bluuebunny/crossref_metadata_2025_split huggingface dataset:
Vertical zonation and community transition of sea-ice diatoms in fast ice and platelet layer, Weddell Sea, Antarctica
Authors: Günther Sven , Dieckmann Gerhard S. 
Published: November 2007

AbstractChanges in the taxonomic composition of diatoms in fast ice as well as in the underlying platelet layer were followed from June to December 1995 in Atka Bay Antarctica. Four communities were clearly distinguished: (1) an interior community dominated by flagellates in spring; (2) a bottom community dominated by a small form ofFragilariopsis cylindrus;(3) a platelet-ice layer dominated byAmphiprora KufferathiiandThalassionemasp. growing attached to the ice platelets; and (4) an interstitial community dominated byChaetoceros neglectusgrowing in the water between the platelets. Species composition distribution and succession in these communities were related to changes in silicate concentration, pore space and ice-formation processes and the ability of some cells to grow attached to ice platelets. The presence of the platelet-layer communities may have implications for paleoglaciology
Properties and structure of the seasonal snow cover in the continental regions of China
Authors: Wenshou Wei , Dahe Qin , Mingzhe Liu 
Published: November 2007

AbstractThe continental regions of China are extensively covered by snow during winter. In this paper, the seasonal snow cover in the Tien Shan and Altay mountains is observed and analyzed, based on the characteristics of the dry-cold snow cover accumulating under the continental climatic conditions in northwest China. Compared with the humid-warm snow cover, the dry-cold snow cover is characterized mainly by small density, low water content, large temperature gradient, thick depth hoar, etc., and its metamorphism is dominated by the thermal exchange and the pressure of the overlying snow layers. According to the observed data, the solar radiation flux on the snow surface is dominated by a negative balance in the arid areas in China during the snow season; the albedo on the new-fallen-snow surface is up to 96%, and the transmission depth of shortwave radiation in dry-cold snow cover is 28 cm. During the snowmelt season in spring, the thickness of the depth hoar can occupy 80% of the whole snow cover.
Time–space linear regression analysis of the snow cover in a pre-Alpine semi-forested catchment
Authors: Stähli Manfred , Papritz Andreas , Waldner Peter , Forster Felix 
Published: November 2007

AbstractSub-grid variability of the snow cover is an important issue with regard to catchment runoff or mesoscale meteorological modeling. Here, an evaluation is presented of spatial snow measurements conducted on 5 days in winter 1998/99 and 2 days in winter 1999/2000 in a 0.7 km2Swiss pre-Alpine catchment. Snow-depth data were analyzed with two different linear regression models, one including altitude, terrain slope, terrain aspect and canopy density, and one using altitude and simple land-use indicators. For the single measurement date/the first model was somewhat superior to the indicator model. The error term of the regression models showed only weak spatial dependence. Finally, a time-space linear regression model describing both the temporal development and the spatial distribution of the snow cover was fitted with the measurements of the first winter and tested with measurements of the second winter. The validation showed a satisfactory match between measurements and models in late December, but a slight overestimation of the measurements by the models in early April. In view of the models’ability to reproduce the snow-depth patterns satisfactorily at this rather detailed scale, it was concluded that such regression models might be a suitable tool to treat sub-grid variability of snow depth in larger-scale models.
Past 220 year bipolar volcanic signals: remarks on common features of their source volcanic eruptions
Authors: Kohno Mika , Fujii Yoshiyuki 
Published: November 2007

AbstractDuring the past 220 years, prominent signals of non-sea salt sulfate ion (nssSO42–) concentration exceeding the background level, including both marine biogenic and anthropogenic SO42–, were found in shallow ice cores from site H15 in East Antarctica and Site-J in southern Greenland. They were mostly correlated with past explosive volcanic eruptions. on the basis of this result and published results of shallow ice cores and snow pits at various locations on the Antarctic and Greenland ice sheets, eight common signals were found, of which six were assigned to the following explosive eruptions: El Chichόn, Mexico, in 1982; Agung, Indonesia, in 1963; Santa Maria, Guatemala, in 1902; Krakatau, Indonesia, in 1883; Cosiguina, Nicaragua, in 1835; an unknown volcano between 1831 and 1834; Tambora, Indonesia, in 1815; and an unknown volcano in 1809. Volcanic eruptions which have a potential to imprint their signals in both the Antarctic and Greenland ice sheets were characterized by (1) location in low latitudes between 20˚N and 10˚ S, and (2) eruption column height ≥25 km, corresponding to a volcanic explosivity index (VEI) ≥5.
High net accumulation rates at Campo deHielo Patagόnico Sur, South America, revealed by analysis of a 45.97 m long ice core
Authors: Shiraiwa Takayuki , Kohshima Shiro , Uemura Ryu , Yoshida Naohiro , Matoba Sumito , Uetake Jun , Godoi Maria Angelica 
Published: November 2007

