bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evolution of under Water Sides of Ice Shelves and Icebergs
Authors: Orheim Olav 
Published: February 2017

A systematic programme of side-scan sonar and plumb- line soundings was carried out in the Weddell Sea area in 1985 to measure the under-water sides of ice shelves and icebergs. From these observations the following model is suggested for the evolution of the ice front:(1)Initial stage: fracturing of the ice shelves takes place along smooth, curvi-linear segments with vertical faces.(2)Formative stage: the freshly formed vertical face is eroded both by wave and swell action around the water line, by small calvings from the undercut, overhanging subaerial face, and by submarine melting. The melting has a minimum at 50–100 m depth, and increases with depth to a rate of around 10 m a−1at 200 m, This is about twice the rate of erosion at the water line. The variation in melting with depth results from a combination of summer melting by near-surface water, and year-round melting by water masses that are increasingly warmer than the pressure melting-point with depth.(3)Mature stage: this stage is reached after a few years of exposure. The backward erosion of the face leads to a shape with a prominent under-water “nose” with a maximum projection to more than 50 m at 50–100 m depth. The ramp above this slopes upwards to meet the vertical wall about 5 m below the water line. The ice below the nose is melted back beyond the above-water face. There is no net buoyancy and ice shelves at this mature stage are generallynotup-warped at the front.
Mapping of Amery Ice Shelf, Antarctica, Surface Features by Satellite Altimetry
Authors: Partington K.C. , Cudlip W. , McIntyre N.F. , King-Hele S. 
Published: February 2017

Ice shelves are important regions to observe because they are likely to be sensitive indicators of climatic change. The satellite-borne radar altimetry is highly suited to ice-shelf monitoring; experience with Seasat, which flew in 1978, has demonstrated that a height-measurement precision of the order of 1 m can be obtained over ice surfaces (Brooks and Others 1983).
We identify subtle changes in altimeter wave forms associated with crevassed zones and the grounding line. Normal retracking procedures are shown to be inadequate in detecting such changes, and so methods which provide sensitive indication of the presence of these features in the sampled areas are devised. By ranging to the first return in the echo, the grounding line is identified, and by differencing this measurement with the half-peak power range, a measure of surface roughness is obtained which can be used to detect crevassed zones.
Detection of crevassed shear zones allows delimitation of distinct zones of flow in the ice shelf which can be monitored by future altimeter missions. Monitoring of the grounding-line position can provide sensitive indication of mass-balance conditions over the grounded part of the drainage basin.
Satellite Snow-Cover Monitoring in the Qilian Mountains and an Analysis for Characteristics of Stream Snow-Melt Run-Off in the Hexi Region, Gansu, China
Authors: Qunzhi Zeng , Shunying Zhang , Xianzhang Chen , Jian Wang 
Published: February 2017

The images of NOAA/TIROS-N APT, AVHRR and a few Landsat MSS obtained from 1980 to 1985 are analysed in this paper. It is found that the snow-cover distribution in Qilian Mountains is above 3700 m a.s.l. during winter to spring every year. There are two concentrations of snow cover. One is on Mount Leng Longling in the upper reaches of the Shiyang River and the other is located between Hala Lake and Mount Danghe Nanshan.Based on preliminary investigations, it is known that the surface water resource in the Hexi region is 68 8 × 108m3, of which about 24.8% is from glaciers and melting, and the snow-melt run-off is 7.63 × 108m3, equal to 62.6% of the total amount of spring run-off.The average value of Cv for spring run-off in the Shiyang River, Heihe River, and Shule River is 0 32 and the Cv value of snow-melt run-off in spring is 0.41, about three times as much as that of the annual run-off in the Hexi, region. A prediction model of spring snow-melt run-off at the Ying Louxia Hydrometric station in the Heihe River area can be constructed by using hydrometeorological data and snow-cover percentage for the Heihe River basin obtained from NOAA/TIROS-N APT, and AVHRR images. The prediction models (2) and (3) have been tested by the Water Resources Management Office of the Heihe River basin in the Zhangye and Flood Prevention Office of Gansu Province. The prediction accuracy is suitable for demands.
Acoustical Reflection and Scattering from the Underside of Laboratory-Grown Sea Ice: Measurements and Predictions (Abstract)
Authors: Jezek K.C. , Stanton T.K. , Gow A.J. 
Published: February 2017

