bluuebunny/crossref_metadata_2025_split huggingface dataset:
The carbon isotopic composition of dissolved inorganic carbon in perennially ice-covered Antarctic lakes: searching for a biogenic signature
Authors: Neumann Klaus , Lyons W. Berry , Priscu John C. , Desmarais David J. , Welch Kathleen A. 
Published: November 2007

AbstractThe stable-isotopic signature of dissolved inorganic carbon (DIC) has been routinely used in temperate lake systems to investigate the biogeochemical dynamics of carbon. We studied seven perennially ice-covered lakes in the McMurdo Dry Valleys, Antarctica, to ascertain how carbon cycling affects the δ13C of DIC in water columns of these systems. Unlike temperate lakes and, in fact, most polar lake systems, the permanent ice covers of these lakes eliminate physical mixing (turnover) and hence redistribution of DIC in the lakes, as well as minimize CO2 exchange with the atmosphere. These important and unique physical constraints have significant impact on carbon dynamics in the lakes, and important consequences for the δ13C distribution. The geochemistry in these lakes is influenced in varying amounts by landscape position, hydrologic input and their evolutionary history. Five of these lakes (both lobes of Lake Bonney, and Lakes Fryxell, Miers and Vanda) have surface water δ13C ratios of 0–4‰, Lake Hoare has more negative values, while Lake Joyce, the highest-elevation lake, has a much higher value (10.5‰). All of the lakes have upper- to mid-depth δ13C maxima reflecting biological uptake of 12C. Only four of the lakes (Lakes Vanda, Joyce, Hoare and Fryxell) have deep waters with negative values of δ13C, implying rigorous remineralization of 12C at depth. Lake Miers, the only lake that is not closed basin, has the smallest δ13C variation with depth, indicating that hydrologic exchange greatly influences the δ13C signal.
Elemental indicators of natural and anthropogenic aerosol inputs to Law Dome, Antarctica
Authors: Vallelonga Paul , Barbante Carlo , Cozzi Giulio , Gaspari Vania , Candelone Jean-Pierre , Van De Velde Katja , Morgan Vin I. , Rosman Kevin J. R. , Boutron Claude F. , Cescon Paolo 
Published: November 2007

AbstractA selection of elements (Bi, Ca, Cd, Co, Cu, Mn, Na, Sr, U, V, Zn) were measured by high-resolution inductively coupled plasma sector-field mass spectrometry in firn- and ice-core samples from Law Dome, Antarctica, corresponding to the period 4500 BC to AD 1989. Concentrations of rock dust and sea salts were calculated for each sample and then used to determine concentrations of each element originating from crustal and marine aerosol emissions, respectively. Where calculated contributions from crustal and marine aerosol sources failed to account for the total measured concentration of an element, the remainder was apportioned to volcanic and/or anthropogenic sources and defined as an enrichment. On this basis, it was determined that Bi and Cd concentrations in Law Dome ice are overwhelmingly influenced by volcanic emissions (enrichments 150–250x crustal and marine inputs); Co, Cu, Pb and Zn concentrations in Law Dome ice are largely influenced by volcanic emissions (enrichments 16–36x crustal and marine inputs); and Mn, Sr, U and V concentrations in Law Dome ice are minimally influenced by volcanic emissions (enrichments 1.5–4x crustal and marine inputs). During the 20th century, enrichments of Pb and Cu concentrations were observed to be greater than in earlier centuries, consistent with increasing anthropogenic emissions of Pb and Cu in the Southern Hemisphere over that period.
Investigating the potential to determine the upstream accumulation rate, using mass-flux calculations along a cross-section on a small tributary glacier in Heimefrontfjella, Dronning Maud Land, Antarctica
Authors: Pohjola Veijo Allan , Hedfors Jim , Holmlund Per 
Published: November 2007

