bluuebunny/crossref_metadata_2025_split huggingface dataset:
Snow-accumulation variability from seasonal surface observations and firn-core stratigraphy, eastern Wilkes Land, Antarctica
Authors: Goodwin Ian D. 
Published: September 2017

AbstractAnnual accumulation records were derived from two firn cores drilled at GD03 (69° 00’S, 115° 30’E, 1835m) and GD15 (69° 00’S, 130° 48’E, 2155m), which are separated by 750 km along the 2000 m contour in eastern Wilkes Land. The accumulation records, spanning the period 1930–85, show that annual accumulation has increased by 25% from 1960 to 1985, resulting in the highest accumulation rates in the 55 year records. Annual accumulation layers were identified in the firn cores using a firn-stratigraphic model (based on the observed characteristics and variability of the seasonal snow-surface layer) together with seasonal oxygen-isotope ratios. The accumulation records support other evidence for a similar recent increase across Antarctica. The greater increase over the long-term mean for 1930–85 in eastern Wilkes Land was observed at GD15 which is located on a northeast aspect slope near Terre Adèlie. It is suggested that the increase is the result of changes in the general atmospheric circulation pattern which have produced a higher annual frequency of precipitation events.
The duration of the active phase on surge-type glaciers: contrasts between Svalbard and other regions
Authors: Dowdeswell Julian A. , Hamilton Gordon S. , Hagen Jon Ove 
Published: September 2017

AbstractMany glaciers in Svalbard and in other glacierized areas of the world are known to surge. However, the time series of observations required to assess the duration of fast motion is very restricted. Data on active-phase duration in Svalbard come from aerial photographs, satellite imagery, field surveys and airborne reconnaissance. Evidence on surge duration is available for eight Svalbard ice masses varying from 3 to 1250 km2. Worldwide, active-phase duration is recorded for less than 50 glaciers. Few observations are available on high polar ice masses. The duration of the active phase is significantly longer for Svalbard glaciers than for surge-type glaciers in other areas from which data are available. In Svalbard, the active phase may last from 3 to 10 years. By contrast, a surge duration of 1–2 years is more typical of ice masses in northwest North America, Iceland and the Pamirs. Ice velocities during the protracted active phase on Svalbard glaciers are considerably lower than those for many surge-type glaciers in these other regions. Mass is transferred down-glacier more slowly but over a considerably longer period. Svalbard surge-type glaciers do not exhibit the very abrupt termination of the active phase, over periods of a few days, observed for several Alaskan glaciers. The duration of the active phase in Svalbard is not dependent on parameters related to glacier size. The quiescent phase is also relatively long (50–500 years) for Svalbard ice masses. Detailed field monitoring of changing basal conditions through the surge cycle is required from surge-type glaciers in Svalbard in order to explain the significantly longer length of the active phase for glaciers in the archipelago, which may also typify other high polar ice masses. The finding that surge behaviour, in the form of active-phase duration, shows systematic differences between different regions and their environments has important implications for understanding the processes responsible for glacier surges.
Thermal behaviour of glacier and laboratory ice
Authors: Nye J. F. 
Published: September 2017

AbstractWater is present in glaciers in the form of veins at the three-grain junctions. This water remains unfrozen even many degrees below the normal freezing point, mainly because it contains much of the soluble impurity content of a glacier, but also because of the microscopic curvature of the ice–water interfaces. As the temperature is lowered and the veins shrink, the concentration of impurities in them increases, and the curvature effect also increases. The predicted relation between vein size and temperature has now been verified by laboratory experiments.Because of the latent heat of the vein water, the ice behaves macroscopically as a continuum with an anomalous specific heat capacity that depends strongly on temperature. From this point of view, a polythermal glacier is a single medium with continuously varying properties, rather than consisting of distinct cold and temperate phases with sharp boundaries between them. The paper sets up differential equations for heat diffusion in such a continuum. To explain the local uniformity of the vein system seen under the microscope, it is found necessary to include the effect of diffusion of solutes along the veins.Solutions are presented for a model in which two semi-infinite slabs, initially having different temperatures, impurity concentrations and vein sizes, are instantaneously brought into contact. In this way, transition thicknesses between cold and temperate ice are estimated, and also the velocities of various kinds of waves that are generated from the original discontinuity at the interface.
Glaciological and Oceanographic Calculations of the Mass Balance and Oxygen Isotope Ratio of a Melting Ice Shelf
Authors: Potter J. R. , Paren J. G. , Loynes J. 
Published: September 2017