AbstractA 45.97 m long ice core was recovered in the accumulation area of Glaciar Tyndall (50˚59’05’’ S, 73˚31’12’’W; 1756ma.s.l.), Campo de Hielo Patagόnico Sur (southern Patagonia icefield), during December 1999. the firn core was subjected to visual stratigraphic observation and bulk density measurements in the field, and later to analyses of water isotopes (δ18O, δD), major dissolved ions and snow algal biomass. the drillhole remained dry down to about 43 m depth, where a water-soaked layer appeared. Seasonal cycles were found for δ18O, δD and the D-excess, although the amplitudes of the cycles decreased with depth. Major dissolved ions (Na+, K+, Mg2+, Ca2+, Cl–, SO42–) and algal biomass exhibit rapid decreases in the upper 3 m, probably due to meltwater elution. Annual increments defined by the δ18O and D-excess peaks suggest that the minimum net accumulation rates at this location were 17.8ma–1 in 1997/98–1998/99 and 411.0 ma–1 in 1998/99–1999/2000. These are much higher values than those previously obtained from past ice-core studies in Patagonia, but are of the same order of magnitude as those predicted from various observations in ablation areas of Patagonian glaciers.
Electrical measurements on the 2503 m Dome F Antarctic ice core
Authors: Fujita Shuji , Azuma Nobuhiko , Motoyama Hideaki , Kameda Takao , Narita Hideki , Fujii Yoshiyuki , Watanabe Okitsugu 
Published: November 2007

AbstractThe 320 kyr climatic record from the 2503 m Dome Fuji (Antarctica) ice core was analyzed using two electrical methods: AC-ECM and ECM (electrical conductivity measurements). AC-ECM is a method to detect the complex admittance between electrodes dragged on the ice surface with mm-scale resolution and uses 1V and 1 MHz. the ratio of the real to imaginary part of the admittance is the AC loss factor, which responds linearly to the amount of sulfuric acid and hydrogen ions. Both the AC loss factor and the ECM current respond to acid, but the ECM signal tends to saturate at high acidities. Dome Fuji ice was measured to be highly acidic, with background values of 2–7 μM, and had 4500 major peaks with acidities of up to 90 μM. This ice-core evidence and earlier snow-chemistry survey around the dome region indicates that Dome F may have a better connection to the stratosphere than have sites at lower altitude, which allows more stratospheric aerosol and gases to reach the snow surface. Acidity tends to be high in interglacial periods, but correlation between acidity and δ18O is not straightforward. Electrical signals decreased and smoothed out with increasing depth; the diffusion coefficients deduced from this smoothing were 10–102 times greater than in solid ice. the ice core exhibited electromechanical effects and expelling effects from sulfate peaks.
Cold firn in the Mont Blanc and Monte Rosa areas, European Alps: spatial distribution and statistical models
Authors: Suter Stephan , Hoelzle Martin 
Published: November 2007

AbstractNear-surface firn temperatures were measured in 22 steam-drilled boreholes in the summit region of Mont Blanc (France and Italy) at 3800 –4800ma.s.l. in June 1998 and in 31 boreholes in the Monte Rosa area (Italy and Switzerland) at 3900– 4500ma.s.l. in May–July 1999. Borehole temperatures were logged to 22 m depth. the temperatures at 18 m depth ranged between temperate conditions and approximately –15˚C. In a small altitude band, the observed distribution pattern suggests a strong influence of shortwave radiation and turbulent heat exchange (being generally more effective at wind-exposed sites). These two energy fluxes mainly determine the melt-energy input into the snow and firn during summer and, thereby, the measured near-surface temperatures. A statistical analysis of the measured firn temperatures revealed altitude-dependent firn temperature gradients of –1.48 and of –2.36˚C (100m)–1 for the Mont Blanc and Monte Rosa areas, respectively. the high lapse rates, as compared to the air-temperature lapse rate, are the result of englacial latent-heat contribution. the parameters elevation, potential direct solar radiation, slope and accumulation explain 480% of the variation of the mean annual firn temperatures. Aspect-dependent lower boundaries for the cold-firn occurrence in the two areas ranged between 3500 and 4100 ma.s.l.
Retrieval of snow reflectance from Landsat data in rugged terrain
Authors: Xin Li , Koike Toshio , Guodong Cheng 
Published: November 2007

