bluuebunny/crossref_metadata_2025_split huggingface dataset:
Can the mass balance of the entire glacier area of the Tien Shan be estimated?
Authors: Dyurgerov M.B. , Kunakhovitch M.G. , Mikhalenko V.N. , Sokalskaya A. M. , Kuzmichenok V. A. 
Published: September 2017

The total area of glacierization of the Tien Shan in the boundary area of the USSR is about 8000 km2. The computation of mass balance was determined for this area in 12 river basins.In computation procedure, the vertical profile of snow accumulation in these regions and exponential dependence of variation of ablation with altitude are used. Thus the mass balance in each basin, bn, was calculated on the basis of these curves and represented in its relation with the equilibrium line altitude (ELA). It is shown that the relation ELA = f(bn) is linear when the range of bn values is close to zero, and in all altitude intervals this relation can be described by hypsographic curves, in all basins bn positive up to an ELA elevation of 3450 to 3500 m a.s.l. For average annual altitude of ELA, bn is negative for all regions. So the glaciers of these mountains add about 4 km3 of water to the total annual runoff.
Glacial and lake fluctuations in the area of the west Kunlun mountains during the last 45 000 years
Authors: Chaohai Liu , Shijie Li , Yafeng Shi 
Published: September 2017

There appear to have been several important glacial advances on the southern slope of the west Kunlun mountains, Tibetan Plateau, since 45 000 a BP. Based on the record of alternating till and lacustrine sediments and 14C determinations, these advances are dated to 23 000–16 000, 8500–8000, and 4000–2500 a BP, and to the 16th–19th century AD, with regional variations occurring during each of the advances. The glaciation of 23 000–16 000 a BP is equivalent to the last glacial maximum (LGM) and its scope and scale were much larger than any of the others.Lake changes are a response to both tectonic uplift of the plateau and global climatic change. With regard to the latter, both changes in precipitation and changes in the extent of glaciation can affect lake levels. High lake levels occurred during interstadial conditions between 40 000 and 30 000 a BP, when the area experienced a relatively warm and humid climate, and during the LGM, between 21 000 and 15 000 a BP. During the Holocene, lakes have been shrinking gradually, coincident with the dry climate of this period of time.
Field experiments on “living” snow fences
Authors: Naaim-Bouvet Florence , Mullenbach Pierre 
Published: September 2017

In Franee, drifting snow is generally controlled using artificial snow fences. Living snow fences are not a new concept but they have only been used on a limited scale. Research directly related to natural plant barriers is limited. We therefore decided to study the behaviour of species that would survive and grow satisfactorily in the French Alps.In the first experiment, we compared the storage capacity of several different kinds of living fences consisting of pruned spruces, unpruned spruces and sorbs.Field observations during the winter of 1995-96 proved that deciduous trees such as sorbs are effective, and that pruning the lower 50 cm is not effective at the end of the season because of the weight of snow on low branches.However, the use of natural plant barriers has disadvantages: a living snow fence takes time to reach an effective height and is difficult to establish on windy sites at a high altitude. This is a real problem. Therefore, in a second experiment, we studied the death rate of larches planted behind a fence. We noticed that the snow fence had several effects, snow accumulation (until the planted trees grew up) and protection of the planted trees.
Simulations of dense-snow avalanches on deflecting dams
Authors: Irgens Fridtjov , Schieldrop Bonsak , Harbitz Carl B. , Domaas Ulrik , Opsahl Runar 
Published: September 2017

Two models simulating snow avalanches impacting retaining dams at oblique angles of incidence are presented.First, a lumped-mass model applying the Voellmy-Perla equation is used to calculate the path of the centre-of-mass along the side of a retaining dam.Secondly, a one-dimensional continuum model, applying depth-integrated equations of balance of mass and linear momentum, is expanded to take into account that real avalanche flows are three-dimensional. The centre-line of the avalanche path is determined by the flowing material as it progresses down the channelized avalanche path. The nonlinear constitutive equations comprise viscosity, visco-elasticity and plasticity.Both models are calibrated by simulations of a registered avalanche following a strongly curved channel. The path and the run-up height of the avalanche on the natural deflecting dam with oblique angle of incidence as calculated by the two models, are compared with the observations made.
Infrasonic monitoring of snow-avalanche activity: What do we know and where do we go from here?
Authors: Adam V. , Chritin V. , Rossi M. , Lancker E. Van 
Published: September 2017

