bluuebunny/crossref_metadata_2025_split huggingface dataset:
The englacial stratigraphy of Wilkes Land, East Antarctica, as revealed by internal radio-echo sounding layering, and its relationship with balance velocities
Authors: Rippin David M. , Siegert Martin J. , Bamber Jonathan L. 
Published: November 2007

AbstractThe disruption of internal layering visible in radio-echo sounding (RES) data from East Antarctica has, to date, been attributed to ice flow around bedrock topography. However, observations of internal layer disruption in the Siple Coast ice streams of West Antarctica have led to the suggestion that increased strain at the margins of ice streams may also be responsible for the disruption of internal layers. Here we present a re-analysis of the extensive RES dataset collected between 1967 and 1979 over a large part of Wilkes Land, East Antarctica, and relate the location of continuous and disrupted internal layers to modelled balance velocities. We show that the mean balance velocity associated with all areas of disrupted layers is 2.5 times higher than that associated with areas of continuous layers. We also demonstrate that disrupted layers are associated not only with ice streams, but also with areas of enhanced ice flow, which penetrate inland from the grounding line up to several hundred kilometres into the interior of East Antarctica. Continuous layers always overlie disrupted layers, suggesting either a depth dependency in the process responsible for layer disruption, or subsequent deposition of continuous layers. In some cases, disrupted layers occur outside fast-flow features, and continuous layers occur within fast-flow features. Such regions are explained by short-term flow patterns, but might also be attributed to inaccuracies in the balance-velocity calculations.
From surge-type to non-surge-type glacier behaviour: midre Lovénbreen, Svalbard
Authors: Hansen Siri 
Published: November 2007

AbstractSince the beginning of the 1900s, the polythermal valley glacier midre Lovénbreen (area 5 km2) in northwestern Svalbard has retreated approximately 1km. The glacier has not surged for at least 110 years, and the present smooth longitudinal profile and negative mass balance suggest that it is not currently building up to a surge. Based on limited evidence, it has often been assumed that midre Lovénbreen surged around 1880. The ongoing retreat is probably due to quiescent-phase stagnation amplified by 20th-century climate change, as is the case for several other glaciers in Svalbard. Recently, small eskers have been found in the glacier forefield. Based on their geomorphological appearance, these are interpreted as concertina eskers, and they add to the dynamic history of the glacier. Midre Lovénbreen is interpreted as an example of a change from surge-type to non-surge-type glacier behaviour.
Seasonal variations in ice deformation and basal motion across the tongue of Haut Glacier d’Arolla, Switzerland
Authors: Willis Ian , Mair Douglas , Hubbard Bryn , Nienow Peter , Fischer Urs H. , Hubbard Alun 
Published: November 2007

AbstractRecords of surface motion, englacial tilt and repeat inclinometry are used to determine patterns of surface, internal and basal motion across the tongue of Haut Glacier d’Arolla, Switzerland, over temporal scales ranging from days to months. Findings are interpreted with reference to contemporaneous measurements of subglacial water pressures, and prior knowledge of the glacier’s subglacial drainage-system structure. Long-term inclinometry results show pronounced extrusion flow over a subglacial drainage axis, with basal velocities up to twice those measured at the glacier surface. Deformation profiles are more conventional away from the drainage axis, with basal velocities ∼60–70% of surface velocities. Comparison of long-term tilt rates from repeat inclinometry and englacial tiltmeters shows close correspondence. Englacial tiltmeter data are used to reconstruct internal velocity profiles and to split surface velocities into internal deformation and basal motion contributions over spring, summer and autumn/winter periods. Although, spatial patterns of surface movement are similar between periods, patterns of internal and basal motion are not. Results are interpreted in terms of the location of sticky and slippery spots, with temporally changing patterns of basal drag reflecting changing distributions of water pressure.
Is Vostok lake in steady state?
Authors: Royston-Bishop George , Tranter Martyn , Siegert Martin J. , Lee Victoria , Bates Paul D. 
Published: November 2007

