bluuebunny/crossref_metadata_2025_split huggingface dataset:
Initial experiments on the effects of particles at grain boundaries on the anelasticity and creep behavior of granular ice
Authors: Song Min , Cole David M. , Baker Ian 
Published: November 2007

AbstractExperimental observations of the influence of particles at grain boundaries on the anelasticity and creep behavior of granular fresh-water ice are presented. Ice with particle contents of 0–4 wt.% was investigated under both reversed direct-stress and creep loading conditions at –12˚C. The results show that the particles decreased the grain-boundary relaxation by suppressing grain-boundary sliding at higher frequencies (10–1 to 101 Hz). In addition, the modulus increased by up to 30%, and the internal friction decreased by up to 30% at a frequency of 1 Hz. Staged creep tests showed that the particles affected the creep rate substantially. The minimum creep rate of ice containing 1 wt.% particles is 40% higher than that of particle-free ice, indicating that mechanisms besides dislocation glide aid the creep deformation.
Sensitivity of chemical species to climatic changes in the last 45 kyr as revealed by high-resolution Dome C (East Antarctica) ice-core analysis
Authors: Udisti Roberto , Becagli Silvia , Benassai Silvia , De Angelis Martine , Hansson Margareta E. , Jouzel Jean , Schwander Jacob , Steffensen Jørgen P. , Traversi Rita , Wolff Eric 
Published: November 2007

AbstractTo assess the cause/effect relationship between climatic and environmental changes, we report high-resolution chemical profiles of the Dome C ice core (788m, 45 kyr), drilled in the framework of the European Project for Ice Coring in Antarctica (EPICA). Snow-concentration and depositional-flux changes during the last deglaciation were compared with climatic changes, derived by δD profile. Concentration and temperature profiles showed an anticorrelation, driven by changes in source intensity and transport efficiency of the atmospheric aerosol and by snow accumulation-rate variations. The flux calculation allowed correction for accumulation rate. While sulphate and ammonium fluxes are quite constant, Na+, Mg2+ and Ca2+ underwent the greatest changes, showing fluxes respectively about two, three and six times lower in the Holocene than in the Last Glacial Maximum. Chloride, nitrate and methanesulphonic acid (MSA) also exhibited large changes, but their persistence depends on depositional and post-depositional effects. The comparison between concentrations and δD profiles revealed leads and lags between chemical and temperature trends: Ca2+ and nitrate preceded by about 300 years the δD increase at the deglaciation onset, while MSA showed a 400 year delay. Generally, all components reached low Holocene values in the first deglaciation step (18.0–14.0 kyr BP), but Na+, Mg2+ and nitrate show changes during the Antarctic Cold Reversal (14.0– 12.5 kyr BP).
Distribution and pattern of shallow melting at the local glaciers of Terra Nova Bay (Antarctica) coast
Authors: Motta Luigi , Motta Michele 
Published: November 2007

AbstractMelting is a fundamental process in glacier mass balance as well as in other glacial processes such as ice movement, ice avalanches and snow metamorphism. At Terra Nova Bay, Antarctica, the annual mean temperature is <0˚C but melting is not negligible. Our data show that melting is present up to 1300ma.s.l. The distribution and relative importance of melting change with elevation and exposure. At low elevation and with a southerly exposure, melting is one of the major summer ablation processes, synergetic with dry calving and katabatic wind. Meltwater seepage reaches the glacier substrate. Discharge appears to be linked to irradiation, offset by a few hours relative to it. The frontal area of the glaciers therefore behaves like an aquifer, and its characteristics depend on the morphology of the front. As elevation increases, melting at first becomes limited to the snowpack, then to low-albedo cases, for example when dust is brought in from the areas surrounding the glacier. In this case, melting limits ablation, providing the snow with increased resistance to wind erosion.
Geostatistical estimation from radar altimeter data with respect to morphological units outlined by SAR data: application to Lambert Glacier/Amery Ice Shelf, East Antarctica
Authors: Stosius Ralf , Herzfeld Ute C. 
Published: November 2007