AbstractGlaciological estimates of the ice supply to George VI Ice Shelf are obtained by integrating the accumulation over the catchment. The basal melt (or possible shelf thickening) rates for the ice shelf are calculated by balancing the accumulation with calving and melting. We calculate an average equilibrium melt rate for the ice shelf of 2 m a −1. If the ice shelf is in mass balance it alone provides 53 km3a −1 melt from its base compared to a total for Antarctica of only 320 km3a −1.The mean oxygen isotope composition of recent accumulation on the catchment is determined by using accumulation and isotope data, supplemented by temperature measurements and a close empirical relationship between isotope ratio and temperature. The catchment has a mean isotope ratio of −20.8‰ relative to SMOW.Oceanographic work has previously shown that the sea-water under the ice shelf at the north of George VI Sound is Warm Deep Water modified by melting ice. The melting ice has an isotope ratio of −20.3‰. The good agreement in isotope ratios suggest that the melting ice is from the catchment and because the basal ice of George VI Ice Shelf represents accumulation over the last few millennia the implication is that there has been no systematic change in the isotope composition of the accumulation during this period. This implies no secular change in either the elevation or the climatic temperature of this part of the ice sheet.
Terminus Response of Lewis Glacier, Mount Kenya, Kenya, to Sinusoidal Net-Balance Forcing
Authors: Kruss Phillip 
Published: September 2017

AbstractClimatic change occurs over a wide range of time scales. Each glacier responds in a unique fashion to this spectrum of climatic forcings. The response of the extent of the Lewis Glacier terminus to sinusoidal fluctuation in the net balance is calculated. The net balance versus elevation profile is separately translated along the orthogonal balance and elevation axes. Net balance amplitudes of 0.1 to 0.5 m a−1 of ice and 10 to 50 m elevation, respectively, and periods ranging from 20 to 1000 years are covered. The time lag between forcing and terminus response is dependent on applied period, reaching a maximum of about 30 years at 1000 years period, but is independent of applied amplitude. For the shorter applied periods the response amplitude increases rapidly with period but asymptotically approaches a maximum at periods above approximately 200 years; it is linearly dependent on applied amplitude. Consideration of the Lewis Glacier response taken in perspective with similar results for other alpine glaciers identifies general characteristics of the terminus response.
A Model Investigation of Interannual Sea-Ice Variability in the Beaufort Sea
Authors: Ross Becky 
Published: September 2017

AbstractModel-generated ice-thickness fields for the period 1961–80 are examined in the context of summertime sea-ice predictability in the Beaufort Sea. The correspondence between the modeled and observed fluctuations of ice-covered area is found to be quite good. Lag correlation coefficients based on departures from 20 year “normals” of the ice thicknesses show that the ice anomalies are persistent throughout the August–May period. However, because the thickness anomalies undergo large fluctuations during July and August, only a small amount of summertime predictability can be derived from the thickness data. The findings are consistent with the observational results of Rogers (1978), who found that summertime temperatures and wind directions accounted for much of the variability of Beaufort Sea ice during August and September.
A Field Study of Rough Shore-Fast Sea Ice
Authors: O’D Thomas , Hanley S.J. 
Published: September 2017

AbstractDuring December 1973 the initial smooth ice cover on the Chukchi Sea near Barrow, Alaska, broke away from the shore during a period of strong wind and was replaced by a cover of broken, rafted ice which remained for the rest of the winter. Cores pulled from this cover were examined visually, and the salinity and density of sections of the cores were measured. Temperatures at several depths in the ice were recorded continuously, and these are presented near the date when the temperature gradient changed sign. Despite large deviations probably due to the irregularity of the ice cover, thickness and salinity followed the patterns seen by other observers.
Rates of Deposition on Lateral Moraine Embankments, Glacier De Tsidjiore Nouve, Valais, Switzerland
Authors: Small R. J. , Beecroft I. R. , Stirling D. M. 
Published: September 2017

