bluuebunny/crossref_metadata_2025 huggingface dataset:
Airborne surface profiling of glaciers: a case-study in Alaska
Authors: Echelmeyer Κ. A. , Harrison W. D. , Larsen C. F. , Sapiano J. , J. E. Mitchell , De Mallie J. , Rabus B. , Adalgeirsdóttir G. , Sombardier L.
Published: September 2017

A relatively lightweight and simple airborne system for surface elevation profiling of glaciers in narrow mountain valleys has been developed and tested. The aircraft position is determined by kinematic global positioning system (GPS) methods. The distance to the glacier surface is determined with a laser ranger. The accuracy is about 0.3 m, sufficient to permit future changes to be observed over short time intervals. Long-term changes can be estimated by comparison of profiles with existing maps. Elevation profiles obtained in 1993–94 from three glaciers in central and south-central Alaska are compared with maps made about 1950. The resulting area-averaged, seasonally corrected thickness changes during the interval are: Gulkana Glacier (central Alaska Range)–11 m, Worthington Glacier (central Chugach Mountains) +7 m, and Bear Lake Glacier (Kenai Mountains) −12 m. All three glaciers retreated during the interval of comparison. The estimated uncertainty in the average thickness change is ±5 m. which is mainly due to errors in the existing maps. Constraints on the accuracy of the maps are obtained by profiling in proglacial areas.
Estimation of ice-sheet motion using satellite radar interferometry: method and error analysis with application to Humboldt Glacier, Greenland
Authors: Joughin Ian , Kwok Ron , Fahnestock Mark
Published: September 2017

Satellite radar interferometry provides glaciologists with an important new tool for determining the motion and topography of large ice sheets. We examine the sources of error in interferometrically derived ice-motion measurements, including those errors due to inaccurate estimates of the interfero-metric baseline. Several simulations are used to assess baseline accuracy in terms of tie-point error and the number and distribution of tie points. These results give insight into how best to select tie points, and also demonstrate the level of accuracy that can be achieved. Examination of two representative cases likely to occur in mapping ice-sheet motion leads to the conclusion that with adequate tie-point information ice velocity can be measured accurately to within a few meters per year. A method to correct horizontal velocity estimates for the effect of vertical displacement using surface slopes is also developed. Finally, we estimate the single-component velocity field for an area on Humboldt Glacier, northern Greenland, using interferograms formed from ERS-1 SAR image. We estimatе that these velocity measurements are accurate to within 2.3 m year1.
A new high-precision borehole-temperature logging system used at GISP2, Greenland, and Taylor Dome, Antarctica
Authors: Clow Gary D. , Saltus Richard W. , Waddington Edwin D.
Published: September 2017

We describe a high-precision (0.1–1.0 mK) borehole-temperature (BT) logging system developed at the United States Geological Survey (USGS) for use in remote polar regions. We discuss calibration, operational and data-processing procedures, and present an analysis of the measurement errors. The system is modular to facilitate calibration procedures and field repairs. By interchanging logging cables and temperature sensors, measurements can be made in either shallow air-filled boreholes or liquid-filled holes up to 7 km deep. Data can be acquired in either incremental or continuous-logging modes. The precision of data collected by the new logging system is high enough to detect and quantify various thermal effects at the milli-Kelvin level. To illustrate this capability, we present sample data from the 3 km deep borehole at GISP2, Greenland, and from a 130 m deep air-filled hole at Taylor Dome, Antarctica. The precision of the processed GISP2 continuous temperature logs is 0.25–0.34 mK, while the accuracy is estimated to be 4.5 mK. The effects of fluid convection and the dissipation of the thermal disturbance caused by drilling the borehole are clearly visible in the data. The precision of the incremental Taylor Dome measurements varies from 0.11 to 0.32 mK. depending on the wind strength during the experiments. With this precision, we found that temperature fluctuations and multi-hour trends in the BT measurements correlate well with atmospheric-pressure changes.
The determination of glacier speed by time-lapse photography under unfavorable conditions
Authors: Harrison W.D. , Echelmeyer K.A. , Cosgrove D.M. , Raymond C. F.
Published: September 2017

Two practical problems in the use of time-lapse photography for the measurement of speed were encountered during the recent surge of West Fork Glacier in the central Alaska Range, Alaska, U.S.A. The first is severe rotational camera instability; we show how natural, unsurveyed features on the valley wall can be used to make the necessary corrections. The second problem is the computation of absolute speed when many different, unsurveyed glacier-surface features are used as targets. We give a method for connecting the data obtained from different targets, and for determining the scale using limited information obtained by surveying. Severe systematic errors can occur unless the angle between the axis of the lens and the direction of horizontal motion is determined.
Recent fluctuations of glaciers in Valtellina (Italian Alps) and climatic variations
Authors: Pelfini Manuela , Smiraglia Claudio
Published: September 2017

