bluuebunny/crossref_metadata_2025_split huggingface dataset:
An observational and modelling analysis of Laptev Sea (Arctic Ocean) ice variations during summer
Authors: Görgen K. , Bareiss J. , Helbig A. , Rinke A. , Dethloff K. 
Published: November 2007

AbstractIn this study we investigate the relationship of the atmospheric circulation and the sea-ice distribution in the Laptev Sea, Arctic Ocean, in the summers 1979−96. Sea-ice data from passive-microwave radiometers, global atmospheric data analyses, cyclone statistics and simulations of the regional climate model HIRHAM4 were analyzed to find out if periods of reduced or increased sea-ice concentrations are linked to synoptic patterns (circulation anomalies, cyclone activity). A canonical correlation analysis between Arctic sea-level pressure and sea-ice concentration anomalies confirms large-scale relationships among these variables. We did not find a simple relationship between sea-ice area anomalies and cyclone activity in the Laptev Sea area
Observation of sea-ice thickness fluctuation in the seasonal ice-covered area during 1992−99 winters
Authors: Tateyama Kazutaka , Enomoto Hiroyuki 
Published: November 2007

AbstractSea-ice fluctuations in the Sea of Okhotsk and the Bering Sea during the winters of 1992−99 were investigated by using the Special Sensor Microwave/ Imager dataset and a new ice-property retrieval algorithm This algorithm can distinguish between ice types such as fast ice floes, young ice and new ice, in an area covered by concentrations of >80% ice, and also has improved display resolution because it uses one of the 85 GHz channels. The ice thicknesses derived from the ice-thickness parameter of the new algorithm were compared with ship-based ice-thickness measurements, and were assumed to be 1−10, 11−34, 35−85 and 86−120 cm for new ice, young ice, floes (first-year ice) and fast ice, respectively. The results showed that ice volume can be small even if the ice area is large, due to thinness of the ice (e.g. in 1999 in the Sea of Okhotsk). A significant out-of-phase response, i.e. ice volume is larger in the Sea of Okhotsk when ice volume is smaller in the Bering Sea, was observed. The period of this see-saw showed two different time-scales, which were short (1 week) and long (2−4 weeks).
Principal-component analysis of sea-ice motion from satellite data
Authors: Zhao Yunhe , Liu Antony K. 
Published: November 2007

AbstractThe two-dimensional wavelet transform is a highly efficient band-pass filter, which can be used to track features in satellite images from sequential paths. Wavelet analysis of NASA scatterometer and Special Sensor Microwave/Imager data has been used to obtain daily sea-ice drift information for the Arctic region. Comparison with ice motion derived from ocean buoys shows good quantitive agreement. Furthermore, the scatterometer results definitely complement passive-microwave radiometer results when there are cloud or surface effects. This outcome allows three sets of sea-ice-drift daily results from scatterometer, radiometer and buoy data to be merged as a composite map by data-fusion techniques. Based on the composite maps, the ice-flow streamlines are highly correlated with surface air-pressure contours. In order to quantify the wind effects on ice motion, empirical orthogonal functions are used in the principal-component analysis to isolate generalized patterns inherent in 6 months (fall/winter) of daily sea-ice motion data. It is found that 30% of sea-ice motion is highly correlated with 50% of the pressure field in modes 1 and 2. For the higher modes, sea-ice motion is also affected by ocean current, bathymetry and coastal boundary and therefore is not highly correlated with the wind field.
A case-study in tracking 1998 polynya ice dynamics in Smith Sound, North Water polynya region, Canadian Arctic, using RADARSAT-1 data
Authors: Wilson K. J. , King D. J. , Barber D. G. 
Published: November 2007