AbstractHow well can we estimate the incoming ice flux by calculating the ice flux through a well-defined cross-section? We test this by comparing calculated ice flux out from the small glacier Bonnevie-Svendsenbreen with the measured accumulation rate integrated over the well-defined catchment area in the Sivorgfjella plateau, Dronning Maud Land, Antarctica (74˚45’ S, 11˚10’ W). The ice flux is calculated using ice-dynamical properties from an ice temperature model and the distribution of forces calculated using a force-budget model. The input we use includes velocity data of the glacier surface, combined with ice-thickness measurements. The result is an accumulation rate on the Sivorgfjella plateau of 0.50 ± 0.05 mw.e. a–1. We find that this is similar to the accumulation rate recorded by ground-penetrating radar work in the area. We therefore find the balance-flow method, in combination with the force-budget technique and ice temperature modeling, to be a useful tool for studies of mass fluxes in a catchment area. The most important source of uncertainty in these calculations is the quality and the spatial distribution of the ice surface velocity data. The high accumulation rate shows the effect of orographic enhancement on accumulation in montane areas in Antarctica.
Climatic conditions, mass balance and dynamics of Larsen B ice shelf, Antarctic Peninsula, prior to collapse
Authors: Skvarca Pedro , De Angelis Hernán , Zakrajsek Andrés F. 
Published: November 2007

AbstractFollowing the collapse of Larsen A in 1995, about 3200 km2 of Larsen B ice shelf disintegrated in early 2002 during the warmest summer recorded on the northeastern Antarctic Peninsula. Immediately prior to disintegration the last field campaign was carried out on Larsen B. Measurements included surface net mass balance, velocity and strain rate on a longitudinal transect along Crane Glacier flowline and over a remnant section confined within Seal Nunataks that survived the collapse. In addition, an automatic weather station located nearby allowed derivation of melt days relevant to the formation and extent of surface meltwater. Repeated surveys allowed us to detect a significant acceleration in ice-flow velocity and associated increasing strain rates along the longitudinal transect. It may be possible to use this acceleration as a predictor of imminent ice-shelf collapse, applicable to ice shelves subject to similar climatic conditions. Additional information on recent ongoing changes was provided by a visible satellite image acquired in early 2003.
Geophysical survey at Talos Dome, East Antarctica: the search for a new deep-drilling site
Authors: Frezzotti Massimo , Bitelli Gabriele , De Michelis Paola , Deponti Alberto , Forieri Alessandro , Gandolfi Stefano , Maggi Valter , Mancini Francesco , Remy Frédérique , Tabacco Ignazio E. , Urbini Stefano , Vittuari Luca , Zirizzottl Achille 
Published: November 2007

AbstractTalos Dome is an ice dome on the edge of the East Antarctic plateau; because accumulation is higher here than in other domes of East Antarctica, the ice preserves a good geochemical and palaeoclimatic record. A new map of the Talos Dome area locates the dome summit using the global positioning system (GPS) (72˚47’ 14’’S, 159˚04’ 2’’ E; 2318.5m elevation (WGS84)). A surface strain network of nine stakes was measured using GPS. Data indicate that the stake closest to the summit moves south-southeast at a few cm a–1. The other stakes, located 8 km away, move up to 0.33ma–1. Airborne radar measurements indicate that the bedrock at the Talos Dome summit is about 400m in elevation, and that it is covered by about 1900 m of ice. Snow radar and GPS surveys show that internal layering is continuous and horizontal in the summit area (15 km radius). The depth distribution analysis of snow radar layers reveals that accumulation decreases downwind of the dome (north-northeast) and increases upwind (south-southwest). The palaeomorphology of the dome has changed during the past 500 years, probably due to variation in spatial distribution of snow accumulation, driven by wind sublimation. In order to calculate a preliminary age vs depth profile for Talos Dome, a simple one-dimensional steady-state model was formulated. This model predicts that the ice 100m above the bedrock may cover one glacial–interglacial period.
Spatial distribution of surface mass balance on Amundsenisen plateau, Antarctica, derived from ice-penetrating radar studies
Authors: Rotschky Gerit , Eisen Olaf , Wilhelms Frank , Nixdorf Uwe , Oerter Hans 
Published: November 2007

