bluuebunny/crossref_metadata_2025 huggingface dataset:
Large-Scale Numerical Modelling of the Antarctic Ice Sheet
Authors: Budd W.F. , Smith I.N.
Published: February 2017

A large-scale dynamic numerical model of the Antarctic ice sheet has been developed to study its present state of ice flow and mass balance as well as its response to long-term changes of climate or sea-level.

The flow of ice over a two-dimensional grid is determined from the ice thickness, the basal shear stress, the bedrock depth, and ice flow parameters derived from velocities of existing ice sheets. The change in ice thickness with time is governed by the continuity equation involving the ice flux divergence and the ice accumulation or ablation. At the ice sheet seaward boundary, a floating criterion and floating ice thinning rate apply. Bedrock depression with a time-delayed response dependent on the history of the ice load is also included.

A 61 × 61 point grid with 100 km spacing has been used to represent the ice-sheet surface, bedrock, and accumulation rate. The model has been used to simul a te the growth of the present ice sheet and i ts reaction to changes of sea-level, bedrock depression, accumulation rate, ice flow parameters, and the iceshelf thinning rate.

Preliminary results suggest that the present ice sheet is not in equilibrium but rather is still adjusting to changes of these parameters.
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: February 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 × 106km3. Frequency distributions for subgladal bedrock elevations for East and West Antarctica are presented. They conform approximately to Gaussian (normal) functions.
A Comparison of Ice Fabrics and Textures at Camp Century, Greenland and Byrd Station, Antarctica
Authors: Herron Susan L. , Langway Chester C.
Published: February 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.
Dynamics of Erebus Glacier Tongue
Authors: Holdsworth G.
Published: February 2017

Recent measurements conducted on Erebus Glacier Tongue (EGT) have enabled improvements to be made to previous analyses of earlier data (Holdsworth 1974). The use of LANDSAT imagery and controlled aerial photography up to 1978 have enabled glacier flow rates and hence strain-rates to be determined more accurately than before. Re-analysis of the stress and strain-rate data leads to flow law constants which are now more compatible with those of Thomas (1973). The thinner ice appears to be “softer” than the thicker ice. Bending of EGT appears to be the result of current pressure exerted on the south side of the glacier, and computed bending strains seem to account for most of the observed curvature of EGT.

Basal ice melting predominates over any possible refreezing; melt rates along the south edge exceed basal melt rates by a factor of 5-10. Short-period, pseudo-elastic deformations occurring in EGT as a result of ocean wave-induced motion may be responsible for continually activating crevasses and producing the apparent “softening” effect in the creep of the thinner ice. Such oscillations may also lead to the calving of EGT although recent observations suggest that a hinge-line calving due to horizontal bending of EGT may be just as likely.
Large-Scale Investigations of the Deformation Behaviour of Layers of Ice Shelves
Authors: Jessberger Hans L. , Dörr Rudolf
Published: February 2017

For the investigation of time-dependent vertical deformation of upper layers of ice shelves loaded by accumulated snow and/or structures a large-scale field test was started in 1980-81 at Georg von Neumayer station (70°37´S, 8°22´W), Antarctica. Specially developed base plugs were fixed to the bottoms of 5.0 and 10.0 m deep bore holes by melting and refreezing the surrounding firn. The deformations of the snow firn layers will be measured between these base plugs and metal plates placed on the snow surface during installation. The bore holes are kept open by tubes of different diameters in order to allow for load-induced vertical deformations of snow and firn. Some measurements are directly affected by the presence of the station. The design of the measuring device, the procedure of installation, and the measurement of deformation are described. The results of calculations of deformation and measurements of first settlement are presented.
Antarctic Ice Elevation Maps From Balloon Altimetry
Authors: Levanon Nadav
Published: February 2017

Antarctic ice-elevation maps are presented, based on 4 000 measurement points, analysed from traverses made by constant-density balloons. These balloons were launched during the Tropical Wind, Energy Conversion and Reference Level Experiment (TWERLE). The TWERLE data yielded daily maps of the elevation of the 150 mbar pressure surface in the southern hemisphere. These maps serve as a reference level from which the altimeter readings are subtracted to yield the ice elevation.

The accuracy of the ice-elevation data is estimated at better than 60 m. The accuracy of the contouring depends on the density of measurements in the particular area. Two contouring techniques were used. One is based on generating elevation data at fixed grid-points from arbitrarily distributed measurements, using Cressman's method. The second is a surface spline interpolation technique by Duchon.