Valtellina, located in the Italian Alps of Lombardy, is extensively glaciated. Since 1925, terminal variations of the glaciers have been recorded. By analysing a significant sample of valley glaciers, we have recognized a rapid retreat of the termini which occurred between 1925 and the early 1970s. A period of advance followed, which stopped in the second half of the 1980s. The mean summer-temperature fluctuations at the meteorological station of Sondrio at the centre of Valtellina, show that the period 1925–52 was very warm, and then the temperatures dropped. The most intense winter precipitation occurred in the period 1925–37. The behaviour of these glaciers is similar to that of other Alpine glaciers, although time of response may be different.
Sea-ice motion in the Weddell Sea from drifting-buoy and AVHRR data
Authors: Crane David , Wadhams Peter
Published: September 2017

A study of sea ice in the northern Weddell Sea was done, relating the ice motion, determined using an array of satellite-tracked drifters, deployed into ice floes, to parameters describing the nature of the ice cover, obtained from an analysis of Advanced Very High Resolution Radiometer (AVHRR) imagery. It was found that the ice motion was predominantly wind-driven, responding to the passage of low-pressure systems across the area. The correlation length of the strain field over the entire measurement period was around 200 km. At high concentrations the ice responded as a rigid body with coherent motion, but below a concentration of around 93%, differential motion occurred. The nature of the ice motion was found to depend upon the lead parameters, with low values of pure convergence and divergence and larger values of vorticity and deformation of the ice field. The vorticity was found to be well correlated with the atmospheric pressure, with a time lag of less than 3 h, implying an almost instantaneous response of the ice cover to meteorological forcing.
Interferometric radar observations of Glaciar San Rafael, Chile
Authors: Rignot Eric , Forster Richard , Isacks Bryan
Published: September 2017

Interferometric radar observations of Glaciar San Rafael, Chile, were collected in October 1994 by NASA’s Spaceborne Imaging Radar C (SIR-C) at both L- (24 cm) and C-band frequency (5.6 cm), with vertical transmit and receive polarization. The C-band data did not yield good geophysical products, because the temporal coherence of the signal was significantly reduced alter 24 h. The L-band data were, however, successfully employed to map the surface topography of the icefield with a 10 m uncertainty in height, and measure ice velocity with a precision of 4 mm d−1 or 1.4 m a−1. The corresponding error in strain rates is 0.05 a −1 at a 30 m horizontal spacing. The one-dimensional interferometric velocities were subsequently converted to horizontal displacements by assuming a flow direction and complemented by feature-tracking results near the calving front. The results provide a comprehensive view of the ice-flow dynamics of Glaciar San Rafael. The glacier has a core of rapid flow, 4.5 km in width and 3.5° in average slope, surrounded by slower-moving ice, not by rock. Ice velocity is 2.6 m d−1 or 0.95 km a−1 near the equilibrium-line altitude (1200 m), increasing rapidly before the glacier enters the narrower terminal valley, to reach 17.5 md−1 or 6.4 k ma−1 at the calving front. Strain rates are dominated by lateral shearing at the glacier margins (0.4–0.7 a−1), except for the terminal-valley section, where longitudinal strain rates average close to 1 a−1. This spectacular longitudinal increase in ice velocity in the last few kilometers may be a fundamental feature of tidewater glaciers.
The surface albedo of the Greenland ice sheet: satellite-derived and in situ measurements in the Søndre Strømfjord area during the 1991 melt season
Authors: Knap Wouter H. , Oerlemans Johannes
Published: September 2017

The temporal and spatial variation in the surface albedo of the Greenland ice sheet during the ablation season of 1991 is investigated. The study focuses on an area east of Søndre Strømfjord measuring 200 km by 200 km and centred at 67°5′ N, 48° 13′W. The analysis is based on satellite radiance measurements carried out by the Advanced Very High Resolution Radiometer (AVHRR). The broad-band albedo is estimated from the albedos in channel 1 (visible) and channel 2 (near-infrared). The results are calibrated with the surface albedo of sea and dry snow.

Satellite-derived albedos are compared with GIMEX ground measurements at three stations. There is a high degree of consistency in temporal variation at two of the three stations. Large systematic differences are attributed to albedo variations on sub-pixel scale.

In the course of the ablation season four zones appear, each parallel to the ice edge. It is proposed that these are, in order of increasing altitude: (I) clean and dry ice, (II) ice with surface water, (III) superimposed ice, and (IV) snow. An extensive description of these zones is given on the basis of the situation on 25 July 1991. Zones I, III and IV reveal fairly constant albedos (0.46, 0.65 and 0.75 on average), whereas zone II is characterised by an albedo minimum (0.34). Survey of the western margin of the Greenland ice sheet (up to 71° N) shows that the zonation occurs between 66° and 70° N.
Measured Re-advance of a Debris-covered Glacier Terminus in the President Range, Yoho National Park, British Columbia, Canada
Authors: Rogerson R.J.
Published: September 2017

Measurements made at the terminus of Emerald Glacier in the Rocky Mountains of Canada indicate terminal re-advance in the order of one to two metres per year sustained since 1978 at least. Re-advance is maximum along that part of the terminus which is heavily covered with supraglacial debris, where ice remains in contact with a push-moraine all summer. Re-advance may represent fluctuations of a small, responsive ice mass, or the early effects of recent climatic deterioration.
Snow Profiles and Avalanche Activity in the Cairngorm Mountains, Scotland
Authors: Ward R. G. W. , langmuir E. D. G. , Beattie B.
Published: September 2017