AbstractIn the last decade deposition on lateral moraine embankments of glacier de Tsidjiore Nouve has been re-activated on a large scale. An attempt has been made to reconstruct, from the dimensions of the embankments, average rates of debris accumulation on the moraines during the Neoglacial period. These are compared with rates of deposition over the period 1977–82, calculated from detailed changes in moraine profiles (surveyed by ground- and air-based photogrammetry) and measured rates of ice-margin ablation. At present total output of sediment, by marginal deposition and transport by melt-water streams, from glacier de Tsidjiore Nouve is in the order of 6400–9500m3/a; this suggests the possibility of a high average erosion rate within the glacier catchment of 1.55–2.29 mm/a.
Analyzing the Spatial Distribution of Drumlins: A Two-Phase Mosaic Approach
Authors: Boots B. N. , Burns R. K. 
Published: September 2017

AbstractResearchers have analyzed various properties of drumlins within individual drumlin fields in order to provide evidence to help in identifying the processes involved in drumlin formation. One property which has been examined is the spatial distribution of drumlins within a field. Traditionally, in such endeavours the individual drumlins have been represented as points and their distribution examined using techniques of point-pattern analysis. We suggest that not only is such a representation inappropriate at this scale, it also introduces statistical bias which makes the results of such analyses questionable. Consequently, we propose an alternative approach which involves representing individual drumlins as areal phenomena and considering their pattern as a two-phase mosaic. The advantages of such an approach are discussed and it is illustrated by applying it to two different drumlin fields.
A New Dry Extraction System for Gases in Ice
Authors: Moor Ernst , Stauffer Bernhard 
Published: September 2017

AbstractA new extraction system has been designed and constructed which allows the extraction of gases from air bubbles in ice without melting it. The ice sample of about 500 g is crushed an evacuated container by a milling cutter, and the gas escaping from the opened bubbles is collected by condensation at 15K. Results of CO2 analyses of extracted gases are discussed with respect to possible contamination risks by the system.
On the Isotopic Composition in δD and δ18O of Water and Ice During Freezing
Authors: Souchez R. A. , Jouzel J. 
Published: September 2017

AbstractExperiments on progressive unidirectional freezing are conducted to determine the evolution inδD andδ18O of successive water samples and ice layers taken during the course of freezing. Results indicate that this evolution takes place, in aδD–δ18O diagram, along a straight line with a characteristic slope. This slope, different from that due to the precipitation effect, gives a finger-print of the occurrence of a freezing or of a melting–refreezing process in the studied reservoir.
A Reconsideration of the Mass Balance of a Portion of the Ross Ice Shelf, Antarctica
Authors: Jezek Kenneth C. , Bentley Charles R. 
Published: September 2017

AbstractThe identification of a small region of grounded ice in the north-western sector of the Ross Ice Shelf has forced a re-evaluation of the mass-balance calculations carried out by Thomas and Bentley (1978). Those authors concluded that the Ross Ice Shelf up-stream of Crary Ice Rise was thickening, but they did not take into account the effects on the velocity field of grounded ice (of which they were unaware), which is located near the input gate to their volume element. Reasonable estimates of the degree to which the ice velocity just up-stream of the grounded ice is diminished indicate that it is no longer possible to conclude that the ice shelf is thickening using Thomas and Bentley’s original flow band. Therefore, a new flow band was chosen which was grid east of Thomas and Bentley’s band and unaffected by any nearby grounded areas. The mass balance in this flow band was found to be zero within experimental error; a difference exceeding about 0.2 m a−1 in magnitude between the thickening and bottom freeze-on rates is unlikely.
Audibility within and Outside Deposited Snow
Authors: Johnson Jerome B. 
Published: September 2017