The elevation data are of special value on the inland plateau areas. There, the typical distance between balloon measurements is sufficiently small, relative to the typical distance between contour lines at 100 m intervals. Furthermore, the inland areas are the least accessible to other mapping techniques.
Structural Studies Of Bare Ice Near The Allan Hills, Victoria Land, Antarctica: A Mechanism Of Meteorite Concentration
Authors: Nishio Fumihiko , Azuma Nobuhiko , Higashi Akira , Annexstad John O.
Published: February 2017

Structural laboratory studies were made of ice collected at the surface and from a shallow bore hole in the bare ice near the Allan Hills, Victoria Land, Antarctica. The results obtained were combined with glaciological survey data to describe the mechanism of accumulation of meteorites by ice flow in a marginal area of the East Antarctic ice sheet. The age of the bare ice, approximately 20 ka, was estimated by fabric characteristics and grain size of the ice. This conforms to the minimum value of the terrestrial age of the meteorites found in the same area. The several hundred meteorite finds concentrated in the bare-ice area can be explained by an expanded catchment area during a previous ice age, or by a correction factor for the estimate of the influx rate of meteorite fall, or more probably by a combination of both.
Gas Extraction From Polar Ice Cores: A Critical Issue For Studying The Evolution of Atmospheric CO2 and Ice-Sheet Surface Elevation
Authors: Raynaud D. , Delmas R , Ascencio J.M. , Legrand M.
Published: February 2017

The measurement of gases enclosed in polar ice cores provides valuable Information concerning the history of the ice sheets and their environment. The extraction of gases from ice is a critical step in the experimental procedure. We found that the most efficient methods of gas extraction for 20 to 50 g samples were ice melting and controlled refreezing of the melt water for the total gas content and ice crushing far the CO2content. These two experimental methods are described in detail.

It is shown, in particular, that ice is easily contaminated by carbonate dust during sample preparation. This contamination introduces an excess of CO2when gases are extracted using a procedure involving ice melting.
Deep Geoelectric and Radar Soundings at Dome c, East Antarctica (Abstract only)
Authors: Shabtaie Sion , Thyssen Franz , Bentley Charles R.
Published: February 2017

Deep geoelectric soundings using a Schlumberger array were carried out at Dome C, Antarctica. To penetrate the 3 500 m thick ice, electrode half spacings up to 8 km (the largest yet made on polar ice) were used. A constant-current dc transmitter with voltages up to 10 kV, resulting in constant currents of up to 10 mA, was employed; potentials were measured with an electrometer and recorded continuously on an x-y recorder.

A computer program has been developed to calculate apparent resistivities on an ice sheet in which the density, temperature, and impurities, and thus the actual resistivity, vary continuously with depth. Preliminary models show that the actual resistivity at a depth of about 500 m increases downward by a factor of about three, and that elevated resistivities must persist to much greater depth. This change in resistivity appears to be linked to transition from ice-age to Holocene ice.

The cause of this resistivity increase is not well understood, and may be attributed to any of several physical and chemical changes that also occur at about the same depth.
Derived Characteristics of the Ross Ice Shelf, Antarctica (Abstract only)
Authors: Thomas R.H. , Macayeal D.R.
Published: February 2017

Results of the Ross Ice Shelf Geophysical and Glaciologlcal Survey (RIGGS) provide the most complete data set available for any large portion of the polar ice sheets. In this paper, we use RIGGS data to calculate some ice-shelf characteristics. These include steady-state particle trajectories through the ice shelf and the depth of isochronous surfaces, which are of particular importance in choosing a drilling site where ice from the grounded West Antarctic ice sheet is likely to be near the surface. Our estimates for depth to ice originating from the 500 m elevation contour show good agreement with depths to a glaciochemical transition in four ice cores that is believed to be associated with this elevation. This suggests that, for much of the ice shelf, there have been no dramatic and sustained departures from steady state during the past 1.5 to 2.5 ka. With the RIGGS data and an assumed bottom melting rate distribution we calculate steady-state temperature profiles at each of the measurement stations. Then, adopting an ice-flow law deduced from laboratory experiments and ice-shelf measurements, we obtain an effective flow-law parameter for each of these sites. Using these values, the measured strain rate field is transformed to an equivalent stress field over the ice shelf. The stresses are determined by the ice-shelf freeboard and by the force field exerted on the ice shelf by its sides and by ice rises, and our analysis yields estimates of these restraining forces F for the Ross Ice Shelf. An apparent increase in F very close to the ice front suggests that the ice shelf possesses a narrow seaward fringe of anomalously stiff ice. We suspect that this represents the effects of increased bottom-melting rates (and therefore colder and stiffer ice) very close to the ice front.

In order to illustrate the role of the restraining forces in controlling ice-shelf behavior, we calculate the strain-rate field for an unrestricted Ross Ice Shelf, i.e. one that is detached from its sides and contains no ice rises. Currently the creepthinning rate for most of the ice shelf is 0.5 to 1m a−1 for an unrestricted ice shelf, but it would increase to 1 to 10 m a −1, with values up to 60 ma− 1 up-stream of the ice rises

This paper has been accepted for publication in the Journal of Glaciology.
Estimation of Precipitation and Accumulation for the Iagp Area from Rawinsonde Data (Abstract only)
Authors: Bromwich D.H.
Published: February 2017

Routine upper-air observations for the year 1972 are used to construct the atmospheric water vapor budget between the coast and the line joining the highest points of the terrain between the meridians 55°E and 110°E. This gives seasonal and annual values of precipitation for an area of 2.4 × 106 km2. Annual accumulation amounts are then estimated for the whole budget region. By assuming that the accumulation poleward of the 2 000 m elevation contour equals the 1972 precipitation, the annual areallyaveraged precipitation (and thus the accumulation) is computed for the coastal slopes below 2 000 m.