The paper presents data on the snow cover in the Cairngorm Mountains, Scotland, and compares typical Scottish snow profiles with those measured in alpine, continental, and polar areas. The paper shows that in the Cairngorms snow temperatures are higher and as a result densities and ram penetration resistances are also higher. Typical densities are between 350 and 500 kg m−3 and ram resistances are frequently above 50 or even 100 kg. Typical profiles show large masses of windslab above an equigranular basal layer of old snow, and ice layers are common throughout the profile. Avalanche activity is related to two types of profile both of which share low ram resistance in common. Dry-slab avalanches release when densities are of the order of 250 kg m−3 or less and snow temperatures down to – 10° C in the upper layers. Wet slabs and sluffs fall when the snow is isothermal at the melting point. Densities are usually over 450 kg m−3 and may reach over 600 kgm−3 in slush layers supported by ice lenses.
Derived Characteristics of the Ross Ice Shelf, Antarctica
Authors: Thomas R. H. , MacAyeal D. R.
Published: September 2017

Results of the Ross Ice Shelf Geophysical and Glaciological Survey (RIGGS) provide the most complete data set available for any large portion of the polar ice sheets. In this paper, we use the RIGGS data to calculate some of the ice-shelf characteristics. These include steady-state particle trajectories through the ice shelf and the depth of isochronous surfaces, which are of particular importance in choosing a drilling site where ice from the grounded West Antarctic ice sheet is likely to be near the surface. Our estimates for depth to ice originating from the 500 m elevation contour show good agreement with depths to a glaciochemical transition in four ice cores that is believed to be associated with this elevation. This suggests that, for much of the ice shelf, there have been no dramatic and sustained departures from steady state during the past 1500 to 2500 years. With the RIGGS data and an assumed bottom melting rate distribution we calculate steady-state temperature profiles at each of the measurement stations. Then, adopting an ice flow law deduced from laboratory experiments and ice-shelf measurements, we obtain an effective flow-law parameter for each of these sites. Using these values, the measured strain-rate field is transformed to an equivalent stress field over the ice shelf. The stresses are determined by the ice-shelf freeboard and by the force field exerted on the ice shelf by its sides and by grounded ice rises, and our analysis yields estimates of these “restraining” forces F for the Ross ice Shelf. An apparent increase in F very close to the ice front suggests that the ice shelf possesses a narrow seaward fringe of anomalously stiff ice. We suspect that this represents the effects of increased bottom melting rates (and therefore colder and stiffer ice) very close to the ice front. In order to illustrate the role of the restraining forces in controlling ice-shelf behavior, we calculate the strain-rate field for an unrestricted Ross Ice Shelf—one that is detached from its sides and contains no ice rises. Currently the creep-thinning rates for most of the ice shelf is (0.5–1) m year−1; for an unrestricted ice shelf, they would increase to ( 1–10) m year−1, with values up to 60 m year up stream of the ice rises.
210Pb-Dating of Cold Alpine Firn/Ice Cores From Colle Gnifetti, Switzerland
Authors: Gäggeler H. , von Gunten H. R. , Rössler E. , Oeschger H. , Schotterer U.
Published: September 2017

The 210Pb(210Po) method has for the first time been successfully applied for dating cold alpine firn/ice cores. The mean accumulation rate on Grenzgletscher near Colle Gnifetti (Switzerland, altitude 4 450 m) is found to be 37 cm year−1 and 32 cm year−1 for the two ice cores drilled down to 32 m and 65 m in 1976 and 1977, respectively. The surface activity amounts to 4 dpm kg−1 ice. It is shown that a good agreement between the data of the two ice cores is reached with a model taking into account an effect of decreasing annual ice layers with depth. With this thin-out correction, the accumulation rate in the 1977 core increases to 39 cm year−1.
A Note on the Constitutive Law for Sea Ice
Authors: Smith Ronald B.
Published: September 2017

The derivation of a constitutive law to describe large-scale sea-ice deformation commonly uses the so-called “flow rule”. This method introduces a mathematically imposed relationship between shear strength and dilatation which is not based on physical postulates. In this note a more general procedure is described which uses the Reiner–Rivlin equation as a starting point. The method is illustrated by deriving a particular constitutive law and applying it to a simple problem of sea ice blown against a shoreline.
Characteristics of Two Full-Depth Slab Avalanches on Meall Uaine, Glen Shee, Scotland
Authors: William Davison Richard , Keith Davison Steven
Published: September 2017

The characteristics of two full-depth slab avalanches that occurred in 1982 and 1984 at the same location on Meall Uaine in Glen Shee, Scotland, are described. Notable features include the relatively low altitude of the site (c. 670 m) compared to sites of other avalanches observed elsewhere in Scotland, the depth of snow involved (up to 4 m), a snow-pack similar to those recorded in the Cairngorm Mountains, and the entrainment, transport, and deposition of boulders and turf. The probability of the two avalanches occurring when they did was greater than 60%. It is suggested that further observations of full-depth slab avalanches might be obtained by identifying terrain similar to that of the site studied here.
Extrusion Flow Demonstrated by Bore-Hole Deformation Measurements Over a Riegel, Storglaciären, sweden
Authors: Hooke Roger Leb. , Holmlund Per , Iverson Neal R.
Published: September 2017