AbstractThe distribution of surface mass balance on Amundsenisen, Dronning Maud Land, Antarctica, is investigated along a continous profile line. Ice-penetrating radar is used to map variations in ice-layer thickness within the upper 100 m of the ice sheet. The route passes several firn- and ice-core drilling sites over a distance of 320 km. Dielectric-profiling data of ice cores are used to calculate the depths of selected reflection horizons and the cumulative mass of the ice column. The local surface mass balance is determined as a temporal average, covering a time-span of almost two centuries. The findings indicate a complex accumulation pattern superimposed on a generally low surface mass balance, which is related to small-scale surface undulations. The results of the radar soundings are in general in good agreement with surface mass-balance data derived from firn-core studies. Discrepancies between these two datasets can be explained by spatial mismatch or by minor quality of either ice-core profiles or radar data. For regional comparison of radar-based accumulation data we use an accumulation distribution interpolated from point measurements. The surface mass balance varies up to 50% over short distances, with correlation lengths of <10 km. We conclude that the current utilization schemes of point sampling are only capable of reproducing local values and regional trends but provide no information on the small-scale variability of surface mass balance.
Antarctic ice volume and deep-sea temperature during the last 50 Myr: a model study
Authors: Oerlemans Johannes 
Published: November 2007

AbstractA simple quasi-analytical model is used to study the sensitivity of the Antarctic ice sheet to climate change. The model is axisymmetrical and has a profile that only depends on the ice-sheet radius. The climatic conditions are represented by three parameters: the altitude of the runoff line, the accumulation rate above the runoff line, and the balance gradient below the runoff line. The ice sheet may extend into the sea. At the grounding line the ice velocity is assumed to be proportional to the water depth. For this set-up, an explicit algebraic expression for the total mass budget of the ice sheet can be derived. After calibration of the model with respect to the present-day ice sheet, equilibrium states are studied for a wide range of temperatures. The model predicts a maximum ice volume (+3.4%) for a temperature that is 2.5 K above the present value. For a temperature increase of 7 K, mass loss by runoff and calving are about the same. In this case the ice volume is about 82% of the current value. The ice-sheet model is used to correct the Cenozoic deep-sea temperature record (δ18O record from benthic foraminifera in ocean sediments) for Antarctic ice volume. The model is forced with the oxygen isotope record, which is then corrected for the calculated ice volume. Therefore, the resulting deep-sea temperature and Antarctic ice-volume curves are mutually consistent. It is concluded that for the last 35×106 years the δ18O record truly is a mixed temperature/ice-volume record, in which the contributions from these parameters have the same order of magnitude.
Two-dimensional numerical modelling of surface wind velocity and associated snowdrift effects over complex mountainous topography
Authors: Durand Yves , Guyomarc’h Gilbert , Mérindol Laurent , Corripio Javier G. 
Published: November 2007

AbstractA new experimental software for blowing snow, SYTRON2, is presented. It takes advantage of the previous limited realization SYTRON1 and of the entire real-time operational environment of the automatic chain SAFRAN–Crocus–MÉPRA (SCM). It runs presently on a rectangular grid, with a mesh size of about 45 m, covering an area of 3.0 × 3.0km2 around the observation test site Col du Lac Blanc, French Alps (2700m a.s.l., near the Alpe d’Huez ski resort). SYTRON2 is initialized with a realistic snowpack representation derived from the SCM outputs and coupled to a wind field computed by the new SAMVER model. The final aim is to build a fully embedded tool, suitable for representing snowdrift effects with a better resolution at different specific locations. The different tools and operators used are described, as well as the field validation processes which are based on remote identification of the eroded and accumulated areas using digital pictures.
Validation of the energy budget of an alpine snowpack simulated by several snow models (Snow MIP project)
Authors: Etchevers Pierre , Martin Eric , Brown Ross , Fierz Charles , Lejeune Yves , Bazile Eric , Boone Aaron , Dai Yong-Jiu , Essery Richard , Fernandez Alberto , Gusev Yeugeniy , Jordan Rachel , Koren Victor , Kowalczyk Eva , Nasonova N. Olga , Pyles R. David , Schlosser Adam , Shmakin Andrey B. , Smirnova Tatiana G. , Strasser Ulrich , Verseghy Diana , Yamazaki Takeshi , Yang Zong-Liang 
Published: November 2007