AbstractWe developed a model to calculate the spectral reflectance of snow by normalizing the topographic effect and correcting the atmospheric effect simultaneously. This model considers the shadowing effect of the surrounding terrain on both direct and diffuse irradiance by using the obstruction coefficient in sun-ray direction and introducing the isotropic view factor. In addition, a new method to calculate the surrounding-reflected irradiance by introducing the shape factor which can account for the radiation reflected from the surrounding pixels was developed. The model was tested in the upper stream of the Heihe river basin, Qilian mountains, China, using a subscene of a Landsat Enhanced Thematic Mapper Plus (ETM+) image acquired on 20 April 2000. The result showed that the model could eliminate most of the shadowing effect of rugged terrain and could estimate snow reflectance correctly. The problem of data saturation when retrieving snow reflectance is also discussed.
RADARSAT interferometry for Antarctic grounding-zone mapping
Authors: Gray L. , Short N. , Bindschadler R. , Joughin I. , Padman L. , Vornberger P. , Khananian A. 
Published: November 2007

AbstractSatellite radar interferometry (SRI) is used to provide new information on grounding zones in areas of the eastern Ross Ice Shelf and the Filchner Ice Shelf, Antarctica. At the times of the RADARSAT SRI passes, separated by 24 days, a tidal model predicts a change in vertical displacement of the freely floating ice of >1 m in both areas. The change in vertical position occurs over a 5–10 km flexure zone adjacent to the grounding line and would lead to a relatively high interferometric phase fringe rate. This was observed in some areas, and suitable imagery has been used to map the grounding-zone position to an estimated accuracy of 1–2 km. Results for the ice-plain area upstream of the Crary Ice Rise are consistent with the tidal model and improve the previous grounding-line estimates based on field surveys and Système Probatoire pour l’Observation de la Terre (SPOT) data. The results support the suggestion of increased ice grounding in this area, and show that a sub-ice-shelf water channel around the southern end of the Crary Ice Rise is unlikely. Results for the Filchner Ice Shelf also show that existing maps of the grounding zone can be refined. In particular, we identify a large ice rise close to the mouth of the Bailey Ice Stream.
Usage of high-resolution Landsat 7 band 8 for single-band snow-cover classification
Authors: W.Vogel Stefan 
Published: November 2007

AbstractWith the launch of Landsat 7 a new band was added to the Landsat Enhanced Thematic Mapper Plus (ETM+). The new panchromatic band 8 covers wavelengths of 0.52–0.92μm and extends over band 2 (0.525–0.605 μm), band 3 (0.630–0.690 μm) and band 4 (0.750–0.900 μm). Its high resolution, with a pixel length of 15 m, is of interest for high-spatial-resolution analysis. This project focused on using Landsat 7 band 8 as a precise tool to obtain remotely the size and shape of permanent snowpatches in the mountainous area west of Abisko, Sweden. In the supervised classification employed, shadowed and non-shadowed areas were classified separately. Supervision of the classification was based on ground-truthing consisting of photographic mapping of the snow cover in the study area. The results from this single-band classification were compared to the results from the normalized- difference snow index (NDSI) and false-color images using bands 2, 4 and 5. This comparison showed similar estimates of the total amount of snow-covered area, with the additional advantage that the Landsat 7 band 8 (LB8) classification detects details in the extent of individual snowfields. This new application and the insights documented here support the use of Landsat 7 band 8 for snow-cover investigations in the future.
A comparison of Eulerian and Lagrangian methods for dating in numerical ice-sheet models
Authors: Rybak Oleg , Huybrechts Philippe 
Published: November 2007

