bluuebunny/crossref_metadata_2025_split huggingface dataset:
A mechanism for differential frost heave and its implications for patterned-ground formation
Authors: Peterson Rorik A. , Krantz William B. 
Published: November 2007

AbstractThe genesis of some types of patterned ground, including hummocks, frost boils and sorted stone circles, has been attributed to differential frost heave (DFH). However, a theoretical model that adequately describes DFH has yet to be developed and validated. In this paper, we present a mathematical model for the initiation of DFH, and discuss how variations in physical (i.e. soil/vegetation properties) and environmental (i.e. ground/air temperatures) properties affect its occurrence and length scale. Using the Fowler and Krantz multidimensional frost-heave equations, a linear stability analysis anda quasi-steady-state real-time analysis are performed. Results indicate that the following conditions positively affect the spontaneous initiation of DFH: silty soil, small Young’s modulus, small non-uniform surface heat transfer or cold uniform surface temperatures, and small freezing depths. The initiating mechanism for DFH is multidimensional heat transfer within the freezing soil. Numerical integration of the linear growth rates indicates that expression of surface patterns can become evident on the 10–100 year time-scale.
Development, structure and composition of land-fast sea ice in the northern Baltic Sea
Authors: Granskog Mats A. , Martma Tõnu A. , Vaikmäe Rein A. 
Published: November 2007

AbstractThe structural and stable-oxygen-isotopic properties of sea-ice samples collected on land-fast sea ice in the northern Baltic Sea, at 60.2–65.7° N, 21.3–26.9° E, were used to estimate the contribution of snow ice to the total sea-ice thickness, and the fraction of snow in the snow-ice layers and in the total sea-ice thickness. The textural analysis of the sea-ice cores revealed a general structure of a granular surface layer and a columnar basal layer. Using different isotopic criteria to distinguish snow-ice layers, we estimate that snow-ice layers contributed on average 24–32% of the total ice thickness in the study region. Transition ice (intermediate granular–columnar ice) also contributed significantly to the total ice thickness. The snow in the snow-ice layers contributed on average 18–21% of the total sea-ice thickness (by mass), a significant contribution when compared to other regions with sea-ice cover. The methods used could be improved to give more accurate estimates, especially by improving knowledge of the temporal variability of the isotopic properties of the snow incorporated into the sea-ice cover. However, our results can be regarded as plausible estimates for the contribution of snow ice and snow to sea-ice growth in the study area.
Triaxial tests on snow at low strain rate. Part I. Experimental device
Authors: Moos Markus von , Bartelt Perry , Zweidler Adrian , Bleiker Ernst 
Published: November 2007

AbstractA deformation-controlled triaxial apparatus has been developed in order to investigate the mechanical behaviour of alpine snow. Cylindrical specimens (58 mm in diameter, 126 mm in height) can be axially deformed by applying tensile or compressive strain rates between 2.4 × 10−7s−1and 2.4 × 10−2s−1. Compressed air is used to laterally load the snow specimens with pressures of up to 40 k Pa.The volumetric deformation is found by carefully encapsulating the snow samples in an airtight Mylar foil and measuring the expelled pore air during sample deformation. The multidimensional stress–strain behaviour can therefore be determined, and constitutive theories of snow advanced. The device is located in the cold rooms of the Weissfluhjoch research station of the Swiss Federal Institute for Snow and Avalanche Research. Some 180 tests have been performed over the last four winters. The density of the snow specimens varied between 190 and 435 kg m−3. Part I of this two-part paper discusses the development of the apparatus and the applied testing methodology. Qualitative results are provided. In Part II, a detailed analysis of the results is presented and the viscoelastic properties of snow quantified.
Ice cores from Arctic sub-polar glaciers: chronology and post-depositional processes deduced from radioactivity measurements
Authors: Pinglot Jean Francis , Vaikmäe Rein A. , Kamiyama Kokichi , Igarashi Makoto , Fritzsche Diedrich , Wilhelms Frank , Koerner Roy , Henderson Lori , Isaksson Elisabeth , Winther Jan-Gunnar , Van de wal Roderik S.W. , Fournier Marc , Bouisset Patrick , Meijer Harro A.J. 
Published: November 2007