AbstractMany snow models have been developed for various applications such as hydrology, global atmospheric circulation models and avalanche forecasting. The degree of complexity of these models is highly variable, ranging from simple index methods to multi-layer models that simulate snow-cover stratigraphy and texture. In the framework of the Snow Model Intercomparison Project (SnowMIP), 23 models were compared using observed meteorological parameters from two mountainous alpine sites. The analysis here focuses on validation of snow energy-budget simulations. Albedo and snow surface temperature observations allow identification of the more realistic simulations and quantification of errors for two components of the energy budget: the net short- and longwave radiation. In particular, the different albedo parameterizations are evaluated for different snowpack states (in winter and spring). Analysis of results during the melting period allows an investigation of the different ways of partitioning the energy fluxes and reveals the complex feedbacks which occur when simulating the snow energy budget. Particular attention is paid to the impact of model complexity on the energy-budget components. The model complexity has a major role for the net longwave radiation calculation, whereas the albedo parameterization is the most significant factor explaining the accuracy of the net shortwave radiation simulation.
Estimating snow conditions in Finland in the late 21st century using the SNOWPACK model with regional climate scenario data as input
Authors: Rasmus Sirpa , Räisänen Jouni , Lehning Michael 
Published: November 2007

AbstractAn assessment of possible snow changes in a changing climate for Finland is presented. The snowpack structure model SNOWPACK (developed at the Swiss Federal Institute for Snow and Avalanche Research) was used for calculating snow conditions at six different locations in Finland for the decades 1980–89 and 2080–89. Regional climate model (RCAO) data from the Rossby Centre, Sweden, were used as input to the SNOWPACK model. Ten years from the RCAO control run and scenario run were chosen, and the snow conditions for different snow zones were calculated for these winters. The snow-cover depth and duration decreased at all locations in the scenario run cases, and the snow-cover quality also changed between the control and scenario runs: grains were bigger, snow was warmer and denser, and the fraction of faceted snow decreased while the fraction of icy or melting snow increased, even in mid-winter. Finally, the variability between different global climate predictions was analyzed. Significant differences were found between different climate-model outputs. The inter-model variability is comparable to the interannual variability of a single model. The qualitative conclusions from the scenario run do not critically depend on the climate-model variability.
Slushflow hazard prediction and warning
Authors: Hestnes Erik , Bakkehøi Steinar 
Published: November 2007

AbstractParameters critical to slushflow release have been studied during 11 winters in Rana, North Norway. Slushflows occurred during 16 periods within the research areas and during another 13 in the district. A noticeable rise of water in snowpack was registered 49 times. Field predictors of acute-hazard and critical water influxes related to different snowpack conditions are identified. Threshold values for acute-hazard prediction based on five main combinations of winter snowpack and current rise of water in snowpack were identified and checked against the registered slushflows, with promising results. Cohesionless new snow and coarse-grained snow are most liable to start flowing. A snowpack reinforced by layers of crust and ice is normally the most stable. An automatic system for supervising slushflow hazard based on the defined criteria is presented. The system can be tailored for any location and problem owner.
The mass balance of a dry snow surface during a snowstorm
Authors: Bintanja Richard 
Published: November 2007