AbstractStable-isotope (δD and δ18O) data from the Vostok (East Antarctica) ice core are used to explore whether or not subglacial Vostok lake is in isotopic steady state. A simple box model shows that the lake is likely to be in steady state on time-scales of the order of 104–105 years (three to four residence times of the water in the lake), given our current knowledge of north–south and east–west gradients in the stable-isotopic composition of precipitation in the vicinity of Vostok station and Ridge B. However, the lake may not be in perfect steady state depending on the precise location of the melting area, which determines the source region of inflowing ice, and on the magnitude of the east–west gradient in isotopic compositions in the vicinity of Vostok station and Ridge B.
L-band ice-sheet brightness temperatures at Dome C, Antarctica: spectral emission modelling, temporal stability and impact of the ionosphere
Authors: Drinkwater Mark R. , Floury Nicolas , Tedesco Marco 
Published: November 2007

AbstractThe temporal thermal stability, size, structure and spatial uniformity of Antarctic Plateau regions such as Dome C make them ideal candidates for external calibration and validation, or radiometric performance monitoring of planned space-borne L-band radiometers such as the Soil Moisture and Ocean Salinity (SMOS) radiometer. As experimental observations do not exist at this frequency, a combination of historical Ka-, X- and C-band data are used together with electromagnetic and ionospheric models to extrapolate to this longer wavelength. Dome C is demonstrated to exhibit negligible seasonal variability (<0.1 K) and may prove to be a suitable candidate, provided the effects of atmospheric and ionospheric perturbations can be mitigated.
Topographic control of regional accumulation rate variability at South Pole and implications for ice-core interpretation
Authors: Hamilton Gordon S. 
Published: November 2007

AbstractSnow-accumulation rates are known to be sensitive to local changes in ice-sheet surface slope because of the effect of katabatic winds. These topographic effects can be preserved in ice cores that are collected at non-ice-divide locations. The trajectory of an ice-core site at South Pole is reconstructed using measurements of ice-sheet motion to show that snow was probably deposited at places of different surface slope during the past 1000 years. Recent accumulation rates, derived from shallow firn cores, vary along this trajectory according to surface topography, so that on a relatively steep flank mean annual accumulation is ∼18% smaller than on a nearby topographic depression. These modern accumulation rates are used to reinterpret the cause of accumulation rate variability with time in the long ice-core record as an ice-dynamics effect and not a climate-change signal. The results highlight the importance of conducting ancillary ice-dynamics measurements as part of ice-coring programs so that topographic effects can be deconvolved from potential climate signals.
Monsoonal circulation of the McMurdo Dry Valleys, Ross Sea region, Antarctica: signal from the snow chemistry
Authors: Bertler Nancy A. N. , Mayewski Paul A. , Barrett Peter J. , Sneed Sharon B. , Handley Michael J. , Kreutz Karl J. 
Published: November 2007

AbstractMcMurdo Dry Valleys (MDV; Ross Sea region, Antarctica) precipitation exhibits extreme seasonality in ion concentration, 3–5 orders of magnitude between summer and winter precipitation. To identify aerosol sources and investigate causes for the observed amplitude in concentration variability, four snow pits were sampled along a coast–Polar Plateau transect across the MDV. The elevation of the sites ranges from 50 to 2400 m and the distance from the coast from 8 to 93 km. Average chemistry gradients along the transect indicate that most species have either a predominant marine or terrestrial source in the MDV. Empirical orthogonal function analysis on the snow-chemistry time series shows that at least 57% of aerosol deposition occurs concurrently. A conceptual climate model, based on meteorological observations, is used to explain the strong seasonality in the MDV. Our results suggest that radiative forcing of the ice-free valleys creates a surface low-pressure cell during summer which promotes air-mass flow from the Ross Sea. The associated precipitating air mass is relatively warm, humid and contains a high concentration of aerosols. During winter, the MDV are dominated by air masses draining off the East Antarctic ice sheet, that are characterized by cold, dry and low concentrations of aerosols. The strong differences between these two air-mass sources create in the MDV a polar version of the monsoonal flow, with humid, warm summers and dry, cold winters.
Variations of glacier frontal positions on the northern Antarctic Peninsula
Authors: Rau Frank , Mauz Fabian , De Angelis Hernán , Jaña Ricardo , Neto Jorge Arigony , Skvarca Pedro , Vogt Steffen , Saurer Helmut , Gossmann Hermann 
Published: November 2007

