bluuebunny/crossref_metadata_2025_split huggingface dataset:
The IGS Symposium on Ice and Climate Modeling: An Overview
Authors: Radok Uwe 
Published: September 2017

The Symposium on Ice and Climate Modeling was staged by the International Glaciological Society (IGS) with the co-sponsorship of the American Meteorological Society to bring glaciologists into direct contact with modelers of the Earth’s climates during interglacials (such as the present) and glacial episodes. The purpose of mutual familiarization was served by reviews of the hierarchies which now exist for models of atmosphere, ocean, and climate. These reviews emphasized the actual or potential uses of ice data and parameterizations, and both general and specific aspects of coupling and sensitivity testing. The glaciologists in their turn reviewed the problems of exploring different ice forms and simulating their responses to climatic forcing. Interspersed with the didactic presentations important new results were reported. The most significant concerned atmospheric concentrations of carbon dioxide deduced from ice core analyses, which were put into a wider context by a new interpretation of the ocean as a chemical system.The presentations and discussions highlighted a wide range of problems ripe for collaborative study. Topics recommended for priority attention include contemporaneous changes in the properties of ice cores from Greenland and Antarctica, links between weather sequences and the stable isotope contents of polar precipitation, systematic intercomparisons of a wide range of model results, and the construction of intermediate-complexity sea-ice models for use in climate simulations.
Closer to a True Value for Heavy Metal Concentrations in Recent Antarctic Snow by Improved Contamination Control
Authors: Wolff E.W. , Peel D.A. 
Published: September 2017

Recent snow from two sites in the Antarctic Peninsula has been analyzed for Al, Cd, Cu, Pb and Zn. Measurement of full procedural blanks and of the extent of penetration of surface contamination has allowed a rigorous appraisal of both sampling and analytical methods. Whilst the particular samples of cored firn used here have been shown to be unsuitable due to penetration of surface contamination into their interiors, surface samples collected directly into acrylic tubes showed very limited penetration of contamination. The surface samples gave the following average concentrations: Al: 0.7±0.3 ng g−1, Cd: 0.26±0.09 pg g−1, Cu: 1.9±0.5 pg g−1, Pb: 6.3±3.3 pg g−1 and Zn: 3.3±1.7 pg g−1. The Pb concentration agrees well with data from other workers for recent snow from East Antarctica, while the values for Cd, Cu and Zn are about ten times lower than have been reported previously, even for ancient Antarctic ice. Although these data refer to only one site and a short time period, it is believed that they are representative of modern Antarctic snow.The true concentrations of Cd, Cu, Pb and Zn in ancient Antarctic ice are not yet established. However the following limits are suggested for increases over natural background levels due to anthropogenic emissions: Pb 1 to 40 times, Cd 1 to 180 times, Cu 1 to 4.5 times and Zn 1 to 6 times. These results indicate that contamination may have been responsible for reports of anomalous enrichment of several heavy metals in Antarctic snow.
Characteristic Growth Processes of Ice Crystals on the Antarctic Ice Sheet
Authors: Nishimura Hiroshi , Maeno Norikazu 
Published: September 2017

Characteristic growth processes were investigated by measuring cross-sectional areas of ice crystals for four 30 m snow cores drilled in Mizuho Plateau, Antarctica. Considerable difference was found in the growth rate of crystals between a temperature-gradient layer above 6 m depth and an isothermal layer below 10 m depth: the growth rate in the temperature-gradient layer was much larger than that in the isothermal layer. In the isothermal layer, temperature dependence of the growth rate K was expressed by an equation K = K0 exp(−E/RT), where R and T are the gas constant and absolute temperature respectively. The apparent activation energy E is 44.7 kJ mol−1.On the other hand, in the temperature-gradient layer, the apparent activation energy was as small as 12 kJ mol−1: the difference was explained as due to the temperature gradient. Using the temperature profiles in snow that have been estimated from the meteorological data from several stations, the growth rates in the temperature-gradient layer were calculated. The calculated temperature dependence of the growth rates, taking into consideration vertical flux of water vapor between ice particles caused by the temperature gradient, showed good agreement with measured results. It is concluded that the growth process in the layer above 6 m depth is mainly due to vapor transport under the vertical temperature gradient.
Ekström Ice Shelf, Antarctica
Authors: Thyssen F. , Grosfeld K. 
Published: September 2017