AbstractThe response of Arctic ice masses to climate change is studied using ice cores containing information on past climatic and environmental features. Interpretation of this information requires accurate chronological data. Absolute dating of ice cores from sub-polar Arctic glaciers is possible using well-known radioactive layers deposited by atmospheric nuclear tests (maximum fallout in 1963) and the Chernobyl accident (1986). Analysis of several isotopes (3H, 137Cs) shows that 3H provides the most accurate dating of the 1963 maximum, as indicated also in comparison with results from total-beta measurements (90Sr and 137Cs). Mean annual net mass balances are derived from the dated ice cores from 1963 up to the date of the drillings. The 137Cs and 3H deposited by nuclear tests, after decay correction, are used to define a melt index for all 13 ice cores studied. The relative strength of melting and percolation post-depositional processes is studied on the basis of these 137Cs and 3H deposits.
Responses of various-sized alpine glaciers and runoff to climatic change
Authors: Baisheng Ye , Yongjian Ding , Fengjing Liu , Caohai Liu 
Published: November 2007

AbstractThis paper presents a glacier ice-flow model that simulates changes to alpine glaciers of various sizes and their runoff response to climate change in the Yili river basin in the Tien Shan mountains, northwestern China. It is suggested that the sensitivity of glaciers to climatic change is determined by glacier size. The change in glacial runoff does not keep pace with climatic change. As climate warms and glaciers retreat, the glacier runoff tends to increase and then decrease. The runoff peak and its timing depend not only on glacier size but also on the rate of air-temperature rise.
Quiescent-phase dynamics and surge history of a polythermal glacier: Hessbreen, Svalbard
Authors: Sund Monica , Eiken Trond 
Published: November 2007

AbstractHessbreen is a 5km2, polythermal glacier in southern Spitsbergen. It is believed to have surged at the end of the 19th century, and another surge started in 1969, not in 1972 as earlier studies suggested. The surge was probably triggered in the middle section of the glacier and affected the upper part approximately 4 years before including the whole glacier. Present velocities are low, increasing from 0.3m a-1 at the snout to 4.8 m a-1 above the equilibrium line. A distinct velocity reduction occurs where the glacier narrows. This suggests the velocities here are affected by the cold marginal and frontal ice. Large seasonal variations, with summer velocities of more than twice the winter velocities in the middle part of the glacier, indicate a seasonal change in the drainage system in this area. In the lower part there is no apparent sliding. The balance-flux estimate indicates that the actual ice flux is only about 50% of that required for steady state, so Hessbreen appears to be building up in the accumulation area. The surge duration is now estimated to be 8 years.
Probing the till beneath Black Rapids Glacier, Alaska, USA
Authors: Harrison William D. , Truffer Martin , Echelmeyer Keith A. , Pomraning Dale A. , Abnett Kevin A. , Ruhkick Richard H. 
Published: November 2007

AbstractA heavy down-hole hammer actuated from the surface by a light composition rope was used to place instrumented probes into the active, 7m thick, clast-rich till underlying a site on Black Rapids Glacier, Alaska, USA, where the ice is 500m thick. A till penetration of about 2.5m was obtained, and greater depths seem possible. The probes measured pore-water pressure and two axes of tilt, which they broadcasted, without wires, to a receiver just above the ice–till interface.
Can climate warming induce glacier advance in Taylor Valley, Antarctica?
Authors: Fountain Andrew G. , Neumann Thomas A. , Glenn Paul L. , Chinn Trevor 
Published: November 2007

AbstractChanges in the extent of the polar alpine glaciers within Taylor Valley, Antarctica, are important for understanding past climates and past changes in ice-dammed lakes. Comparison of ground-based photographs, taken over a 20 year period, shows glacier advances of 2-100 m. Over the past ~103years the climate has warmed. We hypothesize that an increase in average air temperature alone can explain the observed glacier advance through ice softening. We test this hypothesis by using a flowband model that includes a temperature-dependent softness term. Results show that, for a 2˚C warming, a small glacier (50 km2) advances ~25m and the ablation zone thins, consistent with observations. A doubling of snow accumulation would also explain the glacial advance, but predicts ablation-zone thickening, rather than thinning as observed. Problems encountered in modeling glacier flow lead to two intriguing but unresolved issues. First, the current form of the shape factor, which distributes the stress in simple flow models, may need to be revised for polar glaciers. Second, the measured mass-balance gradient in Taylor Valley may be anomalously low, compared to past times, and a larger gradient is required to develop the glacier profiles observed today.
The Kolka-Karmadon rock/ice slide of 20 September 2002: an extraordinary event of historical dimensions in North Ossetia, Russian Caucasus
Authors: Haeberli Wilfried , Huggel Christian , Kääb Andreas , Zgraggen-Oswald Sonja , Polkvoj Alexander , Galushkin Igor , Zotikov Igor , Osokin Nikolay 
Published: November 2007

