bluuebunny/crossref_metadata_2025 huggingface dataset:
Surface Features of Ice Stream B, Marie Byrd Land, West Antarctica
Authors: Vornberger P.L. , Whillans I.M.
Published: February 2017

Aerial photographs have been obtained of Ice Stream B, one of the active ice streams draining the West Antarctic Ice Sheet. A sketch map made from these photographs shows two tributaries. The margin of the active ice is marked by curved crevasses and intense crevassing occurs just inward of them. Transverse crevasses dominate the center of the ice streams and diagonal types appear at the lower end. A “suture zone” originates at the tributary convergence and longitudinal surface ridges occur at the downglacier end. The causes of these surface features are discussed and the relative importance of four stresses in resisting the driving stress is assessed. We conclude that basal drag may be important, longitudinal compression is probably important at the lower end, and longitudinal tension is probably most important near the head of the ice stream. Side drag leads to shearing at the margins, but does not restrain much of the ice stream.
Flow Near an Ice Divide: Analysis Problems and Data Requirements
Authors: Waddington E.D. , Fisher D.A. , Koerner R.M. , Paterson W.S.B.
Published: February 2017

Climate studies using ice cores require knowledge of the ice deformation at a detailed level, obtainable only by integrated surveying and flow modelling. Field programs should consider model abilities and requirements at the planning stage. Strain and topographic surveys should enclose the flowlines to all boreholes and extend beyond. Only then is it possible to (1) calculate representative slopes at the drill sites and (2) use simple boundary conditions at locations where they do not affect the calculated flow near the holes. Mass conservation models, which may include a parameterized velocity field, estimate the imbalance between integrated accumulation and ice discharge. Momentum conservation models find the actual velocity field, and can reveal a more detailed flow history, but require detailed survey information for boundary conditions. A mass conservation model suggested that flow near core sites at Agassiz Ice Cap, Ellesmere Island, had been steady for more than 3000 years; however, a momentum conservation model showed that either the present transverse strain rate is much smaller than required by the mass conservation model, or the ice is much stiffer than accepted values. It also revealed transients in the flow and microclimate οf which the impact on the derived climate still needs to be assessed by integrated modelling and surveying.
Characteristics of Surge-Type Glaciers (Abstract)
Authors: Clarke G.K.C. , Schmok J. , Ommanney C.S.L.
Published: February 2017

Glaciers can be separated into two classes according to their flow behaviour: normal (relatively steady, annually-averaged, flow rates) and surge-type (pronounced non-annual fluctuations in flow rates). Using glacier inventory data, we compared the population statistics of 1637 normal and surge-type glaciers in the St. Elias Mountains, Yukon Territory, Canada. Within the 38 drainage basins analysed, there is a pronounced spatial variation in the concentration of surge-type glaciers, but no obvious environmental control can be evinced. Analysis of the length distribution function for surge-type glaciers reveals that long glaciers (length exceeding 15 km) have a greater tendency to be surge-type than short glaciers.
Ice Streams and Grounding Zones of West Antarctica and the Ross Ice Shelf (Abstract)
Authors: Shabtaie S. , Bentley C.R.
Published: February 2017

In 1984-85, airborne radar soundings were carried out over West Antarctic ice streams A, B, and C, the neighboring parts of the Ross Ice Shelf, and Crary Ice Rise. Here we use the radar data to map the boundaries of the ice streams, to calculate surface elevations, and to measure ice thicknesses. Lee thicknesses and surface elevations have been used together to map the grounding zones and ice rises (Figure 1).
Compilation of Glacier Maps for Some Mountains (Abstract)
Authors: Pei Gu , Jueying Bu
Published: February 2017

Chinese Glacier Inventory is part of International Glacier Inventory, and glacier maps are important components of the glacier inventory.

Since 1979, we have completed glacier maps for Qilianshan, Altaishan, Tianshan and Pamier mountain systems one after another, about 40% of the whole work.

In order to improve the quality and accuracy of the maps, we fully considered the principles for the compilation of the International Glacier Inventory with due respect to the specific conditions in China as follows;

1.

Materials and data.

Newly published aerial topographic maps of 1:50 000 and 1:100 000 are used as basic maps with aerial photographs as supplementary data for checking and correction.

2.

Scale and projection.

According to the use of the glacial maps, the shape and size of the surveyed area and base data, the scale of the maps of drainage basins is fixed at 1:250 000 and 1:400 000, with Gauss projection. For the distribution maps of glaciers and their geographic landscape and characteristics, and for coding key maps, scales of 1:1 000 000 and 1:2000 000 are used, respectively, and their projection is the normal, minimum-error, conformal, conical projection, with two standard parallels.

3.

Synthesis and presentational method.

To show the location, type, shape, direction of movement and dependent drainage basin of glaciers is the most important task for the compilation of glacier inventory. Therefore, it is very necessary to carry out scientific summarization during compilation and to decide the acceptance or rejection of the surveyed features. In addition, the key elements of drainage basins, ridges, etc. are also given in detail.

