bluuebunny/crossref_metadata_2025_split huggingface dataset:
Accumulation Distribution in the IAGP Area, Antarctica: 90°E-150°E
Authors: Young N. W. , Pourchet M. , Kotlyakov V. M. , Korolev P. A. , Dyugerov M. B. 
Published: February 2017

The distribution of mean net accumulation rate over a large sector (90°E to 150°E) of the IAGP (International Antarctic Glaciological Project) area in Antarctica is presented in map form. The basic data have been compiled from direct measurements of accumulation at stake networks, and by dating horizons in the snow pack by gross β-activity measurements, on four long traverse routes. The spatial variability can be high, over 40%, for a single year, and typically about 20% for multiyear averages. Local surface topography in the form of undulations of several kilometres wavelength can account for about 35% of the variance. Averaging over Intervals of 50 km or more will give the smooth large-scale distribution pattern. But the resultant values can still deviate from the long-term average accumulation by 25% or more due to temporal variability over time scales of years to decades.A very high correlation (r = 0.97) was found for the relationship a = 1414 exp (0.060 θ10) between accumulation, a kg m−2a−1, and 10 m depth snow temperature, θ10°C, when the data set was limited to a single large drainage basin in Wilkes Land.
The Heat Regime of the Central Parts of the Antarctic Ice Sheet with Changing Climate (Abstract only)
Authors: Barbash V.R. , Zotikov I.A. 
Published: February 2017

The heat regime and dynamics of the Antarctic ice sheet are studied using numerical modelling for two flow lines, one of which passes Vostok station and the other Byrd station. A two-dimensional non-steady heat-transfer equation with an energy dissipation term was used. The study consists of two parts. The first is a study of velocity and temperature distributions within the glacier under steady-state conditions. The second study was performed assuming surface temperature changes intended to model palaeoclimatic changes for the last 100 ka and also to model future climate changes due to a possible "greenhouse" effect.
Computer numerical modelling shows that the Antarctic ice sheet retains a record of the climatic temperature minimum 18 ka BP. Numerical modelling of the greenhouse effect assumes a temperature increasing by 10 deg within the next 100 a; its influence increases after this even if the surface temperature then remains the same for the next 20 ka. It is shown that for the next 1 ka the temperature wave will penetrate only a thin surface layer of the ice. Even in 20 ka the bottom temperature of the ice sheet will still be unchanged. Small increases of ice velocity can produce ice-sheet thinning of the order of 10 mm a−1.
The Vertical Structure of the Antarctic Ice Sheet and Palaeoclimatic Interpretation of the Data (Abstract only)
Authors: Korotkevich Ye. , Petrov V.N. , Barkov N.I. , Lipenkov V.Ya. 
Published: February 2017

The ice core from the 1 415 m Vostok bore hole has been studied. It was found that the ice-grain size increases with depth in the upper 700 m, a sharp gradient change occurring in the 300 to 400 m range. The grain cross-section area at depths of 100, 200, 300, 400, 500, 600, and 700 m was 1.1, 2.0, 1.5, 1.9, 2.6, and 3.3 mm2 respectively. Since grain size is a function of age, and is determined by initial size and growth rate, the latter being exponentially related to ice temperature, an attempt was made to interpret the obtained data in terms of palaeoclimatology.
Calculations show that the upper part of the ice sheet (down to 300 m depth) formed during the past 12 ka, and grew under temperatures higher than those at which the lower part of the ice formed, that is ice at 300 to 700 m depth. This conclusion was confirmed by the results of oxygen isotope analysis.
The air content of ice at depths 100 to 650, 650 to 850, 850 to 1 100, and 1 100 to 1 400 m reduced to normal conditions was 65, 70, 75, and 70 mm3 g−1 respectively. Calculations suggest that 3 to 30 ka BP the ice-sheet elevation at Vostok station was close to the present one, while 30 to 40, 40 to 55, and 55 to 75 ka BP it was 500, 1 000, and 500 m lower than at present, respectively.
Ice Flow Along AN Iagp Flow Line, Wilkes Land, Antarctica (Abstract only)
Authors: Young N.W. , SheehY D. , Hamley T. 
Published: February 2017

