bluuebunny/crossref_metadata_2025 huggingface dataset:
Molecular Orbital Calculations of Water-Ice Surface Interactions
Authors: Plummer Patricia L. M.
Published: September 2017

Detailed knowledge of the energetics of the interaction of a water monomer with an ice surface is important in understanding the factors which control both the nucleation and the growth of ice. In this work we model this interaction by using a small section of an ice surface and semi-empirical quantum-mechanical calculations of the CNDO/INDO type to investigate the energetics of a gas-phase molecule approaching the surface. In the attempt to simplify the system as much as possible while retaining the essential features of the "real" physical situation, 13 water molecules arranged in the lattice positions for ice Ih were used to represent the surface. Electron-density plots for both basal and prism surfaces were generated. Potential-energy curves were calculated for a monomer approaching a number of different sites on each type of surface. Monomer-surface binding energies varied from approximately 17 to 33 kJ/mol for the surface sites examined. Ion pairs of the H30+-OH- type were included in the surface and their effect on the energy of interaction with an incoming monomer calculated. For these studies no distortion of the ice surface was allowed. The energies found follow the same trends as observed for a free monomer-ion interaction.
Frazil Nucleation Mechanisms
Authors: Hanley Thomas O'D.
Published: September 2017

Previously the author had suggested that frazil nucleation occurs by a mechanism analogous to spinodal decomposition, aided by turbulence. After further study the following points are made: (1) No critical point exists between solid and liquid; this rules out true spinodal decomposition. (2) Pure water can be supercooled to -40°C; at -40°C the theoretical energy barrier to nucleation is about 10 -19 J. Frazil forms after supercooling less than 0.1 deg; at this temperature the theoretical energy barrier is about 10-14 J. (3) Theory shows that turbulence increases the energy barrier. (4) Turbulence may aid dissipation of heat of solidification, but not sufficiently to account for observed frazil formation at small supercoolings. (5) The author's evidence that frazil can begin to form at supercoolings as small as 0.02 deg suggests that no nucleus except ice itself can account for "heterogeneous" nucleation of frazil.
X-Ray Diffraction Topographic Observations of the Large-Angle Grain Boundary in Ice Under Deformation
Authors: Hondoh T. , Higashi A.
Published: September 2017

Large-angle tilt grain boundaries in artificially-grown ice bicrystals were observed by the method of X-ray diffraction topography. In bicrystals for which misorientation angles satisfy the conditions of a high-density coincidence site lattice (CSL) at the boundary, the images of fine parallel line defects appear on the topograph taken immediately after a light deformation. Since these images disappear in a time period between several hours and a few days and reappear again at the same sites when the specimen is deformed subsequently, it is concluded that these line defects are not stable like the boundary dislocations but may be steps generated on the boundary to form facets which coincide with the high-density CSL plane. X-ray topographic images of boundaries which do not satisfy the conditions of a high density CSL are complex and difficult to interpret, although some of the images indicate that there may be different types of structures on such boundaries.
Dielectric Behaviour of Ice Microcrystals: A Study Versus Temperature
Authors: Boned Christian , Lagourette Bernard , Clausse Marc
Published: September 2017

Dispersions of ice microcrystals were obtained from the breakdown of super-cooling of water-in-oil type emulsions whose disperse phase was either resin-exchanged water or aqueous solutions of NH4C1. Their complex permittivity ϵ* = ϵ′ - ϵ″ was studied versus their temperature T, up to the melting point of the ice microcrystals, by means of an automatically balancing admittance bridge (General Radio 1680A) working at 400 Hz and 1 kHz. The plots ϵ′(T), ϵ″(T), and ϵ″(ϵ′) reveal that these systems exhibit two distinct dielectric relaxations located on both sides of a temperature Tm which was found to be equal to about —20°C in the case of water and lower than —20°C in the case of aqueous solutions of NH4C1. The relaxation located in the lower temperature range arises from the Debye dipolar absorption of ice while the other one could be related to structural changes occurring within the lattice of ice as T approaches its melting point. These results are consistent with those obtained by investigating versus frequency the dielectric behaviour of ice microcrystals, at discrete sub-zero temperatures close to their melting point.

This paper has been accepted for publication in full in a forthcoming issue of the Journal of Glaciology.
In Situ Measurements of the Activation Energy for D.C. Conduction in Polar Ice
Authors: Bentley Charles R.
Published: September 2017

During the 1976-77 Antarctic field season, electrical resistivity profiling was carried out in the south-eastern quadrant of the Ross Ice Shelf. Drilling to a depth slightly greater than 300 m at the same site, where the total ice thickness is 425 m, permitted tem-perature determinations (personal communication from B. L. Hanson and J. H. Rand) that can be extrapolated to the ice-water boundary. Numerical modelling of the apparent resistivity, allowing for a continuous variation of temperature and density, and hence con-ductivity, with depth, was done in the same manner as has been described previously (Bentley, 1977). Temperatures calculated by assuming no basal melting or freezing show excellent agreement with those measured. Two models of apparent resistivity, taking the activation energy in the solid ice to be 0.15 eV and 0.25 eV, respectively, bracket the observed data, with the points tending to favor the lower value. This is in satisfactory agreement with (although perhaps slightly lower than) other measurements on polar ice. Assuming that the same temperature model applies at the site of the earlier measurements (Bentley, 1977), only 30 km away and approximately "up-stream", leads to apparent resistivity models, with activation energies of 0.15 eV and 0.25 eV, that again bracket the observations. The effect of other possible causes for the change of conductivity with depth besides temperature, such as varying grain size, crystal orientation, CO2 content, etc., is unknown but believed to be small because of the similar history of all the ice in the relevant depth range, about 100-350 In, over which the conductivity increases by a factor of 2. The conductivity in the ice at 100 m depth (temperature —23°C) at both sites is within ± 10% of 1.4 × 10-5 Ω-1. We conclude that an activation energy of 0.20 ± 0.05 eV not only can be used for modelling, but also closely represents the true value for ice-shelf ice.
Comparison of Electromagnetic and Seismic-Gravity Ice Thickness Measurements in East Antarctica
Authors: Drewry David J.
Published: September 2017