Rigorous analysis of the rawinsonde data from five coastal stations and one on the plateau is a feature of this study. A special attempt is made to resolve the key boundary-layer properties. A systematic and important bias in the record due to missed observations during storms is demonstrated. The use of estimates for these missing values, which are obtained from multilinear regression equations, increases the computed annual poleward water-vapor transport at two stations by more than 30%.

Regions of net water-vapor inflow to and outflow from the continent were found to be organized in the same fashion as the mean circulation in the lower troposphere: the budget region is under the influence of a cyclonic vortex centered offshore. There was a poleward-directed, integrated (surface to 300 mbar) eddy flux of water vapor at all points along the coast. 43% of the annual precipitation fell during the period June to August due to a particularly stormy sequence mainly at one station.

The annual accumulation between the coast and the crest of the terrain is estimated with an uncertainty of 17%, and for the coastal slopes with an uncertainty of 39%. Comparison of the multiannually averaged accumulation derived from glaciological measurements with the computed values for a single year shows agreement within the limits of error.

In conclusion, the water-vapor budget approach produces accumulation values similar to the glaciological measurements. This approach offers a viable alternative method for monitoring the seasonal and annual accumulation over large parts of East Antarctica.
Radio Echo-Sounding of Riiser-Larsenisen (Abstract only)
Authors: Orheim Olav
Published: February 2017

The Norwegian Antarctic Research Expedition 1978–79 used the Scott Polar Research Institute Mk IV radio echo-sounding system fitted in a Bell 206B helicopter to survey 620 km of Riiser-Larsenisen and 100 km across the outer part of Stancomb-Wills Ice Stream. Observed thicknesses of Riiser-Larsenisen decrease from 700 m at the grounding line to less than 200 m at the ice front. The thickness of Bllenga ice rise varied between 200 and 450 m. The ice shelf thins towards the east, and seems there to flow obliquely to the ice front (Fig.1).

Step-like change in thickness of >150 m over 500 m horizontal distance i s observed in the central part of the ice shelf. The records also demonstrate undulations in ice thickness of 600 to 700 m wavelength and 50 m amplitude, and various types of rifts and crevasses. Internal layering is recorded at 250 to 300 m depth over Blåenga and i n the ice shelf up-stream of this ice rise.

Observed ice thicknesses on Stancomb-Wills Ice Stream range from 130 to 220 m, with no systematic decrease towards the ice front. The records include long sections of heavy scatter from densely spaced rifts and bottom crevasses. This ice stream attains velocities > 4 km a−1, and is much more active than Riiser-Larsenisen. This high activity has resulted in extensive fracturing of the ice shelf.
Modelling Temperature Distribution in Alpine Glaciers
Authors: Blatter Heinz , Haeberli Wilfried
Published: February 2017

Modelling temperature distribution in non-temperate mountain glaciers presents problems not normally encountered when modelling ice sheets or ice shelves. These problems are mainly concerned with numerical instabilities caused by the high, nonuniform gradients of various input parameters (geometry, mass balance, surface temperature, and flow velocity). Steady-state solutions must be used to check and complete data sets, before using models of greater complexity to calculate temperature fields in a more realistic way. Test runs with a computer model, which allows for true two-dimensional solutions and realistic velocity fields, are described for two examples from the Swiss Alps. These steady-state calculations illustrate, in a semi-quantitative way, that advection of cold ice by glacier flow strongly influences the temperature distribution in both an existing large valley glacier with a cold accumulation zone (Grenzgletscher), and a large piedmont glacier of the last ice age, around 18 ka BP (Rheingletscher). Non-steady-state models are being prepared and tested for future calculations.
Measurement of Surface Deformation of the Greenland Ice Sheet by Satellite Tracking
Authors: Drew Alice Remington , Whillans Ian M.
Published: February 2017

Seven Magnavox MX1502 satellite receivers were used during the summers of 1980 and 1981 to obtain the coordinates of 22 stations in three locations on the Greenland ice sheet. Two of the receivers were located at stationary sites on the west coast of Greenland for both seasons. This allowed the short-arc method to be used to obtain relative coordinates with high precision. The stations were located at about 65° N, and positions on the ice sheet were obtained with formal accuracies of better than 0.20 m. From the coordinates, the station velocities, ice-sheet slopes, baseline lengths (between the stations) and strain-rates were calculated. Our results show that the two stations just to the east of the ice crest are not moving in the expected direction (north-east) but are moving in a direction slightly west of north. Hence, the positions of the ice crest and the ice divide do not coincide. The other stations are moving approximately as expected. No major velocity differences between, neighboring flow lines are apparent. The magnitudes of the maximum strain and the velocities increase away from the ice divide and with increasing slope.
Geothermal Effects of 18 ka BP Ice Conditions in the Swiss Plateau
Authors: Haeberli Wilfried , Rellstab Werner , Harrison William D.
Published: February 2017