Trilateration and single line surveys have been made to about 900 km inland of Casey, Wilkes Land, to measure surface elevation, ice thickness, horizontal velocity, and other parameters. On the large scale the velocity U increases smoothly from 8 m a−1, 800 km inland, to 280 m a−1 inland of the fast outlet streams. This increase in velocity is associated with a corresponding increase in the large-scale smoothed (over about 30 ice thicknesses) basal shear stress τb from 0.4 to 1.5 bar. The mean shear strain-rate through the ice sheet U/Z = kτb4
, where Z is the ice thickness (range 4 500 to 1 700 m).
At scales of one to several ice thicknesses large variations occur in surface slope and ice thickness without proportionally large velocity variations, because of the effect of the longitudinal stress. Detailed measurements made over a 30 km section indicated that the surface longitudinal strain-rate gradient varied from -1.7 to +1.3×l0−6 a−1 m−1 along with variations in surface slope of from -3.5 to +1.5%.
A multilayer model, based on the solution of the biharmonic equation for the stream function, was used in a study of the ice flow associated with these surface undulations. Given the bedrock topography and large-scale flow parameters, the model closely predicted the measured surface profile when the variation of the surface accumulation rate over an undulation was also considered.
Energy Balance at the Surface of the Ice Sheet in the Coastal Area of Adélie Land, Antarctica (Abstract only)
Authors: Blaix P.-L , Delaunay D , Poggi A 
Published: February 2017

Hourly measurements of wind, temperature, and humidity were made between elevations of 1 and 20 m in the coastal area of Adélie Land over a period of 45 d in January and February 1978. About 1000 profiles are available.
The height of the constant flux layer is &gt;5 m despite the influence of katabatic winds, the wind profile is logarithmic with a mean standard deviation from the logarithmic law of 15 mm s−1. The potential temperature profile is also logarithmic with a mean standard deviation of 0.04°C. The most important deviation from the logarithmic law appears between -4 and 0°C.
Humidity was measured at two points only, between 1 and 20 m; the mean gradient was about 0.01 mbar m−1 and the flux of latent heat was generally negligible.
Net radiation was measured for only 10 d because of radiometer failure. All the fluxes are calculated using data for the 5 m layer. For the 10 d period, the heat loss was about 3 Wm−2 with a mean heat flux of -27.5 Wm−2 and mean net radiation of -10.5 Wm−2(the minus sign signifying the flux is towards the surface). In general, the heat flux is towards the surface (92% of the cases) but is away from the surface in the afternoon. The ablation during the 10 d period without snow-fall was about 200 mm of ice.
The Importance of Pressurized Subglacial Water in Separation and Sliding at the Glacier Bed (Abstract only)
Authors: Bindschadler Robert 
Published: February 2017

The effect of pressurized sub-glacial water on the sliding process is quantified by calculating a “bed separation index”. The water pressure distribution i s calculated assuming the existence of a Rothlisberger channel at the bed. Kamb's formulation is used to describe the variation of normal stress over periodic bed undulations. The hypothesis is that as either basal shear stress or water pressure is increased the extent of ice-bedrock separation (on the down-glacier side of undulations) increases and enhanced sliding occurs
Data from three glaciers of widely varying size are used to test this hypothesis. For Columbia Glacier and “Ice Stream B” the importance of including the effects of water pressure in any “sliding law” are pronounced. More complete data from the third test case, Variegated Glacier, are used to compare a number of possible formulations of sliding law which encompass the above hypothesis. A modified Weertmantype law appears to be most preferable while while some possibilities, including Budd's lubrication factor hypothesis, are tentatively rejected.
Consideration of the temporal variations of the “bed separation index” reemphasize that, especially in the short time scale, variations of water pressure can dominate the sliding process. An order of magnitude increase in water discharge causes a hundred fold transient increase in the water pressure.
This paper has been accepted for publication in the Journal of Glaciology
Sea-Ice and Snow-Cover Data Availability, Needs and Problems
Authors: Barry R. G. , Crane R. G. , Weaver R. L. , Anderson M. A. 
Published: February 2017