The errors involved in ice thickness determinations in Antarctica by seismic reflection shooting, gravity observations and radio-echo sounding are briefly discussed. Relative accuracies of 3%, 7-10% and 1.5% have been suggested. Double checks of ice depths from radar sounding in east Antarctica indicate an internal consistency of measurement for this technique of <1%. Comparison of carefully executed seismic shooting and routine radio-echo sounding results against absolute ice thickness values from two deep core drilling sites show no significant differences between these two remote methods (i.e. both are better than 1.5%).

Over 60 comparisons are examined between radar ice thicknesses and over-snow measurements obtained on eight independent traverses in east Antarctica. Three traverses exhibit consistently unacceptable results-U.S. Victoria Land Traverse II (southern leg), Commonwealth Transanlarctic Expedition and the U.S.S.R. Vostok to South Pole Traverse—which probably result from misinterpretation of “noisy” seismograms. The remaining comparisons indicate mean differences, including some navigational uncertainty, of ≈3%, <8% and 5% between radio-echo and (1) seismic, (2) gravity, and (3) gravity tied to seismic determinations, respectively.
Temperature Measurement of Ice and Water Surfaces in the North Water Area Using an Airborne Radiation Thermometer
Authors: Müller F. , Blatter H. , Kappenberger G.
Published: September 2017

Ice and water surface temperatures were measured with an airborne radiation thermometer PRT-5 over the North Water polynya during three missions between late winter and early summer 1974. Error corrections, problems of data analyses and mapping are discussed. Attempts are made to relate the main types of sea ice to temperature ranges, which then are used in conjunction with satellite pictures to produce surface temperature maps.
Characterization of Cold-Regions Terrain Using Airborne Laser Profilometry
Authors: Hibler W. D.
Published: September 2017

This paper provides a review of the characteristics of airborne laser profilometry and its application to quantitative characterization of cold-regions terrain. The limitations of profilometry due to the profiler instrumental characteristics and instability of the aircraft platform (resulting from variations in aircraft altitude and attitude) are discussed. For typical aircraft speeds of the order of 100 m/s these limitations restrict the accurately measured roughness content to the approximate wavelength range 2 m to 300 m. Digital filtering and hardware techniques for removing the aircraft motion, and hence extending the long wavelength validity of the profile, are discussed.

Regarding terrain characterization, particular attention is given to Arctic, sea ice. Ridge height and spacing distribution models for sea ice in conjunction with digitally processed laser profiles allow efficient characterization of sea-ice ridging using only a few parameters. In particular, a single ridging intensity parameter has been found to allow reasonable estimation of the number of ridges encountered at any height level along a straight-line path. Examination of spectral characteristics of first-year and multi-year ice suggest that laser profiles may be used to identify the ice type of floes and ridges. Comparisons of laser data and submarine sonar data are made which suggest that ratios of c. 6.5: 1 can be used to estimate ridge keel depths from laser data. Use of laser profilometry to characterize tundra and indirectly 10 measure variation in snow depth is briefly discussed.
Antarctic Sea-Ice Variations from Satellite Sensing in Relation to Climate
Authors: Budd W. F.
Published: September 2017

An analysis of records of annual mean temperatures around Antarctica shows large-scale anomalies of thousands of kilometers extent with typical variations of a deg from one year to another From 1967 on, composite satellite photographs are available which show considerable variation in the sea-ice extent in different years up to about 5º of latitude. These largest differences seem to persist over entire seasons. In general there seems to be considerable association between the region around the Antarctic with the coldest temperatures and the regions of greatest sea-ice extent. An analysis of long-term records at a single location near the edge of the Antarctic sea ice indicates a strong correlation between variations in the annual mean temperature and the duration of the sea ice, such that a change of 1 deg in the annual mean temperature corresponds to about 70 d variation in the duration of the sea ice. A relation is obtained between variations of annual mean temperature and the mean extent of the sea ice, viz. a 1 deg change corresponds to approximately 2.5º latitude variation in the maximum sea-ice extent. The magnitude of the variations in the sea-ice extent observed from the satellite data in comparison with the large-scale temperature anomalies is compatible with the above relations, although some rotational shifts appear to take place.
Glaciological Studies in Iceland with Erts-I Imagery
Authors: Williams Richard S. , Bödvarsson Ágúst , Rist Sigurjón , Sæmundsson Kristján , Thorarinsson Sigurdur
Published: September 2017

Under a long-term, bi-national, multi-disciplinary research project between the U.S. Geological Survey and various Icelandic scientific organizations, MSS imagery from the ERTS-I satellite is being used to study the varied dynamic environmental phenomena of Iceland, including its glaciers and ice caps. Initial analysis of the ERTS-I imagery has shown the importance of the repetitive imagery to:

Record relatively short-term glaciological changes. According to measurements made on two ERTS-I images, taken 11 months apart, an outlet glacier in the north-east part of Vatnajökull, had surged 1.8 km. A combination of field observations and analysis of ERTS imagery shows a total surge in excess of 3 km which probably took place in a few months, perhaps in as little as a few weeks. Contorted moraines on another of Vatnajökull’s outlet glaciers, Skeiðararjökull, on the south-east coast, show a movement of 600 m in an 11 month period even though the snout of the glacier remained in essentially the same position.

