bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mechanical Tests of Fresh Ice Core (Abstract only)
Authors: Shoji H. , Langway C.C. 
Published: February 2017

Uniaxial compression tests (UCT) under constant cross-head speed and simple shear tests (SST) under constant load have been carried out in a snow cave at -16°C on ice cores within at most one month of extraction from depths of 235, 504, 708, and 896 m at Dye-3, Greenland, as part of the Greenland Ice Sheet Program (GISP), in order to improve understanding of flow behavior. UCT specimens had their stress axis at 45° from the core axis and SST specimens had their shear parallel to the horizontal plane of the core, so that in both cases maximum resolved shear stress was in the horizontal plane of the ice sheet.
Fracture stresses in UCT had characteristic values for each depth corresponding to core quality. When effective strain-rate was plotted against effective shear stress on a double logarithmic plot, (1) data from the same depth fell on the same straight line for both tests, (2) for a given stress, strainrate varied with core-depth by less than half an order of magnitude, and (3) the stress exponent lay between 2 and 2.5, significantly less than the 3 to 4 reported for polycrystalline ice.
Values extrapolated from the present data agree quite well with those deduced from bore-hole tilting measurements at Byrd station, Antarctica, and Camp Century, Greenland.
A Three-Dimensional Time-Dependent Model of the West Antarctic Ice Sheet
Authors: Budd W. F. , Jenssen D. , Smith I. N. 
Published: February 2017

The area of West Antarctica which drains into the Ross Ice Shelf is examined for the purpose of understanding its dynamics and developing a numerical model to study its reaction to environmental changes. A high resolution 20 km grid is used to compile a database for surface and bedrock elevation, accumulation, and surface temperatures. Balance velocities Vbare computed and found to approximate observed velocities. These balance velocities are used with basal shear stress and ice thickness above buoyancy Z*to derive parameters k2, p and q for a sliddinq relation of the formReasonable matching is obtained for p = 1, q = 2 and k2= 5 × 106m3bar−1a−1. This sliding relation is then used in a first complete dynamic and thermodynamic velocity calculation for West Antarctica and for an improved simulation of the whole Antarctic ice sheet.
Atmospheric Trace-Gas Variations as Revealed by Air Trapped in an Ice Core from Law Dome, Antarctica
Authors: Etheridge D.M. , Pearman G.I. , de Silva F. 
Published: February 2017

A technique for extracting and analysing large air samples from bubbles occluded in an Antarctic ice core is discussed. Core samples of up to 1400 g were milled to release approximately 120 cm3 of air, which was dried, collected in a cold finger and then analysed by gas chromatography. The concentrations of atmospheric carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) over the past 450 years have thus been revealed. Measurements of a chlorofluorocarbon (CCl2F2) in the ice-core air were used to check core quality and the air-occlusion process.
The ice core, designated BHD, was thermally drilled from the summit of Law Dome, Antarctica, where the average accumulation rate is 0.65 m a-1 water equivalent and the annual average temperature is –22°C. Ice dating was achieved by counting annual cycles of oxygen-isotope ratio and d.c. conductivity, and air dating was deduced from the density profile.
The results show the pre-industrial concentrations of the gases to be 288 ± 5 ppm volume for CO2, 800 ± 50 ppb volume for CH4 and 285 ± 10 ppb volume for N20.
The Anthropogenic Impact on Snow Chemistry at Colle Gnifetti, Swiss Alps
Authors: Wagenbach D. , Münnich K.O. , Schotterer U. , Oeschger H. 
Published: February 2017