AbstractAccurate dating in ice sheets is required for a correct interpretation of palaeoclimatic records and for incorporation of material characteristics in the flow law which depend on ice age. In this paper, we make a comparison between a Lagrangian and Eulerian approach to the ice advection problem in numerical ice-sheet models. This comparison is first performed for a schematic two-dimensional ice sheet of Nye–Vialov type with a prescribed stationary velocity field. Severalcases are examined which incorporate basal melting, basal sliding and an undulating bed. A further comparison is made with an analytical solution for the ice divide. Both methods are also applied in a thermomechanical model of the Antarctic ice sheet for steady-state present-day conditions. Our main conclusion is that, for similar discretization parameters, the Lagrangian method produces less error than an Eulerian approach using a second-order upwinding finite-difference scheme, though the difference is small (<1%) for the largest part of the model domain. However, problems with the Lagrangian approach are introduced by the dispersion of tracers, necessitating the use of interpolation procedures that are a main source of additional error. It is also shown that a cubic-spline approximation of Lagrangian trajectories improves accuracy, but such a method is computationally hardly applicable in large-scale ice-sheet models.
Relationship between topography and flow in the north polar cap on Mars
Authors: Hvidberg Christine Schøtt 
Published: November 2007

AbstractAssuming that the permanent north polar cap of Mars consists of flowing water ice, the relationship between topography and flow is examined along a profile extending from the pole in the 160° E direction This profile is intersected by scarps and troughs that are characteristic of the north polar cap The flow is calculated by a finite-element ice-flow model which includes divergence of the flow, longitudinal stresses and temperature effects. Ice-flow velocities are generally on the order of 0.1–1 mm a–1 but are enhanced at scarps and troughs to cm a–1. Ice flow smooths out the troughs. Troughs affect the flow to the bottom of the cap. Beneath a trough, ice is dragged upward. Longitudinal stresses are able to drag the lowest part of the ice past smaller troughs. At the pole-facing side of major troughs, ice is stagnant or flows slowly poleward. Implications for formation mechanisms of scarps and troughs are discussed.
Ice-flow measurements and deformation at marginal shear zones on Sørsdal Glacier, Ingrid Christensen Coast, East Antarctica
Authors: Patrick Benjamin A. , Corvino Adrian F. , Wilson Christopher J.L. 
Published: November 2007

AbstractObservations of crevasse and crevasse trace geometry recorded along marginal shear zones of Sørsdal Glacier, East Antarctica, are presented with fine-spatial-resolution measurements of ice flow collected at three selected study sites. Strain grids established at each site, comprising 254 points, were repeatedly surveyed during the summers 2000/01 and 2001/02 using a semi-kinematic global positioning system technique with relative coordinate precisions at the order of ±2 cm in horizontal and ±5 cm in vertical. The annual results show ice-flow velocities of 2–114 m a–1 across a 2.7 km section of the Sørsdal margin. Comparable ice-flow velocities were also obtained using a Doppler system DORIS. At one study site, covering a planar area of 0.04 km2, a preliminary comparison is made between the crevasse pattern and strain-rate tensors computed for 64 discrete points using the method developed by Nye (1959). The comparison indicates that the most recent crevasses are directly related to the principal strain rates in this zone of simple shear.
Interannual velocity variations and recent calving of Thwaites Glacier Tongue, West Antarctica
Authors: Rabus Bernhard T. , Lang Oliver , Adolphs Ute 
Published: November 2007

AbstractThe surface velocity of Thwaites Glacier (TG), West Antarctica, during the period 1992–2000 is measured with synthetic aperture radar feature-tracking techniques. We find no indication of interannual velocity variations of the grounded ice further than about 20 km inland of the grounding line. The velocity of the floating TG Tongue shows cyclicalvariations with an amplitude of 10%; a minimum around 1997 is bracketed by similarly sized maxima in 1995 and 2000. The observed velocity variations can be explained by time-dependent rotation and deformation superimposed on the steady flow of TG Tongue. The orientation of the rotation is clockwise during the entire observation period; the mean center of the rotation is close to a small ice rise, situated at the east side of the tongue about 20 km past the grounding line. The recent calving of TG Tongue in February 2002 is consistent with continued clockwise rotation that eventually led to cracking from west to east across the tongue. The rotation and deformation of TG Tongue is caused by forces unrelated to glacier dynamics. Analysis of European Centre for Medium-Range Weather Forecasts wind data suggests a synoptic-scale origin for the external forcing that causes the rotation.
Observational verification of predicted increase in bedrock-to-surface amplitude transfer during a glacier surge
Authors: Hilmar Gudmundsson G. , Ađalgeirsdóttir Gudfinna , Björnsson Helgi 
Published: November 2007