In 1980–81, 1983–84 and 1985–86 airborne surveys with an electromagnetic reflection (EMR) system were made of Ekström Ice Shelf, Antarctica. The EMR data were supplemented by measurements of surface elevation with radar altimetry during flights at a constant pressure altitude. The accurate measurement of ice thickness in areas with clearly developed bottom reflectors was used to generate a plot of surface elevation against ice thickness. The effect of changing barometric pressure during the flights could be reduced by this means. Elevations were calibrated over the open sea at the beginning and end of each flight.On the basis of these data, the surface elevation, ice thickness and isostatic anomalies have been mapped over the ice shelf.
Microearthquake Source Locations and Mechanisms: Ice Stream B, West Antarctica (Abstract)
Authors: Anandakrishnan S. , Blankenship D. D. , Bentley C. R. 
Published: September 2017

An array of nine seismographic stations, each sensitive to all three components of motion, was deployed on Ice Stream B, West Antarctica, during the austral summer of 1985–86. The network was sensitive to high-frequency (=400 Hz) seismic activity within a 350 km2 area of the ice stream, and the deployment geometry allows the precise determination of depths for events beneath the 10 km2 array. Microearthquakes from both beneath and beside the ice stream were detected and recorded (Blankenship and others 1987). Inversion of P-wave and S-wave travel times and radiation patterns allows the determination of locations and fault-plane solutions for many of these events.We find that bottom events involve low-angle thrusting, in the down-stream direction, of ice or till; displacement is ∼½ cm per event over a (15 m)2 area. Such faulting is rare and releases an insignificant part of the total energy dissipated by ice flow. However, this is a possible mechanism for plucking of the ice-stream bed.Fault-plane solutions for most major surface events are consistent with the opening of tensional fractures oriented transverse to ice flow. Precise location of these events shows that they correspond to open crevasses, mapped by Vornberger and Whillans (1986), that are oriented transverse to ice flow.In addition, shear-wave splitting observed on some of the microearthquakes shows that the c-axes in the ice stream are slightly, but not strongly, anisotropic. Precise location of the sources requires the use of a detailed velocity-depth profile in the firn, which was obtained by seismic short-refraction studies (Anandakrishnan and others 1988, this volume). A density-depth profile calculated from these velocities agrees well with direct density measurements on a single core nearby (Alley and Bentley 1988, this volume).
Antarctic Icebergs – Production, Distribution and Disintegration (Abstract)
Authors: Orheim Olav 
Published: September 2017

A programme of systematic iceberg observations was initiated in 1981 by Norsk Polarinstitutt through the SCAR Working Group on Glaciology. Icebergs are recorded every 6 h and in five length groups: 10-50, 50-200, 200-500 and 500-1000 m, and those over 1000 m, which are described individually. Data on more than 100 000 icebergs are now on file at Norsk Polarinstitutt, and practically all ships travelling to and from Antarctica participate in the collection of data.This paper presents the first comprehensive analysis of the iceberg data. The quality of the data set is discussed, with consideration of potential errors in and limitations of the data, and various statistical evaluations. Representative distribution data are presented, and used to determine iceberg production, disintegration and mean residence times, and regional and total Antarctic calving rates.The incidence of large-scale calving in particular is evaluated, including the remarkably large break-offs in recent years. These exceed both the total annual accumulation on the Antarctic continent and the mean annual calving rate as determined from ship observations.The results show further: (1) that there are more than 200 000 icebergs south of the Antarctic Convergence, (2) that there are large regional differences in iceberg calving rates and iceberg sizes, and (3) that the calving rate from Antarctica is higher than that given in most previous estimates, which implies (4) that the mass balance of the Antarctic ice sheet is not positive as suggested by most recent estimates.
Force Budget: Numerical Methods and Application to Two-Dimensional Flow Along the Byrd Station Strain Network, West Antarctica (Abstract)
Authors: van der Veen C. J. , Whillans I. M. 
Published: September 2017