Quaternary surface temperature and ice conditions have lowered today’s temperatures in the uppermost 1 to 2 km of the Earth’s crust in the Swiss plateau by about 5 to 6°C in regions of formerly temperate glacier beds, and these effects were even greater on temperatures in formerly periglacial regions. Effects of latent heat exchange during the formation and thawing of ice-rich permafrost in high-porosity sediments enhance the effects of heat diffusion in low-porosity rock. The influence of underground ice formation, however, seems to be limited. This is due both to the limited thickness of high-porosity sediments and to the fact that high post-glacial surface temperatures in the Swiss plateau shortened the thaw time of ice-rich permafrost which formed at the time of maximum glaciation (18 ka BP). The greatest effects of ice conditions in 18 ka BP may therefore be expected outside the plateau in Alpine valleys. Here, advection of cold ice through glacier flow may have cooled high-porosity sediments of considerable thickness well below 0°C.
Late-Glacial Maximum-Holocene Atmospheric and Ice-Thickness Changes from Antarctic Ice-Core Studies
Authors: Lorius C. , Raynaud D. , Petit J.-R. , Jouzel J. , Merlivat L.
Published: February 2017

A review of Byrd, Vostok and Dome C Antarctic ice-core records indicates significant changes in atmospheric characteristics between the late glacial maximum (LGM) and the Holocene. This data is relevant to general circulation model (GCM) boundary conditions and validation of output results. Reciprocally, GCM data could help to interpret ice-core results and to extend observed high-latitude changes to a larger scale.

During the LGM, low troposphere temperatures were colder by about 5 to 7°C and surface temperatures by 8 to 10°C over the Antarctic ice sheet. There are indications that snow accumulation was slightly lower and isotopic data suggests higher relative humidity over the ocean. A large increase in continental dust (up to a factor of 20) and marine aerosols (up to a factor of 5) is observed on the high Antarctic plateau, both explained by the increased (possibly up to 1.4 to 2 times) intensity of the large-scale atmospheric circulation modulated by desert and sea-ice area extension. Ice-core results show large changes in atmospheric CO2concentrations with LGM values around 200 ppmv and “pre-industrial” values of about 260 ppmv. Finally, determinations of total gas content suggest that central West and East Antarctica were not thicker during the LGM, in contrast with higher surface elevations inferred from coastal-ice studies.
Analyses of Two Ice Cores Drilled at the Ice-Sheet Margin in West Greenland
Authors: Clausen H.B. , Stauffer B.
Published: February 2017

In 1978 two ice cores were drilled to depths of 46 and 92 m respectively at Camp 3, at the west margin of the Greenland ice sheet. Both core drillings reached bedrock. In addition, surface samples were collected in the marginal area along an estimated flow line.

The δl8O profiles of the two ice cores and of the surface samples show similar features. All three δ180 records reveal the characteristic shift (of 5–6 per mil for the Pleistocene-Holocene transition 11 000 years ago) observed in Greenland deep ice cores from Camp Century and Dye 3.

The δ18O results, as well as the measured temperature profiles in the bore holes, are used to provide more insight into the rheology of the ice sheet. The analyses of marginal ice samples is an important supplement to deep ice-core analyses.
Basic Properties of Antarctic Sea Ice as Revealed by Textural Analysis of Ice Cores
Authors: Lange Manfred A.
Published: February 2017

Sea ice constitutes a major element in the atmospheric, oceanographic and biological regime of the polar regions. Assessment of its fundamental properties requires interdisciplinary investigations on local, regional and global scales. Sea-ice structure and textural parameters of individual ice cores play a key role in such investigations. A proper characterization of sea-ice micro-structure is essential for an adequate classification of ice cores, an understanding of the growth processes of the sampled floe, and the identification of possible relationships between ice texture, and the physical, chemical and biological properties of sea ice. Investigations on ice cores which were obtained during three recent Antarctic expeditions (1983–85) in coastal waters of the eastern and southern Weddell Sea are reported. The basis for a number of physical, chemical and biological investigations is an assessment of the textural characteristics of each sea-ice core. These are derived by inspection of continuous thick sections, supplemented by an analysis of selected vertical and horizontal thin sections. Major results of this study can be summarized as follows: (i) in addition to the common ice classes, another sea-ice type, platelet ice, is identified; it is apparently unique to the coastal waters of Antarctica, near the ice-shelf edge, and (ii) different physical, chemical and biological sea-ice properties vary systematically with and are probably related to / controlled by the ice texture of the cores.
A Stratigraphic Record of an Ice Core from the Yamato Meteorite Ice Field, Antarctica
Authors: Nakawo Masayoshi , Nagoshi Masayasu , Mae Shinji
Published: February 2017