The glacier map is a basic skeleton for the glacier inventory, giving important basic data for glaciological research and exploitation, as well as the utilization of the ice-snow resources, etc.
Glacial Geomorphological Map (1:200 000) of Mt. Tomur Region, Tianshan (Abstract)
Authors: Benxing Zheng
Published: February 2017

The Glacial Geomorphological Map (1:200 000) of Mt, Tomur Region, Tianshan, covers 78°33′ – 81°10′E and 41° 08′ – 42° 44′N, with high mountains, deep valleys and many snow peaks, the highest being Mt. Tomur (7435.3 a.s.l.). There are many glaciers in this region with a total area of 4553.69 km2. The melt water from glaciers irrigates the large oasis of Aksu, in the piedmont region in southern Xingjiang and waters the valley plain of Teks River in the Yili area. From piedmont plain to highest mountain summit, the vertical zonality of geomorphology is quite clear, rich in various geomorphological types, representing alpine geomorphology of the arid desert in Central Asia.

The author joined the glacial/geomorphological expedition to the Mt. Tomur Region in 1963, 1973 and 1974, and, in the process of mapping, cooperated closely with mapping engineers. This involved extensive use of aerial photographs, satellite images, large-scale topographic maps, geological maps, geomorphological maps and other data, and comprehensive analyses, comparisons, and judgements of data.

Special emphasis was placed on existing glaciers and the geomorphology of Quaternary glaciers, according to form, composition and relative chronological periods. The geomorphology was divided into five great systems, i.e. glacial, fluvio-glacial, fluvial, arid and artificial. Twenty-four geomorphic types were defined as the basic elements of the geomorphological map and shown in different colours and by various marks, while old and Neozoic faults were shown by black line marks. There are representative heights on all geomorphological zones. Colour brush-shading added much to the stereo effect.

Below the main map, the longitudinal and cross sections of Quaternary geology and geomorphology of the Tialan valley, the stratigraphical columnar profile of West Zamtia and the fluvial/lacustrine deposit profile of the Loska basin were attached, showing the stratigraphical relation between the glacial and non-glacial deposit and the basis for the divisions of the glacial and inter-glacial periods.
Results From The Amery Ice Shelf Project
Authors: Budd W. F. , Corry M. J. , Jacka T. H.
Published: February 2017

The major results from a comprehensive study of the Amery Ice Shelf are presented, following the work of a wintering expedition in 1968 and supplemented by further measurements during the summer seasons of 1969 to 1971. The Programme included ice-core drilling, oversnow surveys for ice movement and optical levelling, ice-thickness sounding, and measurements of snow accumulation. The new data obtained provide the basis for a more accurate assessment of the mass balance and dynamics of the ice shelf than was possible from the earlier surveys.

The results indicate a substantial growth of basal ice under the ice shelf inland where the ice thickness is greater than 450 m. Further towards the ice front the high strain thinning is approximately balanced by the horizontal ice advection.

The velocity distribution over the ice shelf is primarily governed by a substantial surface slope towards the ice front and high restraining shear stress along the sides.
Pine Island Glacier and Its Drainage Basin: Results From Radio Echo-Sounding
Authors: Crabtree R.D. , Doake C.S.M.
Published: February 2017

Retreat of the grounding lines of West Antarctic ice streams may lead to the collapse of the West Antarctic ice sheet. Pine Island Glacier has been pinpointed as an ice stream in which rapid retreat is likely, especially as it is not buttressed by an ice shelf. Radio echo-sounding flights have produced a longitudinal thickness profile for the glacier. The ice presently rests on a bedrock sill which may play a crucial role in controlling the position of the grounding line. The profile can be fitted to a steadystate model but this alone is not adequate to determine steady- or non-steady-state behaviour. Landsat images show that the ice front undergoes periodic calving. Mass-balance calculations suggest that accumulation in the catchment may exceed ablation by a factor of 2. However, accumulation data are poor and there is no firm evidence of a build-up of ice within the Pine Island Glacier drainage basin.
Finite Element Analysis of Calving From Ice Fronts
Authors: Fastook James L. , Schmidt William F.
Published: February 2017

The Antarctic ice sheet has almost no net annual ablation on its surface, so most mass losses are by iceberg calving along its perimeter, which may be either grounded in shallow water or floating in deep water. An ice cliff forms along the perimeter in both cases. Wave action undercuts ice margins in the tide-water zone along beaches, and causes coastal calving if the rate of undercutting compares with the forward ice velocity. If the ice velocity is sufficiently greater, the ice sheet advances into deeper water and becomes a float at depths of 200 to 300 m (Robin 1979). A floating ice shelf then forms and icebergs calve along the ice front. Iceberg calving along this ice front may be due to several causes (Holdsworth 1977,Robin 1979). Since iceberg calving, either from ice shelves or in the tidewater zone of beaches between ice shelves, is the principal ablation mechanism of the Antarctic ice sheet, it is important to understand calving dynamics quantitatively. This paper presents the results of a finite-element examination of calving along floating margins of the ice sheet.
Numerical Modeling of Ice-Shelf Motion
Authors: MacAyeal D. R. , Thomas R. H.
Published: February 2017