Using the partitioning of full stresses into resistive and lithostatic parts, force balance for plane flow is expressed in terms of strain-rates and a vertical coordinate scaled to the ice thickness. The balance equation and constitutive relation can then be used to calculate stresses through a vertical section of a glacier. Because the flow law is highly non-linear, these calculations are done numerically. Starting at the surface, the force-balance equation is solved by using measured surface velocities to calculate vertical shearing, and this yields velocities at a depth just below the surface. These velocities are used to compute vertical shearing at that depth, from which velocities at the next deeper layer follow. In this way, going progressively downward, velocities and stresses are calculated throughout a section of a glacier.The theory for calculating resistive stresses and velocities in a glacier is applied to the Byrd Station Strain Network. Large longitudinal variations in basal drag and in sliding velocity occur and this result is little affected by errors in the input data or by uncertainties in the constitutive relation for ice. The basal drag is usually equal to the driving stress to within 10–20%, and both vary by a factor of about 2 along the strain network. Sites of high drag and little sliding are not always correlated with basal highs, indicating that some process (for example, complex bed drainage) is controlling the friction at the bed of the West Antarctic ice sheet.
Glaciological and Chemical Characteristics of an Antarctic Inland Plateau (Abstract)
Authors: Ageta Y. , Kamiyama K. , Okuhira F. , Fujii Y. , Watanabe O. 
Published: September 2017

A glaciological research project in east Queen Maud Land, Antarctica, has been carried out by the Japanese Antarctic Research Expeditions between 1982 and 1986 (JARE-23 – JARE-27).In this paper, we deal with the area traversed by JARE-25 and JARE-26, a representative inland plateau in Antarctica. In 1984, a team from JARE-25 extended a route from Mizuho Station (MS) to an advanced camp (AC; 74°12′S, 34°59′E; 3200 m a.s.l.) and returned to MS via the Yamato Mountains region. In the following year, 1985, a team from JARE-26 reached the summit (77°22′S, 39°37′Έ; 3810 m a.s.l.) of an ice dome on the plateau behind AC and continued to Asuka camp, north of Sør-Rondane Mountains. Investigations were carried out along the routes as follows:Geomorphological observations: the altitude along the routes was measured, together with the depth of the bedrock, which was obtained by radio echo-sounding. The shape of the dome and the position of ice divides were revealed. Gravity soundings were also carried out along the routes.Depositional and erosional environments of the snow surface: the net accumulation rate was obtained along the routes by the stake method. Sastrugi orientations were recorded in order to gain information on the prevailing wind. At several points, vertical profiles of snow stratigraphy and snow hardness were obtained, together with snow temperatures at 10 m depth. The glaciological characteristics of the plateau are described with reference to these results.Snow chemistry: the values of the electro-conductivity and pH of melted snow along the routes were obtained, and the results show high conductivity and low pH values around the dome region. Quantitative studies on the chemical composition of the samples are continuing.Ice coring: at the dome camp (DC; 77°00′S, 35°00′E; 3760 m a.s.l.), coring was carried out to a depth of 40 m. In the samples, we have been studying the vertical distribution of δ18O and the products of nuclear fission, in order to determine the accumulation rate and the atmospheric environment.On the basis of the results described above, the relationship between meteorological and glaciological conditions in the inland plateau are discussed.
Distribution of Surface Features and Surface Mass Balance of Ice Sheet, East Queen Maud Land, Antarctica (Abstract)
Authors: Fujii Yoshiyuki , Ageta Yukata 
Published: September 2017