Several glacier-margin lakes have been observed to change in size during the year (1972-73), particularly Grjœnalón, which continued to enlarge in area each time it was imaged until its size diminished markedly after a jökulhlaup partially emptied the lake in August 1973. Seasonal changes in the size of sediment plumes along the coast, where glacial rivers debouch their sediment-laden water into the ocean, can also be observed in a time-lapse manner.

Furnish the data necessary to revise certain glaciological features on maps, and to produce ortho-image maps of ice caps directly from ERTS imagery, at least to map scales of 1: 250 000. Sufficient ERTS-I imagery of Iceland from the late summer and early fall of 1973 now exists to map accurately, from a planimetric standpoint, 90% of that area of Iceland covered by glacial ice (previously estimated to be 11.5% of total area of Iceland). Optimum imagery (minimum snow cover, maximum exposure of glacial ice) has been obtained of Vatnajökull, Langjrikull, Hofsjökull, Myrdalsjökull, and Eyjafjallajökull or five (including the four biggest) of the seven largest ice caps in Iceland and five of the smaller (less than 50 km2) ice caps as well. On 19 August 1973 Hofsjökull had an area of 915 km- on ERTS imagery. Its area has usually been cited as 996 km2. On a 1945 Danish Geodetic Institute map (1: 500 000) the area is 981 km2; U.S. Army maps (1 : 250 000, 1969) show an area of 943 km2.

Map subglacial volcanic and structural features. Within or at the margins of the ice caps and outlet glaciers, a number of new glaciological, structural, and volcanic features can be mapped from ERTS-I imagery, particularly at low solar illumination angles (<10°) including several probable subglacial central volcanoes, calderas, and tectonic lineaments. Some of the effects of jökulhlaups can be mapped, including subsidence cauldrons resulting from subglacial volcanic or intense geothermal activity.
Polarization Changes of Radio Signals in Vertical Radio-Echo Sounding of Glaciers
Authors: Bogorodskiy V. V. , Trepov G. V. , Fedorov B. A.
Published: September 2017

An electromagnetic linearly-polarized signal transmitted through the glacier in a vertical direction, reflected from the bedrock, and received with a receiving antenna, is found to be changed into one either partially or elliptically polarized. The polarization changes are believed to be due mainly to the crystal structure of the glacier and anisotropy caused by the pressure of the upper layers.

An analysis of the polarization diagrams obtained is up to the present the main method used for studies of the reflected signal polarization. Evidently using a simple dipole a partially-polarized signal is not distinguishable from one that is elliptically polarized, nor is a nonpolarized signal distinguished from circularly polarized. However, the data recently obtained are of great importance, particularly from studies of glacier crystal structure made in deep core drilling.

Possible reasons for the polarization changes of the signal have been analysed. Results of the analyses of the polarization diagrams obtained both at individual points and along extended traverses are discussed. It has been found that the signal reflected from a considerable ice thickness is polarized in such a way that the parallel orientation of the receiving and transmitting dipoles can be disregarded. En route recordings of the signal fluctuations obtained by parallel and orthogonally polarized dipoles are shown. The results of polarization studies are important for practical purposes. For example, bedrock relief sounding carried out with crossed dipoles makes it possible to get rid of interference signals occurring due to scattering from inhomogeneous structures of the upper part of the glacier.
Interpretation of Radio-Echo Sounding Data on a Temperate Mountain Glacier from its Surface
Authors: Luchininov V. S. , Macheret Yu. Ya.
Published: September 2017

Temperate mountain glaciers have specific peculiarities which make the interpretation of radio-echo sounding data much more difficult than for polar ice sheets. On the A or Z indicators one can observe a plurality of pulses differing in shape, amplitude, and range. Often a gap is observed on the film. The problem is to select the pulses from the bed or internal reflecting horizon and to reconstruct the subglacial relief or internal interface.

During preliminary processing, the radio-coordinates of all marks on a type A radiogram are written into a table. Then non-informative marks are eliminated and informative marks are situated on a continuous line or trace.