By chemical analysis of the upper 40 m of a 124 m ice core from a high-altitude Alpine glacier (Colle Gnifetti, Swiss Alps; 4450 m a.s.l.), records of mineral dust, pH, melt-water conductivity, nitrate and sulfate are obtained. The characteristics of the drilling site are discussed, as derived from glacio-meteorological and chemical analysis. As a consequence of high snow-erosion rates (usually during the winter months), annual snow accumulation is dominated by summer precipitation. Clean-air conditions prevail even during summer; however, they are frequently interrupted by polluted air masses or by air masses which are heavily loaded with desert dust.
Absolutely dated reference horizons for Saharan dust, together with the position of the broad nuclear-weapon tritium peak, provide the time-scale for the following statements:
(1) Since at least the turn of the century the background melt-water conductivity has been rising steadily, as has the mean snow acidity. The trend of increasing background conductivity at Colle Gnifetti (1.9μS/cm around the beginning of this century, and at present 3.4 μS/cm) is found to be comparable with the records of mean melt-water conductivity reported from ice cores from the Canadian High Arctic.
(2) Sulfate and nitrate concentrations are higher by a factor of 4–5 than they were at the beginning of the century. This is to be compared with the two- to three-fold rise in the concentrations in south Greenland during about the same time span.
Depositional Regime of the Katabatic slope from Mizuho Plateau to the coast, East Antarctica
Authors: Watanabe Okitsugu , Fujii Yoshiyuki , Satow Kazuhide 
Published: February 2017

Recently, a 700 m long ice core was drilled at Mizuho Station (2230 m a.s.1.), 270 km south-east of Syowa Station and situated in a typical katabatic-slope region.
In order to obtain basic knowledge for dating the core and for interpreting climatic change and depositional environment change along the core, a study of the regional characteristics of the snow-deposition regime on Mizuho plateau has started. Surface-firn cores 10–30 m deep and snow-stake data obtained along the traverse routes on Mizuho plateau since 1970 were analyzed.
The general trend of annual snow accumulation and the regional characteristics of the δ18O profile of snow cover were obtained.
Structure and Flow in the Margin of the Law Dome Ice Cap. Antarctica (Abstract)
Authors: Young Neal W. 
Published: February 2017

The internal structure of the Law Dome ice cap is being investigated by studying ice cores obtained from several sites along the summit-Cape Folger line. Profiles of measured physical properties for four of the ice cores from near the margin of the ice cap are presented. A comparison of the profiles shows a gradual increase and then decrease in crystal size, and the development of strong crystal anisotropy in the upper half of the ice thickness. But in the lower part there is a complex multi-layer crystallographic structure, with an interleaving of ice which has markedly different physical properties. The development of the physical properties in the ice cores is discussed in terms of the deformation in the ice cap in the neighbourhood of the bore holes and the movement of the ice over the rough bedrock. The interdependence of the physical properties and the flow within the ice cap and their effect on other proxy records obtained from the ice cores are also explored.
The Law Dome is a small ice cap, about 200 km in diameter, adjoining the main Antarctic ice sheet. It is being studied as a model ice cap, using surface surveys and ice-core drilling. It is large enough to have most of the features of larger ice sheets but small enough to be investigated in considerable detail. The four cores were drilled within 10 km of the coast at Cape Folger and lie approximately along a flow line. Each of the cores covers the Holocene and at least the later part of the Last Glacial Maximum. Two of the cores are within 40 m of bedrock and the remaining two, in thinner ice nearer the coast, are within a few metres of bedrock. Physical properties which were measured include: crystal size, texture and orientation; bubble size, orientation and distribution; and visible stratigraphy. The stratigraphy in the upper layers is related mainly to the occurrence of surface melting during the warmer months of the year. Additional supporting information is available from measurements of the physical properties on shallow cores up-stream of the four bore holes, from radio echo-sounding profiles and from other studies on the ice cores. This data is used in the discussion of the velocity field in the ice cap.
Ice Structure and Crystal Fabrics of the 2200 M Ice Core at Vostok Station, Antarctica
Authors: Barkov N.I. , Lipenkov V.Ya. , Petrov V.N. 
Published: February 2017