Finite-element simulations of the Ross Ice Shelf flow yield good qualitative agreement with observation, but velocity magnitudes tend to be too low up-stream of ice rises and too high near the ice front. These errors will be significantly reduced by better model convergence to the flow law, more accurate values of the flow-law parameters, better resolution of the ice streams, and inclusion of subgrid scale stress variability produced by crevassing and ice-fabric orientation. A model run featuring a hypothetical ice rise down-stream of Crary Ice Rise indicates that the distinctive strain-rate patterns produced by an isolated ice rise can be cancelled by neighboring ice rises. This suggests that an isolated ice rise might migrate up-stream along sea-bed ridges unless there are neighboring ice rises acting to stabilize the surrounding ice-thickness tendencies.
Electrical Behaviour of Antarctic Ice and Radio Echo Layers in Ice Sheets
Authors: Maccagnan M. , Duval P.
Published: February 2017

Static electrical conductivity (SEC) and dielectric measurements were made on Antarctic ice cores at -15°C. The observed behaviour is markedly different from that of temperate glacier ice. The influence of impurities on the electrical properties of polar ice is discussed. Variations of SEC do not appear to be correlated with variations in the relaxation frequency when the loss factor is maximal. Different growth conditions coupled to ageing effects in the first few metres of the firn may explain variations in the electrical properties along an ice core. Moreover, it is suggested that the relaxation frequency increases as the specific surface area increases. Defects are produced in the firn near the surface and may be retained in the subsequent ice. Discontinuous changes in the high-frequency electrical conductivity between adjacent layers can induce internal reflections of radio waves within ice sheets.
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: February 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: February 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.
Atmospheric CO2 Content in the Past Deduced from Ice-Core Analyses
Authors: Oeschger H. , Stauffer B. , Neftel A. , Schwander J. , Zumbrunn R.
Published: February 2017

Probably the only direct way to reconstruct historic atmospheric CO2/air ratios is by measuring the air occluded in ice samples. For such studies, ice samples from very cold regions have an advantage in that the snow and ice probably never had been in contact with liquid water, which interacts with trapped atmospheric CO2. However, even ice samples from very cold regions may have additional CO2, which could have been enclosed during the formation of precipitation, adsorbed at the surface of snow and firn grains, or produced in the ice by chemical reactions on impurities. The gas in ice samples from Camp Cenand Byrd station was extracted both by a vacuum-melting and by a mechanical crushing procedure and the CO2abundance measured by two different analytical methods. N2/O2/Ar ratios were also measured. The shift to lower CO2concentration in both cores at a certain depth found previously is confirmed. Changes in the atmospheric CO2concentration at the corresponding time, about the end of the last glaciation, is the probable explanation of our CO2results.
Present-Day Glaciation in the South Shetland Islands
Authors: Orheim Olav , Govorukha L.S.
Published: February 2017

This paper presents mass-balance results from Deception Island for 1968–69 to 1973–74, from King George Island for the balance years 1969–70 and 1970–71, and from Livingston Island from 1971–72 to 1973–74.

The accumulation areas of all localities are in the soaked fades, with a firn/ice transition at King George Island at 12 to 20 m depth. Of the glaciers studied, only “Gl” on Deception Island terminates wholly on land and has a relatively large ablation area.

The mass-balance curves are similar for King George Island and Livingston Island, with equilibrium lines at around 150 m elevation. “Gl“ on Deception Island has more negative summer balances, and the equilibrium line ranged from 275 to 370 m during the six balance years. Here, there were no years of positive net mass balance, and large negative net values during the 1970–71 to 1972–73 balance years. This resulted from a lowered albedo caused by ash from the August 1970 eruption. Ash layers from the Deception Island eruptions are also observed on Livingston Island and King George Island, where they form stratigraphic markers in the accumulation areas of the glaciers.

Annual balance variations from 1957–58 to 1970–71, based on stratigraphic studies at Deception Island and King George Island, show good correlations, indicating that the variations reflect changes in regional climate.
Interannual Sea-Ice Variations and Sea-Ice/Atmosphere Interations in the Southern Ocean, 1973–1975
Authors: Parkinson Claire L. , Cavalieri Donald J.
Published: February 2017

Examination of satellite-derived 1973–75 sea-ice concentrations for the Southern Ocean and comparison with 1 000 mbar temperatures and sea-level pressures reveal considerable Interannual variability in both the ice and atmospheric fields plus strong suggestions of ice/atmosphere interconnections. The mean position of the ice edge undergoes a strong yearly cycle that lags the cycle of the zonally-averaged temperatures by about one month, but the mean ice edge does not contain small-term fluctuations or interannual variability to the same extent as either the temperature or the pressure. Regionally, the ice varies much more noticeably from year-to-year, with the interannual contrasts showing strong spatial dependence in all months and strong spatial coherence in winter. These are illustrated by selected maps of monthly differences in ice concentrations between 1973 and 1974 and between 1974 and 1975. It is shown that the interannual ice differences can, in many cases, be attributed to the Interannual differences in the positioning and intensity of cyclonic and anticyclonic systems.
Glacier Inventory of James Ross and Vega Islands, Antarctic Peninsula
Authors: Rabassa Jorge , Skvarca Pedro , Bertani Luis , Mazzoni Elizabeth
Published: February 2017

