit thickness will tend to thicken as the basal ice cools. In principle, it should be possible to estimate the age of a recently-formed ice rise by examining its temperature/depth profile.
Glacier-Bed Landforms of The Prairie Region of North America
Authors: Moran S. R. , Clayton Lee , Hooke R. Leb , Fenton M.M , Andriashek L.D.
Published: September 2017

Two major types of terrain that formed at or near the bed of Pleistocene continental ice sheets are widespread throughout the prairie region of Canada and the United States. These are (1) glacial-thrust blocks and source depressions, and (2) streamlined terrain.

Glacial-thrust terrain formed where the glacier was frozen to the substrate and where elevated pore-pressure decreased the shear strength of the substrate to a value less than that applied by the glacier. The marginal zone of ice sheets consisted of a frozen-bed zone, no more than 2–3 km wide in places, within which glacial-thrust blocks are large and angular. Up-glacier from this zone, the thrust blocks are generally smaller and smoothed. Streamlined terrain begins 2–3 km behind known ice-margin positions and extends tens of kilometres up-glacier Streamlined terrain formed in two ways: (1) erosion of the substrate as a consequence of basal sliding in the sub-marginal thawed-bed zone, and (2) erosional smoothing accompanied by emplacement of till in the lee of thrust blocks where they were deposited and subsequently exposed to thawed-bed conditions as a result of further advance of the glacier.
Short–Lived Damming of a High–Arctic Ice–Marginal Stream, Ellesmere Island, N.W.T., Canada
Authors: Ballantyne C.K. , McGann S.B
Published: September 2017

The discharge pattern of the “Schei River”, which drains a 91.2 km2 partly glacierized catchment on Ellesmere Island, is dominated by diurnal oscillations reflecting variations in the melt rate of snow and ice in the basin. Superimposed on this diurnal pattern are numerous short–lived discharge fluctuations of irregular periodicity and magnitude. The characteristics of such irregular fluctuations are described and attributed to periodic collapse of the glacier margin and concomitant damming of the main tributary of the “Schei River”. Collapse is initiated by the river undercutting the ice margin, and tends to be most frequent in the latter part of the flow season during periods of high discharge. Release of ponded water following the collapse of such ice dams may engender significant flood events.
A Field and Laboratory Study of Wave Damping by Grease Ice
Authors: Martin Seelye , Kauffman Peter
Published: September 2017

In a field and laboratory study we discuss the formation, growth, and wave-absorption properties of grease ice. Our field observations show that grease-ice formation occurs under cold windy conditions in both leads and polynyas. In leads grease ice forms in the open water, then is herded to the down-wind edge of the lead; in polynyas a Langmuir circulation herds the grease ice into long plumes parallel to the wind. In the laboratory we grow grease ice in a wave tank and measure its wave absorption properties for single-frequency, two-dimensional waves. On a large scale we find that the thickness of the grease ice, which increases away from the paddle, is determined by a balance between the wave-momentum flux and the free-surface tilt. On a small scale our photographs show that the crystals which make up the grease ice consist of discs measuring about 1 mm in diameter and 1–10 µm thick, which at low rates of shear sinter together into larger clumps yielding a viscosity increase. To measure this non-linear viscosity, we study the decay of wave amplitude between two critical distances measured inwards from the leading edge. The first occurs when the depth of grease ice exceeds k−1 where k is the wave number; the second further distance is a line of transition from liquid to solid behavior which we call the dead zone. Between these two distances the wave amplitude decays with a linear slope α, which increases as (a0k)2 where a0 is the wave amplitude in open water. Concurrent measurements of ice concentration show that it increases from values of 18–22% at the leading edge to a local maximum of 32–44% at the dead zone, while the values at the dead zone increase non-linearly with a0k. Finally, comparison of the observed α to that calculated from a yield-stress viscosity model shows if the yield-stress coefficient is proportional to the incident wave-momentum flux, the model predicts the observed α.
Estimating Ratios of Snow Accumulation in Antarctica by Chemical Methods
Authors: Warburton J. A , Young L. G.
Published: September 2017

Snow and firn samples from 2 and 5 m deep pits were analyzed for seven sites on the Ross Ice Shelf, Antarctica. Na, Mg, Ca, and K concentrations change with depth, the range of concentrations being approximately 10 : 1 for all four elements. The changes in concentrations for the four elements at any one site are highly correlated, suggesting that the impurities are introduced into the snow-pack simultaneously by the same mechanisms.

Pronounced periodic structure of the vertical chemical profiles leads to strong correlations (γ> 0.9) of the chemical features from site to site separated by distances up to 440 km.

Assuming that the observed chemical features are periodic as a function of depth due to temporal variations caused by large-scale phenomena, then the wavelength (in depth) of these features should be proportional to the accumulation. Under the assumptions, the linear regression ratio of one site to another will give the relative accumulations at these sites. The ratios of snow accumulation estimated by these chemical methods agree, within a few per cent, with the ratios for the same sites estimated by total β-activity or stratigraphic methods.