Measurements of density, total gas content, δ18O, and electrical conductivity were carried out along a core 100 m long. A profile of in-situ bubble pressure was obtained from the data on density and total gas content, taking into account the volume relaxation of the core in the period between core recovery and density determination. The bubble pressure was appreciably higher than the overburden pressure at corresponding depths. It was considered that the pressure difference was caused by the continuous lifting of the ice, since ice flow was obstructed in the blue-ice area. From the profile of the pressure difference, the vertical distribution of the upward velocity was calculated, which provided a time-scale for the core. It was found that the 100 m long core represented a record of about 104–105a. Since the surface ice was considered to represent a few tens of thousand years B.P., the data obtained on total gas content, δ18O, and electrical conductivity would describe the variations in the climate as well as in the ice sheet during the last glacial period.
A Detailed Analysis of the Rapid Changes in Ice-Core Parameters During the last Ice Age
Authors: Staffelbach T. , Stauffer B. , Oeschger H.
Published: February 2017

Results from deep Greenland ice cores show rapid changes in several parameters in the deepest part. The most probable explanation for these variations is a fast-changing climate during part of the last glaciation. The question arises, however, of whether the observed changes in the ice cores could also be due to, or at least be influenced by, discontinuities in the stratigraphy. We present new CO2 and δ18O data from the Camp Century and Dye 3 deep ice cores. The data show rapid changes in CO2 and δ18O in both cores. One transition which was investigated in detail seems to be more rapid in the ice core from Dye 3 than in the Camp Century core. The broadening of a sharp δ18O transition due to molecular diffusion is discussed. Since this broadening is larger than the observed width of the transition, we discuss the possibility of a mechanism that can produce stratigraphic disturbances on a small scale. This mechanism is based on a calculation of the compression of horizontal layers which have equal density but different viscosities.
10Be Concentrations in Antarctic Ice
Authors: Beer J. , Oeschger H. , Bonani G. , Suter M. , Wölfli W.
Published: February 2017

Measurements of the cosmogenic isotope 10Be (T½ = 1.5 Ma) on Greenland ice cores produced interesting results. Variations in the 10Be concentrations can be interpreted in terms of changes in the production rate and in atmospheric circulation and deposition. During the Holocene, good agreement between short-term variations in 10Be and 14C indicates that the production rate of both isotopes was changing, probably due to solar modulation.

During the last ice age, periods with significantly higher 10Be concentrations are observed. The good anti-correlation between 10Be and δ18O suggests that these intervals correspond to periods of low precipitation rates.

Work on Antarctic ice cores is in progress, but only relatively few 10Be data have been published yet. 10 Be results from Antarctic ice cores are presented and compared with data from Greenland.
Oxygen-Isotope Records Covering the Last 2 KA at South Pole
Authors: Grootes Pieter M. , Stuiver Minze
Published: February 2017

Two cores which had been drilled to a depth of over 200 m were recovered near Amundsen–Scott South Pole Station during the 1980–82 field seasons. A firn core drilled from 3 to 19 m depth was taken in December 1982 from a site about 5 km distant from the two others.

The cores cannot be used to study the seasonal δ18O cycle, because: (i) detailed sampling (1–2 cm increments) provides evidence of isotopic enrichment in the 1 m core sections during storage, both in the field and in the laboratory cold-room, and (ii) low accumulation (9.2 g cm−2a−1, given by Jouzel and others 1983) led to missing years or parts thereof. Estimates of the proportion of missing years range from 1 in 10 (J.R. Petit, quoted in Mosley-Thompson and Thompson 1982) to 1 in 20 (Jouzel and others 1983).

The cores are still useful for studies on a decadal or longer time-scale. The average δ18O value of detailed measurements of the upper 40 m of the 1980 firn core differs by only 0.14±0.05‰ from the average of measurements made about 16 months earlier. Thus, although storage in the cold-room changed the isotopic composition of the outer firn layer, the bulk of the firn core was unaffected. The two measurement series of this profile show a high correlation (r2= 0.75, P<10−6) when smoothed with a I m moving average (equivalent to 4–7 years’ accumulation) in order to reduce noise and the effect of enrichment at the ends of the 1 m sections.

In both long cores and in the short core which was taken in 1982 the δ18O–depth profile shows a long-term trend with superimposed shorter fluctuations. The seasonal signal soon disappears but variability of up to 2‰ on a 3–5 year time-scale persists at depth. Linear-correlation analysis shows a significant correlation between the 1980 firn core and the 1982 short core (r2= 0.32, P = 0.011) for a 1 m moving average of samples 0.25 m long. Some correlation is also observed between the deeper ice parts of the 1982 core (106–227 m) and the 1981 core (100–202.4 m) (r2= 0.087, P = 0.00043, I m moving average), if the relative depths are shifted by 3.75 m. A firm time-scale for both cores is needed to determine whether such a shift corrects for an artefact of the depth logs of the cores, or proves that no real correlation exists between the two cores.