AbstractOn 20 September 2002, an enormous rock/ice slide and subsequent mud-flow occurred on the northern slope of the Kazbek massif, Northern Ossetia, Russian Caucasus. It started on the north- northeast wall of Dzhimarai-Khokh (4780 ma.s.l.) and seriously affected the valley of Genaldon/ Karmadon. Immediate governmental actions, available scientific information, first reconstructions, hazard assessments and monitoring activities as well as initial expert judgments/recommendations are documented in order to enable more detailed analyses and modelling of the event by the wider scientific community. Among the most remarkable aspects related to this event are (1) the relation between the recent event and somewhat smaller but quite similar events that occurred earlier in historical times (1835, 1902), (2) the interactions between unstable local geological structures and complex geothermal and hydraulic conditions in the starting zone with permafrost, cold to polythermal hanging glaciers and volcanic effects (hot springs) in close contact with each other, (3) the erosion and incorporation of a debris-covered valley glacier largely enhancing the sliding volume of rocks, ice, firn, snow, water and probably air to a total of about 100 × 106m3, and (4) the astonishingly high flow velocities (up to 300 km h-1) and enormous length of travel path (18 km plus 15 km of debris/mud-flow). This extraordinary case illustrates that large catastrophic events in high mountain regions typically involve a multitude of factors and require integrated consideration of complex chains of processes, a task which must be undertaken by qualified groups of experts.
West Antarctic ice-stream discharge variability: mechanism, controls and pattern of grounding-line retreat
Authors: Hulbe Christina L. , Fahnestock Mark A. 
Published: November 2007

AbstractWest Antarctic ice streams show pronounced flow variability in their downstream reaches, with changes stranding formerly fast-flowing ice and redirecting discharge. A simple model, in which the temperature gradient in basal ice provides control of fast sliding in the downstream reach, can explain this behavior. Downstream thinning steepens the temperature gradient near the bed, increasing upward heat flow and the tendency toward basal freezing. The basal temperature gradient is steepest and the tendency toward basal freezing the strongest in ice that has experienced the most rapid downstream thinning, that is, the fastest-flowing ice. The most ‘successful’ rapid outflows are regions where basal water from elsewhere is likely to be consumed. Freezing here leads to episodic slow-downs and redirections of flow, the history of which appears in satellite imagery as ice rises, distorted streaklines, and margin jumps created when discharge migrates to areas with more favorable basal conditions. One compelling consequence of this process is that it makes catastrophic collapse less likely; if discharge currents are forced to slow when they become too fast (thin), then there may be an upper bound on the retreat rate and discharge flux of the West Antarctic ice sheet (WAIS) ice-stream system under the present climate.
A comparison of three methods of mass-balance determination in the Tuyuksu glacier region, Tien Shan, Central Asia
Authors: Hagg Wilfried J. , Braun Ludwig N. , Uvarov Vladimir N. , Makarevich Konstantin G. 
Published: November 2007

AbstractA photogrammetric survey in 1998 formed the basis for compiling a map of the Tuyuksu glacier region in the northern Tien Shan, Central Asia. Comparison with a map from 1958 enables calculation of the change in glacier volume over 40 years. The results are compared with direct annual measurements carried out continuously since 1956. Central Tuyuksu glacier shows a mass balance of –12.6 mw.e. for the geodetic method and –16.8 m for glaciological measurements. In view of the high accuracy of the maps, the discrepancy can be explained mainly by deficiencies in the glaciological measurements. Application of the precipitation–runoff model HBV-ETH represents the hydrological method of mass-balance determination and delivers specific mass-balance losses almost twice those indicated by the geodetic observations. This discrepancy is suspected to be caused by erroneous runoff measurements. The volume balance derived by the geodetic method is used to calibrate both the glaciological and the hydrological method.
Ice-flow-induced scattering zone within the Antarctic ice sheet revealed by high-frequency airborne radar
Authors: Matsuoka Kenichi , Uratsuka Seiho , Fujita Shuji , Nishio Fumihiko 
Published: November 2007