AbstractThe objective of this paper is the comparison of two kriging methods, ordinary kriging and kriging within strata, for calculation of digital elevation models (DEMs) from radar altimeter data, and application to the Lambert Glacier/Amery Ice Shelf system, East Antarctica. Two new DEMs are presented. First, a DEM of the Lambert Glacier/Amery Ice Shelf system is calculated from 1997 European Remote-sensing Satellite-2 (ERS-2) radar altimeter (RA) data using geostatistical interpolation. RA data have high along-track density, but gaps between tracks are several kilometers, depending on the observation mode; this requires interpolation. Because the ice-stream/ice-shelf system is of primary interest in glaciological investigations, in the first approach a variogram characteristic of the Lambert Glacier ice surface is used. The resultant map has low errors for the glacier and the ice shelf. To match the surface characteristics of different morphological units that constitute the Lambert Glacier/Amery Ice Shelf region, a second DEM is constructed as follows: We utilize RADARSAT synthetic aperture radar (SAR) data that were collected in 1997 during the first Antarctic Imaging Campaign and composed into a 125m backscatter-data mosaic by Jezek (1999) and we co-reference the 125m mosaic with the altimetry-derived DEM. The Lambert Glacier/Amery Ice Shelf area is then subdivided into several regions which are homogeneous with respect to characteristic surface-morphological properties identified in the SAR mosaic. For those regions, a problem-oriented complex kriging method known as kriging within strata is performed, and the resulting DEM is compared to the DEM that was derived from kriging without regional subdivision.
Dynamics of the Scharffenbergbotnen blue-ice area, Dronning Maud Land, Antarctica
Authors: Sinisalo Anna , Grinsted Aslak , Moore John 
Published: November 2007

AbstractGround-penetrating radar (GPR) surveys in Scharffenbergbotnen valley, Dronning Maud Land, Antarctica, complement earlier, relatively sparse data on the ice-flow dynamics and mass-balance distribution of the area. The negative net surface mass balance in the valley appears to be balanced by the inflow. The flow regime in Scharffenbergbotnen defines four separate mass-balance areas, and about 60 times more ice enters the valley from the northwestern entrance than via the narrow western gate. We formalize and compare three methods of determining both the surface age gradient of the blue ice and the dip angles of isochrones in the firn/blue-ice transition zone: observed and dated radar internal reflections, a geometrical model of isochrones, and output from a flowline model. The geometrical analysis provides generally applicable relationships between ice surface velocity and surface age gradient or isochrone dip angle.
Growth processes of an inland Antarctic ice wedge, Mesa Range, northern Victoria Land
Authors: Raffi Rossana , Stenni Barbara , Flora Onelio , Polesello Stefano , Camusso Marina 
Published: November 2007

AbstractDuring the 16th Italian Antarctic Expedition (2000/01) a geomorphological survey of permafrost-related polygons was carried out in the Mesa Range area, upper Rennick Glacier. The investigated site is located in the uppermost reaches of Pain Mesa, which forms the northern sector of the Mesa Range. An ice wedge was found in a volcanic regolith at about 2200ma.s.l. This altitude is below a well-defined erosional trimline, located at about 2380ma.s.l. in this sector of Pain Mesa. The ice was sampled by inserting an ice screw, with an internal diameter of 14 mm, into the ice wedge in vertical sequences. Oriented block samples for thin sections were taken. A co-isotopic study was performed, measuring both oxygen (δ18O) and hydrogen (δD) isotope compositions. Tritium activity was measured, and major cations and anions were determined. The δ18O and δD obtained showed a strong divergence from the snowfalls expected to occur at this elevation, with extremely negative d excess values. Sublimation processes were taken into account to define the origin of the ice forming the wedge. The tritium data obtained suggest that the growth process of the ice wedge might still be active today.
Modelling the isotopic composition of snow using backward trajectories: a particular precipitation event in Dronning Maud Land, Antarctica
Authors: Helsen Michiel M. , Van De Wal Roderik S. W. , Van Den Broeke Michiel R. , Kerstel Erik R. Th. , Masson-Delmotte Valérie , Meijer Harro A. J. , Reijmer Carleen H. , Scheele Marinus P. 
Published: November 2007