AbstractThe amplitude ratio between surface and bedrock topography has been predicted to depend strongly on the ratio of deformational velocity to mean basal sliding velocity. Observations made prior to and during a surge of Tungnaárjökull, Vatnajökull ice cap, Iceland, allow this prediction to be tested. During the surge, the ratio of internal deformational velocity and basal sliding (slip ratio) changed from about unity to a few hundred. The amplitude ratio changed from about 0.1 to about 0.7. This increase in amplitude ratio is in good overall agreement with predictions based on an analytical perturbation analysis for a linearly viscous medium which includes the effects of horizontal deviatoric stresses on glacier flow. An increase in amplitude ratio of this magnitude is not predicted by a similarly linearized analysis that employs the commonly used shallow-ice approximation. The strong increase in transfer amplitude observed in the surge of Tungnaárjökull is a clear illustration of the effects of horizontal stress transmission on glacier flow reported here for the first time.
Observation of internal structures of snow covers with a ground-penetrating radar
Authors: Yamamoto Tatsuya , Matsuoka Kenichi , Naruse Renji 
Published: November 2007

AbstractTo complement a technique to detect internal structures of seasonal snow covers and glacier firn with ground-penetrating radar (GPR), we carried out calibration experiments and an observation of winter snow cover (5.7m thick dry snow with numerous ice layers) with an 800 MHz GPR. In particular, we aimed to discriminate periodic noise, which is inherent in GPR, from radar echoes and to obtain a relationship between the observed reflection strength and the magnitude of density contrasts. Experiments were done in air to evaluate noise levels and receiver characteristics of this system. Based on these, we removed noise from radar echoes in the snow-cover observation. We recognized numerous marked echoes in a noise-free radargram. The depths of these echoes coincided roughly with those of large density contrasts observed in the snow pit. Thus, we argue that the echoes correspond to thin ice layers. Furthermore, the minimum density contrasts detected by this GPR are found to vary from about 100 to 250 kgm–3 at 1–6m depth in the seasonal snow cover.
Risk assessment in avalanche-prone areas
Authors: Barbolini Massimiliano , Cappabianca Federica , Savi Fabrizio 
Published: November 2007

AbstractThis paper addresses the problem of defining a proper method for formal risk analysis in avalanche-prone areas. In this study, risk is defined as the annual probability of being killed by an avalanche for someone living or working permanently in a building under a hazardous hillside. A new methodology to estimate the hazard component of avalanche risk based on the use of dynamic models is introduced. This approach seems to have some advantages over the current methods based on statistical analysis of historic avalanche data. The vulnerability component of risk is formulated as a function of avalanche velocity, according to previous formulations. However, given the lack of knowledge on how avalanche impact damages structures and causes fatalities, the effect on the resulting risk mapping of using different vulnerability relations is explored. The potential of the proposed approach for evaluating the residual risk after the implementation of defensive structural work is discussed.
A re-analysis of the 58 year mass-balance record of Storglaciären, Sweden
Authors: Holmlund Per , Jansson Peter , Pettersson Rickard 
Published: November 2007

AbstractThe use of glacier mass-balance records to assess the effects of glacier volume change from climate change requires high-quality data. The methods for measuring glacier mass balance have been developed in tandem with the measurements themselves, which implies that the quality of the data may change with time. We have investigated such effects on the mass-balance record of Storglaciären, Sweden, by re-analyzing the records using a better map base and applying successive maps over appropriate time periods. Our results show that errors <0.8 m occur during the first decades of the time series. Errors decrease with time, which is consistent with improvements in measurement methods. Comparison between the old and new datasets also shows improvements in the relationships between net balance, equilibrium-line altitude and summer temperature. A time-series analysis also indicates that the record does not contain longer-term (>10 year) oscillations. The pseudo-cyclic signal must thus be explained by factors other than cyclically occurring phenomena, although the record may still be too short to establish significant signals. We strongly recommend re-analysis of long mass-balance records in order to improve the mass-balance records used for other analyses.