bluuebunny/crossref_metadata_2025_split huggingface dataset:
On probability analysis in snow avalanche hazard zoning
Authors: Harbitz Carl , Harbitz Alf , Nadim Farrokh 
Published: November 2007

AbstractThe reduced societal acceptance of living in regions exposed to snow avalanches, and the increased economic consequences when houses are located within a hazard zone, highlight the uncertainty concerning avalanche run-out prediction. The limitations of today’s zoning procedures are especially pronounced in potential avalanche terrain where there are few observations of snow avalanches, where old buildings are present in the potential run-out zone, and where the local climate does not favour severe snow accumulation. This paper combines a mechanical probabilistic model for avalanche release with a statistical/topographical model for avalanche run-out distance to obtain the unconditional probability of extreme run-out distance. For the mechanical model, a first-order reliability method (FORM) and Monte Carlo simulations are compared. The interpretation of the statistical/topographical model either as an extreme value model or as a single value model is discussed. Furthermore, both a classical approach where the probability of an avalanche occurring is a constant, and a Bayesian approach with stochastic probability, are compared. Finally, example applications in hazard zoning are presented, with emphasis on how the influence of historical observations, local climate, etc., on run-out distance can be quantified in statistical terms and how a specified certainty level can be found from constructing confidence intervals for, for example, the most likely largest run-out distance during various time intervals.
Winter 1999: a valuable test of the avalanche-hazard mapping procedure in Switzerland
Authors: Gruber Urs , Margreth Stefan 
Published: November 2007

AbstractIn Switzerland three large snowfall periods led to numerous large avalanche events, causing the deaths of 17 people, damage to about 1000 buildings and blockage of many important traffic systems. This situation was a valuable test of the avalanche-hazard mapping procedure developed in Switzerland since the last extreme avalanche winter in 1951. In most cases, the avalanches stopped within the avalanche-hazard zones. However, approximately 40 of about 1200 large avalanche events passed the limits of the existing hazard zones. The primary deficiency was underestimation of the hazard of powder-snow avalanches. The other reason the hazard-zone boundaries were passed was multiple avalanche events in a single track within a short time period. In addition, some fracture depths were larger than those used in avalanche-dynamics calculations. Therefore, the guideline assumptions for defining the fracture depths are questioned. Winter 1999 impressively underlined the danger of avalanches in mountainous regions. It emphasized the importance of avalanche-hazard mapping, showed the existing deficiencies and provided a large amount of field data that will help to improve our knowledge of avalanche dynamics.
The skier’s zone of influence in triggering slab avalanches
Authors: Schweizer Jürg , Camponovo Christian 
Published: November 2007

AbstractIn recent years, most avalanche fatalities have been due to dry-snow slab avalanches triggered by the victims themselves during recreational activities, at least in countries where recreational skiing takes place, as in Western Europe and North America. Simple analysis suggests, and previous measurements have shown, that the skier’s dynamic impact is relevant for triggering, decreasing with increasing depth within the snow cover and depending on the layering of the snow cover. The stress distribution below a skier in the snow cover is not known, but is important in view of the critical area required for fracture propagation preceding dry-snow slab avalanche release. The skier’s zone of influence was measured with load cells buried within the snow cover in a level study plot for different depths. The size of the area of influence is of the order of a few 0.1 m2, but also depends on the weak-layer strength. Stresses in the snow cover below skiers who walk behind each other are not cumulative. The effect on the influence size is in accordance with the independent estimate for the critical size (0.1–1 m) for fracture propagation in the case of rapid loading. It supports the hypothesis that skiers induce a brittle fracture within the weak layer or at a weak interface between layers, leading under certain conditions to slab release, without necessarily hitting a pre-existing flaw.
Impact of spatial resolution on the hydrological simulation of the Durance high-Alpine catchment, France
Authors: Etchevers Pierre , Durand Yves , Habets Florence , Martin Eric , Noilhan Joël 
Published: November 2007