AbstractChanges in the ice fronts on the Antarctic Peninsula north of 70˚ S are currently being investigated through a comprehensive analysis of Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and Landsat Thematic Mapper (TM) data as part of the international research initiative ‘Global land Ice Measurements from Space’ (GLIMS). Regional case studies are presented that cover a variety of glacial systems distributed over the northern Antarctic Peninsula and provide data on glacier front variations during the period 1986–2002. The results confirm a general trend of regional glacier front recession, but a range of different glacier variations are observed throughout the study area. Areas of predominant retreat are located in the northeastern and southwestern sectors, while stationary ice fronts characterize glacial behaviour on the northwestern coast of the peninsula. In addition, a significant increase in glacier recession is identified on James Ross Island, where retreat rates doubled during the period 1988–2001 compared to the previous investigation period, 1975–88. These observations are interpreted as being direct consequences of the rapidly changing climate in the region, which differentially affects the local accumulation and ablation patterns of the glacial systems.
Deglacial and Holocene changes in accumulation at Law Dome, East Antarctica
Authors: Van Ommen Tas D. , Morgan Vin , Curran Mark A. J. 
Published: November 2007

AbstractDating constraints have been combined with an ice-flow model to estimate surface accumulation rates at Law Dome, East Antarctica, to approximately 80 kyr BP. Results indicate that the present high-accumulation regime (~0.7ma–1 ice equivalent) was established some time after ~7 kyr BP, following an increase of approximately 80% from early to mid-Holocene. The accumulation rate at the Last Glacial Maximum is estimated at less than ~10% of the modern value. The record reveals an approximately linear dependence between temperature (inferred from isotope ratio) and accumulation rate through the glacial period. This dependence breaks down in the early Holocene, and this is interpreted as a change to a mode in which moisture-transport changes have a stronger influence on accumulation than temperature (via absolute humidity). The changes in accumulation, including the large change in the early to mid-Holocene, are accompanied by changes in sea-salt concentrations which support the hypothesis that Law Dome climate has shifted from a glacial climate, more like that of the present-day Antarctic Plateau, to its current Antarctic maritime climate. The change between these two modes occurred progressively through the early Holocene, possibly reflecting insolation-driven changes in atmospheric moisture content and circulation.
Thermal structure of Dome Fuji and east Dronning Maud Land, Antarctica, simulated by a three-dimensional ice-sheet model
Authors: Saito Fuyuki , Abe-Ouchi Ayako 
Published: November 2007

AbstractThree-dimensional structures of temperature focused on Dome Fuji and east Dronning Maud Land, Antarctica, simulated in a three-dimensional shallow ice model, are reported. With a geothermal heat flux of 54.6 mWm–2, as used in several modelling studies of the Antarctic ice sheet, and an enhancement factor of 1.3, which is smaller than in previous studies, the model result taking into account the glacial cycles is in good agreement with the borehole temperature and surface topography at Dome Fuji. The basal temperature at Dome Fuji must be at or very close to the pressure-melting point. The simulated amplitude of basal temperature through glacial/interglacial cycles is <1 K.
Coastal-change and glaciological map of the Saunders Coast area, Antarctica: 1972–97
Authors: Ferrigno Jane G. , Williams Richard S. , Foley Kevin M. 
Published: November 2007

AbstractSatellite images from 1972 to 1997 have been used to prepare a map showing glaciological features of the Saunders Coast area, Antarctica. Analysis of the imagery shows a trend toward ice-front retreat that may be a result of changing environmental conditions.
Photochemical decomposition of hydrogen peroxide (H2O2) and formaldehyde (HCHO) in artificial snow
Authors: Jacobi Hans-Werner , Kwakye-Awuah Bright , Schrems Otto 
Published: November 2007

AbstractLaboratory-made snow doped with either hydrogen peroxide (H2O2) or formaldehyde (HCHO) was exposed to radiation in the ultraviolet and visible range, resulting in a decomposition of both compounds. These experiments demonstrate that, besides the photolysis of nitrate, further photochemical reactions of atmospheric relevant compounds can take place in snow. Under similar conditions the decomposition of H2O2 is more efficient than that of HCHO. Since the decompositions in the experiments follow first-order reaction kinetics, we suggest that the same products as in photolysis reactions in the liquid phase are produced. If similar reactions also take place in natural snow covers, these reactions would have several important consequences. The reactions could represent pathways for the generation of highly reactive radicals in the condensed phase, enhancing the photochemical activity of surface snow and modifying the oxidation capacity of the atmospheric boundary layer. The photolysis could also constitute an additional sink for H2O2 and HCHO in surface snow, which should be taken into account for the reconstruction of atmospheric concentrations of both compounds from concentration profiles in surface snow and ice cores.
The EPICA deep ice cores: first results and perspectives
Authors: Stauffer Bernhard , Flückiger Jacqueline , Wolff Eric , Barnes Piers 
Published: November 2007