It is suggested that the chemical variations with depth are caused by meteorological events which may have seasonal changes in frequency and intensity. It is also suggested that the most-favored season for the production of chemical-concentration maxima is autumn because of the documented higher frequency of precipitating storms on the Ross Ice Shelf and the minimum in sea-ice extent at that time of year.
Propagating Strain Anomalies during Mini-Surges of Variegated Glacier, Alaska, U.S.A.
Authors: Raymond Charles F. , Malone Stephen
Published: September 2017

Wire strain meters and seismometers spaced longitudinally along the upper part of Variegated Glacier, Alaska, showed quasi-periodic episodes of increased velocity (mini-surges), which lasted about 1 day and recurred at intervals of a few days to 2 weeks during the early part of the melt seasons of 1979, 1980, and 1981. The zone affected by these mini-surges corresponds to the zone of highest velocity and basal stress increase over the previous decade, and the initiation of the most recent surge in 1982. Mini-surges initiate locally; as a single melt season progresses, the later mini-surges start at higher locations and show a distinct down-glacier propagation of a characteristic strain pattern and associated zone of acoustic emissions at speeds of 0.1–0.6 km h−1. During mini-surges, extensile and compressive strain-rates exceed 10 × 10−4 d−1 and 40 × 10−4 d−1, respectively; typical strain-rates between mini-surges were less than 2 × 10−4d−1 in magnitude. Seismic activity jumped by two orders of magnitude and was distinctly audible during a mini-surge. Maximum strain-rate during mini-surges decreased from year to year. The high time resolution of the strain allows short time-scale structure of velocity variations to be deduced. As a propagating mini-surge passes, the velocity anomaly at a fixed location is characterized by a rapid initial rise over a few hours to two distinct peaks separated by a few hours, followed by a slower return to normal velocity taking up to a day. The double peak in velocity may arise from a single, very sharp, transient peak in the basal slip velocity associated with the initial opening of cavities at the base in response to a sudden rise in basal water pressure (observed by Kamb and Engelhardt). This supports an important role for basal cavitation in the mini-surge mechanism.
Modeling the Influence of Till Rheology on the Flow and Profile of the Lake Michigan Lobe, Southern Laurentide Ice Sheet, U.S.A.
Authors: Beget James E.
Published: September 2017

The late Wisconsin Shelbyville till was deposited in southern Illinois c. 20 000–21 000 year B.P. and records the maximum southern advance of the Lake Michigan lobe of the Laurentide ice sheet. The yield strength calculated for a representative till debris flow found just south of the ice margin is 8 kPa (0.08 bar), and probably approximates yield strength of basal Shelbyville till. An ice-profile model assuming plastic behavior in basal till suggests the southern Lake Michigan lobe may have been unusually thin. Reconstructed Laurentide glacier profiles from the south-west and western Great Plains (South Dakota, Alberta, Minnesota, and Montana), and the MacKenzie Delta, N.W.T., are similar to those inferred for the southern Great Lakes area, and much thinner than those of most modern ice sheets. The Pleistocene Laurentide ice sheet may have been asymmetric: thicker in the east than in the west. Glaciers resting on weak sediments can move both by subglacial sediment deformation (creep) and sliding at the sediment–ice interface. Till rheology is complex; shearing of till by over-riding glaciers would increase porosity and further reduce yield strength.
Stress-Gradient Coupling in Glacier Flow: II. Longitudinal Averaging in the Flow Response to Small Perturbations in Ice Thickness and Surface Slope
Authors: Echelmeyer Keith A. , Kamb Barclay , Kamb Barclay
Published: September 2017