We put into practice three methods of interpretation: (1) an envelope method, (2) Harrison’s transformation method, (3) approximation of segments of a trace by straight lines. Harrison’s transformation method is the most general one; the others are useful for the presentation of results in a graphical form. The suggested methods are used for the interpretation of the data from a transverse profile of the valley glacier Lednik Bezengiy, Caucasus, 1970-71. Radar RW-10 with a carrier frequency of 440 MHz and overall receiver sensitivity relative to the transmitter pulse power 130 dB was used. It was revealed that the transparency of the glacier changes from year to year. The maximum ice thickness measured was 33°±15 m. Some extended interfaces in the body of the glacier were discovered. One of them, 80 m deep, coincides with seismic contrast interface and with the 0° C isotherm. Radio-echo sounding data are in agreement with gravity measurements on the same profile.
Study of Antarctic Ice Sheet Motion by Means of Doppler Effect Laser Equipment
Authors: Bogorodskiy V. V. , Belousova I. M. , Ivanov I. P.
Published: September 2017

Doppler-effect laser equipment was successfully employed in Antarctica in 1969-70 to measure the rate of ice-sheet motion. The method is based on measuring differential beat frequency generated by the interaction of the direct pulse and its echo. A He-Ne laser with the wavelength of 6 328 Â was used in the 15th Soviet Antarctic Expedition. The paper gives detailed results of the measurements along with a description of the equipment used and of the observational procedures. A new modified version of the equipment was made ready for 1971-72 Antarctic season, and was used in the 18th Soviet Antarctic Expedition in the vicinity of Mirny station. New results are also discussed. Analysis of all available data makes it possible to believe that the movement of the ice sheet is irregular with occasional stops. The progressive motion of the ice sheet is accompanied by strain oscillations.
Triaxial experiments on iceberg and glacier ice
Authors: Gagnon R. E. , Gammon P. H.
Published: September 2017

Triaxial experiments, at confining pressures in the range 0–13.79 MPa, have been performed on glacial ice collected from four icebergs and one glacier. Tests were conducted at strain rates in the range of 5 × 10−5 to 5 × 10−5s−1 and at four temperatures in the range of −1° to −16°C. Depending on test conditions, the ice failed by one of four possible modes ductile deformation, due to extensive non-interacting microcracks; fracture along a shear plane followed by continuous or stick-slip sliding; large-scale brittle fracture; and combined ductile and shear-plane fracture and slip The strength Increased with decreasing temperature, increasing strain rate up to 5 × 10−3s−1 and increasing confining pressure at the lower temperatures. The strength at 5 × 10−2s−1 was lower than at 5 × 10−3s−1 probably because extension and interaction of microcracks is enhanced at the higher rate. For higher confining pressures at −1°C, the strength decreased due to freezing-point depression. The ice from the different sources exhibited different mean uniaxial compressive strengths. The mean number of air bubbles per unit volume correlated with the mean uniaxial compressive strengths and this may be the dominant factor distinguishing the strengths of the various ice types.
Bubbly-ice densification in ice sheets: II. Applications
Authors: Lipenkov Vladimir Ya. , Salamatin Andrey N. , Duval Paul
Published: September 2017

A mathematical model for simulating the densification of bubbly glacier ice is used to interpret the following experimental data from the Vostok (central Antarctica) ice core: two ice-porosity profiles obtained by independent methods and a bubble-pressure profile obtained by direct measurements of air pressure within individual bubbles. The rheological properties of pure polycrystalline ice are deduced from the solution of the inverse problem. The model and the inferred ice-flow law are then validated, using porosity profiles from seven other ice cores drilled in Antarctica and Greenland, in the temperature range from -55° to -20° C. The following expression is adopted for the constitutive law:

where ė and τ are the effective strain rate and stress, respectively, α is the creep exponent taken as 3.5, Rs is the gas constant and T(Ts) is the temperature (standard temperature). The numerical values obtained for the “linear” and “non-linear” viscosities are: μ1 = 2.9 ± 1.3 M Pa year and μ2 = 0.051 ± 0.019 M Paα year, and the apparent activation energy Q is confirmed to be 60 k J mole−1. The corresponding flow law is in good agreement with results of both mechanical tests and independent estimations based on the analysis of different natural phenomena associated with glacier-ice deformation. When the model is constrained by the porosity and bubble-pressure profiles from Vostok, the mean air content in Holocene ice is inferred to be about 0.088 cm3g−1. The corresponding mean air pressure in bubbles at the end of pore closure is about 0.083 M Pa, whereas the atmospheric pressure at this depth level would be 0.063 M Pa. The influence of the climatic change on the ice-porosity profile is discussed. It resulted in an increased air content in ice at Vostok during the Last Glacial Maximum: 0.096 cm3 g−1.
Pore-water controlled grain fracturing as an indicator for subglacial shearing in tills
Authors: Hiemstra John F. , Van Der Meer Jaap J. M.
Published: September 2017

Genetic classification of glacial deposits still proves to be highly controversial. In many cases, it remains unclear whether a particular sediment has been sub-glacially deformed. In the present paper it is suggested that micromorphological research is helpful where current techniques fail to lead to unambiguous interpretations. It is argued that the occurrence of fractured grains in glacial sediments is indicative of subglacial shearing and that such grains may be used as diagnostic evidence of glaciotectonism. Deformational mechanisms associated with the fracturing process are outlined and explained, using a series of thin sections from Wijnjewoude, The Netherlands.
Glacial regime of the highest Tien Shan mountain, Pobeda-Khan Tengry massif
Authors: Aizen Vladimir B. , Aizen Elena M. , Dozier Jeff , Melack John M. , Sexton David D. , Nesterov Victor N.
Published: September 2017