AbstractMonitoring ice motion provides insight into the relative contributions of atmospheric and oceanic forcing to polynya dynamics In this study ice kinematics in the North Water (NOW) region, northern Baffin Bay Canadian Arctic are determined using time-sequential RADARSAT-1 ScanSARWide imagery (from the period January-December 1998), processed by the automated ice-tracking algorithm (Tracker) currently used at the Canadian Ice Service (CIS). A case-study is then carried out on the Smith Sound region from January till the end of june 1998 to monitor polynya formation, maintenance and disintegration. This has two objectives: (1) to evaluate satellite ice-motion products as a means of better understanding the relative contributions of latent- and sensible-heat mechanisms responsible for the formation and behaviour of the NOW polynya, and (2) to study the influence of winds on regional sea-ice motion. Derived ice-motion maps were validated using in situ ice beacons deployed onto floes in the NOW region during the 1998 ship-based science experiment. Tracker-derived displacement and directional regressions were 0.93 and 0.79, respectively, with a total standard error of 3.6 km in magnitude and 38.8° in direction. Analysis of monthly mean ice-motion maps shows that a significant export of ice occurs from the polynya. A comparison of weekly-averaged ice motion with the mean wind-field data suggests that ice export in Smith Sound is influenced by synoptic-scale atmospheric pressure systems.
Estimation of sea-ice physical parameters using polarimetric SAR: results from Okhotsk and Lake Saroma campaign
Authors: Wakabayashi Hiroyuki , Matsuoka Takeshi , Nakamura Kazuki , Nishio Fumihiko 
Published: November 2007

AbstractWe have acquired ground-truth data at Lake Saroma, northeast Hokkaido, Japan, and the surrounding area since 1993 in order to collect data on regional sea ice in the Sea of Okhotsk. The data were acquired in 1999 by polarimetric and interferometric SAR (Pi-SAR), the dual-frequency, fully polarimetric airborne SAR system jointly developed by the National Space Development Agency of Japan (NASDA) and the Communications Research Laboratory (CRL), simultaneously with ground experiments. This paper describes the results of polarimetric data analysis of typical sea ice observed in the offshore region near Lake Saroma. The polarimetric parameters used were correlation coefficient and phase difference. Based on the analysis of these parameters, we found that the correlation coefficient between RR and LL polarizations can discriminate four categories including three types of ice and open water.
Phase and compositional evolution of the flooded layer during snow-ice formation on Antarctic sea ice
Authors: Maksym Ted , Jeffries Martin O. 
Published: November 2007

AbstractA two-dimensional convective transport model has been been developed to investigate the phase and compositional evolution of a flooded slush layer overlying sea ice. The processes governing the solutal and compositional evolution of the flooded layer are investigated in an attempt to explain field observations of salinity and oxygen isotope ratios. Simulations indicate fairly vigorous convective transport in the slush layer, which may lead to the formation of porous channels, depending on permeability. It is found that the salinity and δ18O composition of the freezing slush layer is determined primarily by the sea-ice permeability. Simulated salinity and δ18O profiles produce varied results, though consistent with observations. The influence of the slush on the salinity and δ18O composition of the underlying ice was found to be minimal.
Ice-floe kinematics in the Ross Sea marginal ice zone using GPS and accelerometers
Authors: Downer Josh , Haskell Timothy G. 
Published: November 2007

AbstractAn experiment to investigate wave-induced floe response and floe-floe interactions was conducted in the Ross Sea marginal ice zone during austral summer 1999. Three types of sensors were used: global positioning system (GPS) receivers; triaxial accelerometers; and compasses. The accelerometer data reveal consistent bands of energy centred at about 0.1 and 1.35 Hz, the latter an unexplained but common feature of such experiments. The GPS data also contain energy near 0.1 Hz, which may suggest that GPS receivers can detect the ocean-wave-induced lateral motion of ice floes.
On large-scale shifts in the Arctic Ocean and sea-ice conditions during 1979−98
Authors: Maslowski W. , Marble D. C. , Walczowski W. , Semtner A. J. 
Published: November 2007

AbstractResults from a regional model of the Arctic Ocean and sea ice forced with realistic atmospheric data are analyzed to understand recent climate variability in the region. The primary simulation uses daily-averaged 1979 atmospheric fields repeated for 20 years and then continues with interannual forcing derived from the European Centre for Medium-range Weather Forecasts for 1979−98. An eastward shift in the ice-ocean circulation, fresh-water distribution and Atlantic Water extent has been determined by comparing conditions between the early 1980s and 1990s. A new trend is modeled in the late 1990s, and has a tendency to return the large-scale sea-ice and upper ocean conditions to their state in the early 1980s. Both the sea-ice and the upper ocean circulation as well as fresh-water export from the Russian shelves and Atlantic Water recirculation within the Eurasian Basin indicate that the Arctic climate is undergoing another shift. This suggests an oscillatory behavior of the Arctic Ocean system. Interannual atmospheric variability appears to be the main and sufficient driver of simulated changes. The ice cover acts as an effective dynamic medium for vorticity transfer from the atmosphere into the ocean.
Avalanche dynamics measurement by pulsed Doppler radar
Authors: Schreiber Helmut , Randeu Walter L. , Schaffhauser Horst , Rammmer Lambert 
Published: November 2007