The first recordings of acoustic signals associated with avalanches go back to the 1970s when premonitory low-frequency acoustic emission was observed in the snow cover just before the setting off of natural avalanches (Sommerfeld, 1977; Sommerfeld and Gubler, 1983). Recently, it has been demonstrated that avalanches also produce strong infrasonic vibrations in air during their movement. These infrasonic vibrations propagate great distances and can follow the natural relief. It was then a question of automatically detecting this emission to monitor avalanche activity, with a view to improving forecasting and assisting in the study of certain aspects of avalanche dynamics.With the double aim of pursuing investigations on the mechanics of the acoustic emission from avalanches and designing an automatic detection system, our laboratory has developed specific instrumentation, the essential link of which is an array of infrasonic microphones associated with a goniometer. Systematic measurements of the infrasonic emissions are being carried out, not only of the natural or released avalanches themselves but of all events with the aim of characterizing the former in relation to “infrasonic noise”.
Global distribution of snow avalanches and changing activity in the Northern Hemisphere due to climate change
Authors: Glazovskaya T. G. 
Published: September 2017

Snow avalanches occur in the mountains of all continents and climatic zones. The lower boundary of avalanche distribution rises from sea level in polar and temperate zones to 6000 m in the tropics. Four altitudinal belts of avalanching are distinguished: (I) permanent snow; (II) stable seasonal snow cover; (III) unstable snow cover; and (IV) rare snowfalls. Most avalanche-danger areas of the world belong to the stable seasonal snow-cover bell.Using data from a GFDL Q-flux Model, we estimated possible changes of the main characteristics of the avalanche regime in the Northern Hemisphere: depth of snow cover, duration of the avalanche-prone period and number of days with avalanche-prone snowfalls. At the beginning of the twenty-first Century, there will likely be a smoothing of the sharp differences in avalanche activity between various mountain regions of the World. Avalanche activity should be less in the most active regions and it is likely to increase in regions with low avalanche activity.
Energy balance and formation of sun crust in snow
Authors: Ozeki Toshihiro , Akitaya Eizi 
Published: September 2017

The mechanism of sun-crust formation was investigated through laboratory experiments in a cold wind tunnel. The experiments were carried out by controlling the energy balance and the sun crust formed was consistent with that observed in Nature, i.e. a thin ice layer composed of ice particles and cavities due to internal melting beneath the sun-crust layer. The surface-cooling rate was between −50 and −100 W m−2, and the absorption of shortwave radiation exceeded 200 W m−2. The energy balance during the formation of the sun crust is consistent with the data observed in Nature.The sources of H2O for the sun-crust formation were investigated through changes in δ18O. Taking into account that the δ value of sun crust was larger than that of the snow beneath it and the calculations of the latent-heat emission with the sun-crust formation, it was concluded that the retention of meltwater by capillary force and refreezing in a thin layer was the dominant mechanism of this metamorphism.
Short-term numerical avalanche forecast used operationally at Météo-France over the Alps and Pyrenees
Authors: Durand Yves , Giraud Gérald , Mérindol Laurent 
Published: September 2017

Avalanche-hazard estimation for the present and the following days is one of the main tasks of the avalanche forecaster. For 4 years, some have used the results of a series of automatic numerical models in the Alpine massifs of France. Thee programs describe in real time the main meteorological conditions (SAFRAN), the evolution of the snow cover (Crocus) and the resulting avalanche risks [MÉPRA) at different elevations, slopes and aspects of the massifs considered.This paper presents the latest evolution of this automatic tool. With the new version it is now possible to provide 1 day forecasts of the state of the snow cover over the massifs of both the Alps and Pyrenees, including the main characteristics of the snowpack and an assessment of the corresponding avalanche hazards.To achieve this result, the main changes were with SAFRAN. Two combined methods are used within the same package: adaptations of larger-scale meteorological forecasts and use of observations of analogous weather situations from the past. These two approaches are complementary especially for evaluating precipitation where the second solution has important fine-scale information while the first exhibits important local biases.Validation of this new application was done carefully and proved the quality of the method, now used in real-time by local forecasters. We present some validation results, concerned both with forecasted precipitation fields at the scale of the massif and forecasted avalanche risks deduced from MÉPRA.
Inferential statistics to verify prediction models
Authors: Bolognesi R. 
Published: September 2017