We have studied acoustical reflection and scattering properties of the underside of laboratory-grown sea ice. Our purpose was to determine the morphologic characteristics of undeformed sea ice that control acoustic scattering and reflection. So our experiments included both detailed studies of the structure of the ice as well as the application of a variety of acoustic methods.
Ice sheets were grown in an outdoor pond (about 6 m by 13 m by 1.5 m) and exhibited features characteristic of undeformed, cold sea ice: an upper granular zone; a columnar zone of crystals with cross-sectional areas of about 1 cm2; vertical sheets of brine pockets; a bulk salinity of 9.1‰ distributed over 9 cm of ice; a dendritic interface at the ice/water boundary with dendrites about 0.5 mm across at the time of our measurements. Echo-amplitude fluctuations of normal-incidence sonar pings (100 kHz to 800 kHz) were measured as the sonars moved horizontally under the ice and accumulated into echo-amplitude histograms. (Data from a deteriorating ice sheet as well as data on lake ice were also collected.) We fitted the Rice probability density function (PDF) to the data and combined the resultant statistical parameter with Eckart acoustic scattering theory. The reflection coefficients calculated using this method ranged from 0.06 to 0.12, depending on environmental conditions. RMS roughness calculated using data from new sea ice was estimated to be about 0.3 mm. Because our ice thin sections show the ice to be porous and permeable at the interface with dendrites 0.5 mm thick, we suspect that the dendrites control the scattering as described by the echo-amplitude histograms. Further, we attribute the low reflection coefficients to the dendritic structure which may act as an impedance-matching zone into the columnar section of the sea ice.
Transmission measurements were performed by positioning a transducer located at the ice/air interface directly over the transducer located in the water. The total attenuation through 18 cm of ice ranged from 12 dB at 50 kHz to 70 dB at 420 kHz (signal levels were measured relative to the same path in water).
Analysis of Simulated Radar Altimetric Wave Forms for Polar Ice and Snow Surfaces (Abstract)
Authors: Novotny Eva 
Published: February 2017

The radar altimeter of the satellite Seasat has proved that ice and snow surfaces in the polar regions can return meaningful signals if the terrain is not excessively rugged or sloping. Because the use of the leading edge of the wave forms for height determination entails inherent uncertainties and, at best, provides only a single datum per wave form, the entire wave forms should be studied. Excesses or deficiencies in amplitude at various ranges within a single wave form, and the changes that occur in successive wave forms, can be analysed to yield information on the geometric and scattering properties of features observed by the altimeter.
Results from computer simulations are presented, showing how (1) a margin of sea ice (sinusoidal in the model) can be mapped, (2) the boundaries of two isolated ice floes can be outlined, (3) sea-ice concentrations can be derived within annuli about the nadir of an individual footprint, and (4) for land ice, the elevations of topographic features, together with the general slope of the ground, can be determined if an imaging instrument that operates simultaneously with the altimeter provides the outlines of these features. In examples (1) and (2), it is assumed that the ice is contiguous wherever that is possible, to permit the analytical reconstruction of the ice margin or individual ice floes in the presence of the inevitable ambiguity in the position of any feature with respect to the two sides of the satellite track. Example (4) requires that the altimeter record correctly records the strongest signals returned by ice-packs. This condition is not fulfilled by any existing radar altimeter, but it may be achieved in the next generation of these instruments. In additional examples of information from entire wave forms, the effects of crevasses and sastrugi in reducing or re-distributing the energy of the returned signals are also illustrated.
Full details of these analyses and results will be published at a later date.
The Timing of Initial Spring Melt in the Arctic from Nimbus-7 SMMR Data (Abstract)
Authors: Anderson Mark R. 
Published: February 2017