AbstractThe water balance of the mountainous Durance river catchment, French Alps, is simulated from 1981 to 1994 with a soil-vegetation-atmosphere transfer (SVAT) model. Particular attention is paid to the snow-cover evolution using a detailed model of the snowpack evolution. The results are validated by comparison of the simulated discharges calculated by the SVAT with daily observations at three gauging stations located in the watershed. Three different spatial resolutions are used (1, 8 and 46 km) in order to evaluate the impact on the surface-water-budget results. Comparison with the finest resolution indicates the need for sub-grid-scale parameterization for the model with larger resolution.
Buoyancy effects induced by drifting snow particles
Authors: Bintanja Richard 
Published: November 2007

AbstractSnowdrift is one of the many manifestations of two-phase flows in which the inherently stably stratified drift-density profile acts to destroy turbulence. This can be quantified by using an appropriate “particle” Richardson number, equivalent to thermally stratified flow. This Richardson number is proportional to the mean fall velocity of the particles (averaged over the particle-size spectrum) and the drift density and therefore depends strongly on height above the surface. It exhibits a maximum close to the surface, where drift densities are largest. It then decreases to minimum values at intermediate heights, above which Richardson numbers increase with height. The particle Richardson number and the associated decrease in turbulent exchange coefficient depend strongly on wind speed, particle-eddy exchange coefficient and mean particle radius It is found that particle-buoyancy effects in snowdrift are non-negligible for large wind speeds and large particle-eddy exchange coefficients.
Drifting-snow studies over an instrumented mountainous site: II. Measurements and numerical model at small scale
Authors: Michaux Jean-Luc , Naaim-Bouvet Florence , Naaim Mohamed 
Published: November 2007

AbstractThe Érosion torrentielle, neige et avalanche (Etna) unit of CEMAGREF and the Centre d’Etudes de la Neige of Météo-France have been working on snowdrift for 10 years. A numerical model was developed at CEMAGREF to simulate snowdrift (Naaim and others, 1998). To validate this model on in situ data, a high-altitude experimental site was developed, located at 2700 m a.s.l. at the Lac Blanc Pass near the Alpe d’Huez ski resort. It is a nearly flat area and faces winds primarily from north and south. After describing the experimental site, we present the processed data of winter 1998/99. First, we analyze the data from CEMAGREF’s acoustic snowdrift sensor. It is sensitive to snow depth and snow-particle type, so additional calibration is necessary. Nevertheless, it allowed us to study non- stationary aspects of drifting snow. An analysis of gust factors for wind and drifting snow indicates that strong wind-gust factors exist in the mountains, and that drifting snow is more important during a regular and strong wind episode than during high wind-gust periods. Therefore, the numerical model presented here uses only the recorded mean wind speed. The model, which attempts to reproduce several days of storm, takes into account the modification of input parameters (e.g wind speed) as a function of time. The comparison between numerical results and measurements for a given meteorological event shows good agreement.
Characteristics of terrain, snow supply and forest cover for avalanche initiation caused by logging
Authors: McClung D. M. 
Published: November 2007

AbstractThis paper contains statistical analyses of parameters to characterize starting zones of destructive avalanches which have resulted from clear-cut logging in British Columbia, Canada. Data from 76 avalanche sites in the Coast Mountains (western British Columbia) and the Columbia Mountains (eastern British Columbia) are analyzed. The parameters include a selection which characterize snow supply (related to potential avalanche frequency), avalanche magnitude and those which are known to affect avalanche formation including terrain features, vegetation density, vegetation height and ground surface roughness. The results provide the data framework for possibly preventing future disasters by altering logging plans.
The effect of wind on the snow cover
Authors: Sokratov Sergey A. , Sato Atsushi 
Published: November 2007