Inclinometry measurements in a 126 m bore hole slightly down-glacier from the crest of a riegel on Storglaciären showed what appears to be indisputable extrusion flow during the last 3 weeks of July 1984. The velocity at the bed was about five times that at the surface, and lay in a direction deviating 50–60° from that at the surface. The increase in velocity with depth began more than 50 m above the bed. In August and the first half of September the flow returned nearly to “normal” with only a slight tendency toward extrusion. The flow in July appeared to be related to a period of large diurnal water-pressure variation and cavity opening at the bed up-glacier from the riegel. Decoupling of the ice from the bed on the lowest parts of the riegel may have permitted the extrusion. The return to more “normal” conditions in August appears to have been related to a decrease in ice flux over the riegel and a widening of the zone of decoupling.
Direct Observation of Basal Sliding and Deformation of Basal Drift at Sub-Freezing Temperatures
Authors: Echelmeyer Keith , Zhongxiang Wang
Published: September 2017

In a tunnel at the base of sub-polar Urumqi Glacier No. 1, China, three new mechanisms of glacier flow at sub-freezing temperatures have been observed. Taken individually or in combination, these modes of flow can account for nearly all (60–80%) of the overall glacier motion and, yet, they act only within the lowermost 1–2% of the effective glacier thickness. These mechanisms are: (1) enhanced deformation of the frozen and ice-laden subglacial drift; (2) motion across discrete shear planes or shear bands within the frozen drift or at the ice-drift interface; and (3) basal sliding at an ice-rock interface at a temperature of nearly −5° C. The ice-laden drift has an effective viscosity of more than one hundred times less than that measured in the overlying ice, thus allowing very rapid shear deformation. The observed rate or basal sliding at the ice-rock interface agrees favorably with that predicted by the recent work of Shreve (1984) if proper account is taken of the measured surface roughness and reduced ice viscosity.
A Thermodynamic Model of the Formation, Growth, and Decay of First-Year Sea Ice
Authors: Gabison R.
Published: September 2017

The formulation and application of a onedimensional sea-ice thermodynamic model is presented in this paper. The model’s sensitivity to changes in oceanic and atmospheric parameters is analyzed and compared with previous studies. The model is next applied to three locations in the Arctic: Cambridge Bay, Frobisher Bay, and Alert Inlet to study the model’s ability to simulate the annual cycle of first-year ice. The model’s results are compared with available climatological data and discussed in terms of the main thermodynamic processes, the combined effects of oceanic tides, and of sea-ice deterioration by melting on the break-up of sea ice.

It is shown that the model is effective in simulating the climatology of the first-year ice thickness at the three Arctic locations. The study also suggests that improved model performance can be expected from additional research and application of flexural forcing of the ice by waves and tides, and of deterioration of ice strength during the melting process.
Stratigraphy, stable isotopes and salinity in multi-year sea ice from the rift area, south George VI Ice Shelf, Antarctic Peninsula
Authors: Tison J.-L. , Morris E. M. , Souchez R. , Jouzel J.
Published: September 2017

Results from a detailed profile in a 5.54 m multi-year sea-ice core from the rift area in the southern part of George VI Ice Shelf are presented. Stratigraphy, stable isotopes and Na content are used to investigate the growth processes of the ice cover and to relate them to melting processes at the bottom of the ice shelf.

The thickest multi-year sea ice in the sampling area appears to be second-year sea ice that has survived one melt season. Combined salinity/stable-isotope analyses show large-scale sympathetic fluctuations that can be related to the origin of the parent water. Winter accretion represents half of the core length and mainly consists of frazil ice of normal sea-water origin. However, five major dilution events of sea water, with fresh-water input from the melting base of the ice shelf reaching 20% on two occasions, punctuate this winter accretion. Two of them correspond to platelet-ice production, which is often related to the freezing of ascending supercooled water from the bottom of the ice shelf.

Brackish ice occurs between 450 and 530 cm in the core. It is demonstrated that this results from the freezing of brackish water (Jeffries and others, 1989) formed by mixing of normal sea water with melted basal shelf ice, with dilution percentages of maximum 80% fresh water.
An efficient method for a delayed and accurate characterization of snow grains from natural snowpacks
Authors: Brun E. , Pahaut E.
Published: September 2017

The authors describe a new method that allows an accurate, cheap and quick characterization of snow grains from natural snowpacks. The method is based on stopping all metamorphism of snow grains by immersing them in cold isooctane. Snow grains are then carried from the field, stored in a cold room and easily observed through a microscope. It then makes possible recording of snow-grain pictures in a state similar to their natural state, even after storage of several months.
Basal Sliding Relations Deduced from Ice-Sheet Data
Authors: Morland L. W. , Smith G. D. , Boulton G. S.
Published: September 2017