Models are powerful tools if their outputs are relevant!Therefore, knowing the reliability of models is essential for people who wish to use them, as well as for researchers who attempt to improve them. Whatever the nature of the model output, objective evaluation consists of comparing predicted or calculated events with observed events.Such comparison can only focus on available samples of observed events. Obviously, the results depend on the choice of the sample. However, inferential statistics enable one to extend results obtained from a random sample to general use.An unbiased method of testing boolean avalanche-prediction models is suggested: the validity of this type of model should be characterized by the probability that the proportion of correct forecasts is within a given confidence interval. This interval is calculated from the sample size, according to the Gaussian table.This unrestricted principle can be used to prove all kinds of static models, if ever their outputs are verifiable, enabling one to calculate the ratios of correct forecasts as well as the ratios of well-predicted events and can also be extended to verify probabilistic predictions.
Temporal evolution of physical and dielectric properties of sea ice and snow during the early melt season: observations from SIMS ’90 experiment
Authors: Shokr Mohammede.E , Barber David G. 
Published: September 2017

AbstractThe first field experiment in the 5 year seasonal Sea Ice Monitoring Site (SIMS) program was conducted in Resolute Passage, Canadian Eastern Arctic, between 15 May and 8 June 1990. This period signals the early melt season of sea ice in that region. A standard array of ice and snow measurements was collected on a daily basis from first-year and multi-year ice to monitor temporal evolution. Measurements included ice salinity, ice temperature and ice-surface roughness, snow salinity, snow temperature, snow density and snow depth. The complex dielectric constant of sea ice was computed from these measurements. Rapid desalination of first-year ice was noticed in the surface layer. Towards the end of the experiment period, salinities of the snow-hoar layer were higher than those of the ice-surface layer. Variation in air temperature is replicated by ice-surface temperature but not by the salinity or dielectric properties. No temporal variation in permittivity and dielectric loss was observed for first-year ice, but a slight increase in both parameters was observed for multi-year ice. As a result, a slight decrease in the microwave-penetration depth was observed for multi-year ice. Physical properties of ice and snow were compared against results obtained from other experiments conducted in different ice-formation regions in the late winter and in the early melt season.
Winter Sea-ice mapping from multi-parameter synthetic-aperture radar data
Authors: Rignot Eric , Drinkwater Mark R. 
Published: September 2017

AbstractThe limitations of current and immediate future single-frequency, single-polarization, space-borne SARs for winter sea-ice mapping are quantitatively examined, and improvements are suggested by combining frequencies and polarizations. Ice-type maps are generated using multi-channel, air-borne SAR observations of winter sea ice in the Beaufort Sea to identify six ice conditions: (1) multi-year sea ice; (2) compressed first-year ice; (3) first-year rubble and ridges; (4) first-year rough ice; (5) first-year smooth ice; and (6) first-year thin ice. At a single polarization, C- (λ = 5.6 cm) and L- (λ = 24 cm) band frequencies yield a classification accuracy of 67 and 71%, because C-band confuses multi-year ice and compressed, rough, thick first-year ice surrounding multi-year ice floes, and L-band confuses multi-year ice and deformed first-year ice. Combining C- and L-band improves classification accuracy by 20%. Adding a second polarization at one frequency only improves classification accuracy by 10–14% and separates thin ice and calm open water. Under similar winter-ice conditions, ERS-1 (Cvv) and Radarsat (CHH) would overestimate the multi-year ice fraction by 15% but correctly map the spatial variability of ice thickness; J-ERS-1 (LHH) would perform poorly;and J-ERS-1 combined with ERS-1 or Radarsat would yield reliable estimates of the old, thick, first-year and thin-ice fractions, and of the spatial distribution of ridges. With two polarizations, future single-frequency space-borne SARs could improve our current capability to discriminate thinner ice types.
Short-term velocity variations and basal coupling near a bergschrund, Storglaciären, Sweden
Authors: Hanson Brian , Hooke Roger leb 
Published: September 2017