AbstractThis paper presents the application of a pulsed Doppler radar for the measurement of dynamic properties of snow and ice avalanches. The instrument was developed and built by the Institute of Communications and Wave Propagation, Technical University Graz, and is operated by the Austrian Institute for Avalanche and Torrent Research (AIATR), Innsbruck. The data acquired by this radar during field campaigns are used to verify and optimize avalanche models and simulation tools. As well as describing the radar’s technical principle, how the dynamic parameters are measured and presented to the user and how these data can be used to accomplish the determination of avalanche velocity and runout distance, the paper deals with the participation of the radar in a successful full-scale snow-avalanche experiment in Ryggfonn, Norway, and evaluates the collected data. This measurement campaign was a joint experiment by the Norwegian Geotechnical Institute, Oslo, and AIATR.
Numerical simulations of Greenland snowpack and comparison with passive microwave spectral signatures
Authors: Genthon Christophe , Fily Michel , Martin Eric 
Published: November 2007

AbstractIn this paper, we show that a detailed snow model (here, the Crocus model) may help to validate large-scale inferred meteorological datasets (e.g. from climate models or analyses) over the data-sparse ice sheets. Two series of snow simulations are carried out with two different meteorological datasets in input to the snow model. Both datasets are extracted from the European Center for Medium-range Weather Forecasts meteorological analyses and forecast archives. First, the microwave signatures of the surface of central Greenland from the Scanning Multichannel Microwave Radiometer (SMMR) are compared with the simulated density, grain-size and stratigraphy. The annual mean gradient ratio and polarization ratio, which are related to the emissivity of snow, are found to correlate spatially with these snow structural parameters. The sensitivity of the snow structure to differences in the two meteorological sets is then examined. It is found to be high for temperature and infrared radiation, precipitation and surface wind. The quantitative value of this result is limited by a still limited snow model validation over Greenland. Also, an optimal use of satellite data and a snow model for meteorological validation would require physically based translation of the simulated snow parameters into radiative properties, i. e radiation transfer modeling.
Mass-flux measurements in a cold wind tunnel: comparison of the mechanical traps with a snow-particle counter
Authors: Font D. , Sato T. , Kosugi K. , Sato A. , Vilaplana J. M. 
Published: November 2007

AbstractDuring September and October 1997, in the framework of a stay at the Shinjo Branch of Snow and Ice Studies, we used a Cryospheric Environment Simulator (Higashiura and others, 1997) and simulated drifting snow to test four mechanical traps. First we present the intercomparison of the four mechanical gauges, then we compare the gauges with the snow-particle counter (SPG). Comparing the four different traps tested, we have observed that the box type (snow collector) is generally more efficient than the net-type collectors. These results confirm the tendency observed in field experiments (Font and others, 1998b). Using the SPG to calibrate the mechanical gauges, we observed that the net-type traps underestimate transport in low-transport conditions, but as transport increases the underestimation tends to zero. Comparing the snow collector with the SPG, we observed good agreement between the two gauges.
Water vapor in the pore space of snow
Authors: Sokratov Sergey A. , Sato Atsushi , Kamata Yasushi 
Published: November 2007

AbstractWater vapor in snow is responsible for two main processes connected to almost all studies where snow cover is involved: the snow-density change with time and snow recrystallization. Both processes are the result of a balance between evaporation and condensation on individual snow-crystal surfaces. However, such micro-scale mass balance has rarely been considered as a component of “macro-” heat and mass transfer in snow cover. The present work is an attempt to find a way of combining these two mass-exchange processes, as occurs in Nature. Density change and snow recrystallization rates are analyzed based on recently published temperature field observations around individual snow crystals, combined with experimental data on temperature distributions and recrystallization rates in snow under applied temperature gradients.
SAFRAN-Crocus snow simulations in an unstable and windy climate
Authors: Haraldsdóttir Svanbjörg Helga , Ólafsson Haraldur , Durand Yves , Mérindol Laurent , Giraud Gérald 
Published: November 2007