The sliding law is defined as a basal boundary condition for the large-scale bulk ice flow, relating the tangential traction τb, overburden pressure pb, and tangential velocity ub on a smoothed-out mean bed contour. This effective bed is a lower boundary viewed on the scale of the bulk ice flow and is not the physical ice/rock or sediment interface. The sliding relation reflects on the same scale the complex motion taking place in the neighbourhood of the physical interface. The isothermal steady-state ice-sheet analysis of Morland and Johnson (1980, 1982) is applied to known surface profiles from the Greenland ice sheet and Devon Island ice cap, with their corresponding mass-balance distributions, to determine τb, pb, and ub for each case. These basal estimates are used in turn to construct, using least-squares correlation, polynomial representations for an overburden dependence λ(pb) in the adopted form of sliding law τb ═ λ(pb)ub1/m with m ≥ 1.

The two different data sets determine functions λ(pb) of very different magnitudes, reflecting very different basal conditions. A universal sliding law must therefore contain more general dependence on basal conditions, but the two relations determined appear to describe the two extremes. Hence use of both relations in turn to determine profiles compatible with given mass-balance distributions can be expected to yield extremes of the possible profiles, and further to show the sensitivity of profile form to variation of the sliding relation. The theory is designed as a basis for reconstruction of former ice sheets and their dynamics which are related to the two fundamental determinants of surface mass balance and basal boundary condition.
Clasts with Stoss-Lee Form in Lodgement Tills: A Discussion
Authors: Krüger Johannes
Published: September 2017

Clasts modified by glacial erosion are described from lodgement tills in front of the glacier Mýrdalsjökull, south Iceland. Many clasts show modification of their lower surfaces in the same way as their upper ones. However, the lower surfaces have a smoothed down-glacier face and a truncated up-glacier face, which is the opposite orientation to that of the upper surfaces. This so-called double stoss-lee form is interpreted as a response to basal transport over abrading materials, following deposition of the clast and succeeded by glacial erosion. It is suggested that clasts with a double stoss-lee form are a diagnostic criterion for subglacial deposition by lodgement. Furthermore, the distribution and orientation of clasts with a stoss-lee form was investigated on a ground-moraine surface. 17.3% of 2199 clasts with an a-axis diameter > 30 cm had a stoss-lee form. The proportion of clasts with their smoothed ends facing up-glacier within ± 22.5° of the ice-flow direction was 72.7%. Thus, the preferred stoss-side orientation is closely related to the ice movement and indicates the direction from which the ice came. Only 11.7% of boulders with a divergent stoss-side orientation are located in connection with annual moraines. It is suggested that such boulders have mainly been re-deposited beneath the ice and not at the ice front by minor advances of the glacier.
Bore-Hole Survey at Dye 3, South Greenland
Authors: Gundestrup N. S. , Hansen B. Lyle
Published: September 2017

In 1983 three directional surveys were made in the bore hole from which a deep ice core was obtained in the summers of 1979–81. The inclination and azimuth of the bore hole were measured on three surveys, temperature was included on two surveys, fluid pressure and hole diameter on one of the surveys. Fluid-pressure measurements show that the ice-overburden pressure was undercompensated in the upper few hundred meters and overcompensated at the bottom of the hole. Diameter measurements show closure in the upper portion and expansion near the bottom beginning at the transition from the Holocene to Wisconsin ice at 1784 m. The hole expansion and increase in inclination correlate with dust and silt content in the Wisconsin ice. Changes in azimuth are due to flow of the ice and are consistent with the direction of flow at the surface. Temperature measurements show that the hole is at or near equilibrium. The gradient of 0.012 K/m below 1400 m is less than the 0.018 K/m at Camp Century. There is a slight reduction in gradient near the bottom from internal friction in the silty ice.
Can the Mass Balance of a Glacier be Estimated from its Equilibrium-Line Altitude?
Authors: Braithwaite Roger J.
Published: September 2017

The possibility of replacing or supplementing direct measurements of mass balance by estimates calculated from equilibrium-line altitude (ELA) measurements is investigated by statistical analyses of data from 31 glaciers. A linear relationship between mass balance and ELA in terms of two parameters, the effective balance gradient and the balanced-budget ELA, is tested. It is concluded that existing mass-balance series can be usefully extrapolated by using ELA data for additional years. However, accurate mass balance cannot be calculated for glaciers where no such measurements have been made because of the difficulties in prescribing the two model parameters with sufficient accuracy. For example, the effective balance gradient is of the order of 5 mm water/m so that errors of only a few decametres in the estimation of the balanced-budget ELA can have a great effect upon calculations of mass balance.
Frazil Formation in Water of Different Salinities and Supercoolings
Authors: Tsang Gee , Hanley Thomas O’D.
Published: September 2017