Surface features were classified morphologically and described along oversnow traverse routes from the coast to the inland high plateau of east Queen Maud Land, Antarctica, during the 1984 and 1985 summer seasons. The distribution of surface features reveals regional characteristics which reflect differences in the regional deposition-erosion process.On the basis of observation of surface features and measurements of surface mass balance, the ice-sheet surface of east Queen Maud Land is sub-divided according to different environmental zones:(1)Ablation zone (below 700 m a.s.l.): melting of snow occurs. Dry snow line approximates the altitude where the maximum air temperature is 0°C.(2)Coastal continuous accumulation zone (700–1800 m a.s.l.): snow accumulation occurs continuously and the surface is flat because of high snow precipitation and a slight katabatic wind.(3)Discontinuous accumulation zone (1800–2500 m a.s.l.): a rough surface of sastrugi dominates this zone. Snow accumulation is discontinuous in space and time because of low snow precipitation and strong katabatic wind. Negative annual snow accumulation was observed at 20–30% of the stakes set every 2 km along the traverse route. Mizuho Station is located in this zone.(4)Long-term accumulation-free zone (2500–3400 m a.s.l.): long-term absence of snow accumulation occurs at the glazed surface, which consists of a multi-layered ice crust several millimetres thick. A glazed surface develops over a distance of 1–20 km when the surface undulation is steeper, and covers 30–50% of the area in this zone. A hiatus sequence of snow accumulation is thought to continue for about 10–100 years over the glazed surface region.(5)Inland continuous accumulation zone (above 3400 m a.s.l.): a flat surface dominates in this zone. Snow accumulation occurs continuously because there is a weak katabatic wind in the central high plateau in spite of a very small amount of precipitation.
Modelling the Evolution of the East Antarctic Ice Sheet: Problems and Perspectives (Abstract)
Authors: Grigoryan S. S. , Ignat’yeva I. Yu. , Krass M. S. , Shumskiy P. A. 
Published: September 2017

Modelling the thermodynamics of a large ice sheet is in essence a problem of the deformation of a non-isothermal and relatively thin viscous layer. Reasons for forecasting the behaviour of a large ice sheet are: (a) to specify the relationship between the existence and development of the ice sheet and regional climatic and tectonic conditions; (b) to study the influence of variations in surface temperature, mass balance, and geothermal flux (as functions of coordinates and time) on the evolution of the thickness of the ice sheet. Hence the principal requirements for modelling are:
1.The model must be evolutionary; in particular, various stationary stages should be derived from it (rather than postulated).2.The model must be non-isothermal because temperature variations amount to some tens of degrees.3.Two-dimensionality of the model is essential if we are to use it for making realistic forecasts.4.Conditions at the boundary between land ice and the sea, which are the basic factors controlling the location of the margin of the ice sheet, should be taken into account.5.Finally, the model must be acceptable for digital analysis by computer.Contemporary mathematical models of the dynamics of the Antarctic and Greenland ice sheets are too simplified and do not fulfil these requirements. Our mathematical model of the evolution of the Antarctic ice sheet is based on temperature parameterization. The parameterization correctly describes the distribution of temperature and its dependence on surface temperature, advection of ice, geothermal flux, and heat losses. The problem reduces to Cauchy’s problem for a non-linear parabolic partial differential equation with three-step dependence of ice temperature on depth. A linear viscous flow law is assumed. Tests treat the whole problem of the thermo-hydromechanics of the ice sheet. The ice sheet is assumed to be bounded by a grounding line or ice wall where the ice is in hydrostatic equilibrium with the sea. In this case, the problem reduces to a non-linear parabolic partial differential equation with a complicated boundary condition at the moving edge. A digital representation of the model is presented first. Tests demonstrated the possibility of using an explicit three-layered scheme. Calculations for the East Antarctic ice sheet indicated that the ice margin should retreat slightly under contemporary climatic conditions (which corresponds to the field evidence). In future the boundary should tend towards a stationary state. A forecast of the behaviour of the ice sheet is derived. The East Antarctic ice sheet is found to be stable during various changes in climatic factors. The calculated hydromechanical characteristics of the ice sheet agree with the observed field data.
Measurements of Strength on Dakshin Gangotri Ice Shelf in East Antarctica (Abstract)
Authors: Sharma Satya S. 
Published: September 2017