AbstractDistance measurements using an automated electronic distance-measurement system in the north cirque of Storglaciären, Sweden, during the summer of 1989, revealed a diurnal variation in glacier speed. Amplitude and timing of the diurnal cycle correlate well with the timing and intensity of the diurnal temperature cycle, indicating that speed responds to variations in daily melt with a lag of approximately 4 h. One 2 d period of non-diurnal velocity variations corresponded with a large rainfall event. Finite-element modeling suggests that these velocity variations must be closely related to water inputs in the cirque rather than to longitudinal coupling with lower parts of the glacier.
An Observation of roll waves in a supraglacial meltwater channel, Harlech Gletscher, East Greenland
Authors: Carver Steve , Sear Dave , Valentine Eric 
Published: September 2017

AbstractObservations of pulsating flow conditions in a supraglacier meltwater channel on Harlech Gletscher, East Greenland, are reported. Waves of water with turbulent wave fronts and smooth recessive limbs were observed passing downstream at regular intervals of 6-7 s. Peak channel discharge was estimated at 0.5-1.0 m3 s−1, in between which discharge was zero. It is suggested that the phenomenon as observed was due to the formation of roll waves in response to channel morphology and prevalent discharge conditions. Measurements of channel morphology are given together with calculations of critical flow conditions, supporting the hypothesis of roll waves in a natural ice channel. A brief introduction to roll waves and the theory regarding their formation is included.
Air-hydrate crystals in deep ice-core samples from Vostok Station, Antarctica
Authors: Uchida T. , Hondoh T. , Mae S. , Lipenkov V.YA. , Duval P. 
Published: September 2017

AbstractMicroscopic observation of air-hydrate crystals was carried out using 34 deep ice-core samples retrieved at Vostok Station, Antarctica. Samples were obtained from depths between 1050 and 2542 m, which correspond to Wisconsin/Sangamon/Illinoian ice. It was found that the volume and number of air-hydrate varied with the climatic changes. The volume concentration of air-hydrate in the interglacial ice was about 30% larger than that in the glacial ice. In the interglacial ice, the number concentration of air-hydrate was about a half and the mean volume of air-hydrate was nearly three times larger than that in the glacial-age ice. The air-hydrate crystals were found to grow in the ice sheet, about 6.7 × 10−12 cm3 year-1, in compensation for the disappearance of smaller ones. The volume concentration of air-hydrate was related to the total gas content by a geometrical equation with a proportional parameter α. The mean value of α below 1250 m, where no air bubbles were found, was about 0.79. This coincided with an experimentally determined value of the crystalline site occupancy of the air-hydrate in a 1500 m core obtained at Dye 3, Greenland (Hondoh and others, 1990). In the depth profile of calculated α for many samples, α in the interglacial ice was about 30% smaller than that in the glacial-age ice.
137Cs Gamma-ray detection at Summit, Greenland
Authors: Dunphy Philip P. , Dibb Jack E. 
Published: September 2017

AbstractGlobal fall-out from atmospheric testing of thermonuclear weapons produced horizon markers corresponding to the initiation of testing in 1953 and the maximum fall-out in 1963. The radioactive isotope 137Cs associated with these events has a half-life of 30.2 years. Therefore, with the appropriate radiation detectors, this fall-out can be used as a long-term temporal indicator in glaciers and snowpack. A prototype γ-ray detector system was successfully tested and was used to make in-situ measurements of the 137Cs marker in a borehole at Summit, Greenland. The system consisted of a 7.6 cm by 7.6 cm NaI(Tl) scintillation crystal/photomultiplier detector, commercial pre-amplifier, amplifier and power supplies, and a microcomputer-based pulse-height analyzer. The measurements were made in boreholes of 25.4 cm and 12.7 cm diameter to depths of 22 m. Based on the results reported here, the γ-ray detection technique promises to be a powerful way to locate quickly horizon markers in the field.
Measuring glacier outflows using a computerized conductivity system
Authors: Kite Geoff 
Published: September 2017