AbstractTwo deep ice cores are being drilled in Antarctica in the frame of the European Project for Ice Coring in Antarctica (EPICA). The Dome C ice core will provide more information about mechanisms of global climatic changes over several climatic cycles. The DML core, drilled at Kohnen station, will provide a detailed record over the last climatic cycle, which can be compared with Greenland records. The drilling at Dome C reached 3200 m depth during field season 2002/03, and the age of the ice at the bottom of the hole could be 900 000 years according to preliminary estimates. The depth at Kohnen station is 1564.6 m at present, corresponding to an age of about 55 000 years. Analyses along the top parts of both ice cores have provided interesting first results. A few selected results from these parts, mostly published already, are summarized. Only a few measurements are available from the deeper parts of both cores. Dielectric profiling and electrical conductivity measurements, performed in the field, provide continuous and high-resolution records concerning the acidity and the salt concentration of the ice. Continuous flow analyses and Fast Ion Chromatography also provide high-resolution records of several chemical compounds. These records give some clues as to the age scale of the EPICA Dome C ice core, but they also leave us with many open questions.
Snow surface height variations on the Antarctic ice sheet in Princess Elizabeth Land, Antarctica: 1 year of data from an automatic weather station
Authors: Dahe Qin , Cunde Xiao , Allison Ian , Lingen Bian , Stephenson Rod , Jiawen Ren , Ming Yan 
Published: November 2007

AbstractThe net surface snow accumulation on the Antarctic ice sheet is determined by a combination of precipitation, sublimation and wind redistribution. We present a 1 year record of hourly snow-height measurements that shows its seasonal variability. The measurements were made with an ultrasonic sensor mounted on an automatic weather station (AWS) installed at LGB69, Princess Elizabeth Land, Antarctica (70.835˚S, 77.075˚E; 1850 ma.s.l.). The average accumulation at this site is approximately 0.70 m snow a–1. Throughout the winter, between April and September, there was little change in surface snow height. The strongest accumulation occurred during the period October–March, with four episodic increases occurring during 2002. These episodic events coincided with obvious humidity ‘pulses’ and decreases of incoming solar radiation as recorded by the AWS. Observations of the total cloud amount at Davis station, 160 km north-northeast of LGB69, showed good correlation with major accumulation events recorded at LGB69. There was an obvious anticorrelation between the lowest cloud height at Davis and the daily accumulation rate at LGB69. Although there was no correlation over the total year between wind speed and accumulation at LGB69, large individual accumulation events are associated with episodes of strong wind. Strong accumulation events at LGB69 are associated with major storms in the region and inland transport of moist air masses from the coast.
Palaeoproductivity in the Ross Sea, Antarctica, during the last 15 kyr BP and its link with ice-core temperature proxies
Authors: Salvi Cristinamaria , Salvi Gianguido , Stenni Barbara , Brambati Antonio 
Published: November 2007

AbstractA detailed study of organic carbon content obtained from two sediment cores collected in the Joides basin, western Ross Sea, Antarctica, was carried out. The variations observed during the last deglaciation and the Holocene were compared to the high-resolution climatic records (EPICA DC and Taylor Dome) preserved in the ice. The importance of the carbon content as a proxy for palaeoclimatic and palaeoenvironmental changes was investigated. A dramatic decrease in the Ross Sea palaeoproductivity was observed during the Antarctic Cold Reversal (12.5–14 kyr BP). Another decrease in total organic carbon in the second half of the Holocene (after 5–6 kyr BP) confirms the climate worsening observed in previous studies.
Ultra-high-resolution seasonality of trace-ion species and oxygen isotope ratios in Antarctic firn over four annual cycles
Authors: Mcmorrow Alison , Van Ommen Tas D. , Morgan Vin , Curran Mark A. J. 
Published: November 2007