Both the ice structure and the ice fabric along the 2200 m ice core at Vostok Station were investigated during the 25th, 29th and 30th Soviet Antarctic Expeditions.
Several kinds of three-dimensional parameters of polycrystalline ice were measured, e.g. the mean diameter and size distribution of ice crystals and air bubbles, and specific volume
The variation in most of these parameters along the core reflects not only the process of metamorphism in ice but also changes in the environmental conditions at the surface. The causes of these variations are discussed, in order to estimate the possibility of a paleoclimatic interpretation.
The evolution of c-axis fabrics with depth is discussed in relation to the ice-deformation conditions.
A comparison of ice fabrics at Vostok, Byrd Station and Camp Century shows that similar mechanisms cause the reorientation of crystals. The role of temperature in fabric development is discussed.
The dramatic retreat of Mount Kenya’s glaciers between 1963 and 1987: greenhouse forcing
Authors: Hastenrath Stefan , Kruss Phillip D. 
Published: February 2017

The retreat of the glaciers on Mount Kenya is quantitatively well documented for the intervals 1899–1963 and 1963–1987. The ice recession between 1899 and 1963 was strongly dependent on solar radiation geometry. By contrast, the ice thinning between 1963 and 1987 amounted to about 15 m for all glaciers regardless of topographic location. This suggests that climatic forcings other than solar radiation have become more prominent.
Sensitivity analyses indicate that the energy supply of about 5 W m−2, required to produce the observed ice thinning through melting, can be accounted for by a combination of climatic forcings. The direct effect of changing atmospheric composition (“greenhouse effect”) on the net longwave radiation could have contributed less than 1 W m−2. A warming of 0.0 to 0.2°C would translate into an additional downward-directed sensible heat transfer of 0.0 to 1.4 W m−2. A 0.1 to 0.2 g kg−1 increase in specific humidity would, through savings in the latent heat transfer, contribute 2 to 4 W m−2.
Long-term station records show little warming trend for East Africa itself. However, mid-tropospheric specific humidity trends of about 0.6 g kg−1 over the past two decades in the equatorial belt have been reported in the literature, and considered to be consequences of “global warming” and the “greenhouse effect”.
Viewed in perspective, the ice wastage on Mount Kenya between 1963 and 1987 appears to have been driven primarily by three climatic forcings, conceivably all steered by the “greenhouse effect”: a direct forcing through the net longwave radiation; an indirect forcing through warming and therefore enhanced sensible heat transfer; and another indirect forcing through warming (not necessarily in the region itself), leading to increased (advected) atmospheric moisture, and hence to reduced latent heat transfer, this last line of control being the most important.
Reactions of a calving glacier to large changes in water level
Authors: Laumann Tron , Wold Bjørn 
Published: February 2017

Austdalsvatn in western Norway was regulated in 1988 as a reservoir for a hydropower development. From a pre-1988 water level of 1157 m a.s.l. the new water level will vary more or less annually from 1170 to 1200 m a.s.l. The outlet glacier Austdalsbreen calves into this reservoir. About 1600 m up-valley from its terminus the glacier flows over a bedrock riegel that is, at its lowest point, ∼ 15 m above the projected maximum lake level of 1200 m. As a result of the increase in water level, the surface velocity near the front has increased from about 0.07 to 0.13 m d−1.Calculations suggest that the glacier terminus will retreat about 750 m in 50 years. The measured response of the glacier terminus for the first three years is in good agreement with the simulations.
A Surface Integral Method for Determining Ice Loads on Offshore Structures from In Situ Measurements
Authors: Johnson Jerome B. 
Published: February 2017