Major processes controlling the existence of a large sub-continental glacier system were identified on the basis of glaciological, meteorological and isotopic analyses using expeditionary and long-term data. Observations were made on the southern Inylchek glacier located in the Pobeda-Khan Tengry massif, the largest sub-continental glacier system on the northern periphery of central Asia. More than 1200 glaciers with a total area of about 4320 km2 comprise the massif. Melt is for the most part caused by radiation and is most intensive during periods of anticyclonic weather with fohn development. The proportion of solar radiation input in relation to heat balance is more than 90%. Evaporation and condensation are negligible during most times and comprise 7% of heat expenditure. Accumulation was associated with cold cyclonic weather. Four ice-formation zones were identified, the upper boundary of liquid runoff is at 5200 m and the recryslallization zone is above 5900 m. The calculated net glacier mass is negative, −318 kg m−2 a−1, and indicates the degradation of modern Pobeda-Khan Tengry glaciers.
Snow accumulation and ice flow at Dôme du Goûter (4300 m), Mont Blanc, French Alps
Authors: Vincent C. , Vallon M. , Pinglot J. F. , Funk M. , Reynaud L.
Published: September 2017

Glaciological experiments have been carried out at Dôme du Goûter (4300 m a.s.l.), Mont Blanc, in order to understand the flow of firn/ice in this high-altitude Alpine glacierized area. Accumulation measurements from stakes show a very strong spatial variability and an unusual feature of mass-balance fluctuations for the Alps, i.e. the snow accumulation does not show any seasonal patterns. Measured vertical velocities which should match with long-term mean mass balance are consistent with observed accumulations. Therefore, the measurement of vertical velocities seems a good way of quickly obtaining reliable mean accumulation values for several decades in such a region.

A simple flow model can be used to determine the main flowlines of the glacier and to propose snow/ice age of core samples from the two boreholes drilled down tο the bedrock in June 1994. These results coincide with radioactivity measurements made to identify the well-known radioactive snow layers of 1963 and 1986. We can hope to obtain ice samples 55–60 years old about 20 or 30 m above the bedrock (110 m deep). Below, the deformation of the ice layers is loo great to be dated accurately.
Changes in glaciers in Hidden Valley, Mukut Himal, Nepal Himalayas, from 1974 to 1994
Authors: Fujita Koji , Nakawo Masayoshi , Fujii Yoshiyuki , Paudyal Prem
Published: September 2017

Glaciological investigations were carried out in 1994 on the glaciers in Hidden Valley, Mukut Himal, Nepal Himalayas, in order to make a comparison with observations made in 1974. Most of the glaciers were found to have retreated by 30–60 m in terminus elevation over the 20 years between the two studies. Rikha Samba Glacier, the longest glacier in the valley, has retreated by about 200m. The areal average of the amount of surface lowering and the volume loss of the glacier was estimated to be 12.6 m ice equivalent and 13% of the total mass, respectively. The annual mass balance of −0.35 m a−1 water equivalent was obtained as an average for 20 years, which is one of the largest negative values amongst small glaciers of the world.
Borehole temperatures at the Colle Gnifetti core-drilling site (Monte Rosa, Swiss Alps)
Authors: Haeberli Wilfried , Funk Martin
Published: September 2017

Measured englacial temperatures at the Colle Gnifetti core-drilling site are presented and compared with model calculations concerning possible effects of 20th century warming. The firn/ice saddle at the 124 m deep saddle borehole is cold throughout with a mean annual surface temperature near –14°C and a basal temperature slightly below –12°C. Influence of refreezing meltwater is weak and limited to near-surface formation of ice layers (recrystallization-infiltration). Temperature gradients in the saddle borehole are positive and increase from 0.015° to 0.019°C m−1 between 30 m depth and bedrock, corresponding to a mean vertical heat flow of around 50mWm−2. The observed temperature profile is close to steady-state conditions. It can well be reproduced with time-dependent model calculations using mean annual air temperatures from the nearby weather station of Grand St. Bernard within the main chain of the Swiss Alps, but it significantly deviates from similar calculations based on Säntis data, reflecting developments of air temperatures on the northern slope of the Alps. 20th century warming of cold Alpine firn seems to be much less pronounced than in polar areas, where strong heat-flow anomalies are commonly observed.
New precipitation and accumulation maps for Greenland
Authors: Ohmura Atsumu , Reeh Niels
Published: September 2017

Annual total precipitation and the annual accumulation on the Greenland ice sheet are evaluated and presented in two maps. The maps are based on accumulation measurements of 251 pits and cores obtained from the upper accumulation zone and precipitation measurements made at 35 meteorological stations in the coastal region. To construct the accumulation map, the annual precipitation was split into solid and liquid precipitation components. Annual total precipitation exceeding 2500mmw.e. occurs on the southeastern tip of Greenland, while the minimum precipitation is estimated to occur on the northeastern slope of the ice sheet. The mean annual precipitation for all of Greenland is 340 mm w.e. The largest annual accumulation of about 1500 mm w.e. is found on the glaciers in the southeastern corner of Greenland, while the smallest accumulation is found on the northeastern slope of the ice sheet west of Danmarkshavn. The mean accumulation on the Greenland ice sheet is estimated at 310mmw.e. The regional difference in accumulation is examined with respect to the 850hPa(mbar) level circulation. The present surface topography is found to play an important role in determining regional accumulation on the ice sheet.
Butyl acetate, an alternative drilling fluid for deep ice-coring projects
Authors: Gosink T.A. , Kelley J.J. , Koci B.R. , Burton T.W. , Tumeo M.A.
Published: September 2017

