bluuebunny/crossref_metadata_2025_split huggingface dataset:
Perspectives on the production of a glacier inventory from multispectral satellite data in Arctic Canada: Cumberland Peninsula, Baffin Island
Authors: Paul Frank , Kääb Andreas 
Published: November 2007

AbstractThe consequences of global warming on land ice masses are difficult to assess in detail, as two-dimensional glacier inventory data are still missing for many remote regions of the world. As the largest future temperature increase is expected to occur at high latitudes, the glaciers and ice caps in the Arctic will be particularly susceptible to the expected warming. This study demonstrates the possibilities of space-borne glacier inventorying at a remote site on Cumberland Peninsula, a part of Baffin Island in Arctic Canada, thereby providing glacier inventory data for this region. Our approach combines Landsat ETM+ and Terra ASTER satellite data, an ASTER-derived digital elevation model (DEM) and Geographic Information System-based processing. We used thresholded ratio images from ETM+ bands 3 and 5 and ASTER bands 3 and 4 for glacier mapping. Manual delineation of Little Ice Age trimlines and moraines has been applied to calculate area changes for 225 glaciers, yielding an average area loss of 11%. A size distribution has been obtained for 770 glaciers that is very different from that for Alpine glaciers. Numerous three-dimensional glacier parameters were derived from the ASTER DEM for a subset of 340 glaciers. The amount of working time required for the processing has been tracked, and resulted in 5 min per glacier, or 7 years for all estimated 160 000 glaciers worldwide.
Basal ice motion and deformation at the ice-sheet margin, West Greenland
Authors: Chandler David M. , Waller Richard I. , Adam William G. 
Published: November 2007

AbstractMeasurements of basal ice deformation at the margin of Russell Glacier, West Greenland, have provided an opportunity to gain more insight into basal processes occurring near the margin. The basal ice layer comprises a debris-rich, heterogeneous stratified facies, overlain by a comparatively debris-poor dispersed facies. Ice velocities were obtained from anchors placed in both ice facies, at three sites under 5–15 m ice depth. Mean velocities ranged from 20 to 43 m a–1, and velocity gradients indicate high shear strain rates within the basal ice. Stick–slip motion and diurnal variations were observed during measurements at short (1–5 min) time intervals. Vertical gradients in horizontal ice velocity indicate two modes of deformation: (1) viscous deformation within the stratified ice facies, and (2) shear at the interface between the two basal ice facies. Deformation mode 1 may contribute to the folding and shear structures observed in the stratified facies. Deformation mode 2 may generate the stick–slip motion and be associated with the formation of debris bands. Active deformation close to the margin suggests that structures observed within the basal ice are only partially representative of processes occurring near the bed in areas away from the glacier margin.
A positive trend in western Antarctic Peninsula precipitation over the last 50 years reflecting regional and Antarctic-wide atmospheric circulation changes
Authors: Turner John , Lachlan-Cope Tom , Colwell Steve , Marshall Gareth J. 
Published: November 2007

AbstractIn situ observations of precipitation days (days when snow or rain was reported in routine synoptic observations) from Faraday/Vernadsky station on the western side of the Antarctic Peninsula, and fields from the 40 year European Centre for Medium-Range Weather Forecasts re-analysis (ERA-40) project are used to investigate precipitation and atmospheric circulation changes around the Antarctic Peninsula. It is shown that the number of precipitation days is a good proxy for mean sea-level pressure (MSLP) over the Amundsen–Bellingshausen Sea. The annual total of precipitation days at the station has been increasing at a statistically significant rate of +12.4 days decade–1 since the early 1950s, with the greatest increase taking place during the summer and autumn. This is the time of year when the Southern Annular Mode (SAM) has experienced its greatest shift to a positive phase, with MSLP values decreasing in the Antarctic coastal zone. The lower pressures in the circumpolar trough have resulted in greater ascent and increased precipitation at Faraday/Vernadsky.
Numerical model studies of Antarctic ice-sheet–ice-shelf–ocean systems and ice caps
Authors: Lange M.A. , Blindow N. , Breuer B. , Grosfeld K. , Kleiner T. , Mohrholz C.-O. , Nicolaus M. , Oelke C. , Sandhäger H. , Thoma M. 
Published: November 2007

AbstractThe cryosphere is an essential component of the global climate system, equally affecting climate processes significantly and being subject, and particularly sensitive, to changes in climate conditions. Numerical models are an important tool for assessing climate-change impacts on the Antarctic ice–sheet–ice–shelf–ocean system. They not only complement field and satellite remotesensing investigations but are often the only feasible alternative for addressing some of the important parameters and processes. Over the last few years, our group has made significant progress in developing and applying innovative numerical methods. In this paper, we provide a brief overview of some of the methods employed and the major results obtained for a number of case studies in the Atlantic sector of Antarctica.
Spatial patterns in mass balance of the Siple Coast and Amundsen Sea sectors, West Antarctica
Authors: Hamilton Gordon S. , Blue spikes V. , Stearns Leigh A. 
Published: November 2007