AbstractWe consider a specific accumulation event that occurred in January 2002 in western Dronning Maud Land, Antarctica. Snow samples were obtained a few days after accumulation. We combine meteorological analyses and isotopic modelling to describe the isotopic composition of moisture during transport. Backward trajectories were calculated, based on European Centre for Medium-Range Weather Forecasts operational archive data so that the history of the air parcels transporting water vapour to the accumulation site could be reconstructed. This trajectory study showed that the air masses were not (super)saturated along most of the transport path, which is in contrast with assumptions in Lagrangian fractionation models and probably true for most precipitation events in Antarctica. The modelled fractionation along the trajectories was too limited to explain the measured isotopic content of the snow. It is shown that the observed isotopic composition of precipitation resulted from fractionation of initially more depleted water. This lower initial isotopic composition of water vapour might result from atmospheric mixing with more depleted air along the trajectory or from earlier condensation cycles, not captured by the trajectories. This is in accordance with isotope fields resulting from general circulation models, indicating a gradient in isotopic composition from the Equator to Antarctica.
A 700 year record of Southern Hemisphere extratropical climate variability
Authors: Mayewski Paul A. , Maasch Kirk A. , White James W. C. , Steig Eric J. , Meyerson Eric , Goodwin Ian , Morgan Vin I. , Van Ommen Tas , Curran Mark A. J. , Souney Joseph , Kreutz Karl 
Published: November 2007

AbstractAnnually dated ice cores from West and East Antarctica provide proxies for past changes in atmospheric circulation over Antarctica and portions of the Southern Ocean, temperature in coastal West and East Antarctica, and the frequency of South Polar penetration of El Niño events. During the period AD 1700–1850, atmospheric circulation over the Antarctic and at least portions of the Southern Hemisphere underwent a mode switch departing from the out-of-phase alternation of multi-decadal long phases of EOF1 and EOF2 modes of the 850 hPa field over the Southern Hemisphere (as defined in the recent record by Thompson and Wallace, 2000; Thompson and Solomon, 2002) that characterizes the remainder of the 700 year long record. From AD 1700 to 1850, lower-tropospheric circulation was replaced by in-phase behavior of the Amundsen Sea Low component of EOF2 and the East Antarctic High component of EOF1. During the first phase of the mode switch, both West and East Antarctic temperatures declined, potentially in response to the increased extent of sea ice surrounding both regions. At the end of the mode switch, West Antarctic coastal temperatures rose and East Antarctic coastal temperatures fell, respectively, to their second highest and lowest of the record. Polar penetration of El Niño events increased during the mode switch. The onset of the AD 1700–1850 mode switch coincides with the extreme state of the Maunder Minimum in solar variability. Late 20th-century West Antarctic coastal temperatures are the highest in the record period, and East Antarctic coastal temperatures close to the lowest. Since AD 1700, extratropical regions of the Southern Hemisphere have experienced significant climate variability coincident with changes in both solar variability and greenhouse gases.
Towards multi-sensor microwave remote sensing of frost flowers on sea ice
Authors: Kaleschke Lars , Heygster Georg 
Published: November 2007

AbstractIt has been hypothesized that frost flowers could be important for tropospheric chemistry and, as a source of sea-salt aerosol, for the interpretation of ice-core data. Furthermore, frost flowers can cause severe errors in sea-ice products derived from remote-sensing data. Up to now there have been few datasets available relating frost-flower distribution and variability in the sea-ice-covered regions. We present a method for frost-flower detection using a combination of active and passive microwave sensors. The vertical polarized C-band radar backscatter of a young sea-ice region covered with frost flowers can be higher than the signal from multi-year ice or from the wind-roughened ocean. Therefore, the classification result of synthetic aperture radar (SAR) sea-ice images can be defective due to the influence of frost flowers. The ambiguity of the open-water and frost-flower backscatter signal was successfully resolved using additional information from the 85 GHz Special Sensor Microwave/Imager (SSM/I) channels. Results of the method were compared to aircraft measurements and observations in the marginal ice zone near Svalbard.
High-time-resolution profiles of soluble ions in the last glacial period of a Dome Fuji (Antarctica) deep ice core
Authors: Iizuka Yoshinori , Takata Morimasa , Hondoh Takeo , Fujii Yoshiyuki 
Published: November 2007