Two methods are presented for calculating ice loads on structures using measurements from sensors imbedded in a floating ice sheet and from instruments attached to a structure. The first method uses a mathematical model describing ice/structure interaction for a cylindrical structure to interpret stress measurements. This technique requires only a few sensors to develop an estimate of ice loads, However, analytical and experimental results indicate that using a mathematical model to interpret stress measurements can result in inaccurate load estimates due to uncertainty in the accuracy of the model and and the uncertainty of using local ice stresses to calculate total ice forces. The second method of calculating ice loads on structures utilizes Euler and Cauchy’s stress principle. In this, the surface integral method, the force acting on a structure is determined by summing the stress vectors acting on a surface which encompasses the structure. Application of this technique requires that the shear and normal components of stress be known along the surface. Sensors must be spaced close enough together so that local stress variations due to the process of ice failure around a structure can be detected. The surface integral method is a useful technique for interpreting load and stress measurements since a knowledge of the mechanism of ice/structure interactions is not needed. The accuracy of the method is determined by the density of sensors along the surface. A disadvantage of the technique is that a relatively large number of sensors are needed to determine the stress tensor along the surface of interest.The surface integral method can be used to examine the effects of grounded ice rubble on structural ice loads. Two instrumented surfaces, one enclosing a structure and the other enclosing the structure and rubble field can be used to estimate the load acting only on the structure and also on the structure/ rubble-field system.
Experimental Studies on Snow Accretion at Subzero Temperatures
Authors: Mizuno Yukiko , Wakahama Gorow 
Published: February 2017

In order to clarify the process of snow accretion, which occurs at a temperature below the melting point of ice, experimental studies were made on the microscopic process of ice Adhesion as well as the tensile adhesive strength of snow onto various kinds of materials.
For this purpose, direct observations were made of the formation of an ice bond developed at the interface between an ice particle and a plate made of a transparent material such as glass, acrylic plastic (polymethyl methacrylate (PMMA)), or ice, and measurements made of the growth rate of the real contact area.
The growth rate of an ice bond formed at the interface between an ice particle and the plate of a hydrophilic material such as glass was equal to or slightly larger than that of ice sintering, while an ice bond was not formed at the interface between an ice particle and the plate of a hydrophobic material such as teflon.
As for adhesive strength, with the lapse of time it increased rapidly at the former interface and slowly at the latter interface. Examinations of fracture planes revealed that at or near the interface a pure adhesive break did not take place with the exception of teflon and vinyl, and that what took place there was a cohesive break or a mixture of cohesive and adhesive breaks.
Measuring Snow Water Equivalent by Cosmic Radiation
Authors: Fritzsche W. 
Published: February 2017

We have reduced the time taken for measurement of snow water equivalent using cosmic radiation by two to four hours with an accuracy of 1 cm of water equivalent. When BF3 counters were used by Kodama in 1975, it took three days. For comparison we sometimes still have to make measurements manually or automatically in flat areas. These measurements can then be compared with measurements from avalanche starting zones where conditions can be quite different because of wind or ablation.
For avalanche forecasting, or in similar situations, when an accuracy of 1 cm is needed within a few hours, we suggest the use of scintillation counters with a doped plastic material. The greatest accuracy is obtained by using a separate site where values are recorded without snow. In this case 200 000 pulses per hour are obtained (absorption length of 400 cm) which after measurements of 2 h duration gives the desired error of 1 cm of water. After 8 h the error is 0.5 cm of water, and after 24 h it is 0.3 cm of water. At an altitude of 2 000 m at which most avalanches are released, the count rate is doubled and the measuring error is 0.7 of that at sea-level. At an altitude of 3 000 m the count rate is four times that at sea-level. In other regions at other latitudes and elevations other values would be found.
The necessary equipment can be built into the ground in autumn so that the surface is level with the ground. A slot antenna of frequency around 400 MHz is used for transmission of the data.
Characteristic Growth Processes of Ice Crystals on the Antarctic Ice Sheet
Authors: Nishimura Hiroshi , Maeno Norikazu 
Published: February 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 = K
0 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.
Antarctic Icebergs – Production, Distribution and Disintegration (Abstract)
Authors: Orheim Olav 
Published: February 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.
Distribution of Surface Features and Surface Mass Balance of Ice Sheet, East Queen Maud Land, Antarctica (Abstract)
Authors: Fujii Yoshiyuki , Ageta Yukata 
Published: February 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.