This paper presents the results of the glacier Inventory of James Ross and Vega islands based on topographic map sheets at 1:250 000 scale, Landsat multi-spectral scanner imagery in bands 4 and 7 at the same scale, and oblique air photographs obtained in 1979–80. Work was completed following the methodology proposed by the Temporary Technical Secretariat of the World Glacier Inventory. This is the first such inventory carried out in Antarctica.
Preliminary Investigations on Accumulation at the Filchner/Ronne ice Shelves and Atka Bay
Authors: Reinwarth O. , Rauert W. , Stichler W. , Moser H.
Published: February 2017

In January 1980, the accumulation rates on the Filchner/Ronne ice shelves and at Atka Bay were determined by snow-pit stratigraphy (at Filchner station) and isotope analyses using a snow pit and a handdrilled core down to about 12 m from the surface. At Filchner station a mean annual net accumulation of 51 cm a−1 of snow representing a water equivalent of 20 g cm−2 was found by stratigraphic measurements. 2H, 180 and 3H analyses led to a value of 55 cm a−1 of snow for the last two decades. At Atka Bay a mean annual accumulation rate of 75 cm a−1of snow resulted from 2H and 180 analyses.
Electrical Resistivity Of George VI Ice Shelf, Antarctic Peninsula
Authors: Reynolds John M.
Published: February 2017

A georesistivity survey was made on part of George VI Ice Shelf (71°55'S, 67°20'W). The principal objectives were to determine the electrical structure of the 1ce shelf, in particular how refrozen melt water differs in electrical behaviour from dry firn, and to Investigate the environment beneath the ice shelf.

Apparent resistivity profiles using a Schlumberger electrode configuration have been interpreted using Ghosh's convolution method for vertical electrical sounding (VES), adapted for use where extreme resistivity contrasts are present.

Warm, wet surface conditions tend to reduce the gross resistivity of shallow permeable layers. The electrical results indicate that the refrozen free water has affected the resistivity only indirectly; the mean density of firn is raised to about 0.915 Mg m−3within the uppermost 10 m of the ice shelf at which point the resistivity is comparable to that of Ice of the same density but formed by compaction of firn. The apparent resistivities in the top 100 m reflect the variation of density with depth; a small range of resistivities implies that the range of density 1s narrow and that densification is affected by the percolation and refreezing of melt water.

The bulk of the ice behaves as if resistivity either Is independent of temperature or has only a slight dependence (activation energy ~0.15 eV) with a basal melting rate in excess of 1 to 2 m a−1. The principal resistivities determined for two sites on George VI Ice Shelf were within 10% of those at station BC on the Ross Ice Shelf, allowing for differences in temperature. This Indicates that polar ice, I.e. non-temperate ice, has a very narrow range of resistivity. The apparent resistivity profiles are consistent with there being sea-water of oceanic salinity under the Ice shelf.
Flow Of Ice Sheets In The Vicinity Of Subglacial Peaks
Authors: Robin G. de Q. , Millar D. H. M.
Published: February 2017

Although changes of surface slope across a subglacial peak can be explained at least semi-quantitatively on a two-dimensional basis in terms of gradients of longitudinal and shear stresses along a flow line, we lack appreciation of flow in the third dimension which may tend to cause lower layers to flow around rather than over a sharp peak. This paper collects and surveys evidence relevant to flow in the third dimension and discusses the processes involved, particularly the evidence from radio-echo layering, and also discusses possible reasons for the lack of radio-echo layers near the base of the Antarctic ice sheet.
Spatial Distribution of Microparticles Within Antarctic Snow-Fall
Authors: Thompson Lonnie G. , Thompson Ellen Mosley
Published: February 2017

The concentration and size distribution of water insoluble microparticles were measured in 2 332 snow and firn samples from (a) two sites on the Antarctic Peninsula, (b) the Byrd station strain network, West Antarctica, (c) the Q-13 and base camp sites on the Ross Ice Shelf, and (d) the South Pole and Dome C sites in East Antarctica. These near-surface microparticle studies indicate that, while the number of particles per unit volume of sample remains fairly uniform from site to site, the annual particle accumulation is greatest at locations nearest the coast and decreases rapidly with distance inland. The relationship between particle accumulation and distance from the coast is analogous to a relationship between snow accumulation and distance from the coast. Ten times more particles are deposited annually at stations within 50 km of the coast than at the South Pole and Dome C sites. The size distribution data reveal that, with the possible exception of the Q-13 site, the particulates deposited in Antarctica are well-sorted, indicating little contribution from local sources.
Anomalous Behaviour of Antarctic ice Cores Studied by Electrical and Mechanical Damping Measurements
Authors: Vassoille R. , Perez J. , Tatibouet J. , Duval P. , Maccagnan M.
Published: February 2017

In order to obtain new information concerning the anomalous properties of Antarctic ice previously observed through electrical measurements, we have studied specimens from a coastal site by means of internal friction measurements in the 1 Hz range. The results have been compared to previous ones obtained with polar ice from Dome C and electrical measurements have been made on the same samples in order to confirm the anomalous behaviour of such material.