Deep-drilling operations in glaciers require a fluid to maintain hydrostatic equilibrium and prevent closure due to plastic flow of the ice. Many past practices have employed various fluid mixtures using fuel oil as the base. The case for butyl acetate is presented here as an adequately dense and environmentally safe drilling fluid. Results from the 1990 drill season are highly favorable.
Ice Floes in Collision
Authors: Weber J. R.
Published: September 2017

An event recorded by a biaxial tilt-meter during a storm at the camp of the AIDJEX Pilot Study located on the pack ice in the Beaufort Sea in 1972 is interpreted as an acceleration caused by the collision of a faster drifting ice floe with the station floe. It is estimated that the acceleration lasted between 20 and 40 s and resulted in a velocity increase of between 84 and 120 m/h. The energy imparted per square kilometer to the station floe during collision is estimated to be between 5.7 and 8.1 MJ.

The station was equipped with an acoustic bottom reference (ABR) system with a sampling rate of one minute. However, the positional scatter is too large and the sample rate too low to be able reliably to identify the collision event from the ABR data alone.
Testing of Radiometric Detection of Avalanche Victims
Authors: Coumes A. , Liva V. , Zadworny F.
Published: September 2017

A radiometer prototype has been constructed using the S band. In this band, a theoretical evaluation of the differences of temperature which are measurable by the radiometric method proves the influence of the parameters liquid-water content of snow and snow thickness.

When there is no victim, the apparent temperature of a snow layer depends on these parameters and presents important variations because of its natural inhomogeneity. In order to detect the local variation of the apparent temperature due to the presence of a victim, we must refer to an average local temperature obtained by a servo-system. Thus, we obtain a certain number of false alarms which can be suppressed only with a manual sounding. The search itself becomes very long and also requires a systematic exploration of the snow surface by parallel traverses spaced every 2 m. This exploration seems impossible on uneven ground such as a real avalanche area.
A Slide of Glacier Ice and Rocks in Western Canada
Authors: Mokievsky-Zubok O.
Published: September 2017

A glacier-caused slide occurred in July 1975 within the Devastation Glacier basin, British Columbia. An estimated 2.5 × 106 m3 of glacier ice, representing about 9% of the total mass, was incorporated into displaced debris. Four human lives were lost.
Avalanche Activity in Iceland, Climatic Conditions, and Terrain Features
Authors: Björnsson Helgi
Published: September 2017

Abstract. Avalance activity in Iceland for the last 860 years is briefly outlined and the present avalanche problems in Iceland are explained. Statistics are given for the number of deaths from avalanches by years, months and avalanche categories (for both residents and travellers).

Climatic conditions and terrain features are described for the main avalanche-hazard areas in Iceland. Data from meteorological stations for precipitation, wind, and air temperatures have been analysed for all the major avalanche cycles in the present century. Synoptic weather patterns that trigger avalanches are explained. A distinction is made between conditions that cause wet and dry avalanches. The results form the basis of an area-wide avalanche forecast in Iceland.
Research on Snow Cover in China and the Avalanche Phenomena of Batura Glacier in Pakistan
Authors: Yafeng Shi , Wenying Wang
Published: September 2017

Abstract. This paper summarizes the state of research in China on snow cover, snow-drift control, and avalanche defences, and also reports the results of observations of avalanching above Batura Glacier, Pakistan, during two expeditions.
Avalanche Hazard in the Cairngorm Mountains, Scotland
Authors: Ward R. G. W.
Published: September 2017

Avalanche accidents are increasing in Scotland and fatalities now average two each year. The victims are either mountaineers or cross-country skiers as the problem is confined to the steeper and remoter slopes. Studies in the Cairngorm Mountains have shown that Scottish snow differs from alpine snow in three respects: depth hoar does not occur in Scotland, higher values are found for density and rammsonde penetration, and ice layers are more abundant. Slab avalanches are found on slopes of about 35° and sluffs on slopes of 30° and steeper. Although most avalanches are small, crown fracture lines reach a maximum length of 500 m, and slabs may be up to eight metres thick. Preliminary correlations between avalanche release and weather conditions have shown the importance of cold periods following heavy snow falls and the significance of thaws. Much more needs to be done before an avalanche-forecasting service could be provided, not the least of which is persuading likely beneficiaries that such a service would be worthwhile.
Satellite Altimeter Results Over East Antarctica
Authors: Brooks R. L.
Published: September 2017

During the operational lifetime of the Seasat altimeter from 3 July to 10 October 1978, more than 450 overflights were made over East Antarctica inland to latitude 72°S. An analysis of selected passes over a variety of ice features demonstrates that the oceanographic altimeter performed surprisingly well over the ice sheet and ice shelves, acquiring useful measurements during approximately 70% of each pass. The altimeter's onboard tracking system dampened out the ice-surface elevations, but post-flight retracking of the stored return waveforms reveals excellent ice-surface details. After waveform retracking, the altimeter repeatability is better than ±1 m.
Radiative Transfer Modeling of Microwave Emission and Dependence on Firn Properties
Authors: Comiso J. C. , Zwally H. J. , Saba J. L.
Published: September 2017

