bluuebunny/crossref_metadata_2025_split huggingface dataset:
Repeated Glacier Mapping for Hydrological Purposes: Water Power Planning
Authors: Østrem Gunnar 
Published: February 2017

Good hydrological knowledge is necessary for the planning of a hydro-electric power installation. Observations of daily discharge in Norwegian streams are available for several decades, but for glacierized basins there is a lack of information. Either the observation period is too short or it comprises mainly years when glaciers retreated and thus produced extra amounts of melt water – a direct result of negative mass balance. Consequently, many discharge figures are too ‘optimistic” — they indicate larger average run-off than would be the case if glaciers were in a steady state, or, even worse, if they started to grow and then started to reduce their melt-water contribution to rivers.
Our means of correcting actually observed discharge figures for glacier influence is to perform annual mass-balance measurements. This has been done since 1948 for one glacier and since 1962 for several glaciers and results have been used in the planning of power stations. The method is, however, relatively costly.
Another method is now being developed. Repeated glacier mapping makes it possible to calculate the average change (decrease) in glacier volume between the years when air photographs were taken. Therefore, several glacier maps have been produced based upon older vertical photographs and new maps are constructed from repeated air photography of the same glaciers. By subtraction, the total decrease in ice volume can be calculated and, hence, corrections of observed discharge be made.
This method is quicker and cheaper than conventional mass-balance measurements. Large potentials for this method lie in future digital maps.
Almost all the detailed (1:10 000) Norwegian glacier maps are printed in four colours and they have a standard UTM coordinate grid and 10 m contours. An example of a recent map is enclosed in the map pocket on the rear cover of this volume.
Surface Topography of the Greenland Ice Sheet by Satellite Radar Altimetry (Abstract)
Authors: Bindschadler R.A. , Zwally H.J. 
Published: February 2017

A map of the surface elevation for the southern half of the Greenland ice sheet has been produced from data gathered by the radar altimeter on board the SEASAT satellite. From June 1978 until September 1978, useful data were collected during most passes over the ice sheet, but data was not collected continuously along each pass. Over 85 000 separate ranges were obtained from the satellite to the surface at points spaced 662 m apart along each orbital pass.
Techniques required for the reduction of the recorded return waveforms to surface elevations have previously been described in a series of papers (Martin and others, 1983; Brenner and others, 1983; and Zwally and others, 1983). Once all corrections have been applied to the range data due to atmospheric effects, ocean and earth tides, and orbital perturbations, the set of ranges at orbital crossing points (where ascending orbits crossed descending orbits) had a mean relative error of 2.9 m, with a standard deviation of ±2.9 m. Elevations over the flatter and smoother portions of the ice sheet have a precision as small as ±0.25 m, while data over sloping and rough areas are of lower quality. Along each orbital track, the data are corrected for the slope-induced error.
The reduced set of surface elevations has been interpolated to assigned elevation values at the nodal points of a regular grid with a 10 km spacing (polar stereographic projection). This grid was then contoured at intervals of 50 m above 2400 m altitude and 100 m at lower elevations. Similar grids of slope-induced error corrections were contoured to provide some measure of its effect on the data. Ancillary plots of parameters of the fitting and gridding process are included to help in estimating the quality of the derived surface topography in different regions.
The surface elevation contour map shows the existence of distinct drainage basins within the ice sheet — most notably in the southern and eastern areas. This detail will prove most useful in the delineation of these basins for hydrological or glaciological studies. In combination with ice-thickness data, these elevation data permit a more accurate measurement of the bedrock elevation. The corrected altimeter data in orbital-pass and map format have been provided to the National Space Science Data Center at Goddard Space Flight Center and to the World Data Center-A, Glaciology, as a source of information to be used by other scientific investigators. These data have already been used to produce detailed maps of the topography in more localized areas (e.g. Figure 2, from Zwally and others, 1983 and Figure 2 of Bindschadler, 1984).
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.
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.
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.
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 &gt;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 &gt; 4 km a−1, and is much more active than Riiser-Larsenisen. This high activity has resulted in extensive fracturing of the ice shelf.
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.
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&lt;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.