bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of heavy snowfall on ground temperature, northern Tibetan Plateau
Authors: Yang Meixue , Yao Tandong , Gou Xiaohua , Wang Huijun 
Published: November 2007

AbstractVery heavy snowfall occurred in the Amdo-Nagqu region during winter 1997/98, and enormous numbers of sheep and yaks died due to starvation and low temperatures. Some observation sites of the GEWEX (Global Energy and Water Cycle Experiment) Asian Monsoon Experiment (GAME)-Tibet are located in this area. In this paper, the variation of the ground temperature (GT) on the northern part of the Tibetan Plateau and its relationship with the heavy snow cover is analyzed based on the GAME-Tibet in situ observational data at several sites. The temporal and spatial differences of the variations of the daily maximum, daily minimum and range in GT are significant in 1997/98 in the northern part of the Tibetan Plateau. For example, at site D110, the daily range in GT fluctuated only 0.2˚C from the end of December 1997 to mid-April 1998, but in the north, at site D66, the daily range in GT fluctuated between 5˚C and ∼20˚C at the same depth and during the same period. At the southernmost site, MS3637, the daily range in GT fluctuated within 1.0˚C from mid-November to early February. From mid-February to mid-March, the daily range in GT increased and the peak was 8.1 ˚C. The temperature variation was related to the heavy snowfall that occurred on the northern Tibetan Plateau in winter 1997/98. The snow-cover conditions at different sites on the northern Tibetan Plateau were evaluated quantitatively from the variation of the GT at shallow depths.
Comparison of Holocene electrical records from Dome C and Vostok, Antarctica
Authors: Wolff Eric , Basile Isabelle , Petit Jean-Robert , Schwander Jakob 
Published: November 2007

AbstractAs part of the European Project for Ice Goring in Antarctica, a new deep ice core is being drilled at Dome C. Two electrical methods have been used on the core drilled so far: a new design of electrical conductivity method (EGM) instrument, and a traditional dielectric profiler. The two profiles are very similar in both peaks and background, consistent with acidity being the dominant influence on both in this part of the record. The Dome C records have been compared to EGM records from Vostok, and a tentative match has been made between them. This suggests a long-term average ratio of accumulation rate of 1.36 between this Dome C core and Vostok, and that the Dome C core analyzed so far (to 358 m) probably includes the very end of the Glacial-Holocene transition.
Spatial variability at shallow snow-layer depths in central Dronning Maud Land, East Antarctica
Authors: Richardson Cecilia , Holmlund Per 
Published: November 2007

AbstractThe spatial variability in snow accumulation varies between different regions in Dronning Maud Land, East Antarctica. This pattern cannot easily be explained by the single action of parameters such as distance to open sea, surface elevation or slope. In 1996-97 we mapped snow-layer depths within the top 11 m of the snowpack with a ground-based radar along a 500 km traverse on the polar plateau in central Dronning Maud Land. The results showed that the general accumulation pattern could be described by three major characteristic sections: a pronounced trend of decreasing net accumulation with increasing altitude from 2400 to 2840 m a.s.l.; relatively high erosion rates and occurrence of areas with net erosion at 2840-3140 m a.s.l.; and a slight trend of decreasing net accumulation with increasing altitude from 3140 to 3450 m a.s.l. The spatial variability in snow-layer depths showed a marked change around 3080 m a.s.l., with high variability at lower elevations and low variability at higher elevations. We also determined the spatial representativeness of 11 firn cores drilled along the traverse. In general, the representativeness of the cores was high. However, the core with the lowest representativeness underestimated the mean accumulation rate around the coring site by 22%. This shows that snow-radar data on spatial snow distribution are important for the interpretation of accumulation rates obtained from firn and ice cores.
Modelling of anisotropic ice flow in Law Dome, East Antarctica
Authors: L.Wang W. , Warner Roland C. 
Published: November 2007