As a result of the coupling effects of longitudinal stress gradients, the perturbations ∆u in glacier-flow velocity that result from longitudinally varying perturbations in ice thickness ∆h and surface slope ∆α are determined by a weighted longitudinal average of ϕh∆h and ϕα∆α, where ϕh and ϕα are “influence coefficients” that control the size of the contributions made by local ∆h and ∆α to the flow increment in the longitudinal average. The values of ϕh and ϕα depend on effects of longitudinal stress and velocity gradients in the unperturbed datum state. If the datum state is an inclined slab in simple-shear flow, the longitudinal averaging solution for the flow perturbation is essentially that obtained previously (Kamb and Echelmeyer, 1985) with equivalent values for the longitudinal coupling length l and with ϕh = n + 1 and ϕα + n, where n is the flow-law exponent. Calculation of the influence coefficients from flow data for Blue Glacier, Washington, indicates that in practice ϕα differs little from n, whereas ϕh can differ considerably from n + 1. The weighting function in the longitudinal averaging integral, which is the Green’s function for the longitudinal coupling equation for flow perturbations, can be approximated by an asymmetric exponential, whose asymmetry depends on two “asymmetry parameters” μ and σ, where μ is the longitudinal gradient of ℓ(= dℓ/dx). The asymmetric exponential has different coupling lengths ℓ+ and ℓ− for the influences from up-stream and from down-stream on a given point of observation. If σ/μ is in the range 1.5–2.2, as expected for flow perturbations in glaciers or ice sheets in which the ice flux is not a strongly varying function of the longitudinal coordinate x, then, when dℓ/dx > 0, the down-stream coupling length ℓ+ is longer than the up-stream coupling length ℓ−, and vice versa when dℓ/dx < 0. Flow-, thickness- and slope-perturbation data for Blue Glacier, obtained by comparing the glacier in 1957–58 and 1977–78, require longitudinal averaging for reasonable interpretation. Analyzed on the basis of the longitudinal coupling theory, with 4ℓ + 1.6 km up-stream, decreasing toward the terminus, the data indicate n to be about 2.5, if interpreted on the basis of a response factor Ѱ + 0.85 derived theoretically by Echelmeyer (unpublished) for the flow response to thickness perturbations in a channel of finite width. The data contain an apparent indication that the flow response to slope perturbations is distinctly smaller, in relation to the response to thickness perturbations, than is expected on a theoretical basis (i.e. ϕα/ ϕh + (n/n + 1) for a slab). This probably indicates that the effective ℓ is longer than can be tested directly with the available data set owing to its limited range in x.
Effects of climatic perturbations on the equilibrium-line altitude, West Greenland
Authors: Ambach Walter
Published: September 2017

Perturbation analysis is applied to the heat balance at the EGIG line (West Greenland) with respect to climatic changes. The shift of the equilibrium-line altitude is obtained for perturbations of temperature, absolute humidity, cloudiness and annual accumulation. The total net ice ablation at the EGIG line increases by 45% with a perturbation of + 1 K. Applying this figure to the entire ice sheet, the total ablation equals the total accumulation at a warming of + 2 K, if refreezing of melt water is neglected.
Internal melting and ice accretion at the bottom of temperate glaciers
Authors: Lliboutry L.
Published: September 2017

Temperate glacier ice is neither dry nor impermeable, as the standard theory of glacier sliding assumes. This fact leads to the already published concept of locally stress-controlled temperatures. Why the temperature is determined by the highest principal pressure, why the microscopic stress equals more or less the macroscopic one, and why water may flow in the capillary network even when water lenses at grain boundaries are freezing is explained. The new concept is applied to ice sliding on a hard bed having a sine profile, without cavitation. First, the stress field for a Newtonian viscous material and a vanishing roughness are used; next, an improved one, that takes into account the non-linear viscosity of ice and the finite amplitude of the micro-relief. It appears that water migrates from the stoss sides of the bumps to the lee sides within a bottom layer of thickness hw. Moreover, there is less ice melting at the sole on the former ones than ice accretion on the latter, a fact that yields a trend of ice accretion at the glacier sole. It is balanced by internal melting near the bed and water oozing at the interface from the soaked ice. Consequently, a thin layer of accreted regelation ice with a constant mean thickness hi should exist at the interface. Modelling realistically mountain glaciers, hw ∼ 20 cm and hi ∼ 3.5 cm are found.
The mass balance of a cirque glacier in the Italian Alps (Ghiacciaio Della Sforzellina, Ortles–Cevedale Group)
Authors: Catasta G. , Smiraglia C.
Published: September 2017

The net mass balance (1986/87–1989/90) was calculated for a small cirque glacier in the Italian Alps (Ghiacciaio della Sforzellina, 0.42 k m2, Ortles–Cevedale Group). Four annual mass balances are presented here. All four balances were negative (mean value: –0.90 m year−1), with a maximum deficit of –1.16 m year−1 in 1989–90. The climatic conditions (which are analyzed using data from the S. Caterina Valfurva Station) consisted of a succession of cold, dry winters with little snowfall. Frontal-variation data available since 1925 show a constant retreat until 1966, followed by a brief advance period which has already terminated.
Global change, Antarctic meteorite traps and the East Antarctic ice sheet
Authors: Delisle G.
Published: September 2017

Numerical models to assess the principal response of large ice caps to climatic changes are used as a guide to the interpretation of field evidence of changes in the glaciological regime in the coastal areas of Victoria Land and north Victoria Land, Antarctica. Based on the theoretical work, the following scenario is proposed: areas within about 300 km from the coast of Victoria Land experienced (i) significantly shallower ice slopes and a lesser degree of glaciation during most of the late Tertiary, (ii) steep slopes and thicker ice than today during glacial stages, and (iii) moderate thinning of the ice in intervening interglacial stages.