Comparison of the long-term trend of the two South Pole cores with the 2.5 ka isotope climatic record from the 1979 Dome C core (Benoist and others 1982) and with the Law Dome core BHD record (Morgan 1985) again suggests possible correlation, but cannot prove it for lack of a firm time-scale. Collaboration with other investigators which brings together data on visible stratigraphy and density (personal communication from A.J. Gow), solid conductivity (Schwander unpublished), acid horizons (Langway and others 1988, this volume) and microparticles may solve this problem.
Isotope Measurements in an Ice Core from a Temperate Alpine Glacier (Vernagtferner, Austria) (Abstract)
Authors: Oerter H. , Moser H. , Rauert W. , Stichler W. , Reinwarth O.
Published: February 2017

In 1979 ice-core drilling was carried out in the accumulation area of the temperate Alpine glacier Vernagtferner (Ötztaler Alpen, Austria). The cores are among the few cores from temperate glaciers in the eastern Alps. Encouraged by the results of the isotope analysis (2H, 18O, 3H) of this core, which proved that it was possible to detect the annual layering in the firn, a second drilling operation was undertaken in 1983. One core (IV) was drilled near the 1979 drilling site, in order to check the results from the first core. A second one (VI) was drilled near the equilibrium line, in order to obtain information on the isotope content of the ice body near the ablation area. In addition, the electrical conductivity was also measured. The paper presents the measurements of the 80 m core VI of 1983: 18O and 2H profile, together with the calculated deuterium excess d, as well as the 3H profile, which gives evidence of the 1952-63 nuclear-bomb tests already at a depth of between approximately 4.5 and 7 m below the surface. There is a discrepancy of about 0.5 m between the maximum 3H peak and the peak of an in-situ gamma-ray log. The latter would coincide better with the 18O layering, so that there remains an uncertainty of 3 years in dating the upper 20 years of accumulation. The annual variations in the isotope content remain recognizable, especially with the aid of the deuterium excess. Thus it is possible to compare the thickness of the annual layers of the earlier core I (in the accumulation area) with that of the later core VI (which is located at a lower elevation) and see how the layers become thinner. Comparing cores I and IV, possible sources of changes in the isotope content, such as melt-water flow, are discussed.
Glacial and lake fluctuations in the area of the west Kunlun mountains during the last 45 000 years
Authors: Chaohai Liu , Shijie Li , Yafeng Shi
Published: February 2017

There appear to have been several important glacial advances on the southern slope of the west Kunlun mountains, Tibetan Plateau, since 45 000 a BP. Based on the record of alternating till and lacustrine sediments and 14C determinations, these advances are dated to 23 000–16 000, 8500–8000, and 4000–2500 a BP, and to the 16th–19th century AD, with regional variations occurring during each of the advances. The glaciation of 23 000–16 000 a BP is equivalent to the last glacial maximum (LGM) and its scope and scale were much larger than any of the others.

Lake changes are a response to both tectonic uplift of the plateau and global climatic change. With regard to the latter, both changes in precipitation and changes in the extent of glaciation can affect lake levels. High lake levels occurred during interstadial conditions between 40 000 and 30 000 a BP, when the area experienced a relatively warm and humid climate, and during the LGM, between 21 000 and 15 000 a BP. During the Holocene, lakes have been shrinking gradually, coincident with the dry climate of this period of time.
Metamorphism of Dry Snow as a Result of Temperature Gradient and Vapor Density Differences
Authors: Adams E. E. , Brown R. L.
Published: February 2017

A heat conduction equation for the determination of the temperature profile in a snowpack is developed. The magnitude of the temperature gradient tends to increase as the snow surface is approached, with local minima through layers of high snow density and local maxima above and below these layers. Calculations are made of the difference in vapor density in the pore and over the ice grain surfaces which border the pore. In the presence of sufficient temperature and temperature gradient, faceted crystals will develop near the top of the pore, as ice is sublimed away from the surfaces in the lower region. There will be a reduction in the percentage of rounded grains as the faceted form develops. The process is demonstrated to be enhanced at warm temperatures and large temperature gradients in low density snow.
Frequency and Characteristics of Glacier Floods in the Swiss Alps
Authors: Haeberli Wilfried
Published: February 2017

Damage due to glacier floods in the Swiss Alps occurs about once every two years at present, despite the pronounced retreat of glaciers during the twentieth century and the installation of many water reservoirs, which act as flood retention basins. Over half (60 to 70%) of the observed floods are caused by outbursts of marginal glacier lakes or sudden breaks of ice dams, and 30 to 40% by ruptures of water pockets. In a glacierized mountain region as densely populated as the Swiss Alps, even debris flows triggered by outbursts of very small water masses may be dangerous. Historical information about glacier floods in the Swiss Alps, although incomplete and heterogeneous, is used as an empirical basis for an attempt to recognize potential hazards at an early stage by considering outburst processes, volumes of water involved, potential peak-discharge values, lithology and inclination within the reach of glacier streams.
Laboratory Experiments on Crystal Orientation in NaCl Ice
Authors: Langhorne Patricia J.
Published: February 2017