AbstractWe measured the depth profiles of soluble ions in the Dome Fuji (Antarctica) ice core to search for possible paleoclimate indications of seasonal climate variations in the last glacial period. A 523 mm long core section between 587.65 and 588.18 m depth was selected for this pilot study, and the high-resolution chemical analysis was done on 2 mm thick samples. Our results indicate that anion– cation trapping in ice affects the profiles of the soluble ions and [Na+] in the core may preserve its seasonal signal. Correlation coefficients and the equivalent balances of the soluble ions suggest the following selective coexistences: (1) [Cl–] = [Na+], (2) [NO3–] = 1/2[Ca2+] + [K+], and (3) [SO42–] = 1/2[Ca2+] + [H+] + [Mg2+]. These coexistences are probably due to (1) a sea-salt source of Na+ and Cl–, (2) reaction of NO3– with dust for Ca2+ and NO3–, and (3) anion–cation trapping in ice for SO42– and Ca2+ (Mg2+), respectively.
Initial borehole results from the Amery Ice Shelf hot-water drilling project
Authors: Craven Mike , Allison Ian , Brand Russell , Elcheikh Alan , Hunter John , Hemer Mark , Donoghue Shavawn 
Published: November 2007

AbstractThe Amery Ice Shelf Ocean Research (AMISOR) project aims to examine and quantify processes involved in the interaction between the ice shelf, the interior grounded ice and the oceanic water masses that circulate beneath it. Two boreholes were melted through the shelf, within 100 km of the calving front, to access the ocean cavity. One (AM02) was at a site where it was believed that basal melt was occurring, and the other (AM01) was in a region with accreted marine ice. At both sites the summertime ocean structure revealed meltwater-modified boundary layers up to 100 m thick immediately beneath the shelf. Salinity and temperature data in the upper cavity at AM02 showed a strong seasonal cycle as a result of a combination of ice-shelf basal melt, and the intrusion of ocean water masses modified by sea-ice processes in Prydz Bay. At AM01, a 200m thick layer of marine ice underlay the meteoric ice, and showed an increase in salinity and decrease in stable-isotope fractionation with depth. The lowest 100m of marine ice was highly permeable, with a rectangular banded textural facies. Other preliminary results from this study are also reported.
Sulfur isotopic measurements from a West Antarctic ice core: implications for sulfate source and transport
Authors: Pruett Lee E. , Kreutz Karl J. , Wadleigh Moire , Mayewski Paul A. , Kurbatov Andrei 
Published: November 2007

AbstractMeasurements of δ34S covering the years 1935–76 and including the 1963 Agung (Indonesia) eruption were made on a West Antarctic firn core, RIDSA (78.73˚ S, 116.33˚ W; 1740ma.s.l.), and results are used to unravel potential source functions in the sulfur cycle over West Antarctica. The δ34S values of SO42– range from 3.1‰ to 9.9‰. These values are lower than those reported for central Antarctica, from near South Pole station, of 9.3–18.1‰ (Patris and others, 2000). While the Agung period is isotopically distinct at South Pole, it is not in the RIDSA dataset, suggesting differences in the source associations for the sulfur cycle between these two regions. Given the relatively large input of marine aerosols at RIDSA (determined from Na+ data and the seasonal SO42– cycle), there is likely a large marine biogenic SO42– influence. The δ34S values indicate, however, that this marine biogenic SO42–, with a well-established δ34S of 18‰, is mixing with SO42– that has extremely negative δ34S values to produce the measured isotope values in the RIDSA core. We suggest that the transport and deposition of stratospheric SO42– in West Antarctica, combined with local volcanic input, accounts for the observed variance in δ34S values.
The role of ice thickness and bed properties on the dynamics of the enhanced-flow tributaries of Bailey Ice Stream and Slessor Glacier, East Antarctica
Authors: Rippin David M. , Bamber Jonathan L. , Siegert Martin J. , Vaughan David G. , Corr Hugh F. J. 
Published: November 2007

AbstractAirborne radio-echo sounding investigations in the upper reaches of Bailey Ice Stream and Slessor Glacier, Coats Land, East Antarctica, have shown that enhanced-flow tributaries are associated with well-defined areas of relatively thicker ice, and are separated from each other by areas of relatively thinner ice. A numerical modelling study has revealed that while internal ice deformation might account for all the observed flow in inter-tributary areas and the majority in the Slessor tributaries, a significant proportion of the flow of Bailey tributary is attributable to basal motion. Further, investigations of depth-corrected basal reflection power indicate that the bed underlying both Bailey and Slessor enhanced-flow tributaries is significantly smoother than in the slower-moving inter-tributary areas. It is thus proposed that enhanced motion within Bailey tributary (and also perhaps Slessor) may be facilitated by a reduction in basal roughness, caused by the accumulation of water and/or sediments within subglacial valleys, or by the erosion and smoothing of bed obstacles.
Variability in accumulation rates from GPR profiling on the West Antarctic plateau
Authors: Spikes Vandy B. , Hamilton Gordon S. , Arcone Steven A. , Kaspari Susan , Mayewski Paul A. 
Published: November 2007