The formation of frazil in water of different salinities and initial supercoolings was studied in the laboratory. Experiments were conducted both on genuine and artificial sea-waters. From analysing the experimental results, it was found that the production rate of frazil is highly sensitive to the initial supercooling of the water and will increase over three orders of magnitude as the initial supercooling increases from zero to 2° C. By properly non-dimensionalizing the parameters, it was found that the normalized concentration of frazil in water is principally a function of the normalized time. For the rate of production of frazil, however, it was found that the normalized rate of frazil production, besides being a function of the normalized time, is also affected by the salinity and the initial supercooling of the water. Different frazil crystals formed in water of different salinities and initial supercoolings are thought to be the reason for the different curves of frazil production rate. The normalization of parameters requires the determination of some characteristic parameters which were found to be well-defined functions of initial supercooling and salinity.
Mixing Formulae and Experimental Results for the Dielectric Constant of Snow
Authors: Sihvola Ari , Nyfors Ebbe , Tiuri Martti
Published: September 2017

This paper discusses dielectric properties of snow according to various dielectric models and compares them with experimental results. The complex permittivity of wet snow is assumed to consist of two parts, being the sum of the permittivity of dry snow (a mixture of ice and air) and the excess permittivity due to liquid water (resulting from the dielectric mixture of water and air). In particular the effect of liquid water is considered. Exponential models and structure-dependent models based on mixture theories by Taylor and Tinga and others are applied. It is shown that the assumption that water inclusions have the form of either randomly oriented discs or needles, or of spheres do, not get empirical confirmation but the inclusions are preferably prolate ellipsoids (ellipticity 0.16) or oblate ellipsoids (ellipticity 0.12), dry snow being a dielectric mixture of randomly oriented disc-shaped ice particles and air.
A Note on the Density Distribution of Dry Snow
Authors: Ling Chi-Hai
Published: September 2017

A simple mathematical expression for the density distribution of dry snow is described in this note. It compares very well with observations.
Detection of the Depth-Hoar Layer in the Snow-Pack of the Arctic Coastal Plain of Alaska, U.S.A., Using Satellite Data
Authors: Hall D. K. , Chang A. T. C. , Foster J. L.
Published: September 2017

The snow-pack on the Arctic Coastal Plain of Alaska has a well-developed depth-hoar layer which forms each year at the base of the snow-pack due to upward vapor transfer resulting from a temperature gradient in the snow-pack. The thickness of the depth-hoar layer tends to increase inland where greater temperature extremes (in particular, lower minimum temperatures) permit larger temperature gradients to develop within the snow-pack. Brightness temperature (TB) data were analyzed from October through May for four winters using the 37 GHz horizontally polarized Nimbus-7 Scanning Multichannel Microwave Radiometer (SMMR). By mid-winter each year, a decrease in TB of approximately 20K was found between coastal and inland sites on the Arctic Coastal Plain of Alaska. Modeling has indicated that a thicker depth-hoar layer in the inland sites could be responsible for the lower TBs. The large grain-sizes of the depth-hoar crystals scatter the upwelling radiation moreso than do smaller crystals, and greater scattering lowers the microwave TB. Using a two-layered radiative transfer model, the crystal diameter in the top layer was assumed to be 0.50 mm. The crystals in the depth-hoar layer may be 5–10 mm in diameter but the effective crystal diameter used in the radiative-transfer model is 1.40 mm. The crystal size used in the model had to be adjusted downward, relative to the actual crystal size, because the hollow, cup-shaped depth-hoar crystals are not as effective at scattering the microwave radiation as are spherical crystals that are assumed in the model. In the model, when the thickness of the depth-hoar layer was increased from 5 cm to 10 cm, a 21K decrease in TB resulted. This is comparable to the decrease in TB observed from coastal to inland sites in the study area.
On the relationship between neck length and bond radius during compression of snow
Authors: Brown R. L. , Edens M. Q.
Published: September 2017

In an earlier study on the variations in micro-structure during large volumetric deformations of snow, the authors observed that, contrary to expectations, the length of necked regions connecting adjacent grains did not necessarily decrease during compression. Rather, there was no discernible or predictable change in neck length, in some cases increasing and in others decreasing. Further evaluations of the data and an analysis of the mechanics of neck deformation determined that the process is complicated by three different effects: (1) increase in coordination number (number of bonds per grain), (ii) plastic deformation of the neck, and (iii) a geometric effect determined by bond growth and grain geometry. It is found that the first two effects tend to decrease the neck length and that the third produces an increase in mean neck length. A set of coupled differential equations is developed describing the variation of neck length and bond radius, and solved numerically for conditions consistent with the experimental data. Calculated results agree well with the data for the bond radius but the results for the neck length are less satisfactory. Reasons for this lie with difficulty in making accurate measurements of mean neck length from two-dimensional surface-section data and in the criteria for the definition of necks.
Length, width and slope influences on glacier surging
Authors: Clarke Garry K. C.
Published: September 2017