Over extensive areas of the Arctic and Antarctic, the c-axes of the grains in a sea-ice sheet develop a preferred orientation in a particular direction in the Horizontal plane, causing the physical and electromagnetic properties of the material to be anisotropic. A number of mechanisms have been proposed for this alignment, the more likely including the tilting of floes, horizontal temperature gradient, horizontal deviatone stresses, and oceanic currents. Laboratory experiments have been performed at the Scott Polar Research Institute to distinguish the effects of these mechanisms on the fabric of sea ice. Ho correlation was found between the development of the preferred orientation of c-axes and any of the first three mechanisms. However, in the presence of a current, the strength of the alignment increases rapidly with depth in the ice, the mean c-axis direction coinciding with the current direction. A significant reduction in alignment was produced when the flow was reduced to zero. In addition, upstream deflection of the columnar axis was observed in flowing brine. These results indicate the importance of fluid motion in controlling the rate of transport of solute from the interface and hence the relative growth rates of grains of different orientations.
Water Temperature Measurements in Turbulent Streams During Periods of Frazil-Ice Formation
Authors: Osterkamp T. E. , Gilfilian R. E. , Gosink J. P. , Benson C. S.
Published: February 2017

Field measurements of water temperatures in two turbulent streams in interior Alaska have been made during periods of frazil-ice production. The measured equilibrium temperature of the water Te-0.005°C agrees with the value calculated from the electrical conductivity of the water. Average cooling rates of the streams during the summer-to-fall stream cooling period were on the order of several tenths of a degree per day with average surface heat losses of -5 to -18 W m−2. Just prior to a frazil-ice event, the water-cooling rates were -1 to -3 mK min−1with surface heat losses of -47 to -140 M m−2Supercooling at the water surface of a stream prior to and during frazil-ice production does not exceed 0.2°C as shown by measurements of air-water temperature profiles and by radiometer measurements. Mater supercooling at the time of frazil-ice nucleation was <10 mK. These measurements show that frazil-ice nuclei in streams must be other ice particles, cold organic materials, cold soil particles, or a combination of these, that may be introduced into the stream by mass exchange processes at the air-water interface.

The maximum observed supercooling was ΔTm40 mK. Two measured values for the residual supercooling were 3 and 9 mK. Frazil growth rates calculated from the observed values of supercooling show that, unless the period of residual supercooling is very long, most of the frazil-ice production during one night of supercooling occurred in the transient thermal period from the time of nucleation to the time that the water became residually supercooled.
The Institute for Snow and Avalanche Research at Weissfluhjoch/Davos: The First Five Years (1943 to 1948)
Authors: Quervain Marcel R. de
Published: February 2017

This essay is not a scientific paper in the usual sense; it is rather a personal retrospective view, presented as an oral account of a period of snow research spent almost in isolation. For this printed version a few adaptations have been made, including a reduction in the number of figures. Original illustrations from the Interval Reports of the Institute of Snow and Avalanche Research were used to illustrate the talk and have been retained for publication. Although some information is in German, the essential content of the figures is repeated in English in the captions.
Sulphuric and Nitric Acid Concentrations and Spikes Along A 200 m Deep Ice Core at D 57 (Terre Adélie, Antarctica)
Authors: Zanolini Françoise , Delmas Robert J. , Legrand Michel
Published: February 2017

D 57 station in Terre Adélie lies between the coast and the central Antarctic plateau. A 200 m ice core was recovered in summer 1980–81 at this location and analyzed by an electroconductometric method to detect exceptional acid levels linked to fallout from major volcanic eruptions. Several signals were indeed found. The corresponding ice-core sections were then analyzed for mineral acids (H2SO4 and HNO3). We detected several large volcanic events, in particular two eruptions identified as Tarabora (1815) and Galunggung (1822). The background concentration of sulphate was found to be relatively low (about 0.5 μeq 1−1). On the other hand nitrate values were higher than at coastal or central Antarctic locations (except for the Sauth Pole). Two spikes were found in the nitrate profile at depths of 140 and 148 m. It is thought that they could be either linked to the 1604 and 1572 supernovae Kepler and Tycho or correspond to epochs of particularly high solar activities. With the aid of these sulphate and nitrate exceptional events, a dating of the D 57 ice core can now be proposed which corresponds to a mean snow accumulation rate of 22 cm of ice equivalent per year over the last four centuries.
10Be in Polar Ice and Atmospheres
Authors: Raisbeck G.M. , Yiou F.
Published: February 2017

We briefly review the application of cosmogenic 10Be measurements in ice and polar atmospheres to: (i) the dating of ice cores, (ii) the deduction of past accumulation rates, (iii) information on the influx of stratospheric aerosols in polar regions, and the mechanism of incorporation of aerosols into the ice. We find that at high latitudes (>74°), the 10Be deposition rate in the ice is more constant than the 10Be concentration.
The Use of Continuum Thermodynamics in the Formulation of Ice-Sheet Dynamics
Authors: Hutter K. , Engelhardt H.
Published: February 2017