AbstractResults of wind-tunnel investigations of the propagation of air within snow showed that the process responsible for causing horizontal air flux in the pore space of snow was not necessarily related to specific surface topography. The reasons for this flux formation are: (i) the near-surface wind characteristics, such as the frequency of the pressure variation related to the turbulent character of the near-surface wind; (ii) the structure of the near-surface snow, responsible for the air exchange between the atmosphere and the pore space; and (iii) the temperature difference between the snow and the atmosphere, forming the air-density difference which augments or decreases the air exchange. This paper summarizes the experimentally observed effects that the wind and the air flux generated in the pore space had on snow. These included isothermal temperature distributions throughout the artificial snow cover, snow-density change and snow recrystallization.
The influence of tree and branch fracture, overturning and debris entrainment on snow avalanche flow
Authors: Bartelt P. , Stöckli V. 
Published: November 2007

AbstractA simple center-of-mass avalanche model that accounts for avalanche flow in forests is presented. The model applies the principle of conservation of energy to calculate the deceleration of avalanches caused by tree fracture, overturning and debris entrainment. The model relates the physical properties of forests (tree spacing, tree age, tree type, soil conditions) to avalanche flow. Modified dry-Coulomb and velocity-dependent friction parameters commonly used in avalanche runout calculations are derived. Example calculations demonstrate how the model can be applied to back-calculate observed avalanche events. The model quantitatively explains why large avalanches can destroy forests without significant deceleration. Furthermore, it shows why tree fracture consume/little of the avalanche’s energy. Finally, the model reveals how protective forests in avalanche tracks can be maintained over time to provide the best protective capacity against snow avalanches.
The response of the Greenland ice sheet to climate changes in the 21st century by interactive coupling of an AOGCM with a thermomechanical ice-sheet model
Authors: Huybrechts Philippe , Janssens Ives , Poncin Chantal , Fichefet Thierry 
Published: November 2007

AbstractWe present results from a greenhouse warming experiment obtained from an atmosphere–ocean–sea-ice general circulation model that is interactively coupled with a three-dimensional model of the Greenland ice sheet. the experiment covers the period 1970–2099 and is driven by the mid-range Intergovernmental Panel on Climate Change SRESB2 scenario. the Greenland model is a thermomechanical high-resolution (20 km) model coupled with a viscoelastic bedrock model. the melt-and-runoff model is based on the positive degree-day method and includes meltwater retention in the snowpack and the formation of superimposed ice. the atmospheric–oceanic general circulation model (AOGCM) is a coarse-resolution model without flux correction based on the Laboratoire de Météorologie Dynamique (Paris) LMD 5.3 atmospheric model coupled with a primitive-equation, free-surface oceanic component incorporating sea ice (coupled large-scale ice–ocean (CLIO)). By 2100, average Greenland annual temperature is found to rise by about 4.5˚C and mean precipitation by about 35%. the total fresh-water flux approximately doubles over this period due to increased runoff from the ice sheet and the ice-free land, but the calving rate is found to decrease by 25%. the ice sheet shrinks equivalent to 4 cm of sea-level rise. the contribution from the background evolution is not more than 5% of the total predicted sea-level rise. We did not find significant changes in the patterns of climate change over the North Atlantic region compared with a climate-change run without Greenland fresh-water feedback.
A new deep ice core from Akademii Nauk ice cap, Severnaya Zemlya, Eurasian Arctic: first results
Authors: Fritzsche Diedrich , Wilhelms Frank , Savatyugin Lev M. , Pinglot Jean Francis , Meyer Hanno , Hubberten Hans-Wolfgang , Miller Heinz 
Published: November 2007

AbstractThe paper presents first results from the upper 54m of a 723.91m ice core drilled on Akademii Nauk ice cap, Severnaya Zemlya, Eurasian Arctic, in 1999– 2001, supplemented by data from shallow ice cores. the glacier’s peculiarity is the infiltration and refreezing of meltwater, which changes the original isotopic and chemical signals. Therefore, stratigraphical observations in these ice cores are more difficult than in those from central Greenland or Antarctica. However, the 1963 maximum of artificial radioactivity from atmospheric nuclear tests is clearly detectable in the deep ice core, and the δ18O profile of a 12.82 m shallow core shows annual variations. Consequently, at least for the upper part of the main core, an almost seasonal time resolution of palaeoclimate record could be expected. the Chernobyl layer is detected by increased 137Cs activity at depths of 11.81–12.51m related to the AD 2000 surface. the resulting mean annual net mass balance is 53±2 g cm–2 a–1. Data from dielectric profiling of the main core show considerable peaks in conductivity; one of them is interpreted as a volcano event. According to the resulting chronology, this part of the core represents approximately the last 100 years.
Indian monsoon variability in the Himalaya since AD 1800
Authors: Keqin Duan , Tandong Yao , Weizheng Sun , Xinqin Li 
Published: November 2007