Statistical analysis of 1754 normal and surge-type glaciers of the Yukon Territory, Canada, reveals that the two glacier types have significantly different average geometries. Surge-type glaciers tend to be longer, wider and to have lower overall slope than normal glaciers. Because there are strong intercorrelations involving length, width and slope, it is not immediately clear which relationships are fundamental and which are secondary. Multiple correlation analysis allows these confusions to be resolved and reveals that the correlation between length and surge tendency is the fundamental one. The direct correlation between surge tendency and width and the inverse correlation between surge tendency and slope are entirely a result of the length-width and length-slope correlations. This conclusion may have implications for the glacier-surge mechanism because one prediction of the Kamb theory of surging is that small slopes (as opposed to great lengths) favour surging. Fowler’s theory of surging predicts that glaciers for which the product θw2 (where θ is slope and w is width) is small are more likely to be surge-type than those for which the product is large, but analysis of the correlation between this parameter and surge tendency lends no support to this claim.
The Antarctic Pack Ice
Authors: Herdman H. F. P.
Published: September 2017

Observations on the distribution and movement of the pack ice around Antarctica. These are based mainly on the work of the “Discovery” Committee’s ships between 1925 and 1939, but also include observations from the pelagic whaling fleet for the years 5930–36. The seasonal advance and retreat of the pack ice are considered in detail and information is given of conditions at the ice edge throughout the year. The movement, or drift, of the pack ice is thought to be closely connected with the surface waters around the Antarctic Continent and a brief account of these currents is included. Some outstanding problems are mentioned in connexion with future research and attention is drawn to the need for air reconnaissance.
The Development of Snow and Glacier Research in Switzerland
Authors: Haefeli R.
Published: September 2017

The evolution of snow and glacier research in Switzerland is outlined. The settling, creep, viscosity and slipping of the snow cover are discussed in detail and the relationship of these comparatively simple processes to the more complex movements in a glacier are described. The importance of further research in glacier physics in connection with the crystallographic and mechanical properties of ice is stressed; certain preliminary laboratory experiments and some subjects for further research in the field are suggested. The Great Aletsch Glacier is recommended for this owing to the proximity of the Jungfraujoch Research Institute and facilities for transport by the Jungfraujoch Railway.
Submarine Ice Cliffs on the West Side of McMurdo Sound, Antarctica
Authors: Stockton William L.
Published: September 2017

Eight submarine ice cliffs have been observed on the west side of McMurdo Sound. Three of these cliffs (Miers Valley, Cape Chocolate, and Strand Moraines) are associated with known ice-cored moraines and are justifiably regarded as underwater exposures of ice cores in the adjacent coast. The ice cliffs at Explorers Cove and near Herbertson Glacier may also be underwater exposures of ice cores which may be present in adjacent moraines. Some of these ice cliffs may represent unusual submarine accretionary sea-ice structures.
Surface Lowering of Ice-Cored Moraine by Wandering Lakes
Authors: Pickard John
Published: September 2017

Lake wander is described as a new mechanism for surface lowering of ice-cored moraines. Evidence is provided from Flanders Moraine, Vestfold Hills, Antarctica (lat. 68° 38’ S., long. 78° 12’ E.). Lakes wander when steep ice scarps retreat due to collapse and melt. Rates of wander are c. 1.3 m year−1. Rates of lowering due to lake wander on Flanders Moraine are c. 0.05 m year−1, which is comparable to rates from elsewhere attributed to different processes.
Radiation and Cloud Observations on a High Arctic Plateau Ice Cap
Authors: Serreze M.C. , Bradley R.S.
Published: September 2017

Hourly measurements of incoming short-wave and long-wave radiation, surface albedo, and net radiation were made on and around a plateau ice cap on north-eastern Ellesmere Island during the summers of 1982 and 1983. These data were stratified by cloud type and amount. All cloud types increased incoming long-wave radiation, especially low dense clouds, fog, and clouds associated with snowfall. Relative transmission of incoming short-wave radiation, expressed as a percentage of clear-sky radiation receipts, was high for all cloud types compared to clouds at lower latitudes. With high surface albedo (≥0.75), net radiation was strongly and positively correlated with net long-wave radiation but showed little relationship to net short-wave radiation. By contrast, with low surface albedo (≤0.20) net radiation was negatively correlated with net long-wave radiation but positively correlated with net short-wave radiation. Under high-albedo conditions, an increase in cloudiness led to higher values of net radiation but under low-albedo conditions net radiation decreased as cloud cover increased. Survival of a snow cover would seem to be favoured if the seasonal decline in albedo is accompanied by a corresponding increase in cloudiness.
Methods of Calculation and Remote-Sensing Measurements for the Spatial Distribution of Glacier Annual Mass Balances
Authors: Konovalov V.G.
Published: September 2017

The areal distribution of glacier annual mass balance b(z) is an important characteristic of the existence of glacierization and its evolution. At present the measured value of annual mass balance at different elevations is only available for a limited number of mountain glaciers of the globe, because of the great amount of labour required for such measurements.

The analysis of long-term mass-balance measurements made at Abramova glacier, Limmerngletscher, White Glacier, Hintereisferner, and Peyto Glacier has revealed that for each year the spatial distribution of annual mass balance is well described by quadratic equations. The main variable in these equations is altitude (z). The various parameters of these formulae are estimated by the author for mean weighted height of the ablation and accumulation areas, and for the glaciers as a whole. It is found that the parameters of annual mass balance for each glacier can be calculated from formulae which include combinations of the following variables: annual balance at one of the three weighted altitudes, maximum annual snow-line elevation, annual and seasonal amounts of precipitation, and air temperatures at nearby meteorological stations.