The microwave emission from a model polar firn was calculated using a numerical solution of the radiative transfer equation that included angledependent Rayleigh scattering. The depth-dependent parameters in the equation were physical temperature and the coefficients of scattering and absorption. The coefficients were based on Rayleigh scattering from the snow grains. The bulk emissivity and the seasonal dependence of brightness temperature were calculated for seven locations at which grain sizes were measured as a function of depth. When the absorption and scattering coefficients are adjusted, the modeled emissivities agree with observed emissivities at these locations. The modeled seasonal dependence of brightness temperatures also compares well with values obtained at 1.55 cm wavelength by the Nimbus-5 satellite. Good agreement with data did not occur when the imaginary part of the index of refraction (and, hence, the absorption coefficient) had a significant temperature dependence between 210 and 250 K.
Measured Properties of the Antarctic Ice Sheet: Surface Configuration, Ice Thickness, Volume and Bedrock Characteristics
Authors: Drewry D.J. , Jordan S.R. , Jankowski E.
Published: September 2017

Results of airborne radio echo-sounding (RES) in Antarctica are presented. Flight tracks covering 50% of the Antarctic Ice sheet on a 50 to 100 km square grid, flown using Inertial navigation, have errors <<5 km. Ice thicknesses determined from 35, 60, and 300 MHz RES records are accurate to 10 m or 1.5% thickness (whichever is greater). Altimetry, determining surface and sub-surface elevations, after corrections have errors <<50 m. An up-to-date coastline compiled from satellite imagery and all recent sources has frequencies for various coastal types of: ice shelves (44%), ice streams/outlet glaciers (13%), ice walls (38%), and rocks (5%). A new map of the ice sheet surface has been compiled from 101 000 RES data points, 5 000 Tropical Wind, Energy conversion and Reference Level Experiment (TWERLE) balloon altimetry points, geodetic satellite and selected traverse elevations. The volume of the Antarctic ice sheet Including ice shelves has been calculated principally from RES data using various techniques as 30.11±2.5 × 106 km3. Frequency distributions for subgladal bedrock elevations for East and West Antarctica are presented. They conform approximately to Gaussian (normal) functions.
Techniques for Thermal Conductivity Measurements in Antarctica
Authors: Ewing Richard E. , Falk Richard S. , Bolzan John F. , Whillans Ian M.
Published: September 2017

An accurate knowledge of the thermal properties of firn and ice within a glacier is essential for any reliable mathematical model of heat transfer. This paper considers the problem of determining the thermal properties of firn at Dome C, Antarctica, for use in such a model.

First, the difficulties in accurately determining thermal properties are discussed. Then a physical experiment which can be performed under field conditions, but which will yield a well-posed mathematical problem for determining the unknown properties, is presented. Next, two different numerical techniques for solving the mathematical problem are discussed. Finally, some numerical approximations and error estimates are presented for the results of applying our numerical procedure to data from Dome C. Although insufficient data were obtained to test our methods fully, we have established a measurement procedure and a method of analysis which appear to be promising.
A Comparison of Ice Fabrics and Textures at Camp Century, Greenland and Byrd Station, Antarctica
Authors: Herron Susan L. , Langway Chester C.
Published: September 2017

A comparison of the crystalline texture and fabric of the two deep cores to bedrock from Camp Century, Greenland, and Byrd station, Antarctica, reveals striking similarities. Each core exhibits a fabric profile which progresses from depositional fabrics at shallow depths through multi-maxima transitional stages into single maximum distributions. The major difference between the two cores occurs near the base where the Camp Century fabrics maintain a high degree of orientation while the Byrd station fabrics break up into a diamond pattern. The most remarkable similarity between the two profiles occurs at the glacial-interglacial transition where crystal sizes decrease and crystal orientations strengthen significantly over a very short interval. Similar changes occur in other deep ice cores, thus indicating the possibility that the late Wisconsin ice has a unique crystallographic signature.
Did the West Antarctic Ice Sheet Create the East Antarctic Ice Sheet?
Authors: Hughes T. J.
Published: September 2017

The mostly terrestrial East Antarctic ice sheet is ten times larger and probably more stable than the mostly marine West Antarctic ice sheet. It is natural to suppose that the former appeared first, and that perhaps the latter was partially formed from an outflow of East Antarctic ice onto the West Antarctic continental shelf. Alternatively, the largely marine West Antarctic ice sheet may have appeared first, provided that post-Eocene continental drift allowed heavy snow precipitation over the West Antarctic island archipelago, but prevented warm South Pacific ocean currents from entering. Sea ice could then thicken and ground from surface accumulation and basal freezing, creating broad marine ice domes in shallow West Antarctic embayments. These marine ice domes could then merge with ice caps on the islands to create a marine ice sheet that could expand into East Antarctica and merge with highland ice caps to form the terrestrial East Antarctic ice sheet. A Cenozoic glacial history of Antarctica is outlined, based on this marine ice transgression hypothesis.
Acidity Levels in Ice Sheets from Radio Echo-Sounding
Authors: Millar D. H. M.
Published: September 2017