AbstractFactors which control the audibility within and outside deposited snow are described and applied to explain the preferential detection of sound by persons buried under avalanche debris as compared to persons on the overlying snow surface. Strong attenuation of acoustic waves in snow and the small acoustic impedance differences between snow and air are responsible for the strong absorption and transmission-loss characteristics that are observed for snow. The absorption and transmission-loss characteristics are independent of the direction of propagation of acoustic signals through the snow. The preferential detection of sound by a person buried under snow can be explained by the relatively higher level of background acoustic noise that exists for persons above the snow surface as compared to an avalanche burial victim. This noise masks sound transmitted to persons on the snow surface, causing a reduction of hearing senstitivity as compared to the burial victim. Additionally, the listening concentration of a buried individual is generally greater than for persons working on the snow surface, increasing their subjective awareness of sound.
Changes in Texture and Fabric of Particles in Glacial Traction with Distance from Source, Mỳrdalsjökull, Iceland
Authors: Humlum Ole 
Published: September 2017

AbstractEvolution of sedimentological characteristics for traction debris is investigated along a transport path down-glacier from a subglacial point source at the northern rim of the ice cap MỲrdalsjökull, Iceland. Losses and gains from this path are discussed. Close to mature characteristics as to particle size, shape, roundness, and fabric are developed after only short basal transport, about 500 m, while further transport only results in minor changes. This development is interpreted as the result of selective subglacial lodgement of large particles and/or particles with longitudinal α-axis orientation, while particles of median size and/or oblique orientation tend to stay in basal transport. Implications for basal sliding and subglacial sedimentation patterns are discussed.
Measurement of the Fracture Toughness of Glacier Ice
Authors: Andrews R.M. 
Published: September 2017

AbstractFracture-toughness testing of both fresh-water and sea ice has used specimen geometries designed for metals. These designs are too large and difficult to manufacture for testing material cored from a glacier. This paper presents an alternative specimen, a radially cracked ring fractured by internal pressure. Tests using this specimen on the Bersærkerbræ, a valley glacier in the Stauning Alper, north-east Greenland, gave a mean fracture toughness of 58 . This is half the value typically obtained by other workers in laboratory tests. The results are compared with other data and the reasons for the disagreement discussed.
Cylindrical Flow in and Over Channels of Irregular Shape
Authors: Shoemaker E. M. 
Published: September 2017

AbstractEarlier work by Nye (1965), who obtained numerical solutions for axial independent flow of a non-linear Glen material in channels of rectangular, elliptic, and parabolic cross-sections with a null-slip basal condition, is extended by using an inverse technique. Exact analytical solutions are obtained for flow in irregular-shaped channels (subject to symmetry restrictions) for both a Newtonian and an n = 3 Glen material. The cross-sections are regulated by multi-parameters. Solutions are obtained for two types of channel: (a) those whose side walls meet the free ice surface vertically, and (b) periodic channel arrays whose basal profiles do not intersect the free ice surface, i.e. overfilled channels. Solutions for the second type have not been presented previously. The solutions for the n = 3 Glen material employ a small parameter which limits the geometry variation to perturbations on semicircular or uniform-depth channels. Basal slip conditions can be incorporated although results are not presented here.
A Reconstruction of Snow-Avalanche Characteristics in Montana, U.S.A., Using Vegetative Indicators
Authors: Butler David R. , Malanson George P. 
Published: September 2017

AbstractWidespread wet-snow avalanches were observed on the southern boundary of Glacier National Park, Montana, in February 1979. Severe tilting, scarring, and breakage of trees were observed along a transverse trim-line of one path, 70 m from a wet-snow deposit. Tree-ring data were used to establish the date of occurrence, and the nature of damage was used to characterize the avalanche event. The event probably included a previously unrecognized dry-snow avalanche and associated wind blast. Such events present different problems for natural-hazard planning. The nature of vegetative damage along the margins of avalanche paths is shown to be a useful indicator of the characteristics of past unobserved avalanche events.
Examination of Selected Microparticles from the Sentik Glacier Core, Ladakh Himalaya, India
Authors: Goss Emily , Mayewski Paul A. , Lyons William Berry 
Published: September 2017