The model predicts, for central regions of Antarctica, a slightly thinner ice cap (lower snow-accumulation rate) during glacial stages, but an estimated 200 m thicker ice cap in warmer Tertiary climates than today. The calculated “Tertiary ice caps” indicate a probable tendency of periodic surges due to basal melting at the outer fringes.

Only modest changes of the ice thickness in reasonably good agreement with the model predictions for the current interglacial stage have been observed on four blue-ice fields, all located within 250 km of the coastline. Investigated ice fields include two meteorite traps — the Allan Hills Icefield and the Frontier Mountain meteorite fields. Antarctic meteorite traps are sustained by very specific glaciological conditions — in particular, only moderate changes in ice thickness over time. The sub-ice topography of these fields was determined by radar measurements and reveals a former, very different glaciological regime, which is interpreted as being associated with glacial processes, operative during the late Tertiary.

Field evidence for a hypsithermal event during the Holocene is presented.
Surface Movement and its Relationship To The Average Annual Hydrological Budget of Lemon Creek Glacier, Alaska
Authors: Wilson Charles R.
Published: September 2017

The object of the 1957 program of the Juneau Ice Field Research Project on Lemon Creek Glacier was (1) to obtain data on surface movement in the accumulation region, and (2) to relate the movement to the average annual hydrological budget. Results show a net loss of ice over the past four years, although this deficit does not appear to be reflected by the movement of the ice. Lemon Creek Glacier appears to be in approximate equilibrium.
Preliminary Results of the Glaciological Work on the Trans-Antarctic Expedition, 1955–58
Authors: Stephenson P. J. , Lister H.
Published: September 2017

At the inland station “Southice” (at approximately lat. 82° S., long. 29° W.) investigation in firn to 45m. included profiles of temperature, density, granularity and crystal size. Mean annual accumulation and temperature are interpolated and crystal fabric analyses briefly discussed. A study of drifting snow is outlined.

Similar studies, but without crystal observations, were continued across the continent using snow cores to 11 m. depth and supplemented by Rammsonde soundings. These sub-surface observations with the sastrugi forms noted, permit the interpolation of the mean accumulation, temperature and wind direction at different heights across the continent. Radiation flux, wind speed and air and snow temperature profiles were recorded at various halts.
Some Observations on the Glaciers of Mt. Kenya
Authors: Charnley F. E.
Published: September 2017

The glaciological work of the I.G.Y. Mt. Kenya Expedition, 1957–58, is described and some results are given.

The stages of retreat of the Mt. Kenya glaciers from their former limits are considered with reference to moraine evidence and existing records. A chronology is suggested for fluctuations during the last century.

Mapping of the present glaciers has been carried out. The changes undergone by the Lewis Glacier since a previous survey in 1934 are considered. The surface movement of the Lewis Glacier has been measured and its economy examined in relation to the meteorological and climatic environment.
Expédition Glaciologique Internationale Au Groenland 1957–60 (E.G.I.G.)
Authors: Finsterwalder Richard
Published: September 2017

Detailed account of the work to be undertaken by the International Glaciological Expedition to Greenland during 1959, together with brief notes on the previous researches which have led up to this work.
Accumulation and Temperature on The Inland Ice of North Greenland, 1959
Authors: Langway Chester C.
Published: September 2017

Twelve deep pits (5 to 5.5 m.) revealed between 6 and 13 years of snow accumulation. The results show an average net accumulation of 18.5 g./cm.2 per year. Accumulation decreases inland at a mean rate of 1.5 g./cm.2 per 100 m. rise in elevation. Temperature measurements at 100 m. in all pits give a mean temperature-altitude gradient of 0.77° C. per 100 m. Evidence of melt was observed in all pits, the most pronounced melt occurring in 1954. The mean density reflects the local climate. Other empirical correlations of these data show linear trends that vary systematically with surface slope and local climate.
The Glide Direction in Ice
Authors: Kamb W. Barclay
Published: September 2017

The failure to detect experimentally a glide direction in the ice crystal is satisfactorily explained by assuming that the crystal glides simultaneously in three symmetry-equivalent directions with a response to the shear stress component in each direction that is the same as that observed for the crystal as a whole or for polycrystalline aggregates—the typical non-linear, power-type flow law. A hexagonal crystal responding to stress by this type of “non-linear crystal viscosity” behaves very differently from a tetragonal one. For a tetragonal crystal, the glide directions are well defined in the response of the crystal if the power-flow-law exponent n exceeds n ~ 1·5, whereas for a hexagonal crystal a well-defined glide direction can be observed only if n > c. 5. The response of a hexagonal crystal is entirely independent of a-axis orientation if n = 3 exactly. For 3 < n < c. 5 the true glide direction should be weakly apparent, whereas for 1 < n < 3 the crystal should show a response weakly suggestive of preferred glide in a direction perpendicular to the true glide direction. In the observed range of n values for ice, 2 < n < 4, the expected response to simultaneous glide differs so slightly from the hitherto-postulated a-axis-independent, “non-crystallographic” glide as to be practically undetectable experimentally. This circumstance makes it possible to identify <>as the glide direction, from structural considerations alone, and to accommodate the plastic properties of the ice crystal into the modern concepts of crystal plasticity. It may be expected that hexagonal close packed and face-centred cubic metals at high temperatures, in steady state creep, will show translation gliding without well-defined glide directions.
Milton Mt. Mckinley Range Expedition, 1960
Authors: Carter Adams , Atherton David
Published: September 2017