AbstractA model for ice flow in a polar ice sheet is presented. It is based on laboratory measurements of ice rheology, and includes the effect of anisotropic-flow enhancement in tertiary creep as the ice progresses through a range of stress regimes as it passes through the ice sheet. This flow model is applied to the transect from the summit of Law Dome, East Antarctica, to Gape Folger. In the upper layers of the ice sheet good agreement is found between the shear strain-rate profiles from the model and borehole-inclination measurements. Modifications of the simple model predictions for high shear strain rates in the lower layers of the ice cap are required in order to match the observed surface velocities. In these lower regions reductions in both the enhancement of shear flow and shear stress appear to be required, and this suggests that more attention needs to be given to the dynaimcs deep within ice sheets.
The Weddell Sea region: an important precipitation channel to the interior of the Antarctic ice sheet as revealed by glaciochemical investigation of surface snow along the longest trans-Antarctic route
Authors: Dahe Qin , Mayewski Paul A. , Jiawen Ren , Cunde Xiao , Junying Sun 
Published: November 2007

AbstractGlaciochemical analysis of surface snow samples, collected along a profile crossing the Antarctic ice sheet from the Larsen Ice Shelf, Antarctic Peninsula, via the Antarctic Plateau through South Pole, Vostok and Komsomolskaya to Mirny station (at the east margin of East Antarctica), shows that the Weddell Sea region is an important channel for air masses to the high plateau of the Antarctic ice sheet (>2000 m a.s.l.). This opinion is supported by the following. (1) The fluxes of sea-salt ions such as Na+, Mg2 + and CF display a decreasing trend from the west to the east of interior Antarctica. In |eneral, as sea-salt aerosols are injected into the atmosphere over the Antarctic ice sheet from the Weddell Sea, large aerosols tend to decrease. For the inland plateau, few large particles of sea-salt aerosol reach the area, and the sea-salt concentration levels are low (2) The high altitude of the East Antarctic plateau, as well as the polar cold high-pressure system, obstruct the intrusive air masses mainly from the South Indian Ocean sector. (3) For the coastal regions of the East Antarctic ice sheet, the elevation rises to 2000 m over a distance from several to several tens of km. High concentrations of sea salt exist in snow in East Antarctica but are limited to a narrow coastal zone. (4) Fluxes of calcium and non-sea-salt sulfate in snow from the interior plateau do not display an eastward-decreasing trend. Since calcium is mainly derived from crustal sources, and nssSO42- is a secondary aerosol, this again confirms that the eastward-declining tendency of sea-salt ions indicates the transfer direction of precipitation vapor.
Different post-depositional processes of NO3– in snow layers in East Antarctica and on the northern Qinghai-Tibetan Plateau
Authors: Shugui Hou , Dahe Qin , Jiawen Ren 
Published: November 2007

AbstractThrough comparison of snow-pit NO3– profiles from central East Antarctica and the northern Qinghai-Tibetan Plateau (QTP), we conclude that NO3– peaks in the uppermost surface snow layers in central East Antarctica are not related to an atmospheric signal and that they need to be accounted for by post-depositional effects. Such effects, however, are not found in the snow-pit NO3– profiles from the northern QTP. NO3– can be deposited as a gas (HNO3–) or as a neutral salt, particularly by reaction with ammonia to form NH4NO3, or fixed by sea salt or terrestrial dust (Mulvaney and others, 1998). Thus, a difference in speciation between NO3– in snow layers in East Antarctica and at the northern QTP is suggested as the reason for the different post-depositional processes of NO3– in the two areas.
The variability of the Antarctic ice-sheet response to the climatic signal
Authors: Pattyn Frank 
Published: November 2007

AbstractHigh-resolution numerical model experiments were carried out along two flowlines in Dronning Maud Land, Antarctica, one flowline passing through the central part of a coastal mountain range and the other along a major continental ice stream (Shirase Glacier). Results showed that ice-sheet behaviour in response to the climatic signal differs locally. Response patterns are different for the inland ice sheet, for the coastal ice sheet and around marginal (subglacial) mountains. Modelled response time series were analyzed by lag-correlation, range and fractal analysis. Local differentiation in ice-sheet response is primarily related to the sensitive interplay between surface accumulation patterns, thermomechanical properties of the ice sheet and bedrock roughness.
Velocity difference between the surface and base of Ice Stream B2, West Antarctica, from radar fading-pattern experiment
Authors: Liu C. , Bentley C. R. , Lord N. E. 
Published: November 2007