During the first wintering by Indian scientists in Antarctica, from December 1983 to February 1985, year-round measurements of the strength of the snow cover were carried out to a depth of 1 m on Dakshin Gangotri Ice Shelf in East Antarctica, around the Indian Antarctic research station Dakshin Gangotri (70°05′S, 12°E). The measurements covered an area of 625 km2 around Dakshin Gangotri Station. Ten to 15 snow-hardness profiles per month were taken at different locations, using a Swiss ramsonde, and the values of ram resistance so obtained at different depths were averaged for each profile at depth intervals of 15 cm. These values were later tabulated and the minimum, maximum and average values obtained for each month were calculated. The values of ram resistance so obtained for each period were then used for determining unconfined compressive-strength profiles of the snow cover during different winter periods, using the correlation function given by Abele (1963).Based on these values, the average unconfined compressive strengths of snow cover were calculated for different depths in the ranges 0–30 cm, 0–45 cm, 0–60 cm, 45–100 cm, 60–100 cm, and 75–100 cm. Preliminary results show that the snow cover below 45 cm generally has high strength throughout the year, whereas the strength of the snow cover from 0 to 45 cm varies greatly with the time of year. This layer from 0 to 45 cm shows a general increase in strength from January to September, with peak values occurring between June and September. Strength decreases gradually from October to December, which is the warm period in Antarctica.The hardness-profile values obtained by ramsonde, when duly converted into unconfined compressive strength, give a fair indication of trafficability of wheeled and tracked vehicles at different times of the year on the ice shelf. They also indicate the load-bearing capacity of the surface snow for landing light- to medium-weight aircraft.
Pack-Ice Drift off East Antarctica and some Implications
Authors: Ian Allison 
Published: September 2017

Three satellite-tracked data buoys were deployed between 70° and 80°E south of 65°S in February-March 1985. These buoys were subsequently trapped within the expanding seasonal sea ice and drifted with the ice. The buoys measured air temperature and pressure, and water temperatures to 100 m depth. Data from the buoys are used to describe the ice drift and environment within the winter sea-ice zone in this region, both north and south of the Antarctic Divergence. Additional preliminary data from a further six buoys deployed in the same area in March 1987 are also presented.Besides providing information on the broad-scale drift of the ice in the Prydz Bay region, data from the buoys have shown: (i) the important role that ice drift plays in determining the autumn and winter expansion of Antarctic sea ice; (ii) the highly mobile nature of the ice, even hundreds of kilometres from the ice edge; (iii) the role that ocean-bottom topography has in determining ice drift over the continental shelf; and (iv) the modifying influence that an ice cover has on regional climate.A qualitative assessment is made of the relative importance of the major forces driving the ice, although the data are insufficient for a detailed study of the ice dynamics.
Development and Certification of A Visibility-Range Monitor By Image Processing
Authors: Ishimoto Keishi , Takeuchi Masao , Naitou Shigeyuki , Furusawa Haruki 
Published: September 2017

A new visibility-range measuring system has been developed which uses a video camera, and with which visibility can be estimated by measuring the brightness contrast of a black target against a standardized background. This principle has been applied to development of the new visibility-range monitor described in this paper. In this monitor, a charge-coupled device (CCD) video camera measures the brightness of an arbitrary area in its range of vision, and visibility range measured by the video camera in blowing snow can be compared with that measured by the transmissometer-type visibility-range monitor and can also be calculated by direct observation using optical targets.The new sytem can monitor visibility and record information about traffic on highways at 1 s intervals for a maximum of six separate positions. The vertical distribution of visibilities over a snow surface has been observed, and it has been found that the fluctuation in visibility is greatest at lower levels above the ground in blowing snow.