Two possible explanations of the anomalous properties of polar ice are discussed, namely the role of impurities and the ageing effect. It seems improbable that impurities could be responsible for such properties due to their low concentration. Some experiments, however, lead us to interpret the behaviour of polar ice in terms of modifications with time of the concentration and distribution of intrinsic point defects present at the beginning of the existence of the ice microcrystals
The Radiation Budget At Mizuho Station, Antarctica, 1979
Authors: Yamanouchi Takashi , Wada Makoto , Mae Shinji , Kawaguchi Sadao , Kusunoki Kou
Published: February 2017

Radiation budget measurements were made at Mizuho station (70°42'S, 44"20'E, 2 230 m a. s.1.), East Antarctica, in 1979, within the framework of the Japanese POLEX-South programme. Global, and reflected short-wave and downward and upward long-wave radiat i on fluxes were measured at the snow surface and at the top of a 30 m tower. Direct solar radiation was also measured at the snow surface.

Seasonal variations of net radiation and net short-wave and net long-wave radiation are presented. Daily variation of net radiation is also presented with the daily value of meteorological elements. The monthly amounts of net radiation in winter months had very large negative values of about -80 MJ m−2 month−1. (-2 kly month−1). Daily totals of net radiation for clear skies were negative even i n summer, and were always smaller than those for cloudy skies. Monthly amounts of net radiation in summer months (about -1 MJ m−2 month−1 in December) were the smallest among the several Antarctic stations compared, and whether the balance was negative or positive depended on the ratio of clear and cloudy days. Comparison of seasonal variations of radiation components was made and the dominant cause of the radiation balance was discussed.
Accumulation Distribution in the IAGP Area, Antarctica: 90°E-150°E
Authors: Young N. W. , Pourchet M. , Kotlyakov V. M. , Korolev P. A. , Dyugerov M. B.
Published: February 2017

The distribution of mean net accumulation rate over a large sector (90°E to 150°E) of the IAGP (International Antarctic Glaciological Project) area in Antarctica is presented in map form. The basic data have been compiled from direct measurements of accumulation at stake networks, and by dating horizons in the snow pack by gross β-activity measurements, on four long traverse routes. The spatial variability can be high, over 40%, for a single year, and typically about 20% for multiyear averages. Local surface topography in the form of undulations of several kilometres wavelength can account for about 35% of the variance. Averaging over Intervals of 50 km or more will give the smooth large-scale distribution pattern. But the resultant values can still deviate from the long-term average accumulation by 25% or more due to temporal variability over time scales of years to decades.

A very high correlation (r = 0.97) was found for the relationship a = 1414 exp (0.060 θ10) between accumulation, a kg m−2a−1, and 10 m depth snow temperature, θ10°C, when the data set was limited to a single large drainage basin in Wilkes Land.
Seismic Investigations of The Firn-Ice Structure at Dome C, East Antarctica (Abstract only)
Authors: Blankenship Donald D. , Gassett Roger M. , Bentley Charles R.
Published: February 2017

An extensive program of seismic refraction and reflection shooting was undertaken in the vicinity of Dome C station, East Antarctica (latitude 74°39'S, longitude 124°10'E). Refraction experiments (1978–79, 1979–80) were performed at 37 different shot-point-to-center-of-spread distances along four lines of different azimuth using receiver spacings of 2 to 30 m. The principal result is an extremely well-determined velocity-depth relation for the upper few hundred meters of the ice sheet. Availability of good bore-hole control at Dome C allows us to demonstrate the validity of Kohne's (1972) density-velocity formula, which was developed for warmer ice. Also, after a careful search for azimuthal dependence of variations in the time-distance relationship along different refraction lines, deviations from transverse isotropy in the firn and upper ice are not indicated. Our reflection work (1979–80), conducted along three mutually-centered lines (10.2, 10.2, and 10.7 km in length) oriented at 60° angles to one another, used a series of 16 bore holes, each 30 m in depth, and 18 separate 24-channel recording stations. This extensive coverage combined with common reflection-point shooting geometries (to minimize topographic error) and small charge sizes (to increase resolution) yielded the highest quality set of reflection data yet obtained in East Antarctica. Significant crystalline anisotropy in the lower portion of the ice sheet is indicated. A model with 75% of the ice thickness below the firn (approximately 2 400 m) having c-axes distributed throughout a vertical cone with a semi-apex angle of 20° gives good agreement with the field observations.
Structure Of The Energy Balance In The Ice Sheet-Atmosphere System As An Index Of Antarctic Glaciation (Abstract only)
Authors: Aver'yanov V. G.
Published: February 2017