It has been suggested (Hammer 1977, Gudmandsen and Overgaard 1978, Millar 1981) that layers of acidic ice, formed after large volcanic eruptions, are a cause of radio echo layering. The power reflection coefficient (PRO of these reflecting layers may be related to their acid content and thickness. The present paper makes estimates of ice acidity from radio echo-sounding (RES) and compares them with measured values along Greenland ice cores. Dated Antarctic PRC/depth profiles are also presented, and acidity estimates made which give a crude indication of past volcanic activity in the southern hemisphere to ~150 ka BP.
Outlet Glacier and Mass-Budget Studies in Enderby, Kemp, and Mac. Robertson Lands, Antarctica
Authors: Morgan V.I. , Jacka T.H. , Akerman G.J. , Clarke A.L.
Published: September 2017

A detailed survey has been made of outlet glaciers between longitudes 48°E and 62°E. Surface and bedrock profiles were constructed from radio echo-sounding data and glacier grounding lines were located by changes in the characteristics of bedrock echoes. A preliminary investigation of the dynamics of these fast-moving (~1 km a−1) glaciers is presented. From the measurements, the ice-mass flux through each glacier can be calculated. Mass-budget studies inland (Morgan and Jacka 1981) are thus extended to the coast. In the inland region, an excess of accumulation over outflow of ~100% was estimated, while a near balance condition appears likely for the coastal region
Radio Echo Determination of Basal Roughness Characteristics on the Ross Ice Shelf
Authors: Neal C. S.
Published: September 2017

The small-scale roughness characteristics of the bottom surface of the Ross Ice Shelf (RIS) are determined at two locations using airborne radio echo-sounding results. Small-scale roughness is not resolvable by an echo sounder, but may be quantified by examination of the fading pattern of the received echo. A full interpretation of the bottom echo requires a knowledge of the modulation imposed upon the radar signal by the ice/air boundary. This is obtained by determining the roughness scales of the ice-shelf surface. Its effect on estimates of basal roughness is investigated and is found to be unimportant in most cases.
Recent Variations in Heavy Metal Concentrations in Firn and Air From the Antarctic Peninsula
Authors: Peel D. A. , Wolff E. W.
Published: September 2017

A snow-pit and hand-drilled core have been sampled at Spaatz Island in the Antarctic Peninsula to obtain evidence on the importance of short-term fluctuations of heavy metal (Cd, Cu, Pb, and Zn) concentrations. A programme of air sampling was undertaken at the same time to investigate directly the link between concentrations in air and in snow. The snow samples and air filters have been analysed by atomic absorption spectrometry (AAS) following preconcentration on tungsten wires and by differential pulse anodic stripping voltammetry (DPASV). One sequence of snow samples was preconcentrated in the field and analysed later for Cd in the laboratory.

The snow analyses confirm that year-to-year variations in heavy metal concentrations may be comparable with changes due to long-term variations in global emission rates to the atmosphere from industrial sources. The importance of understanding these apparently meteorologically controlled processes is underlined. Averaged data from the combined air/snow sampling programme show a satisfactory linear relationship between concentrations in air and in snow for both the heavy metals and for the cation component of the marine aerosol. The results, considered in the light of Junge's model for static rainout, give a ratio for concentration in air (ng m−3)/concentration in snow (ng g−1) of 0.6±0.3.
Landsat Images and Mosaics of Antarctica for Mapping and Glaciological Studies
Authors: Williams Richard S. , Ferrigno Jane G. , Kent Tina M. , Schoonmaker James W.
Published: September 2017

The preparation of a US Geological Survey Professional Paper, “Satellite image atlas of glaciers”, has produced a 1:5 000 000 scale “Landsat index map of Antarctica”, in which each of the 2 470 Landsat nominal scene centers is represented by a symbol showing the suitability of available Landsat images for the preparation of planimetric image maps and for glaciological studies. Landsat has the potential for imaging about 79% of the area of Antarctica, and 70% of the Landsat imaging area, or about 55% of the continent, was found to have excellent or good (less than 10% cloud cover) coverage.

Australia, Japan, New Zealand, the United Kingdom, and the United States of America have published Landsat image maps, either as single Landsat scenes or as mosaics of two or more images. The Federal Republic of Germany and the Republic of South Africa also plan to publish Landsat image maps in the near future.

Available Landsat images could be used, in combination with Doppler satellite technology for geodetic control, to triple the area of Antarctica presently mapped at scales of 1:250 000 or larger. Landsat-3 RBV images can also be used to prepare 1:100 000 scale image maps.In addition to eventually using Landsat images to compile an accurate coastline of Antarctica, Landsat images have been successfully used for glaciological studies. Recent measurements of successive images of Pine Island Glacier, Walgreen Coast, West Antarctica, showed an average speed of flow of the terminus of 6 m d−1 over 750 d.
Implications for the Late Wisconsin-holocene Extent of the West Antarctic Ice Sheet from Regional Free-air Gravity Anomalies in the Ross Embayment (Abstract only)
Authors: Greischar Larry L. , Bentley Charles R.
Published: September 2017

Gravity data from cruises 32, 51, and 52 of the USNS Eltanin (Hayes and Davey 1975), approximately adjusted to the new gravity datura (IGSN 71) and reference system (GRS 67), have been used to extend the Ross Ice Shelf gravity map to the edge of the Ross Sea continental shelf. Various regional gravity anomaly fields obtained by applying low-pass filters to these data are strongly negative over the entire Ross embayment; values increase gradually from approximately -300 gu (-30 mgal) near the Siple Coast to -150 gu (-15 mgal) near the edge of the Ross Sea continental shelf.