Various types of sea-ice and snow-cover data are required for operational purposes in real time, for engineering assessments of associated hazards and for regional to global-scale modeling of the climate system. Data on the primary characteristics of ice and snow (extent, depth or thickness, and ice concentration) are becoming available to meet many present types of modeling requirement but secondary properties such as snow-water content, ridging intensity, open-water fraction and ice drift are less readily available.
Data for these major variables of snow and ice cover are considered with respect to problems encountered in obtaining and using digital information necessary for modern computer analyses. Such problems include the limitations of the basic observations (observational or sensor accuracy), the spatial and temporal resolution of different data sets, varying national practices of observing and reporting, and the problems of meshing data collected by different means and having spatial differences and temporal changes of observation time, site location, sensor system and resolution, etc. The relative reliability and climatic “information content” of some historical data sets are briefly examined and available digital data sets on modern global ice- and snow-cover conditions are described.
Ice-Shelf Densities from a Comparison of Radio Echo and Seismic Soundings
Authors: Doake C. S. M. 
Published: February 2017

A 40 km line across George VI Ice Shelf was sounded in January 1981 by both radio echo and seismic reflection methods. Because the velocities of radio and seismic waves vary with ice density in different ways, an accurate comparison of travel times from the two methods allowed the average density of the ice shelf to be calculated.A distinguishable echo from the base of the ice shelf was recorded at 22 out of 23 seismic stations. Continuous radio echo profiling was achieved in ice varying in thickness from about 200 to 350 m. The calculated mean densities fell into two groups, In an area where summer meltwater frequently floods the surface the average densities were around 0.915 Mg m−3, while in the drier areas the average densities were around 0.884 Mg m−3. Apart from this division, there was no apparent systematic variation of average density with position. The sounding was carried out approximately along a flowline on the ice shelf.The variation of ice density with depth and position is difficult to allow for when modelling the deformation of ice shelves. Measured values of surface strain-rate, for example, may in some circumstances need to be corrected for effects due to the compressibility of snow.
Introduction to a New Sea-Ice Database
Authors: Knight Richard W. 
Published: February 2017

An important new sea-ice database is presently being created at the National Climatic Data Center in Asheville, North Carolina, USA. The data are digitized from weekly charts prepared at the US Navy/National Oceanic and Atmospheric Administration (NOAA) Joint Polar Ice Center and converted into a digital format prescribed by the World Meteorological Organization. The data cover both the Arctic and Antarctic for a ten-year period of record. The grid points are identified by earth coordinates and have a resolution of 15 nm or better.
This paper is intended to inform potential users of sea-ice data about the availability of the new data set. Topics covered are (1) data source, (2) brief description of the processing procedures, (3) the SIGRID output format, and (4) future plans.
Ice-Age Climate and Continental Ice Sheets: Some Experiments with A General Circulation Model
Authors: Manabe S. , Broccoli A. J. 
Published: February 2017