The paper describes the expedition’s work on the north fork of the Eldridge Glacier, which is found to be of the temperate alpine type. Velocity profiles show both slip at the glacier’s edge and shear in the adjacent layers. A summer accumulation pattern is demonstrated which makes the glacial balance unusually delicate. It is concluded that glaciers in this region are near their recent maxima because the high altitude accumulation offsets the shrinking of the lower tributary glaciers. Examination of an ice-dammed lake shows the main Eldridge Glacier to be near the maximum of the last major advance which raised the level of the ice at least 60 m.
Bubble Pressure in Greenland Icebergs
Authors: Scholander P. F. , Nutt D. C.
Published: September 2017

A simple technique for measuring the pressure in individual bubbles of gas in glaciers is described. By this technique, bubble pressures in twenty-six west Greenland icebergs were measured. The bubbles were for the most part tubular in shape and oriented parallel, lending a fibrous and sometimes stratified appearance to the ice. Various suggestions are offered for the formation of these bubbles. Most bubbles had a pressure of 4–5 atmospheres, and pressures as high as 20 atmospheres were recorded. In closely adjacent bubbles differences of 2–5 atmospheres were often measured, which indicated diffusion tightness and lack of plasticity in the ice. When the ice surface melts, the bubbles expand at the cost of water extrusion. The various factors contributing to the maintenance of vertical walls characteristic of tabular bergs are discussed.
Recent Progress in North American Avalanche Forecasting and Control
Authors: LaChapelle E. R.
Published: September 2017

The techniques of avalanche forecasting and control have found increasingly wide adoption in North America in the past decade. Numerous government and private agencies are now engaged in work to protect ski areas, highways, railroads and power lines. Practical control measures such as artillery fire have been developed to a high degree of effectiveness, but the construction of permanent defense structures other than snow sheds is still in its infancy. Experimental work on instrumentation, forecasting, defense structures and the use of explosives, artillery and jet aircraft is currently in progress.
Quaternary Glaciations in Southern Victoria Land, Antarctica
Authors: Bull C. , McKelvey B. C. , Webb P. N.
Published: September 2017

In the coastal mountain chain of southern Victoria Land approximately 4,000 km.2 of glacier-cut valleys and dividing ranges are almost completely ice-free, while the surrounding areas are fully glacierized.

In the ice-free Wright Valley and Victoria Valley systems evidence of four glaciations is recognized. The earliest two glaciations were the most extensive; glaciers flowed eastwards from the ice plateau through the coastal ranges and cut broad valleys extending to McMurdo Sound and the Ross Sea. The moraines of these glaciations are thin and highly weathered. The third glaciation was less extensive, consisting of advances by smaller glaciers derived from the inland ice plateau, the Wilson Piedmont Glacier and névé fields in the dividing ranges. The surfaces of moraines of this glaciation are now partly covered by saline lakes, evaporite deposits and extensive areas of desert pavements strewn with ventifacts. The fourth and youngest glaciation comprised small advances by remnants of the plateau-fed valley glaciers. Thick boulder moraines of this glaciation overlie earlier deposits.

During each glaciation the greatest volume of ice was derived from the inland ice plateau. The volume of ice entering the valleys was dependent on the difference in altitude between the plateau surface and subglacial rock thresholds at the valley heads. Decrease in the surface level of the inland ice plateau caused the rock thresholds to increasingly hinder the eastward flow of plateau ice until practically no ice could flow down into the valleys, thereby terminating the glaciation. Such a condition exists at the present time.
Origin of Debris-Covered Icebergs and Mode of Flow of Ice Into “Miller Lake”, Martin River Glacier, Alaska
Authors: Reid John R. , Callender Edward
Published: September 2017

During the summer of 1963. a drift-veneered mass of ice suddenly emerged at the surface of “Miller Lake”, art ice-walled lake at the terminus of the Martin River Glacier, Alaska. Subsequent fathometer traverses, together with the fact that the ice was not at the pressure melting point, revealed that it had been derived from a hole approximately 40 m. below the surface of the lake. There are numerous large debris-covered icebergs in the lake and presumably at least some are formed in this manner. Others are derived through differential ablation of projections of the glacier into the lake. Only the small icebergs are formed through calving. The interpretation of the mechanism of release of ice from the bottom of the lake, and the observation and interpretation of a rising ice-cored island in the same lake suggest that the ice on the bottom is deforming plastically and that it is undergoing compressive flow. Much of the movement may be along shear planes actually found in icebergs derived from the bottom of the lake.
A Numerical Method of Inferring the Budget History of a Glacier from its Advance and Retreat
Authors: Nye J. F.
Published: September 2017