AbstractThe traditional method of calculating glacier outflows by measuring velocities and areas is difficult, inaccurate and sometimes dangerous in fast mountain streams. The salt-dilution method offers a more accurate alternative but, until now, its use has been restricted because of the difficulty of mixing chemical solutions and measuring chemical concentrations in the field. A computer program has been written which uses a laptop microcomputer to control measurements of stream conductivity and which quickly computes the stream flow directly in the field. The development of this method is described and examples are presented of the application of the method for glaciers in the Rocky Mountains and the Coast Mountains of Canada.
Ploughing of subglacial sediment
Authors: Fischer URS H. , Clarke Garry K. C. 
Published: September 2017

AbstractMechanical conditions at the base of Trapridge Glacier, Yukon Territory, were investigated using a “ploughmeter”. We describe the physical characteristics and the theory of this new instrument as well as its operation. Observational results reveal variations in ploughmeter response that might be attributed to spatial variability in subglacial processes or spatial variation in sediment granulometry. Quantitative analysis of the interaction of the ploughmeter with the basal layer yields estimates of rheological parameters. If the sediment is assumed to behave as a Newtonian viscous fluid, the estimated effective viscosity is 3.0 × 109−3.1 × 1010Pas; if it is assumed to behave as an ideal plastic solid, the estimated yield strength is 48–57 kPa. In both cases, the estimated shear resistance of subglacial material is comparable to but somewhat less than that required to balance fully the applied basal shear stress.
Melt-layer thickness measurements during crushing experiments on fresh-water ice
Authors: Gagnon R.E. 
Published: September 2017

AbstractA stainless-steel platen, with a centrally located pressure sensor on the front face, has been used to crush mono-crystalline, bubble-free fresh-water ice samples. Two electrical conductors, located on the face of the pressure sensor, were connected to a bridge circuit so that the presence of liquid between the two conductors could be detected and its thickness measured. Video records of the ice/ steel contact zone during crushing were obtained by mounting samples on a thick Plexiglas plate which permitted viewing through the specimen to the ice/steel interface. Total load and pressure records exhibited a sawtooth pattern due to the compliance of the ice and the testing apparatus, and spalling of ice from the contact zone. When the region of contact was in the vicinity of the pressure transducer, liquid was detected and peaks occurred in the liquid sensor output when load drops occurred. Contact between the platen and the ice consisted of low pressure zones of highly damaged crushed and/or refrozen ice, opaque in appearance, and transparent, high-pressure regions of relatively undamaged ice. Upper limits for the liquid-layer thickness on the high-pressure undamaged ice were ~3 µm on the ascending sides of the sawteeth in the load records and ~ 21 µ on the sharp descending sides.
Strain in the ice sheet deduced from the crystal-orientation fabrics from bare icefields adjacent to the Sør-Rondane Mountains, Dronning Maud Land, East Antarctica
Authors: Fujita S. , Mae S. 
Published: September 2017

AbstractStructural analyses of ice collected from the bare ice surface in the region of the Sør-Rondane Mountains were carried out. Crystal-orientation fabrics and the disposition of surface cracks were investigated to determine the stress/strain configuration in the ice sheet near the mountains. Single-maximum fabric patterns with the axis of the maximum roughly perpendicular to the flow line on the horizontal plane were observed. It was deduced from the observations that the ice exhibits a fabric pattern indicating that the ice sheet is subjected to vertical shear strain between the ice flow and the nunataks.
Capture and scanning electron microscopy of individual snow crystals
Authors: Wolff E. W. , Reid A. P. 
Published: September 2017

AbstractA snow crystal has been successfully collected on to a scanning electron microscope (SEM) stub in central Greenland. It was preserved at liquid-nitrogen temperature for 5 months, prior to examination in the SEM. This is believed to be the first time a snow crystal has been observed directly in the SEM and offers some new experimental methods for understanding crystals and their chemistry.