AbstractSAFRAN and Crocus are simulation systems developed at the Centre d’Etudes de la Neige, the snow research department of Météo-France. SAFRAN analyzes weather parameters relevant to snow on the ground, and Crocus simulates the build-up of the snowpack. In this study simulated snow depths and measured snow depths at three locations in Iceland were compared. The main study was performed for the Hveravellir weather station located 640 m a.s.l. in central Iceland. The results from three winters, 1994–97, were analyzed. In Iceland the “Alpine” version of the models systematically underestimated the snow depth and density of the snowpack. Corrections for the effect of wind on snow density and on precipitation measurements led to significant improvements in simulated snow depths. The simulations are sensitive to the threshold temperature between snow and rain. The remaining problems in simulating the snowpack are mainly related to transport of snow by wind, which is not accounted for in the models, and to some extent to melting and sublimation in strong winds.
Heavy rain on snow cover
Authors: Kohl B. , Fuchs M. , Markart G. , Patzelt G. 
Published: November 2007

AbstractHeavy rain on snow often leads to disastrous damages in torrent watersheds. In January 1998 a project was started to investigate “runoff and infiltration characteristics of different alpine soil/vegetation units under snow cover”. One aim was to determine the runoff rates from snow-covered, differently cultivated soil/vegetation units (pastures, dwarf-shrub stands, forests), especially under conditions of sparse snow cover and frozen soil. Differences in runoff formation between artificially snowed skiing areas and plots with natural snow cover were also of interest. Heavy rain (intensity 100 mm h–1) was simulated on four plots by using a transportable spray irrigation installation. The investigations showed runoff coefficients of 0.4–0.7. The lowest runoff values were found where the soil under snow cover was not frozen, but even on these stands the runoff coefficient exceeded 0.4. Snow depth and runoff delay are strongly correlated (R2 = 0.8). An increment in snow of 10 cm is followed by a runoff delay of 3.6 min. Divergences from this coherence are due to the composition of the snowpack, especially in case of artificial snow. This result is encouraged by runoff simulations performed for the irrigated plots by use of a hydrological model.
Rheological measurements of the viscoelastic properties of snow
Authors: Camponovo Christian , Schweizer Jürg 
Published: November 2007

AbstractIn order to determine the viscoelastic properties of snow, torsional shear measurements were performed in a cold laboratory with a stress-controlled rheometer. Small samples (60 mm in diameter and about 7 mm thick of natural snow collected from the nearby study plot were loaded in simple shear with monotonically increasing stress (stress ramp) and with sinusoidally varying stress (oscillation). The dynamic measuring method allows the deformation process to be separated into a time-independent part (elastic) and a time-dependent part (viscous). The applied torque is sufficiently small to prevent destructive deformation, generally permitting the true viscoelastic properties of a sample to be obtained over a large range of frequency and temperature. The limit strain for linear viscoelastic deformation was found to be very small (0.5−5 × 10−4). Experiments performed beyond the linear range imply important textural changes (damage, breaking of bonds). The large strain reached during stress-ramp experiments showed that the ongoing damage process must be balanced by a healing (sintering) process. The usefulness of a rheometer was proven. It is a precise method for measuring with high reproducibility the rheological parameters of snow, and data gained with it improve our understanding of the deformation process under shear loading.
The low-frequency conductivity of snow near the melting temperature
Authors: Takei Iwao , Maeno Norikazu 
Published: November 2007