The paper considers how to calculate the budget history of a glacier from the historical record of its advance and retreat. The linearized differential equations developed in previous papers are used to compute a series of coefficients g(n). The g(n) operate directly on a record of annually spaced observations of the position of the glacier terminus, to give the time variation of net budget. The g(n) are calculated for South Cascade Glacier, Washington, U.S.A. and for Storglaciären, Kebnekaise, Sweden, and are applied to the terminus records of these two glaciers. The results indicate that the figures for the retreat during individual years are not sufficiently reliable to deduce annual net budget changes with confidence. But the coarser features of the terminus records give net budget figures that agree well with the 9 yr. or 10 yr. means of recent observations. The theory extends the generalized budget record of Storglaciären back by several decades. and shows an increase in net budget in the 1930’s that is not immediately apparent in the terminus record.
The Flow of a Glacier in a Channel of Rectangular, Elliptic or Parabolic Cross-Section
Authors: Nye J. F.
Published: September 2017

Numerical solutions are found for the steady rectilinear flow of ice, obeying Glen’s non-linear flow law, down uniform cylindrical channels of rectangular, semi-elliptic and parabolic cross-section. The results are also directly applicable to the pumping of a non-Newtonian fluid down a pipe. There is assumed to be no slip of the ice on the channel surface. Certain results on the centre-line velocity in symmetrical channels may be derived purely from dimensional and symmetry principles. An analytical solution due to Dr. W. Chester is given for a semi-elliptic channel section which departs only slightly from a semi-circle. Contrary to a view sometimes held, the maximum shear stress at the ice surface in a parabolic channel and in some elliptical channels does not always occur at the edge. With the flow law, strain-rate proportional to (stress)3, the velocity averaged across the ice surface, which is easily measured with a line of stakes, is close to the average velocity over the whole section for a wide range of parabolic sections; the hydrological importance of this result is that the discharge may be inferred without the need to measure the velocity at depth. Arguments are given to show that the result still holds when there is slipping on the bed and when the power in the flow law differs somewhat from 3, Depending on the amount of bed slip and the shape of the channel section, the kinematic wave velocity for a range of parabolic channels is between 2.0 and 2.3 times the centre-line velocity of the ice, and between 2.0 and 3.5 times the mean surface velocity of the ice.
Experimental Study of Non-Basal Dislocations in Ice Crystals
Authors: Levi L. , de Achaval E. M. , Suraski E.
Published: September 2017

Structures produced by chemical etching on the basal plane of ice crystals have been studied and are discussed in terms of non-basal glide features. Slip bands, revealed by parallel rows of etch pits, generally result from a rapidly applied stress. Etch channels were observed relatively rarely in these experiments; they can be interpreted as trails of dislocations moving slowly under the action of local stresses, sometimes to stresses produced during the etching process. Features of the channels indicate that the dislocations emerging on the basal plane are screw dislocations; their Burgers vector was considered by previous authors to be in the direction <1123>, gliding on {1122}and {101o} slip planes. This assumption is inconsistent with the changes of channel direction we observed, for which the {0111}and {2421}slip planes would have to be considered. As a simpler hypothesis the glide system 〈0001〉, {101o} and 〈0001〉, {1120}is proposed.
Snow Surface Elevation in the Filchner Ice Shelf Area, Antarctica
Authors: Behrendt John. C.
Published: September 2017

Altimeter observations made on flights during the austral summer 1963–64 in the vicinity of the Filchner Ice Shelf have allowed the construction of a new topographic map of the snow surface in that area. The ice stream flowing into the ice shelf from the polar plateau is more clearly defined. A previously shown connection from Berkner Island to the grounded ice to the west-south-west appears not to exist. The mass flux from the drainage basin on the polar plateau can be accounted for by a reasonable ice-shelf flow rate. The area of the ice shelf shown on the map is 0.43×106 km.2.
Velocity Fluctuations of the Bersækerbræ, East Greenland
Authors: Friese-Greene T. W. , Pert G. J.
Published: September 2017

The results of measurements of surface flow and ablation on the glacier Bersækerbræ, in the Staunings Alper, East Greenland, are presented. A correlation is shown between the rate of flow and rate of ablation, as suggested by current theory.
New Light on the Mode of Uplift of the Fish and Fossiliferous Moraines of the Mcmurdo Ice Shelf, Antarctica
Authors: Gow A. J. , Weeks W. F. , Hendrickson G. , Rowland R.
Published: September 2017