AbstractTo better understand how internal radar echoes depend on ice-flow conditions and radar polarization, we surveyed two basins in East Antarctica using 179 MHz airborne radar. We compared radar echoes from three ice-flow conditions: parallel sheet flow in the main stream of a basin, convergent flow towards an ice stream, and longitudinal compression by nunataks. We detected a distinct zone of high radar scattering several hundred meters thick at middle depths in the latter two regions. This high-scattering zone was detected only when the radar polarization plane was parallel to the compression axis in ice. Such a high-scattering zone was not found in the parallel-flow region, regardless of the polarization. Using a recently developed theory of radar scattering in ice, we interpret the high-scattering zone as being caused by crystal-orientation-fabric alternations among adjacent ice layers due to difference in horizontal strain components. We argue that the spatial variation of the high-scattering zone is crucial for understanding past and present flow features.
Distribution of soluble impurities in cold glacial ice
Authors: Barnes Piers R.F. , Wolff Eric W. 
Published: November 2007

AbstractUnderstanding the microstructure of ice underpins the interpretation of ice-core measurements and many ice-sheet properties. A detailed study of polar snow and ice using scanning electron microscope (SEM) and X-ray analysis revealed the micro-structural distribution of soluble impurities. Sublimation under vacuum (etching) concentrated impurity from both the bulk and grain boundaries on to the specimen surfaces in detectable quantities. Sublimation in the cold room before examination (pre-etching) collected previously unobservable quantities of impurity at triple junctions. A heterogeneous distribution of impurities was observed. Chloride was frequently found to originate from the lattice, but not usually at triple junctions. Other impurities, particularly sodium chloride, were detected at grain boundaries and bubble surfaces. Sulphate was often found at triple junctions in specimens containing a high bulk concentration of the acid, frequently in conjunction with cations. This suggests the possibility that veins were only filled with significant amounts of impurity when the surrounding grain boundaries were saturated. The model of impurity arrangement inferred from the results reconciles differences between previous SEM studies; additionally it is consistent with and explains recent electrical conduction observations. The disconnected arrangement of impurity-filled grain boundaries and veins limits opportunities for significant post-depositional solute movement.
Vertical-strain measurements in firn at Siple Dome, Antarctica
Authors: Hawley Robert L. , Waddington Edwin D. , Lamorey Gregg W. , Taylor Kendrick C. 
Published: November 2007

AbstractWe measured vertical strain in the firn at Siple Dome, Antarctica, using two systems, both of which measure relative displacements over time of metal markers placed in an air-filled borehole. One system uses a metal-detecting tuned coil, and the other uses a video camera to locate the markers. We compare the merits of the two systems. We combine steady-state calculations and a measured density profile to estimate the true vertical-velocity profile. This allows us to calculate a depth-age scale for the firn at Siple Dome. Our steady-state depth-age scale has ages ≈10-15% younger at any given depth when compared to depth-age scales derived by layer counting in a core 40 m away. The age of a visible ash layer at 97 m in the core is 665 ± 30 years, in agreement with a similar analysis conducted at Taylor Dome, Antarctica, where the same ash is also seen, providing an additional dated tie point between the two cores.
Two-dimensional electrical stratigraphy of the Siple Dome (Antarctica) ice core
Authors: Taylor Kendrick C. , Alley Richard B. 
Published: November 2007