AbstractAs an ice-sounding radar receiver and transmitter are moved together across the snow surface, the returning echoes change rapidly, forming the "spatial fading pattern". Because the fading pattern is determinedly the details of the ice-bed interface" and remains fixed in position relative to that interface while the ice moves, repeated measurements of the fading pattern can reveal the relative displacement between the snow surface and targets near the bed of the ice and/or in the ice. Six high-density grids, comprising flag lines approximately along and normal to the direction of ice flow on Ice Stream B2, West Antarctica, were repeatedly profiled with a digital 50 MHz radar system by triggering a burst of 128 pulses from the radar transmitter every 0.7 m. A highly directional microwave motion sensor and a manual event button provided registration marks along the lines. The original recorded amplitudes were resampled at a constant spatial interval by interpolation between adjacent traces to make possible an analytical comparison of fading patterns. Fading patterns recorded on different days were compared by cross-correlation analysis to estimate the horizontal displacement. Then near-surface crevasses, which locally blocked the transmitted energy, were used to correct for flag-positiomng errors. The results from the three largest grids are significantly different: differential motions between the surface and the bed range from 1 to -0.5 ma−1. We suspect that the differences are related to the complex systems of strains within the ice stream reported by Hulbe and Whillans (1997).
Apparatus for routine measurements of the thermal conductivity of ice cores
Authors: Festa Crescenzo , Rossi Aristide 
Published: November 2007

AbstractAn apparatus is described for measuring the thermal conductivity of ice by the transient hot-wire method. Thermal conductivity A, is determined by tracking the thermal pulse induced in the sample by a heating source consisting of a platinum resistor. A central segment of the same platinum heating resistor acts also as a thermal sensor. A heat pulse transferred to the ice for a period of 40s gives a maximum temperature increment of about 7-14°C. In good experimental conditions, the expected reproducibility of the measurements is within ±3%. The accuracy of the method depends on whether the instrument has been calibrated by reliable standard samples, certified by absolute methods.
Characteristics of air bubbles and hydrates in the Dome Fuji ice core, Antarctica
Authors: Narita Hideki , Azuma Nobuhiko , Hondoh Takeo , Fujii Michiko , Kawaguchi Mituo , Mae Shinji , Shoji Hitoshi , Kameda Takao , Watanabe Okitusgu 
Published: November 2007

AbstractAir bubbles trapped near the surface of an ice sheet are transformed into air hydrates below a certain depth Their volume and number varies partly with environment and climate. Air bubbles and hydrates at 120-2200 m depth in the Dome Fuji (Dome F) ice core were examined with a microscope. This depth range covers the Holocene/Last Glacial/Last Interglacial/Previous Glacial periods. No air bubbles were seen below about 1100 m depth, and air hydrates began to appear from about 600 m. The observed number of air bubbles and hydrates was similar to that found in the Vostok ice core. For the ice covering the Last Glacial Maximum period, however the hydrate concentration in the Dome F core is about half that of the Vostok core. Reference to snow metamorphism and packing does not explain this finding.
The Pinatubo eruption in South Pole snow and its potential value to ice-core paleovolcanic records
Authors: Cole-Dai Jihong , Mosley-Thompson Ellen 
Published: November 2007