AbstractUltra-high-resolution firn-core records covering four annual cycles of oxygen isotope ratios (Δ18O) and trace-ion species were generated from a high-accumulation site on Law Dome, East Antarctica. Event-scale dating of the records was established using hourly snow accumulation measurements from a co-located automatic weather station (AWS). These net accumulation events were used to examine the seasonal timing of Δ18O and a suite of trace-ion species including marine biogenic sulphur compounds (methanesulphonic acid (MSA), non-sea salt sulphate), nitrate and major sea-salt species (sodium, chloride, magnesium). The ultra-high-resolution nature of this study and independent dating scale provide an opportunity to examine exact timings in the seasonality of each species. The traditional summer-maximum species of Δ18O and MSA show consistent relative phasing during midsummer over the four annual cycles. Nitrate shows an erratic seasonal cycle with a general trend characterized by narrow peaks during spring and early summer, preceding the mid-summer peaks in Δ18O and MSA. Non-sea-salt sulphate cycles indicate similar characteristics to MSA signals during summer, but are more comparable to nitrate signals during spring, autumn and winter. This suggests the summer non-sea-salt sulphate signal is driven by biological activity, although this species appears to be linked with nitrate signals outside the summer season. Finally, the sea-salt species indicate a seasonal cycle characterized by maximum concentrations during spring, winter and autumn. Event-scale dating of the firn-core records allows direct comparisons between the seasonal cycles and meteorological conditions. Contemporaneous local air-temperature measurements are compared with the high-resolution Δ18O record. This allows a detailed investigation of the relationship between site temperature and Δ18O signals in the ice core.
Space geodesy as a tool for measuring ice surface velocity in the Dome C region and along the ITASE traverse
Authors: Vittuari Luca , Vincent Christian , Frezzotti Massimo , Mancini Francesco , Gandolfi Stefano , Bitelli Gabriele , Capra Alessandro 
Published: November 2007

AbstractDome C was chosen by the European Project for Ice Coring in Antarctica (EPICA) as the site for the drilling of a deep ice core. This paper presents results from geodetic surveys of ice velocities (absolute and relative) at Dome C and along a transect to Terra Nova Bay. The purpose of the surveys was to provide accurate data for the study of ice dynamics, particularly a strain network comprising 37 poles surveyed in 1995 and again in 1999. Data indicate that the ice surface at the poles closest to the topographic summit moves horizontally by up to a few mm a–1 in a direction consistent with downslope motion of the ice sheet, while 25 km from the summit it moves up to 211 mma–1. The EPICA drilling site yields an interpolated velocity of about 15 ±10mma–1 in a north-northwesterly direction. Analysis of the velocity field and surface topography reveals that the surface flow centre is nearly co-located with the dome summit, and that both are in a steady-state condition. The measured horizontal velocities are consistent with the remote-sensing result and provide accurate ground-truth control for flow mapping. Seven snow–firn cores, up to 53m deep, were drilled during the Terra Nova Bay–Dome C traverse. Submerged velocity systems were installed at the borehole and measured using the global positioning system (GPS). First results show a steady-state condition. Measured (horizontal) ice velocities increase from the summit of the ice sheet to the coast, reaching about 28 ma–1 at site GPS2A.
Methanesulphonic acid movement in solid ice cores
Authors: Smith Barbara T. , Van Ommen Tas D. , Curran Mark A. J. 
Published: November 2007

AbstractMethanesulphonic acid (MSA) is an important trace-ion constituent in ice cores, with connections to biological activity and sea-ice distribution. Post-depositional movement of MSA has been documented in firn, and this study investigates movement in solid ice by measuring variations in MSA distribution across several horizontal sections from an ice core after 14.5 years storage. The core used is from below the bubble close-off depth at Dome Summit South, Law Dome, East Antarctica. MSA concentration was studied at 3 and 0.5 cm resolution across the core widths. Its distribution was uniform through the core centres, but the outer 3 cm showed gradients in concentrations down to less than half of the central value at the core edge. This effect is consistent with diffusion to the surrounding air during its 14.5 year storage. The diffusion coefficient is calculated to be 2 ×10–13 m2 s–1, and the implications for the diffusion mechanism are discussed.