The climatic influence of the land ice which existed 18 ka BP is investigated using a climate model developed at the Geophysical Fluid Dynamics Laboratory of the National Oceanic and Atmospheric Administration. The model consists of an atmospheric general circulation model coupled with a static mixed layer ocean model. Simulated climates are obtained from each of two versions of the model: one with the land-ice distribution of the present and the other with that of 18 ka BP.In the northern hemisphere, the difference in the distribution of sea surface temperature (SST) between the two experiments resembles the difference between the SST at 18 ka BP and at present as estimated by CLIMAP Project Members (1981). In the northern hemisphere a substantial lowering of air temperature also occurs in winter, with a less pronounced cooling during summer. The mid-tropospheric flow field is influenced by the Laurentide ice sheet and features a split jet stream straddling the ice sheet and a long wave trough along the east coast of North America. In the southern hemisphere of 18 ka BP, the ice sheet has little influence on temperature. An examination of hemispheric heat balances indicates that this is because only a small change in interhemispheric heat transport exists, as the In situ radiative compensation in the northern hemisphere counterbalances the effective reflection of solar radiation by continental ice sheets.Hydrologic changes in the model climate are also found, with statistically significant decreases in soil moisture occurring in a zone located to the south of the ice sheets in North America and Eurasia. These findings are consistent with some geological evidence of regionally drier climates from the last glacial maximum.
Reconstruction of the Glacial Ice Covers of Greenland and the Canadian Arctic Islands by Three-Dimensional, Perfectly Plastic Ice-Sheet Modelling
Authors: Reeh N. 
Published: February 2017

A three-dimensional perfectly plastic ice-sheet model, developed for determining the surface elevations and the flow pattern of an ice sheet with given bottom topography and ice-margin positions, is applied to the reconstruction of the glacial ice covers of Greenland and the Canadian Arctic islands. In the northern regions, two different reconstructions have been performed with ice margins along the present 600 and 200 m sea-depth contours, respectively. In central Greenland, the ice margin is considered to be at the outermost ice-margin deposits on the coastal shelf to the west, and at the present 200 m sea-depth contour to the east.The main conclusions to be drawn from the reconstructions are: (1). The flow pattern of the glacial ice cover of Greenland shows a great resemblance to the present one, the central ice divide being displaced less than 50 km from its present position and being no more than 200 m higher than today. (2). The main ice divide of the ice sheet covering the Canadian Arctic islands (the Innuitian ice sheet) was located over the highlands of eastern Ellesmere Island with local domes positioned over the present ice caps, indicating that even the deep ice of Wisconsin age in these ice caps is of local origin. This is also the case for the Devon Island ice cap. (3). Even in the not very likely case of a rather extensive glacial ice cover in north-west Greenland, the ice-flow pattern upstream of the Camp Century deep drill site would not have changed radically compared to the present flow pattern. Thus it is concluded that even advanced ice margins in late-Wisconsin time could at most have resulted in an elevation of the deposition site of the late-Wisconsin ice at Camp Century 600 m higher than at present. The consequences of this conclusion are discussed.
A Model Simulation of 20 Years of Northern Hemisphere Sea-Ice Fluctuations
Authors: Walsh John E. , Hibler William D. , Ross Becky 
Published: February 2017

A dynamic-thermodynamic sea-ice model (Hibler 1979) is used to simulate northern hemisphere sea ice for a 20-year period, 1961 to 1980. The model is driven by daily atmospheric grids of sea-level pressure (geo-strophic wind) and by temperatures derived from the Russian surface temperature data set. Among the modifications to earlier formulations are the inclusion of snow cover and a multilevel ice-thickness distribution in the thermodynamic computations.
The time series of the simulated anomalies show relatively large amounts of ice during the early 1960s and middle 1970s, and relatively small amounts during the late 1960s and early 1970s. The fluctuations of ice mass, both in the entire domain and in individual regions, are more persistent than are the fluctuations of ice-covered area. The ice dynamics tend to introduce more high-frequency variability into the regional (and total) amounts of ice mass. The simulated annual ice export from the Arctic Basin into the East Greenland Sea varies interannually by factors of 3 to 4.
The IGS Symposium on Ice and Climate Modeling: An Overview
Authors: Radok Uwe 
Published: February 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.
Crystal Size and Orientation Patterns in the Wisconsin-Age Ice from Dye 3, Greenland
Authors: Langway C.C. , Shoji H. , Azuma N. 
Published: February 2017