AbstractDielectric measurements of snow were carried out in the temperature range –15° to 0°C and in the frequency range 50 Hz to 5 MHz. The snow samples (about 400 kg m–3 density) used were stored snow (average particle size: 2 mm) and hoar-frost (particle size: <1 to 5 mm). The frequency characteristics of dielectric parameters showed a dielectric dispersion (Davidson-Cole type) around 30 kHz and a low-frequency dielectric dispersion (Cole-Cole circular law type). The a.c. conductivity showed a dielectric dispersion around 30 kHz and two characteristic constant values in the frequency ranges above 1 MHz and below 100 Hz (the high-frequency conductivity σ∞ and the low-frequency conductivity σLOW). The low-frequency conductivity σLOW showed a peak at about –2°C. This behavior has never been noted by previous researchers. The σLOW showed an activation energy of about 1 eV below –5°C. This means that the σLOW is mainly caused by a surface conduction. The activation energy increased with increasing temperature above –5°C. This means that the σLOW in this temperature range is affected by the quasi-liquid layer on ice surfaces. The σLOW above –2°C decreased with increasing temperature. The apparently curious behavior near the melting temperature is attributed to the numerous free ice surfaces within the porous snow. This conclusion was reached because our measurements without the free ice surfaces showed no such conductivity peaks for solid polycrystalline ice samples and for snow samples soaked with kerosene in the cooling process.
A study on the size of snow particles in powder-snow avalanches
Authors: Clément-Rastello Marie 
Published: November 2007

AbstractIn this work, we study the size of the particles involved in a powder-snow avalanche. To determine this value, we study all the phenomena encountered by the particles before they arrive in the “body” of the avalanche. We study the boundary layer which is at the bottom of the avalanche. We determine, with the help of experimental data, the range of sizes of particles that can be entrained by the avalanche. We then examine the possibility of these particles reaching the top of the boundary layer and thus taking part in the avalanche. Our final result is that the typical size of particles suspended in a powder-snow avalanche is < 200 μm.
Impact of a climate change on avalanche hazard
Authors: Martin Eric , Giraud Gérald , Lejeune Yves , Boudart Géraldine 
Published: November 2007

AbstractThe SAFRAN/Crocus/MÉPRA software is used to assess the climatology of the avalanche hazard and its sensitivity to climate change. A natural avalanche-hazard index based on MEPRA analysis is defined and validated against natural avalanche observations (triggered avalanches are not taken into account). A 15 year climatology then allows a comparison of avalanche hazard in the different French massifs. Finally a simple climate scenario (with a general increase of precipitation and temperature) shows that avalanche hazard may decrease slightly in winter (mainly February) and more significantly in May/June. The relative proportion of wet-snow avalanches increases.
Run-up of two avalanches on the deflecting dams at Flateyri, northwestern Iceland
Authors: Jóhannesson Tómas 
Published: November 2007

AbstractTwo deflecting dams were constructed above the village Flateyri, northwestern Iceland, after the catastrophic avalanche accident on 26 October 1995 when 20 people were killed. Both deflectors have since been hit by moderately large avalanches, in each case with a volume of > 100 000 m3 and an estimated return period of 10–30 years. The avalanches hit the deflectors with deflecting angles of 20–25° and a maximum run-up of 12–13 m. They flowed about 500 m along the deflectors after the initial impact and terminated in the ocean on the respective sides of the reef where the village is situated. Back-calculated impact velocities are of the order of 30 m s–1. In both cases, the impact channelized a part of or The whole of the width of the avalanche into a stream 20–80 m wide, the run-out of which is estimated to have been increased by > 100 m by the deflection of the avalanche by the dam. Although the avalanches are much smaller than the design avalanches of the deflecting dams, they have provided avalanche professionals and the public in Iceland with much-welcomed direct evidence of the effectiveness of the defence structures at Flateyri against moderately sized events. They also provide unique direct observations for further scientific investigations of the deflection of avalanches by man-made deflecting dams.
Particle densities, velocities and size distributions in large avalanches from impact-sensor measurements
Authors: Schaer Mark , Issler Dieter 
Published: November 2007

AbstractIn winter 1998/99, high-frequency pressure measurements with 10 cm sensors mounted 1–19 m above ground were carried out in the upper run-out zone of the avalanche test site at Vallée de la Sionne, Switzerland. Two large dry-snow avalanches clearly revealed a three-layered structure, with surprisingly low pressures in the suspension (or powder-snow) layer. The height of the saltation layer varied between 1 and > 3 m. From the duration, impulse and frequency of single-particle impacts (observed in the saltation layer and intermittently in the dense flow),particle-size and velocity distribution functions as well as strongly varying saltation-layer densities were found. With improved methods for peak detection and correction for grazing impacts, pressure measurements will become premier tool for testing granular flow models.