The McMurdo Ice Shelf and associated faunal remains were examined in the vicinity of the easternmost Dailey Island. Stratigraphic, petrographic, and chemical composition studies of cores from two holes drilled through the ice shelf show that at these locations the shelf is composed only of fresh-water ice. Although cores from the deeper hole possessed typically glacial textures throughout, much of the ice from this part of the McMurdo Ice Shelf may have been formed from the freezing of a layer of fresh water found sandwiched between shelf bottom and the underlying sea-water. The existence of fresh water under the ice shelf can most probably be attributed to drainage of surface melt water during the ablation season. There was no evidence to indicate that this part of the McMurdo Ice Shelf is being nourished by the growth of sea ice onto its lower surface. The fish remains found on the ice surface were confined to a narrow zone along the tide crack and are believed to have been left in this vicinity by deep diving seals. The marine invertebrate remains on top of the ice are associated with morainal material and are believed to have been incorporated into the ice at the time of formation of the moraines.
Observations on the Quaternary Firn Line in Peru
Authors: Tricart J.
Published: September 2017

At lat. 7° S. the fern line was at about 3,500 m. during the Riss glaciation, at 3,650 m. during the Würm maximum and at 3,700 m. during a later stage (Würm II?). The moraines were deposited by equatorial-type glaciers from which there was relatively little melt water.

At lat. 14° S., during the Riss glaciation, an important ice cap covered a 3,900–4,000 m. high plateau, the firn line being at about 3,950 m. The role of melt waters was important in the formation of the moraines, suggesting their deposition from tropical-type glaciers. From the evidence of periglacial gravels it appears that this southern region has not been glaciated since Riss times.
A Theoretical Consideration of the Strength of Snow
Authors: Ballard G. E. H. , Feldt E. D.
Published: September 2017

A consideration of possible expressions for the number and size of bonds intersected by a potential failure surface leads to the following expression for the strength of snow, σf, which is age-hardening at a constant porosity n:

where σi is the strength of ice, tf is the time at failure, α is a parameter specifically related to the mechanism of bonding, and ω is a temperature-dependent parameter. Allowing tf to become infinite provides the envelope of maximum strength for fully age-hardened snow at any porosity n.
Light Scattering and Particle Aggregation in Snow-Storms
Authors: Mellor Malcolm
Published: September 2017

Attenuation of visible radiation by falling snow was studied by a method based on brightness contrast between topographic features and the adjacent sky. Extinction coefficient and visual range are related to bulk snow density, and are compared with data for Antarctic blizzards. Since attenuation depends more on the size and concentration of discrete particles than on the mass density of suspended snow, the process of particle aggregation and snow-flake formation during fall is considered by collision theory, and an expression describing aggregation effects is developed. This offers an explanation for the relative constancy of particle concentration observed at ground level during snowfalls of varying intensity. Since there is no strong justification for relating extinction coefficient to snow density, an empirical correlation between extinction coefficient and precipitation rate is given for practical use. It is shown that visual range estimated by eye in hilly terrain may be less than the true value, since sky brightness is locally reduced over broad hill-tops with low albedo.
Instruments and Methods: Improvements in the Measurement of A Lake-Ice Cover
Authors: Adams W. P. , Shaw J. B.
Published: September 2017

A device is described which gives direct measurements of the rates of accretion of ice on both the top and the bottom of lake ice without the necessity for repeated drilling. A method for measuring the hydrostatic water level is also described.
The Recent Surge of Walsh Glacier, Yukon and Alaska
Authors: Post Austin
Published: September 2017

Walsh Glacier, Yukon and Alaska, after 40 years or more of virtual stagnation in the terminal area, began a very rapid surge in late 1960 or 1961. A maximum movement of 10.1 km. occurred in the central portion of the glacier between 1961 and 1965, as shown by aerial photographs of the displacement of surface features, perhaps the greatest such displacement yet reported for any surging glacier.
Drumlins and Pleistocene Ice Flow over the Ards Peninsula/Strangford Lough Area, County Down, Ireland
Authors: Vernon Peter
Published: September 2017

The geographical distribution of the drumlins was studied. They are arranged in bands perpendicular to ice pressure with a weaker alignment parallel to ice flow. An hypothesis of drumlin origin is presented. Two ice flows are present, a strong flow from an Irish centre to the north-west, and a weaker flow of Scottish ice from the north.
An Examination of the Lliboutry Theory of Glacier Sliding
Authors: Weertman J.
Published: September 2017

An examination is made of the Lliboutry theory of glacier sliding. It is concluded that this theory is incompletely developed and therefore it is impossible at present to make meaningful predictions of the sliding velocity from it that might be compared with field data.
The Adhesion of Ice Spheres in Electric Fields
Authors: Latham J. , Saunders C. P. R.
Published: September 2017