AbstractIsochronal layers in firn detected with ground-penetrating radar (GPR) and dated using results from ice-core analyses are used to calculate accumulation rates along a 100 km across-flow profile in West Antarctica. Accumulation rates are shown to be highly variable over short distances. Elevation measurements from global positioning system surveys show that accumulation rates derived from shallow horizons correlate well with surface undulations, which implies that wind redistribution of snow is the leading cause of this variability. Temporal changes in accumulation rate over 25–185 year intervals are smoothed to along-track length scales comparable to surface undulations in order to identify trends in accumulation that are likely related to changes in climate. Results show that accumulation rates along this profile have decreased in recent decades, which is consistent with core-derived time series of annual accumulation rates measured at the two ends of the radar profile. These results suggest that temporal variability observed in accumulation-rate records from ice cores and GPR profiles can be obscured by spatial influences, although it is possible to resolve temporal signals if the effects of local topography and ice flow are quantified and removed.
Aluminium and iron record for the last 28 kyr derived from the Antarctic EDC96 ice core using new CFA methods
Authors: Traversi Rita , Barbante Carlo , Gaspari Vania , Fattori Ilaria , Largiuni Ombretta , Magaldi Lorenzo , Udisti Roberto 
Published: November 2007

AbstractSpectrofluorimetric and spectrophotometric continuous flow analysis (CFA) methods were developed and applied to the determination of aluminium and iron in EPICA Dome C (East Antarctica) ice-core samples (6–585m depth). The methods are able to measure the fraction of Al and Fe which can be detected once the sample is filtered on a 5.0 μm membrane and acidified to pH 2. Both the methods present high sensitivity (detection limit of 10 ng L–1 for Al and 50 ng L–1 for Fe) and reproducibility (5% at sub-ppb level). The Fe and Al profiles show sharp decreases in concentrations in the last glacial/interglacial transition, reflecting the decreasing dust aerosol load. The two elements show a different pattern during the Antarctic Cold Reversal (ACR) climatic change, with high iron concentrations (similar to the glacial period) and low but increasing Al content during the ACR minimum. In order to interpret the Al and Fe data obtained by CFA, a comparison with Al and Fe composition, as measured by inductively coupled plasma sector field mass spectrometry (ICP-SFMS), was performed for Holocene, ACR and glacial periods. The percentage of CFA-Al with respect to ICP-SFMS-Al in the three periods shows a lower variability than CFA-Fe (3% in the glacial period and 64% in the ACR). This pattern may be explained by the different dominant iron sources in the different climatic periods. During the Last Glacial Maximum, Fe is proposed to arise mainly from insoluble continental dust, while a variety of ocean-recycled Fe, mainly distributed in fine particles and as more soluble species, shows a higher contribution in the ACR and, to a lesser extent, in the Holocene.
New bedrock map of Dome C, Antarctica, and morphostructural interpretation of the area
Authors: Forieri Alessandro , Zuccoli Luisa , Bini Alfredo , Zirizzotti Achille , Remy Frédérique , Tabacco Ignazio E. 
Published: November 2007

AbstractA new bedrock map of the Dome C area is presented, based on all radar data collected during Italian Antarctic Expeditions in 1995, 1997, 1999 and 2001. The map clearly distinguishes the Dome C plateau, along with valleys and ridges. The plateau develops at three different altimetric levels, and its morphology is characterized by hills and closed depressions. There are no visible features which can be ascribed to glacial erosion or deposition. The major valley is 15 km wide and 500 m deep; its axis is parallel to that of other valleys and ridges in the plateau. The valley bottom is not flat, but contains a saddle at its centre. The morphology of the major valley may be considered a relict one which was not modified by the overlying ice cap. Two large ridges, characterized by hills, saddles and depressions, lie near the boundaries of the area. The map is used to recalculate ice thickness below the European Project for Ice Coring in Antarctica (EPICA) borehole. The new thickness is 3300 m, 50m greater than before, implying that the expected palaeoclimate record from the ice core could extend back >800 kyr.