AbstractSnow samples collected in the 1996 austral summer at South Pole show that sulfate concentrations in snow and, by inference, sulfur aerosol concentrations in the Antarctic atmosphere were elevated from the end of 1991 to mid-1994 over a stable, non-volcanic background. The new data support earlier findings that the June 1991 Pinatubo eruption and the Hudson eruption in the same year deposited volcanic sulfate and tephra in South Pole snow, and provide strong evidence of the global distribution of volcanic materials from the Pinatubo eruption. In this study, snow samples were taken in six snow pits spatially distributed around the South Pole station in order to evaluate the local spatial variability of volcanic signals due to glaciological variables such as snow-accumulation rates and snow redistribution by wind after initial deposition. The results indicate that Pinatubo sulfate flux varies by as much as 20% throughout a 400 km2 area centered around the South Pole station. This glaciological variability probably represents the likely range of volcanic signals due to variations in snow deposition and post-depositional changes.The Pinatubo eruption provides an unprecedented opportunity to estimate aerosol mass loadings by explosive volcanic eruptions found in Antarctic ice cores via a quantitative relationship between aerosol mass loadings and sulfate flux in Antarctic snow. Here the satellite-estimated Pinatubo SO2 emission and the measured volcanic sulfate flux in snow, with an assumed linearly quantitative relationship, are used to calculate SO2 loadings for several well-known volcanic eruptions in the past 300 years covered by a shallow (42 m) South Pole firn core drilled in 1996. The errors for the calculated mass loadings are estimated by means of the glaciological variability associated with Pinatubo volcanic flux.
New maps of the ice thickness and subglacial topography in Dronning Maud Land, Antarctica, determined by means of airborne radio-echo sounding
Authors: Steinhage D. , Nixdorf U. , Meyer U. , Miller H. 
Published: November 2007

AbstractSince the austral summer of 1994-95 the Alfred Wegener Institute has carried out airborne radio-echo sounding (RES) measurements in Antarctica with its newly designed RES system. Since 1995-96 an ongoing pre-site survey for an ice-coring drill site in Dronning Maud Land has been carried out as part of the European Project for Ice Goring in Antarctica. The survey covers an area of 948 000 km2, with >49 500 km of airborne RES obtained from >200 hours of flight operation flown during the period 1994-97. In this paper, first results of the airborne RES survey are graphically summarized as newly derived maps of the ice thickness and subglacial topography, as well as a three-dimensional view of surface and subglacial bed and outcrop topography, revealing a total ice volume of 1.48 x 106 km3.
Accumulation and proxy-temperature variability in Dronning Maud Land, Antarctica, determined from shallow firn cores
Authors: Isaksson Elisabeth , van den Broeke Michiel R. , Winther Jan-Gunnar , Karlöf Lars , Francis Pinglot Jean , Gundestrup Niels 
Published: November 2007

AbstractDuring 1996-97 a European Project for Ice Goring in Antarctica (EPIGA) pre-site surveying traverse worked in the area between 70° S, 5° E and 75° S, 15° E in Dronning Maud Land. We present data obtained from 10 and 20 m deep firn cores drilled between the coast and 600 km inland (to 3450 m a.s.l.). The cores were analyzed for electrical conductivity measurements and total β activity to obtain accumulation data between known time horizons. In addition, some of the cores were analyzed for oxygen isotopes. Annual accumulation varies from 271 mm we. at Fimbulisen to 24 mm we at 2840 m a.s.l. Accumulation at core sites 2400-3000 m a.s.l. has increased by 16-48% since 1965 compared to the 1955-65 period. However, the core sites above 3250 m a.s.l. and one core location on the ice shelf show a decrease during the same period. Furthermore, no change can be detected at the most inland site for the period 1815-1996. In all the cores the last few years seem to have been some of the warmest in these records.
A model of the glacial retreat of upper Rennick Glacier, Victoria Land, Antarctica
Authors: Meneghel M. , Bondesan A. , Salvatore M. C. , Orombelli G. 
Published: November 2007

AbstractThe morphology of the Lichen Hills in the upper section of Rennick Glacier, Victoria Land, Antarctica, is summarised as follows: (a) a top surface on the volcanic rocks with scattered erratic blocks; (b) an exhumed Kukri Peneplain, sculptured with roches moutonnees with striae and crescentic gouges on which lie moraines and patches of drift of mainly volcanic rocks; (c) a granitic bedrock eroded by glaciers into sharp peaks and cirques on top of which there is a glacial drift attributable to ancient blue-ice areas higher than those observed at present and which may be correlated with the Terra Nova drift (Late Wisconsin); (d) various Holocene ice-cored moraines that are pushed to the lee side of the nunataks arid are often banded in strips of different lithology. The bands of the Holocene moraines are related to the rock complexes that became exposed from the ice during the lowering of the surface of the glacier Analysis of the lithology and pattern of the supraglacial debris, as well as of the blue-ice areas, allows us to construct a depositional model for the moraines, and to relate the glacial drift to blue-ice areas existing since the Last Glacial Maximum (LGM).The proposed model shows the different stages of recession of upper Rennick Glacier that are also valid for similar situations observed in northern Victoria Land. A surface lowering of upper Rennick Glacier of several hundred metres shows that significant changes have occurred at the Pacific edge of the East Antarctic ice sheet since the LGM.
Geoscience Laser Altimeter System waveform simulation and its applications
Authors: Donghui Yi , Bentley Charles R. 
Published: November 2007