The ablation of sea ice is an important feature in the global climate system. During the melt season in the Arctic, rapid changes occur in sea-ice surface conditions and areal extent of ice. These changes alter the albedo and vary the energy budgets. Understanding the spatial and temporal variations of melt is critical in the polar regions. This study investigates the spring onset of melt in the seasonal sea-ice zone of the Arctic Basin through the use of a melt signature derived by Anderson and others from the Nimbus-7 Scanning Multichannel Microwave Radiometer (SMMR) data. The signature is recognized in the “gradient ratio” of the 18 and 37 GHz vertical brightness temperatures used to distinguish multi-year ice. A spuriously high fraction of multi-year ice appears rapidly during the initial melt of sea ice, when the snow-pack on the ice surface has started to melt. The brightness-temperature changes are a result of either enlarged snow crystals or incipient puddles forming at the snow/ice interface.
The timing of these melt events varies geographically and with time. Within the Arctic Basin, the melt signatures are observed first in the Chukchi and Kara/Barents Seas. As the melt progresses, the location of the melt signature moves westward from the Chukchi Sea and eastward from the Kara/Barents Seas to the Laptev Sea region. The timing of the melt signal also varies with year. For example, the melt signature occurred first in the Chukchi Sea in 1979, while in 1980 the signature was first observed in the Kara Sea.
There are also differences in the timing of melt for specific geographic locations between years. The melt signature varied almost 25 days in the Chukchi Sea region between 1979 and 1980. The other areas had changes in the 7–10 day range.
The occurrence of these melt signatures can be used as an indicator of climate variability in the seasonal sea-ice zones of the Arctic. The timing of the microwave melt signature has also been examined in relation to melt observed on short-wave imagery. The melt events derived from the SMMR data are also related to the large-scale climate conditions.
Glaciological and Hydrological Map of the Hornsund Fiord Area: 1:75 000 (Abstract)
Authors: Jania J. , Pulina M. 
Published: February 2017

The problem of how to select and synthesize glaciological and hydrological information for the map of South Spitsbergen is discussed. The area of interest covers aproximately 1700 km2, but not all of it has been explored equally well so far. The map is under preparation for printing. It is one of a series of environmental maps of Hornsund at 1:75 000. Geomorphology and geology have been completed already. The general objective was to reveal the spatial differentiation of glacial and hydrological phenomena in the vicinity of the Hornsund Fiord but particular interest was focused on providing synthesized information about glacial and hydrological phenomena and processes, which had been considered in the context of natural hydrological basins.
The result is a specification of the phenomena represented in the map. It had been divided into five parts;

(1)
elements of geomorphology, geology (lithology) and topography (basemap);

(2)
features of glaciers and glacial phenomena on land;

(3)
physical and chemical properties of on-land streams and glacier streams;

(4)
features of marine environment and Hornsund Fiord bottom (during contruction); and

(5)
general characterization and classification of phenomena occurring in hydrological basins.

The first is of a general nature. Parts two, three and four include detailed, analytical information. Part five comprises synthesized data.
The glaciers of Hornsund are specified by morphological classification, according to PSFG of the IAHS, by the position of the mean firn line and major glacier zones, and by the pattern of the ice flow-lines, along with some information on the velocity of flow. Thermal classification of the glaciers, and data on the oscillations of the glacier fronts in the 20th century are presented.
Of the Hornsund glaciers, Werenskioldbreen (approximately 27 km2)has been exposed in the map at 1.25 000. It has roused the interest of many investigators and is amongst the best explored examples. The available set ot data pertaining to this glacier consists predominantly of analytical, quantifying information, e.g. on the changes of the glacier surface altitude which occurred from 1957 to 1983, on the net balance at selected points of the glacier, on the pattern of englacial and subglacial channels, on the discharge in glacial streams, and on the quantity and degree of mineralization and chemical content of glacial streams, etc.
The result is a coloured map which aims at representing, in a systematic and synthesized manner, contemporary phenomena and processes associated with the glaciers and the water system of the Hornsund Fiord basin.
Techniques for Thermal Conductivity Measurements in Antarctica
Authors: Ewing Richard E. , Falk Richard S. , Bolzan John F. , Whillans Ian M. 
Published: February 2017