Crystal size and c-axis orientation patterns were measured on the Dye 3, Greenland, deep ice core in order to investigate time-dependent changes or alterations in the physical character of the core as a function of time after recovery. The physical measurements were expanded to include depth intervals not previously studied in the field. The recent study focused on core samples located between 1786 m and the bottom of the ice sheet at 2037 m.
Manual c-axis measurements were made on 23 new thin sections using a Rigsby-type universal stage. A new semi-automatic ultrasonic wave-velocity measuring device was developed in order to compare the results with the earlier manual measurements and to study an additional 114 ice-core samples in the Wisconsin-age ice. Crystal-size measurements were made on specimen surfaces by inducing evaporation grooves at crystal boundaries and measuring linear intercepts. The ultrasonically measured test samples were subsequently cleaned and analyzed by ion chromatography in order to measure impurity concentration levels of Cl−, NO3− and SO4
2− and study their effects on crystal growth and c-axis orientation.
Co-Isotopic Signature of Two Mechanisms of Basal-Ice Formation in Arctic Outlet Glaciers
Authors: Souchez R. , Lorrain R. , Tison J.L. , Jouzel J. 
Published: February 2017

Basal ice is formed by regelation as a consequence of both pressure-melting and freezing-on at the glacier sole.
A study of D/H and 18O/16O ratios in basal ice from five Arctic outlet glaciers indicates that a co-isotopic signature exists for these two mechanisms of formation.
The dispersed and stratified facies of basal ice present in these glaciers are related respectively to the occurrence of regelation and to freezing-on at the glacier base. Their origin is tentatively connected with the onset of basal sliding and the zone of bed decoupling due to basal water pressure in these Arctic outlet glaciers.
Antarctic Peninsula Climate Over the Last 400 Years, Deduced from an Ice-Core Record
Authors: Aristarain A.J. , Jouzel J. , Pourchet M. , Lorius C. 
Published: February 2017

Reconstruction of the past climate of the Antarctic Peninsula is of special interest because it represents a possible link between the conditions that predominated over the Antarctic continent and those over South America, only about 1000 km away. From a detailed isotopic study on a core drilled on James Ross Island (64°12′S, 57°40′W), including a comparison with the Orcadas temperature record (which has been available since 1904), we have recently examined the climatic changes which have occurred in this region over the last 130 years (Aristarain and others 1986).
We have now extended this isotope record back to about A.D. 1600 (dating is obtained from a glaciological model). A striking feature of the resulting climatic curve is the significant cooling, estimated at about 2º C, which has been observed since the turn of the century, in comparison with the warmest period of the record (around A.D. 1850). This feature, which is at odds with Northern Hemisphere temperature data, will be examined in the context of factors affecting the Antarctic Peninsula climate. These include sea-ice extent, and the relative influence of a maritime climate in the west and of a continental climate in the east, and the generally high climatic sensitivity theoretically expected in these ice-margin areas. The whole climatic curve will also be compared with other Antarctic and Southern Hemisphere records.
The influence of humidity on the ablation of continental-type glaciers
Authors: Ohno Hiroyuki , Ohata Tetsuo , Higuchi Keiji 
Published: February 2017

The annual evaporation of a continental-type glacier (43°05’ Ν, 86°48’ E) in the Chinese Tien Shan is estimated, based on data derived from four field observations carried out between summer 1987 and spring 1988, and data from a permanent weather station near the glacier. The evaporation during the melting and non-melting seasons is estimated as 81 mm and negligible, respectively. Assuming that the ablation is equivalent to the annual precipitation (650 mm) in 1987, estimated annual evaporation of 81 mm is 12% of the ablation and consumes 54% of the energy which causes the ablation. It can be said that evaporation suppresses ablation by 50% in comparison with the condition in which there is no evaporation.The influence of fluctuations of air temperature and humidity on the ablation of the glacier were evaluated. Changes in temperature and humidity cause larger changes in ablation of glaciers in a cold and dry climate. The influence of humidity change is very important to glaciers located in a relatively warm environment.