AbstractThis paper focuses on the surface mass balance of a horizontally homogeneous snowfield, with emphasis on the effects of snowdrift sublimation. A one-dimensional model of the atmospheric boundary layer that includes snowdrift physics and thermodynamics is used. In sufficiently strong winds, snow particles are eroded from the surface. Once airborne, they are susceptible to sublimation. Averaged over longer time periods, the net erosive flux equals sublimation of snowdrift. However, model results show that there is no such balance in the course of a snowstorm event. They also indicate that snowdrift sublimation tends to enhance net erosion, but the increase occurs more slowly than the mass transfer by snowdrift sublimation, and the maximum is smaller. This difference in temporal behaviour influences the average erosion rate owing to non-linear interactions between snowdrift sublimation, drift density and erosion. Since the increase in relative humidity due to snowdrift diminishes surface sublimation, the average change in total ablation induced by snowdrift sublimation remains small. Observations made during snowdrift episodes in Antarctica agree qualitatively with some of the model results.
Three-dimensional geometric measurements of snow microstructural evolution under isothermal conditions
Authors: Flin Frédéric , Brzoska Jean-Bruno , Lesaffre Bernard , Coléou Cécile , Pieritz Romeu André 
Published: November 2007

AbstractSnow, from its fall until its full melting, undergoes a structural metamorphism that is governed by temperature and humidity fields. Among the many possible mechanisms that contribute to snow metamorphism, those that depend only on curvature are the most accessible to modelling. In this paper, techniques of volume data analysis adapted to the complex geometry of snow are introduced and then applied to experimental tomographic data coming from the isothermal metamorphism of snow near 0°C. In particular, an adaptive algorithm of curvature computation is described. Present results on the evolution of specific surface area and anisotropy already show that such image-analysis methods are relevant tools for the characterization of real snow microstructures. Moreover, the evolution of the curvature distribution with time provides valuable information for the development of sintering models, in the same way as a possible quantitative calibration of snow-grain coarsening laws.
Dendrochronological study of the Canal del Roc Roig avalanche path: first results of the Aludex project in the Pyrenees
Authors: Muntán Elena , Andreu Laia , Oller Pere , Gutiérrez Emilia , Martínez Pere 
Published: November 2007

AbstractHistorical data about ancient avalanches are scarce in the Pyrenees. Dendrochronology can provide new data about past avalanches and their return period, but up to now little research has been carried out with this purpose. The Aludex project aims to obtain information about the frequency and extent of extreme avalanches, using a dendrochronological and a nivo-meteorological approach. In this paper, we present the results of a dendrochronological study of the Canal del Roc Roig avalanche path which was affected by two extreme avalanches in February 1996. This first dendrochronological study has permitted us to assess the tree-ring signals due to avalanche events in 53 out of 132 dated trees. The trees presented a variety of responses to the 1996 avalanche events. It is shown that the type of tree-ring signal depends on tree age. The methodology has proved successful in detecting the 1996 and 1972 documented avalanche events, and provided outstanding evidence of undocumented past events such as one in 1930.
Verification of nearest-neighbours interpretations in avalanche forecasting
Authors: Heierli Joachim , Purves Ross S. , Felber Andreas , Kowalski Julia 
Published: November 2007

AbstractThis paper examines the positive and negative aspects of a range of interpretations of nearest-neighbours models. Measures-oriented and distribution-oriented verification methods are applied to categorial, probabilistic and descriptive interpretations of nearest neighbours used operationally in avalanche forecasting in Scotland and Switzerland. The dependence of skill and accuracy measures on base rate is illustrated. The purpose of the forecast and the definition of events are important variables in determining the quality of the forecast. A discussion of the application of different interpretations in operational avalanche forecasting is presented.
Experimental study of dense snow avalanches: velocity profiles in steady and fully developed flows
Authors: Bouchet Alexi , Naaim Mohamed , Bellot Hervé , Ousset Frédéric 
Published: November 2007

AbstractIn order to study channelled snow flows over rough surfaces, a laboratory-scale experiment was installed at the “Col du Lac Blanc”, a 2800 m high pass in the French Alps, near the Alpe d’Huez ski resort. It consists of a 0.2 mwide, 10 m long channel fed with snow by a motorized hopper. Both the slope of the channel and the feeding rate of the hopper can be modified. Sensors in the channel provide measurements of the velocity profile, the flow height and the shear and normal stresses at the bottom of the flow. Velocity profiles for different slopes are presented in this paper. Results indicate the presence of a highly active layer at the bottom. This layer is mainly responsible for the avalanche velocity, while the upper layer has a much smaller velocity gradient. A first interpretation of both layers is given.