AbstractA two-dimensional array of electrical conductivity measurements (ECM) has been used to image the acidity of the Siple Dome (Antarctica) ice core in a vertical plane. Annual layering and possible stratigraphic discontinuities are apparent. A brief disruption to the chemical stratigraphy is detected at 680 m. Below 800 m, weaker layering occurs and is interpreted as the result of post-depositional migration of chemical species. This technique provides a way to observe the horizontal continuity of chemical layers in an ice core and identify some types of flow irregularity.
Chemical properties of brackish water ice in the Bothnian Bay, the Baltic Sea
Authors: Granskog Mats A. , Virkkunen Kristiina , Thomas David N. , Ehn Jens , Kola Harri , Martma Tõnu 
Published: November 2007

AbstractThe behavior of majorions, δ18O, dissolved organic carbon (DOC) and trace elements was studied during the initial freezing of low-saline water (3 practical salinity units) in a freezing experiment. Samples were also collected from first-year sea ice from pack ice in the Bothnian Bay, northern Baltic Sea. During initial ice formation, the major-ion ratios in sea ice indicated variable behavior, with some ions showing relative enrichment (sulfate, calcium and magnesium), conservative behavior (sodium) or relative depletion (potassium) compared to sea water at the same salinity. DOC, iron and aluminum showed enrichment in the ice, while zinc was depleted to salinity. Lead was detected in surface snow-ice layers only, implying atmospheric accumulation. First-year sea ice, with a variable growth and thermal history, showed behavior for major ions similar to that observed in new ice. However, for trace elements the picture was much more complicated, most likely due to active secondary processes such as atmospheric supply and biological activity. Ice growth has a potential impact on the chemical budgets and cycling of some elements, especially those which are selectively rejected/retained during sea-ice formation, particularly in the shallow parts of the Bothnian Bay covered with a land-fast ice cover.
The basal speed of valley glaciers: an inverse approach
Authors: Truffer Martin 
Published: November 2007

AbstractGeophysical inverse methods are used to calculate the basal motion of a glacier. They are applied to a one-dimensional forward model that can be linearized to make the analysis simpler. The inverse method finds a solution that fits the data within a given error. It selects for smooth solutions to discriminate against unrealistic oscillations. The method is applied to a simple model glacier of uniform shape and thickness to test how well a given basal motion field can be reconstructed. It shows, as expected, that optimizing for smoothness lowers maxima and increases minima of the solution. A step change in basal velocity is drawn out in the inversion over a distance that is given by the half-width of a resolving function. This is typically about three times the ice thickness, but is also affected by the sampling rate of the data. The method is then applied to two glaciers where suitable data are available: Brown Glacier on Heard Island, southern Indian Ocean, and McCall Glacier in the Brooks Range, Alaska, U.S.A. The McCall results agree well with earlier estimates of basal motion.
Automatic glacier ablation measurements using pressure transducers
Authors: Bøggild Carl Egede , Olesen Ole B. , Andreas P.Ahlstrøm , Jørgensen Peer 
Published: November 2007

AbstractAn instrument is described that automatically records ice ablation while eliminating the need for ablation stakes. A pressure transducer placed at the bottom of a hole drilled into the ice is connected by a hose to a bladder lying on the surface. Ice ablation is detected as a reduction in the hydrostatic pressure measured by the transducer.
A sedimentological and isotopic study of the origin of supraglacial debris bands: Kongsfjorden, Svalbard
Authors: Hubbard Bryn , Glasser Neil , Hambrey Michael , Etienne James 
Published: November 2007

AbstractDebris bands associated with supraglacial moraines and associated basal deposits have been logged and sampled for their ice and debris at three glaciers in northwest Spitsbergen, Svalbard. Physical properties, including sediment concentrations, sediment particle-size distributions, clast macro-fabrics, and oxygen isotope compositions, indicate that all transverse and some longitudinal debris bands originate from the basal zone of these glaciers. Transverse supraglacial bands are composed of extensive stratified-facies basal ice that is enriched in 18O and which contains polymodal debris with spatially consistent clast fabrics. These properties suggest initial formation as basal ice and subsequent elevation into an englacial position by thrusting rather than formation as crevasse fills. The formation of longitudinal debris bands results from laterally compressive folding in response to the convergence of multiple flow units into a narrow glacier tongue. In common with transverse debris bands, longitudinal bands appear to be composed of stratified basal ice. The bands exposed at the surface of austre Brøggerbreen comprise two subfacies, strongly suggesting that the glacier was at least partially warm-based in the past, when the basal ice formed.