Ice sheets consist of several disjoint regions, each with physically distinct behavior. Parts are cold; others are temperate and either partly or completely saturated. Varying dust content, impurities, debris content, etc., may affect the ice flow. Usually, these regions are separated by material or non-material surfaces or boundaries. We use mixture concepts, involving the balances of mass, momentum, energy and entropy. When applied to regular domain points these concepts and appropriate constitutive postulates yield the field equations for the evolution of the constituents. When formulated in terms of singular surfaces, boundary and transition conditions emerge. Our presentation takes the form of an extended abstract of work that is presently under consideration (Hutter and Engelhardt 1988; Hutter and Engelhardt, in preparation).
Density-Depth Profile Determined by Seismic-Refraction Studies: Ice Stream B. West Antarctica (Abstract)
Authors: Anandakrishnan S.
Published: February 2017

Detailed seismic short-refraction profiling was conducted on Ice Stream Β (UpB) during the 1983–84 austral summer. A new high-resolution data logger, developed at the University of Wisconsin, recorded both compressional- and shear-wave arrivals. We report here on P-wave and S-wave profiles recorded along a line parallel to the axis of the ice stream. Source-receiver separations up to 720 m yielded seismic velocity-depth curves to below the firn-ice transition zone (slightly greater than 30 m at UpB).

For the compressional-wave profile, geophones were separated by 2.5 m, which yielded a velocity-depth curve with a granularity of ∼1 m. The corresponding density-depth curve agrees well with direct density measurements obtained from a core extracted nearby (Alley and Bentley 1988, this volume). Discontinuities in the velocity gradient do not appear at the “critical densities” as they did at Byrd Station, Antarctica, and elsewhere (Kohnen and Bentley 1973
, Robertson and Bentley 1975).

Two shear-wave profiles were recorded, both with geophone spacings of 5 m, one with longitudinal polarization (SV) and the other with transverse polarization (SH). There is a marked difference in velocity between the SH and SV waves, particularly in the shallow firn. We suggest that a strong vertical shape-and-bonding fabric in the shallow firn, as observed in cores collected at UpB, would account for this disparity.
Short-Term Interactions Between Atmospheric Synoptic Conditions and Sea-Ice Behaviour in the Arctic
Authors: Maslanik James A. , Barry Roger G.
Published: February 2017

Passive microwave data (SMMR) and data from drifting buoys are used to examine atmosphere-ice interactions during autumn 1978 through autumn 1982 in the Canada Basin. SMMR brightness temperatures, ratios, and calculated ice concentrations are compared with surface pressure, temperature, buoy motion, and winds at a coincident location to identify possible linkages operating on daily to weekly time-scales. Inter-annual differences in temperature, pressure, and ice conditions inferred from SMMR data are discussed. Periods of reduced ice concentration as estimated by SMMR are found to occur during late summer and early autumn in 1980, 1981, and 1982. The decreases in ice concentration are concurrent with low-pressure systems and increased divergence in the buoy field in 1980 and 1981. These apparent decreases in ice compactness are discussed in relation to previously reported areas of reduced concentration interpreted from ESMR data. Evidence to support a postulated relationship between atmospheric low pressure and divergence of ice under free-drift conditions is demonstrated for the summer of 1980.
Impacts of Glacier-Related Landslides on the Settlement at Hopar, Karakoram Himalaya
Authors: MacDonald K.I.
Published: February 2017

Slope instability and occasional devastating landslides are well-known hazards in high mountain areas. This paper describes and discusses an example of extensive and recurring damage associated with agricultural settlements around the lower reaches of the rapidly flowing Bualtar and Barpu Glaciers in northern Pakistan. These landslides occur over a zone about 20 km long in response to erosive processes at the ice-slope interface, and slowly descend 150–300 m from the edges of cultivation to the glacier margins. Damage is evident in the loss and/or abandonment of approximately 10 km2 of land, and in the destruction of dwellings and irrigation channels. The daily routine of local villagers is affected because alterations of both the slope and the ice surface destroy frequently used transport routes. Although the landslides have a history decades long, the landslide problem has more recently assumed heightened significance in relation to rapidly occurring economic and social change such as the introduction of wage labour and seasonal outmigration.
Contribution of Viscous Forces to Avalanche Dynamics
Authors: Nishimura K. , Maeno N.
Published: February 2017

Mini-avalanche systems were constructed both in a low-temperature laboratory and in a snowfield, and the behaviour of the flowing snow was observed in each case. Velocity profiles for the individual snow particles were determined and these implied that a viscous force, which has been neglected in most previous numerical simulations of snow-avalanche motion, needs to be taken into account for many avalanches. Kinematic viscosity coefficients for the fluidized snow were also measured using a modified Stormer-type viscometer. Substituting the dry-friction value and the kinematic viscosity coefficient for fluidized snow into the equation for avalanche motion, numerical simulation of natural events was achieved for the Shiai-dani region. Taking viscous resistance factors into account led to the conclusion that the magnitude of turbulent resistance of snow in avalanche systems is probably much smaller than that represented by the values previously in use.