An accurate knowledge of the thermal properties of firn and ice within a glacier is essential for any reliable mathematical model of heat transfer. This paper considers the problem of determining the thermal properties of firn at Dome C, Antarctica, for use in such a model.First, the difficulties in accurately determining thermal properties are discussed. Then a physical experiment which can be performed under field conditions, but which will yield a well-posed mathematical problem for determining the unknown properties, is presented. Next, two different numerical techniques for solving the mathematical problem are discussed. Finally, some numerical approximations and error estimates are presented for the results of applying our numerical procedure to data from Dome C. Although insufficient data were obtained to test our methods fully, we have established a measurement procedure and a method of analysis which appear to be promising.
The Volcanic Record of Antarctic Ice Cores: Preliminary Results and Potential for Future Investigations
Authors: Kyle P. , Palais J. , Delmas R. 
Published: February 2017

Occurrences of tephra layers in four ice cores from Antarctica are reviewed. A new tephra, informally named the Vostok tephra, is described from a depth of 100.85 m in an ice core from Vostok station. Ice associated with four tephra layers at depths between 1390 and 1450 m in the Byrd station ice core shows increased levels of sulfate and nitrate which correlate well with peaks in particle concentrations. High levels of sulfate and nitrate are also associated with the Vostok tephra.Tephra offer great potential as stratigraphic markers and should be useful in providing time planes as well as assisting in correlation between widely spaced ice cores.
Recent Variations in Heavy Metal Concentrations in Firn and Air From the Antarctic Peninsula
Authors: Peel D. A. , Wolff E. W. 
Published: February 2017

A snow-pit and hand-drilled core have been sampled at Spaatz Island in the Antarctic Peninsula to obtain evidence on the importance of short-term fluctuations of heavy metal (Cd, Cu, Pb, and Zn) concentrations. A programme of air sampling was undertaken at the same time to investigate directly the link between concentrations in air and in snow. The snow samples and air filters have been analysed by atomic absorption spectrometry (AAS) following preconcentration on tungsten wires and by differential pulse anodic stripping voltammetry (DPASV). One sequence of snow samples was preconcentrated in the field and analysed later for Cd in the laboratory.
The snow analyses confirm that year-to-year variations in heavy metal concentrations may be comparable with changes due to long-term variations in global emission rates to the atmosphere from industrial sources. The importance of understanding these apparently meteorologically controlled processes is underlined. Averaged data from the combined air/snow sampling programme show a satisfactory linear relationship between concentrations in air and in snow for both the heavy metals and for the cation component of the marine aerosol. The results, considered in the light of Junge's model for static rainout, give a ratio for concentration in air (ng m−3)/concentration in snow (ng g−1) of 0.6±0.3.
Air Content Of The Byrd Core And Past Changes In The West Antarctic Ice Sheet
Authors: Raynaud D. , Whillans I. M. 
Published: February 2017

Analyses of ice cores taken from the Antarctic ice sheet can provide information on the environmental conditions under which the ice was formed. New results from measurements of gas content and stable isotope ratios in the Byrd station ice core are discussed and interpreted in terms of past iceflow changes.165 selected ice samples from 32 different depth levels along the core were processed for total gas content V and stable isotope ratios. This large dataset is used to discuss the variability and significance of the values of V at different depths. The short term variations of V are mainly explained by heterogeneities of the pore volume when the firn pores close off.The general trends in the values of V with depth are then used to investigate the possibility of past changes in the ice sheet. They suggest near-steady flow during the past few tens of thousands of years and that a thickening of about 200 to 250 m occurred in this area of the ice sheet at the end of the last ice age. This thickening could be due to a change in the accumulation rate.
Field Studies of Bottom Crevasses in the Ross Ice Shelf, Antarctica (Abstract only)
Authors: Jezek Kenneth C. , Bentley Charles R. 
Published: February 2017

Surface and airborne radar sounding data were used to identify and map fields of bottom crevasses on the Ross Ice Shelf. Two major concentrations of crevasses were found, one along the grid-eastern grounding line and another, made up of eight smaller sites, grid-west of Crary Ice Rise.
Based upon an analysis of bottom crevasse heights and locations, and of the strength of radar waves diffracted from the apex and bottom corners of the gridcrevasses, we conclude that the crevasses are formed at discrete locations on the ice shelf. By comparing the locations of crevasse formation with ice thickness and bottom topography, we conclude that most of the crevasse sites are associated with grounding. Hence we have postulated that six grounded areas, in addition to Crary Ice Rise and Roosevelt Island, exist in the grid-western sector of the ice shelf. These pinning points may be important for interpreting the dynamics of the West Antarctic ice sheet.
Measurement of Radio Wave Velocities in the Firn Zones of Polar Ice Sheets (Abstract only)
Authors: Shabtaie Sion , Bentley Charles R. 
Published: February 2017