AbstractThree ice cores distributed across Dasuopu (DSP) glacier in the Himalaya were recovered. the annual net accumulation (An) record reconstructed from one of the cores reflects major precipitation variability for the central Himalaya. This record agrees well with precipitation records from Nepal and northeast India, while it does not compare well with the all-India precipitation record. Singular spectrum analysis applied to the 200 year long Dasuopu accumulation (DSP An) record indicates significant variability on interannual and inter-decadal time-scales. the record shows that the early 18th century was dry, wet conditions prevailed during the period 1820–1930, and after 1930 An decreased to its present value. Distinct secular trends were not found in the record. for the period 1950– 94, the variability of DSP An is found to correlate significantly with the thermal contrast between the Tibetan Plateau and the Indian Ocean surface temperature. Additionally, a significant relationship between DSP An and solar activity is detected.
Spatial representativity of air-temperature information from instrumental and ice-core-based isotope records in the European Alps
Authors: Schöner Wolfgang , Auer Ingeborg , Böhm Reinhard , Keck Lothar , Wagenbach Dietmar 
Published: November 2007

AbstractSpatial correlations between Alpine high-elevation and European low-elevation instrumental air temperatures are computed to assess the spatial representativity of a high-Alpine ice-core isotope proxy temperature record. the correlation analyses indicate that air-temperature records at Alpine ice-core drill sites are representative for central Europe, particularly in summer. While Alpine ice cores generally show a large scattering in the conserved section of the year, long-term records from low-accumulation sites consist almost solely of summer precipitation and thus reflect isotope proxy summer-temperature variability. However, correlation between seasonal and annual instrumental air temperature indicates that summer temperature variability provides an adequate approach to annual temperature variability. Comparison of long-term ice-core δ18O records from Colle Gnifetti (4450ma.s.l.), Monte Rosa, Western Alps, with local instrumental summer temperatures inferred from an instrumental network shows good agreement in the long-term scale. Thus Alpine long-term ice-core δ18O records are representative for central European air-temperature variability.
Observations of polar ice from the Holocene and the glacial period using the scanning electron microscope
Authors: Barnes Piers R. F. , Mulvaney Robert , Robinson Kenneth , Wolff Eric W. 
Published: November 2007

AbstractSamples taken from the Dome C ice core, Antarctica, and the GRIP ice core, Greenland, are examined using the scanning electron microscope to determine their microstructure. In both cores, samples are taken from two differing climatic periods: the Holocene and the last glacial period. Many of the usual features observed in similar samples under the light microscope are observed, including: bubbles, grain boundaries and clathrate hydrates. Features not resolvable using the light microscope are also found. Dust particles are found in situ. Eighty-five per cent of those observed contained silicon, which was generally associated with aluminium and magnesium. An estimation is made of the relative proportions of dust particles located at grain boundaries and in the bulk of the ice grain. At Dome C a higher proportion than expected from a random distribution of particles was found located at grain boundaries, although in Greenland this was not found to be the case for most samples. Direct evidence is also presented indicating the role of dust particles and microscopical inclusions in impeding or ``pinning’’ grain-boundary migration. Soluble impurities are also detected at some triple junctions and grain boundaries.
The fast climate fluctuations during the stadial and interstadial climate states
Authors: Ditlevsen Peter D. , Ditlevsen Susanne , Andersen Katrine K. 
Published: November 2007