Various methods have been used to estimate mean multi-year values of moisture, radiation, and heat exchange in the Antarctic ice sheet/atmosphere system. The major components of the balance have been determined as absolute and relative values. The net advection of moisture is taken as 100%, of which 83% is deposited as accumulation on the ice sheet, and the residue in the atmosphere is 15%; loss from the icesheet surface is 2%. In the radiation balance, input at the top of the atmosphere is 57%, absorption in the atmosphere is 43%, loss due to reflected shortwave radiation is 35%, and long-wave radiation from the atmosphere is 78%, while net outgoing long-wave radiation from the surface is 9%. The heat-budget components are:

The Antarctic ice sheet is a vast heat sink. Constant negative surface-radiation balance and low temperature of the ice sheet suggests that it will survive with even small amounts of precipitation. Thus the contemporary glaciation of Antarctica is rather stable.
The Heat Regime of the Central Parts of the Antarctic Ice Sheet with Changing Climate (Abstract only)
Authors: Barbash V.R. , Zotikov I.A.
Published: February 2017

The heat regime and dynamics of the Antarctic ice sheet are studied using numerical modelling for two flow lines, one of which passes Vostok station and the other Byrd station. A two-dimensional non-steady heat-transfer equation with an energy dissipation term was used. The study consists of two parts. The first is a study of velocity and temperature distributions within the glacier under steady-state conditions. The second study was performed assuming surface temperature changes intended to model palaeoclimatic changes for the last 100 ka and also to model future climate changes due to a possible "greenhouse" effect.

Computer numerical modelling shows that the Antarctic ice sheet retains a record of the climatic temperature minimum 18 ka BP. Numerical modelling of the greenhouse effect assumes a temperature increasing by 10 deg within the next 100 a; its influence increases after this even if the surface temperature then remains the same for the next 20 ka. It is shown that for the next 1 ka the temperature wave will penetrate only a thin surface layer of the ice. Even in 20 ka the bottom temperature of the ice sheet will still be unchanged. Small increases of ice velocity can produce ice-sheet thinning of the order of 10 mm a−1.
The Vertical Structure of the Antarctic Ice Sheet and Palaeoclimatic Interpretation of the Data (Abstract only)
Authors: Korotkevich Ye. , Petrov V.N. , Barkov N.I. , Lipenkov V.Ya.
Published: February 2017

The ice core from the 1 415 m Vostok bore hole has been studied. It was found that the ice-grain size increases with depth in the upper 700 m, a sharp gradient change occurring in the 300 to 400 m range. The grain cross-section area at depths of 100, 200, 300, 400, 500, 600, and 700 m was 1.1, 2.0, 1.5, 1.9, 2.6, and 3.3 mm2 respectively. Since grain size is a function of age, and is determined by initial size and growth rate, the latter being exponentially related to ice temperature, an attempt was made to interpret the obtained data in terms of palaeoclimatology.

Calculations show that the upper part of the ice sheet (down to 300 m depth) formed during the past 12 ka, and grew under temperatures higher than those at which the lower part of the ice formed, that is ice at 300 to 700 m depth. This conclusion was confirmed by the results of oxygen isotope analysis.

The air content of ice at depths 100 to 650, 650 to 850, 850 to 1 100, and 1 100 to 1 400 m reduced to normal conditions was 65, 70, 75, and 70 mm3 g−1 respectively. Calculations suggest that 3 to 30 ka BP the ice-sheet elevation at Vostok station was close to the present one, while 30 to 40, 40 to 55, and 55 to 75 ka BP it was 500, 1 000, and 500 m lower than at present, respectively.
Ice Flow Along AN Iagp Flow Line, Wilkes Land, Antarctica (Abstract only)
Authors: Young N.W. , SheehY D. , Hamley T.
Published: February 2017

Trilateration and single line surveys have been made to about 900 km inland of Casey, Wilkes Land, to measure surface elevation, ice thickness, horizontal velocity, and other parameters. On the large scale the velocity U increases smoothly from 8 m a−1, 800 km inland, to 280 m a−1 inland of the fast outlet streams. This increase in velocity is associated with a corresponding increase in the large-scale smoothed (over about 30 ice thicknesses) basal shear stress τb from 0.4 to 1.5 bar. The mean shear strain-rate through the ice sheet U/Z = kτb4
, where Z is the ice thickness (range 4 500 to 1 700 m).

At scales of one to several ice thicknesses large variations occur in surface slope and ice thickness without proportionally large velocity variations, because of the effect of the longitudinal stress. Detailed measurements made over a 30 km section indicated that the surface longitudinal strain-rate gradient varied from -1.7 to +1.3×l0−6 a−1 m−1 along with variations in surface slope of from -3.5 to +1.5%.