The force F required to separate two ice spheres was measured as a function of environmental temperature T, relative humidity H and the strength E of the external electric field in which the spheres were situated. It was found that over the entire attainable range of T and H, F increased rapidly with increasing E. The increased adhesion was not accompanied by an increase in the rate of growth of the ice bridge between the two spheres and is explicable in terms of Davis’s (1964) calculations of the purely electrostatic forces between two spheres situated in an electric field. The experiments indicate that the rate of growth of snowflakes in a cloud by means of ice crystal aggregation will be markedly enhanced if the cloud is highly electrified.
Pleistocene Periglacial Topography in Southern Africa
Authors: Sparrow G. W. A.
Published: September 2017

Studies in the south-eastern part of the Drakensberg mountains and the Basutoland uplands, above the 6,000 ft. (1,830 m.) level, of Southern Africa have yielded evidence for a periglacial regime during the Pleistocene. The limited earlier work in Southern Africa suggested that the Pleistocene climate was too dry for glaciation to have occurred, but the existence of oversteepened slopes, solifluction slumps and cirques is indicative of a periglacial environment. There is some correlation between the respective altitudes and latitudes of these periglacial features.
Planar and Layered Structures in Glacial Ice
Authors: Ragan Donal M.
Published: September 2017

In metamorphic rocks a sharp distinction between planar structures (e g. in schiste) and layered structures (e.g. in banded gneisses) is generally made. This same distinction has not been maintained in descriptions of analogous structures in glacial ice. At least part of the problem lies with the use of the term foliation, which, unfortunately, has been applied to both types of structures. On historical and etymological grounds, as well as on the basis of widespread acceptance by petrologists and structural geologists, it is argued that foliation should apply to planar structures in both rocks and glacial ice.
Calculated Patterns of Accumulation on the Greenland Ice Sheet
Authors: Mock Steven J.
Published: September 2017

All available mean annual accumulation data on the Greenland ice sheet (excluding the Thule peninsula) have been collected and analyzed using multiple regression techniques to develop equations capable of predicting mean annual accumulation. The analysis was carried out for north Greenland, south Greenland, and for the transition zone between the two major regions. The resulting equations show that mean annual accumulation can be predicted from the independent parameters latitude, longitude and elevation. The patterns of accumulation are shown in a series of isohyetal (contours of accumulation in terms of water) maps. The major feature shown is a well defined asymmetry in accumulation; a pronounced east-slope maximum in south Greenland and an equally pronounced west-slope maximum in north Greenland. Poleward of lat. 69° N., isohyets decrease in elevation to the north. Mean annual accumulation ranges from >90 g./cm.2 in south-east Greenland to <15 g./cm.2 in north-east Greenland. A brief discussion of mass balance estimates of the Greenland ice sheet and of the relevance of this study to them is included.
Photogrammetry Applied to Avalanche Studies
Authors: van Wijk M. C.
Published: September 2017

Stereophotogrammetric techniques were used for a study of snow avalanches. The contour lines of the avalanche slope were mapped from stereo-photographs taken before and after the occurrence of the avalanche. The outline of the avalanche front at certain time intervals and the contours of the snow cloud were also plotted. A relative accuracy for the different maps of 0.7 m. on the terrain was established.

The volume of the snow cloud at four different stages of the avalanche was determined from the maps. These volumes were also computed independently from coordinate readings that were made in the stereo models. The standard errors of both methods of volume determination were estimated to be 450 m.3 and 290 m.3 respectively, representing errors of 5 per cent and 3 per cent of the average cloud volume.

The photographs were taken with an accurately determined time interval. Therefore, the velocity of the avalanche front could be determined from the photogrammetric measurements.
Early Discoverers XXVI: Another Forgotten Pioneer of the Glacial theory James Hutton (1726–97)
Authors: Davies Gordon L.
Published: September 2017

The problem of erratic boulders lying far from their place of origin attracted considerable attention during the closing decades of the eighteenth century. More especially, interest focused upon the blocks of Mont Blanc granite resting on the flanks of the Jura. Various fanciful explanations, ranging from debacles to gigantic explosions, were offered to account for such phenomena (some of the early explanations have been reviewed by Agassiz (1840) and North (1943)) but the true explanation long eluded even the most astute observers. It was not that there was a failure to appreciate the transportive power of glaciers—de Saussure (1786–96, Vol. 2, p. 21) and others recognized the ability of glaciers to move large boulders—but a failure to recognize that glaciers had recently extended far beyond their present limits.
The Midsummer Heat Balance of an Alaskan Maritime Glacier
Authors: Streten N. A. , Wendler G.
Published: September 2017

The heat balance of an Alaskan mountain glacier located close to the sea is calculated for a period of 16 d in midsummer—a period which is typical of the summer in this region in its high cloudiness and in its temperature and humidity conditions. The radiative and the combined sensible and latent heat components are found to contribute equally to the observed high rate of ice melting.