AbstractSeveral characteristics and interpretative comments are reported for microparticles from selected samples in the Sentik Glacier core. Four basic morphologic groups are defined: platy, angular, biogenic, and anomalous.
Icing on a Non-Rotating Cylinder Under Conditions of High Liquid Water Content in the Air: II. Heat Transfer and Rate of Ice Growth
Authors: Launiainen Jouko , Lyyra Markku 
Published: September 2017

AbstractThe rate of ice growth and heat transfer during a stationary wet-growth icing was studied, based on wind-tunnel experiments of Reynolds numbers of I04 to 105, and air temperatures of 0°C to –13°C. The convective heat-transfer coefficient, a quantity of primary importance entering the heat-balance equation of a freezing surface, was found to depend strongly on the liquid water content in the air (or rather, on the impinging water flow on the surface). The convective heat-transfer coefficient was considered theoretically and the dependence is thought to be caused by an increase in the surface roughness and, especially, by an effect of the impinging water droplets on viscous sub-layers and on turbulent heat transfer near the icing boundary. The above evaluation allows us to calculate an accretion efficiency for each icing condition.
Subglacial Hydrology for an Ice Sheet Resting on a Deformable Aquifer
Authors: Shoemaker E. M. 
Published: September 2017

AbstractSubglacial hydrology is investigated for an ice sheet where the substrate consists of a deformable aquifer resting on an aquitard. If sliding velocities are low or absent, subglacial melt-water drainage is dominated by drainage through the aquifer to water channels. Drainage along the bed is negligible. Efficient melt-water drainage requires that a system of subglacial water channels exists; otherwise, pore-water pressures will exceed the overburden pressure. In general, aquifer deformation near (away from) the terminus is most likely to occur during the winter (summer). The effect of short-term high channel pressures is, in general, not critical to aquifer deformation because the pressure pulse does not propagate far into the aquifer. (For aquifers of high permeability, short periods of high channel pressures constitute the most critical condition.) Aquifer deformation at the terminus is very likely to occur if the terminus ice slope exceeds tan ϕ, where ϕ is the Coulomb friction angle of the aquifer material. Upwelling of basal melt water near the terminus will normally cause soil dilation if the aquifer has a low permeability (e.g. till). Maximal profiles are computed corresponding to various aquifer materials using channel spacings which provide efficient drainage. (A maximal profile is the highest ice profile which the aquifer can sustain without deformation.) In general, maximal profiles lie well above observed profiles (such as h(x) = 3x1/2 (m)) except near the terminus. However, if channel spacings are sufficiently large, pore-water pressures are increased and maximal profiles can lie well below h(x) = 3x1/2.
Glacial Erosion of a High Arctic Valley
Authors: England John 
Published: September 2017

AbstractA large valley, ideally suited for “selective linear erosion” by ice, extends from the Kreiger Mountains to Tanquary Fiord, north–central Ellesmere Island. During the last glaciation, the outlet glacier at the head of the valley advanced 18 km and was at least 250 m thick where it contacted the sea in the lower valley. Erosion of bedrock inside the last ice limit is recorded by an abraded diabase dike, and by crag–and–tail features developed in limestone. During deglaciation (7800 B.P.), melt–water streams along the ice margin incised a large alluvial fan that pre–dates the last glaciation. The fan shows little alteration by the over–riding ice and its final erosion by the melt–water streams incised, but did not remove, its original ice–wedge polygons.The preservation of the fan indicates that the glacier was locally non–erosive and that it probably advanced across the fan by over–riding a protective frontal ice apron. Although it is commonly assumed that such alluvial fans occupying glaciated valleys are of post–glacial age, this need not be the case in permafrost terrain. In fact, at this site, there has been a net increment of alluvium versus glacial erosion or deposition spanning the last glacial cycle. The paper discusses the processes of erosion associated with sub–polar glaciers and questions whether erosion by them or more pervasive ice is responsible for such High Arctic valleys and fiords.