A multilayer model, based on the solution of the biharmonic equation for the stream function, was used in a study of the ice flow associated with these surface undulations. Given the bedrock topography and large-scale flow parameters, the model closely predicted the measured surface profile when the variation of the surface accumulation rate over an undulation was also considered.
Energy Balance at the Surface of the Ice Sheet in the Coastal Area of Adélie Land, Antarctica (Abstract only)
Authors: Blaix P.-L , Delaunay D , Poggi A
Published: February 2017

Hourly measurements of wind, temperature, and humidity were made between elevations of 1 and 20 m in the coastal area of Adélie Land over a period of 45 d in January and February 1978. About 1000 profiles are available.

The height of the constant flux layer is >5 m despite the influence of katabatic winds, the wind profile is logarithmic with a mean standard deviation from the logarithmic law of 15 mm s−1. The potential temperature profile is also logarithmic with a mean standard deviation of 0.04°C. The most important deviation from the logarithmic law appears between -4 and 0°C.

Humidity was measured at two points only, between 1 and 20 m; the mean gradient was about 0.01 mbar m−1 and the flux of latent heat was generally negligible.

Net radiation was measured for only 10 d because of radiometer failure. All the fluxes are calculated using data for the 5 m layer. For the 10 d period, the heat loss was about 3 Wm−2 with a mean heat flux of -27.5 Wm−2 and mean net radiation of -10.5 Wm−2(the minus sign signifying the flux is towards the surface). In general, the heat flux is towards the surface (92% of the cases) but is away from the surface in the afternoon. The ablation during the 10 d period without snow-fall was about 200 mm of ice.
Some Evidence of Long-Distance Transport, Local Sources and Fractionation Between Air and Snow for Metallic Aerosols Deposited in Antarctic Snows Since the 1880s (Abstract only)
Authors: Buat-Menard P , Boutron C
Published: February 2017

Using instrumental neutron activation analysis, we have determined the concentrations of Na, CI, Al, Sc, V, Cr, Mn, Co, Fe, Zn, As, Se, Br, Sb, and J in ultra-clean dated snow samples collected in central East Antarctica. These samples had been previously analysed by flameless atomic absorption spectrometry (Boutron 1980). For the elements determined by both techniques (Na, Al, Mn, Fe, and Zn) the results are in remarkable agreement. These new data confirm and extend the conclusion that background concentrations of trace elements observed at present in Antarctic snow are close to those observed about 100 a BP and thus that Antarctic aerosol is still little affected by global atmospheric pollution. These data also confirm that, for several metals, episodes of anomalously high concentrations are in phase with increased sulphate and acidity, which could result from volcanic fallout. However, during such episodes, a straightforward relationship between the rate of increase in trace metals and the rate of increase in sulphate and acidity is not observed. This also affects volatile elements such as Cl, Br, Se, and I. This is probably due to a combined effect of local versus long-range transport of volcanic aerosols together with a physico-chemical segregation between the various components of this aerosol.
The Importance of Pressurized Subglacial Water in Separation and Sliding at the Glacier Bed (Abstract only)
Authors: Bindschadler Robert
Published: February 2017

The effect of pressurized sub-glacial water on the sliding process is quantified by calculating a “bed separation index”. The water pressure distribution i s calculated assuming the existence of a Rothlisberger channel at the bed. Kamb's formulation is used to describe the variation of normal stress over periodic bed undulations. The hypothesis is that as either basal shear stress or water pressure is increased the extent of ice-bedrock separation (on the down-glacier side of undulations) increases and enhanced sliding occurs

Data from three glaciers of widely varying size are used to test this hypothesis. For Columbia Glacier and “Ice Stream B” the importance of including the effects of water pressure in any “sliding law” are pronounced. More complete data from the third test case, Variegated Glacier, are used to compare a number of possible formulations of sliding law which encompass the above hypothesis. A modified Weertmantype law appears to be most preferable while while some possibilities, including Budd's lubrication factor hypothesis, are tentatively rejected.

Consideration of the temporal variations of the “bed separation index” reemphasize that, especially in the short time scale, variations of water pressure can dominate the sliding process. An order of magnitude increase in water discharge causes a hundred fold transient increase in the water pressure.

This paper has been accepted for publication in the Journal of Glaciology
Antarctic Anion Glaciochemistry (Abstract only)
Authors: Herron Michael M.
Published: February 2017

Snow and ice-core samples from a number of sites in Antarctica and Greenland have been analyzed for the major anions Cl−, NO3
−, and SO4
2- by ion chromatography. Reproducibility on adjacent core or pit samples is ±10% at the 95% confidence level. Chloride is of marine origin except following some major volcanic eruptions. Chloride concentrations decrease exponentially with increasing site elevation with a scale height of about 1.5 km. For sites of comparable elevation, Antarctic Cl− concentrations are only slightly higher than in Greenland. Sulfate concentrations, corrected for the marine aerosol contribution, show an inverse dependence on snow accumulation rate. For sites of comparable accumulation rate, Greenland concentrations exceed those in Antarctica by a factor of 2 to 3. Nitrate concentrations also decrease with increasing accumulation rate and for comparable sites Greenland NO3
− concentrations are a factor of 2 higher than in Antarctica. There is no evidence of solar modulation or supernova perturbation of Greenland NO3
− concentrations. The Byrd deep core is shown to have distinct seasonal variations in Cl− and SO4
2- that may be used for dating. In addition, the Byrd core contains volcanic signals similar to those found in Greenland. Recent Greenland snow contains about 4 times as much SO4
2- and 2 to 3 times as much NO3
− as is found in older ice due to modern fossil fuel combustion.
Iceberg Response to Sea State (Abstract only)
Authors: Orheim Olav , Wadhams Peter , Kristensen Monica
Published: February 2017