Therefore, in order to calculate the distribution of annual mass balance as a function of absolute altitude, it is sufficient to obtain a value for mass balance measured only at a single point on a glacier, and common meteorological observational data. A comparison of actual and calculated values of mass balance has shown good agreement between them.

Considering the successful use of aerial remote-sensing for the measurement of snow depth in mountains by means of special stakes, it is satisfactory to accept this method for the assessment of annual mass balance at the mean weighted altitude of the ablation zone. It is possible to use aerial photo-surveys or stereophotogrammetry to resolve this problem. Then annual mass balance for the whole area of a glacier is calculated by using data from one point together with data from a nearby meteorological station.
Early Discoveries of the Effects of Ice Action in Australia
Authors: Banks Maxwell R. , Colhoun Eric A. , Hannan David
Published: September 2017

The effects of past glaciation in what is now Australian territory were first recognized on Macquarie Island, probably by David Ramsay, in 1821. The recognition by Darwin in 1836, and reporting by Milligan in 1848 of ice-transported pebbles and boulders in late Palaeozoic marine rocks in Tasmania, showed on the one hand participation in and on the other familiarity with the controversy in Great Britain at that time on the origin of erratics and drift currents. Reports by Clarke (1852), Daintree in 1859, Selwyn (1860), and Gould (1860) of the effects of land ice on Mount Koscuisko (New South Wales), Bacchus Marsh (Victoria), Inman Valley (South Australia), and the Central Highlands (Tasmania), respectively, reflect the increasing recognition in Great Britain of the erosional and depositional effects of glaciers. Daintree, Selwyn, and Gould were all closely connected with A.C. Ramsay, the main British protagonist of the glacial theory at the time, whereas David Ramsay and Milligan were probably influenced by Robert Jameson of Edinburgh.
Victoria Lower Glacier and Ross Sea Glaciation, Dry Valleys Area, South Victoria Land, Antarctica
Authors: Chinn T.J.H.
Published: September 2017

Victoria Lower Glacier is a complex structure of ice from two distinct sources (Schultz Glacier to the north and a local névé of Victoria Lower Glacier) that join at a broad median shear zone. Evidence from the margins suggest that both are currently retreating. Algae in a block of frozen stratified sediment from within the ice of the terminal margin has a radiocarbon age of 20 200 ± 2400 year BP (NZ 6531 A), indicating that the glacier has advanced since that time. Superposition of ice levels of Ross Sea I glaciation on a radio echo–sounding profile of bedrock beneath the glacier indicates that it is unlikely that Ross Sea I ice entered the valley. The radiocarbon date supports this finding.
On the Relation of Net Balance, Ice Flow, and Surface Lowering of Lewis Glacier, Mount Kenya, East Africa, 1982–86
Authors: Hastenrath Stefan
Published: September 2017

The second 4 year phase of a long-term observation program on Lewis Glacier, Mount Kenya, was completed in March 1986. As for the 1978–82 interval, net-balance results at a stake network and repeated mapping of the ice-surface topography allowed assessment of the mass economy by both “glaciological” and “geodetic” methods.

The general findings from the 1978–82 observations are confirmed: the vertical flow component is directed downward in the upper glacier, and upward in the lower glacier; surface lowering and negative net balance increase down-glacier; ice flow mitigates surface lowering by the negative net balance in the lower glacier, but enhances it in the upper glacier. However, the major difference between the 1982–86 and 1978–82 periods is the progressive slow-down of ice flow. This entails a reduction of mass redistribution, in consequence of which the surface lowering becomes increasingly dependent on the in-situ net balance. It is expected that this circumstance will simplify any inference on future glacier behavior.
Thermal Characteristics of the Permafrost within an Active Rock Glacier (Murtèl/Corvatsch, Grisons, Swiss Alps)
Authors: Mühll Daniel Vonder , Haeberli Wilfried
Published: September 2017

Temperatures from a bore hole through an active rock glacier in the eastern Swiss Alps are presented and thermal conditions within the slowly creeping permafrost are analyzed. Present mean annual temperature in the uppermost part of the permafrost is −3°C. Permafrost is 52 m thick and reaches heavily fissured bedrock. Thermal conductivity as determinedin situfrom seasonal temperature variations and measured in a cold laboratory using frozen samples is close to 2.5–3.0 W m−1°C−1. Vertical heat flow is anomalously high (around 150 mW m-2), probably due to heat advection from circulating ground water or air within the fissured bedrock zone. Beneath this zone, which could in fact represent a non-frozen intra-permafrost layer or “talik”, relic permafrost from past centuries may possibly exist as indicated by a corresponding heat-flow inversion. Given the current temperature condition at the surface of the rock glacier and the fact that the twentieth century is among the warmest in post-glacial time, permafrost conditions may be assumed to have existed during the whole of the Holocene and, hence, during the entire time of rock-glacier formation.