AbstractTo study the relationship between surface topography and satellite laser altimetry waveform, a numerical model that simulates an ideal satellite laser altimeter has been developed. It has a Gaussian beam pattern and a Gaussian pulse shape. Different three-dimensional surface topographies have been used in the simulation to generate waveforms. Using a non-linear least-squares method, the generated waveforms were fitted to theoretical models to calculate surface roughness and surface slope. The outputs from the models were then compared with the values calculated from the given assumed surfaces. There is no way to distinguish between a horizontal, randomly rough surface and a smoothly sloping surface from waveform fitting alone. However, if either the surface roughness or the surface slope can be acquired independently, the other one can be determined through waveform fitting.
Geomorphological criteria for identifying Pleistocene ice streams
Authors: Stokes Chris R. , Clark Chris D. 
Published: November 2007

AbstractIce streams are critical regulatory mechanisms in contemporary ice sheets. It has been inferred that they also had a significant effect on the dynamics of former ice sheets. Subsequently, many people have invoked their widespread occurrence from a variety of formerly glaciated areas. Hypothesised locations, however, have often outweighed meaningful evidence. This paper addresses the problem, using the characteristics of contemporary ice streams as a basis for their identification from former ice-sheet beds. A convergence of knowledge gained from contemporary ice-stream research, coupled with theories of glacial geomorphology, allows several geomorphological criteria to be identified as suggestive signatures of ice-stream activity. It is envisaged that the geomorphological criteria developed here will introduce a more objective approach to the study of former ice streams. The criteria are used to construct conceptual land-system models of the beds of former ice streams, and it is hoped such models can provide an observational template upon which hypotheses of former ice streams can be better based.
Was the cirque glaciation of Wales time-transgressive, or not?
Authors: Evans Ian S. 
Published: November 2007

AbstractThe lowest glacial cirques in Wales are in the South Wales Coalfield and in western mid-Wales: the highest are in the northeast and on the highest mountains. Floor altitudes show great local variability, but in general rise to the northeast in most of Wales and northward in southern Wales, as does the former glaciation level (from 470–710 m a.s.l.). The pattern is similar for reconstructed Younger Dryas glaciers, which occupied the higher and even some of the lower cirques. If cirque development had spread to lower areas as the ice sheet built up, cirques would be expected in peripheral areas such as the northeast and southwest, away from the main ice-sheet sources. This is not seen and there is no clear evidence of time-transgressive cirque glaciation. Cirques relate to phases of glaciation with an ELA a little below that in the Younger Dryas.
Katabatic wind influence on meltwater supply to fuel glacier–substrate interactions at the grounding line, Terra Nova Bay, East Antarctica
Authors: Bouzette A. , Souchez R. 
Published: November 2007

AbstractThe co-isotopic composition, both in δDand in δ18O, of interbedded debris-rich and clear ice layers, thought to have been formed at the grounding line of Hells Gate Ice Shelf, indicates freezing by a double-diffusion effect between continental meltwater and sea water within a subglacial sediment. A source of meltwater is required to sustain the process, since the temperature of the bed is below the freshwater melting point. The most likely source is a surficially frozen meltwater lake.Rock outcrops, kept mostly snow-free by the action of katabatic winds, absorb solar radiation so local production of liquid water becomes possible in an area with year-round subfreezing air-temperature conditions. The meltwater accumulated in a marginal lake can eventually reach the subglacial substratum near a pinning point where the ice is relatively thin and fractured.