Data from instruments placed on tabular Antarctic icebergs show that they flex, heave, and roll in response to ocean waves. One iceberg was monitored for 13 months in the Weddell Sea by an automatic data collection platform deployed by the Norwegian Antarctic Research Expedition 1978-79. The temperature sensors demonstrated burial by snow-fall during autumn and winter, but melting during the following summer led to a net annual surface mass balance of -0.1 m water equivalent and to snow and firn temperatures being raised to the melting point. Strain and tilt instruments showed flexure and tilt with main frequencies around 15 to 20 s, but short sampling periods made it difficult to conduct comprehensive statistical analysis of the data.
Sea-Ice and Snow-Cover Data Availability, Needs and Problems
Authors: Barry R. G. , Crane R. G. , Weaver R. L. , Anderson M. A.
Published: February 2017

Various types of sea-ice and snow-cover data are required for operational purposes in real time, for engineering assessments of associated hazards and for regional to global-scale modeling of the climate system. Data on the primary characteristics of ice and snow (extent, depth or thickness, and ice concentration) are becoming available to meet many present types of modeling requirement but secondary properties such as snow-water content, ridging intensity, open-water fraction and ice drift are less readily available.

Data for these major variables of snow and ice cover are considered with respect to problems encountered in obtaining and using digital information necessary for modern computer analyses. Such problems include the limitations of the basic observations (observational or sensor accuracy), the spatial and temporal resolution of different data sets, varying national practices of observing and reporting, and the problems of meshing data collected by different means and having spatial differences and temporal changes of observation time, site location, sensor system and resolution, etc. The relative reliability and climatic “information content” of some historical data sets are briefly examined and available digital data sets on modern global ice- and snow-cover conditions are described.
Ice-Shelf Densities from a Comparison of Radio Echo and Seismic Soundings
Authors: Doake C. S. M.
Published: February 2017

A 40 km line across George VI Ice Shelf was sounded in January 1981 by both radio echo and seismic reflection methods. Because the velocities of radio and seismic waves vary with ice density in different ways, an accurate comparison of travel times from the two methods allowed the average density of the ice shelf to be calculated.

A distinguishable echo from the base of the ice shelf was recorded at 22 out of 23 seismic stations. Continuous radio echo profiling was achieved in ice varying in thickness from about 200 to 350 m. The calculated mean densities fell into two groups, In an area where summer meltwater frequently floods the surface the average densities were around 0.915 Mg m−3, while in the drier areas the average densities were around 0.884 Mg m−3. Apart from this division, there was no apparent systematic variation of average density with position. The sounding was carried out approximately along a flowline on the ice shelf.

The variation of ice density with depth and position is difficult to allow for when modelling the deformation of ice shelves. Measured values of surface strain-rate, for example, may in some circumstances need to be corrected for effects due to the compressibility of snow.
Sea Ice Budget Studies of Baffin Bay Using A Numerical Ice Model
Authors: Keliher T. E. , Foley J. S.
Published: February 2017

The dynamic-thermodynamic model of sea ice due to Hibler (1979) has been adapted for simulations of the Baffin Bay pack. The simulations were carried out for wind fields characteristic of the more common synoptic situations for July, the ice conditions of July 1969 being taken as typical of this month to initialize the model. Average long-term currents were also used. The modelled ice characteristics were consistent with expected results for the forcing fields and rheology of the ice. A comparison of advectional ice losses through Davis Strait with the melt in situ shows the melt to be an order of magnitude larger. However, the melt alone cannot clear the ice out of Baffin Bay. It seems that the mechanism for this process involves a slow consistent melt coupled with a short period of northwesterly winds.
Introduction to a New Sea-Ice Database
Authors: Knight Richard W.
Published: February 2017

An important new sea-ice database is presently being created at the National Climatic Data Center in Asheville, North Carolina, USA. The data are digitized from weekly charts prepared at the US Navy/National Oceanic and Atmospheric Administration (NOAA) Joint Polar Ice Center and converted into a digital format prescribed by the World Meteorological Organization. The data cover both the Arctic and Antarctic for a ten-year period of record. The grid points are identified by earth coordinates and have a resolution of 15 nm or better.

This paper is intended to inform potential users of sea-ice data about the availability of the new data set. Topics covered are (1) data source, (2) brief description of the processing procedures, (3) the SIGRID output format, and (4) future plans.