AbstractRapid climate changes during the last glacial period were first observed in ice-core records (Dansgaard and others, 1982). These shifts between interstadials, called Dansgaard–Oeschger (D-O) events, and stadials or deep glaciation were later seen in Atlantic sediment records (Bond and others, 1993), pointing to the ocean circulation as a strong component in the dynamics of these shifts (Wright and Stocker, 1991). the interstadial states are observed to have a characteristic ``sawtooth’’ shape, indicating a gradual drift of the stable interstadial state toward the stable stadial state. In order to contrast the two climate states, we have separated the δ18O signal from the Greenland Icecore Project ice core into periods corresponding to the two states. the climate variability in the two different climatic states is different (Johnsen and others, 1997). We find that the standard deviation is significantly larger in the stadial than in the interstadial state. Both states are found to have a larger standard deviation than the Holocene part of the record. the correlation times in the different states are difficult to obtain because of limited data resolution and diffusion of the isotopic signal. However, using a statistical technique, we have estimated the correlation times. We do not find significant differences in the correlation times, which are of the order of months, in the different climatic states. These findings are interpreted in the context of a simple linear stochastic model which provides information about the relative roles of the climatic forcing and the stability of the climate state governing the climate variability.
Measuring stable isotopes of hydrogen and oxygen in ice by means of laser spectrometry: the Bølling transition in the Dye-3 (south Greenland) ice core
Authors: van Trigt Radboud , Meijer Harro A. J. , Sveinbjörnsdóttir Arny E. , Johnsen Sigfús J. , Kerstel Erik R.Th. 
Published: November 2007

AbstractWe report on the first application of a new technique in ice-core research, based on direct absorption infrared laser spectrometry (LS), for measuring 2H, 17Oand 18O isotope ratios. the data are used to calculate the deuterium excess d (defined as δ2H– 8δ18O) for a section of the Dye-3 (south Greenland) deep ice core around the Bølling transition (14 500 BP). the precision of LS is slightly better than that of most traditional methods for deuterium, but not for the oxygen isotopes. the ability to measure δ17O is new and is used here to improve the precision of the δ18O determination. Still, the final precision for δ18O remains inferior to traditional isotope ratio mass spectrometry (IRMS). Therefore, deuterium excess was calculated from a combination of the LS and IRMS isotope determinations.
Using characteristic times to assess whether stable isotopes in polar snow can be reversibly deposited
Authors: Waddington Edwin D. , Steig Eric J. , Neumann Thomas A. 
Published: November 2007

AbstractStable isotopes in ice cores are used as a proxy for the temperature at the time of snow formation. Where net accumulation rate is relatively high, snow is buried quickly and initial isotopic values are preserved. However, in low-accumulation areas, snow is exposed to lengthy vapor exchange with the atmosphere. the original isotopic signature of this snow may be modified by equilibration with atmospheric water vapor in the boundary layer over the snow surface in summer. We estimate the characteristic times for equilibration by using an electrical resistor network analogue. Warm, windy summers and low accumulation rate enhance equilibration. Although equilibration of the complete snowpack is unlikely, significant post-depositional change may occur in some Antarctic environments.
An ice-marginal δ18O record from Barnes Ice Cap, Baffin Island, Canada
Authors: Zdanowicz Christian M. , Fisher David A. , Clark Ian , Lacelle Denis 
Published: November 2007

AbstractBarnes Ice Cap, Baffin Island, Canada, is a remnant of the Laurentide ice sheet that separated from it about 8500 years ago. Owing to recession of the ice cap during the Holocene, Pleistocene-age ice is now exposed along the margin in a distinctive bubble-rich white band. δ18O variations across the white ice resemble those in Canadian Arctic ice cores, suggesting that Barnes Ice Cap preserves a climatic record through the last glacial period, possibly reaching back into the previous (Sangamon) interglacial. the δ18O shift at the Wisconsin–Holocene transition (15‰) exceeds that in other Canadian and Greenland records and cannot be explained solely in climatic terms. A steady-state model reconstruction of the Laurentide ice sheet during the Last Glacial Maximum suggests that Late-glacial strata in Barnes Ice Cap originated high up (>2400ma.s.l.) and far “inland” on the ice sheet, along a ridge that extended between the ancestral Foxe and Keewatin ice domes.