A common-reflection point profiling experiment to obtain electromagnetic wave velocities in the ice at Dome C at 35 MHz was carried out to a maximum antenna separation of 2 km. Four different recording systems were used for this experiment. The echoes from numerous internal reflecting horizons within the ice and the bedrock were recorded in four different ways: in A-display form on film using an oscilloscope, in intensity-modulated form using the Honeywell Visi-corder and thermal intensifier on heat-sensitive silver paper, and in both raw and signal-averaged form on magnetic tape.Travel times of oblique reflections from nearly 160 internal layers down to a depth of 2 600 m and reflections from the ice bottom were measured at each station along the profile. The average wave velocities from the surface of each internal layer were measured to obtain a continuous mean velocity vs depth profile.Velocity-density models derived from the dielectric mixture equations of Looyenga, Böttcher, Lichtenrecker, Hanai-Bruggeman and Wiener were compared against the measurements. In addition Robin's empirical relationship was also used in this study. The preliminary results show that the observed velocity depth profile for the ice column is compatible with Wiener's equation (with Formzahl = 0) and a newly derived empirical relationship (from this study) ofwhere γiis ice density, γffirn density, ε dielectric constant of mixture, and εidielectric constant of ice; γf&gt;0.55 kg m−3. It appears that the electromagnetic wave velocity in the firn is 20 m MS−1or more, which is higher than previously assumed.The above models were also compared with velocity measurements in the Devon Island bore holes (Robin 1975) and at several sites on the Ross Ice Shelf where the ice is relatively thin compared to Dome C so that the effect of firn on mean velocities is more pronounced. The results for these sites suggest again that Wiener's equation and empirical relationship from this study produce velocities compatible with the observed values.
Geocryological Zones Of Antarctica (Abstract only)
Authors: Vtyurin B.I. 
Published: February 2017

Criteria for the determination of geocryological zones are: (1) distribution of permafrost, (2) the mean annual temperature of permafrost, (3) thickness of the active layer, (4) types of ground ice and ice content of permafrost, (5) regularities of cryogenic structure, (6) cryogenic phenomena, and (7) types of cryogenic relief.
Interpretation of the available data allows us to delineate the following geocryological zones in the Antarctic: (1) sub-Antarctic islands, (2) coastalcontinental, and (3) intercontinental. The brief general geocryological characteristic of these zones is given in the paper.
The sub-Antarctic island zone features discontinuous and continuous permafrost. The mean annual temperature of the permafrost is near 0°C and the maximum thickness is several tens of metres. The seasonal thawed zone has a thickness of 0.4 to 1.2 m. There are visible ice inclusions and very small ice forms in the permafrost and seasonal frost. Frost action causes frost sorting, hill - slope forms, and thermokarst. Ice-wedges are not found in the sub-Antarctic zone.
The coastal-continental zone has continuous permafrost. The mean annual temperature of the permafrost therejs -1°C in the Antarctic Peninsula and up to -5 to -7°C in East Antarctica. Maximum thickness of the permafrost is over 100 m and the active layer is 0.3 to 1 m. The ground ice is mainly pore ice but in some places there is buried glacier ice in moraine. Frost action, frost sorting, creep, nivation, and pre-glacial slope forms are developed in the coastalcontinental zone.
The intercontinental zone consists of continuous permafrost only. The mean annual temperature of the permafrost there is -10°C or lower. Thickness of this permafrost is several hundreds of metres and of the active layer is 0.1 to 0.5 m. The ice content is low with only small ice forms. The cryogenic structure of the permafrost is the same as the coastal-continental zone. Because alternate freezing and thawing is infrequent in the intercontinental zone all cryogenic processes are less rapid than in the other zones. Thermokarst is not found there and 1n general the intercontinental zone is not as well studied as the two other zones.