AbstractLocal rates of change in ice-sheet thickness were calculated at 15 sites in West Antarctica using the submergence velocity technique. This method entails a comparison of the vertical velocity of the ice sheet, measured using repeat global positioning system surveys of markers, and local long-term rates of snow accumulation obtained using firn-core stratigraphy. Any significant difference between these two quantities represents a thickness change with time. Measurements were conducted at sites located ~100–200km apart along US ITASE traverse routes, and at several isolated locations. All but one of the sites are distributed in the Siple Coast and the Amundsen Sea basin along contours of constant elevation, along flowlines, across ice divides and close to regions of enhanced flow. Calculated rates of thickness change are different from site to site. Most of the large rates of change in ice thickness (~10cm a–1 or larger) are observed in or close to regions of rapid flow, and are probably related to ice-dynamics effects. Near-steady-state conditions are calculated mostly at sites in the slow-moving ice-sheet interior and near the mainWest Antarctic ice divide. These results are consistent with regional estimates of ice-sheet change derived from remote-sensing measurements at similar locations in West Antarctica
Bedrock topography and wind erosion sites in East Antarctica: observations from the 2002 US-ITASE traverse
Authors: Welch Brian C. , Jacobel Robert W. 
Published: November 2007

AbstractIce stratigraphy from deep-penetrating radar data collected during the 2002 US International Trans-Antarctic Scientific Expedition (US-ITASE) traverse shows evidence of a significant erosion surface and drift-filled basin related to a previously undiscovered 1400m subglacial mountain between Hercules Dome (87˚420S, 108˚W) and South Pole. The 3MHz radar profile crosses three subglacial mountains at approximately 458to the ice-flow direction. Cross-cutting reflectors in the top 500m of ice stratigraphy are interpreted as angular unconformities resulting from wind erosion as the ice deforms over the mountain tops. The unconformities correlate locally with zones of high RADARSAT reflectivity. Several nearby sites with similar relatively high RADARSAT reflectivity adjacent to the traverse indicate that active wind erosion may be taking place at these locations as well. Based on the local correlation between surface wind scour and subglacial topography, we interpret the nearby cluster of bright RADARSAT reflectivity to indicate the presence of a small range of subglacial mountains. The ability to trace isochronal stratigraphy, associated with scour sites using shallow and deep radar, to nearby dated ice cores presents the possibility of exploiting wind-scour zones to access well-dated older ice with shallow-coring equipment.
An ice-core proxy for Antarctic circumpolar zonal wind intensity
Authors: Yan Yuping , Mayewski Paul A. , Kang Shichang , Meyerson Eric 
Published: November 2007

AbstractUsing US National Centers for Environmental Prediction/US National Center for Atmospheric Research re-analysis data, we investigate the relationships between crustal ion (nssCa2+) concentrations from three West Antarctic ice cores, namely, Siple Dome (SD), ITASE00-1 (IT001) and ITASE01-5 (IT015), and primary components of the climate system, namely, air pressure/geopotential height, zonal (u) and meridional (v) wind strength. Linear correlation analyses between nssCa2+ concentrations and both air-pressure and wind fields for the period of overlap between records indicate that the SD nssCa2+ variation is positively correlated with spring circumpolar zonal wind, while IT001 nssCa2+ has a positive correlation with circumpolar zonal wind throughout the year (r > 0.3, p < 0.01). Intensified Southern Westerlies circulation is conducive to transport of more crustal aerosols to both sites. Further correlation analyses between nssCa2+ concentrations from SD and IT001 and atmospheric circulation suggest that the high inland plateau (represented by core IT001) is largely influenced by transport from the upper troposphere. IT015 nssCa2+ is negatively correlated with westerly wind in October and November, suggesting that stronger westerly circulation may weaken the transport of crustal species to IT015. Correlations of nssCa2+ from the three ice cores with the Antarctic Oscillation index are consistent with results developed from the wind-field investigation. In addition, calibration between nssCa2+ concentration and the multivariate El Niño–Southern Oscillation (ENSO) index shows that crustal species transport to IT001 is enhanced during strong ENSO events.
High-resolution ice cores from US ITASE (West Antarctica): development and validation of chronologies and determination of precision and accuracy
Authors: Steig Eric J. , Mayewski Paul A. , Dixon Daniel A. , Kaspari Susan D. , Frey Markus M. , Schneider David P. , Arcone Steven A. , Hamilton Gordon S. , Blue Spikes V. , Mary Albert  , Meese Deb , Gow Anthony J. , Shuman Christopher A. , White James W.C. , Sneed Sharon , Flaherty Joseph , Wumkes Mark 
Published: November 2007

AbstractShallow ice cores were obtained from widely distributed sites across the West Antarctic ice sheet, as part of the United States portion of the International Trans-Antarctic Scientific Expedition (US ITASE) program. The US ITASE cores have been dated by annual-layer counting, primarily through the identification of summer peaks in non-sea-salt sulfate (nssSO42–) concentration. Absolute dating accuracy of better than 2 years and relative dating accuracy better than 1 year is demonstrated by the identification of multiple volcanic marker horizons in each of the cores, Tambora, Indonesia (1815), being the most prominent. Independent validation is provided by the tracing of isochronal layers from site to site using high-frequency ice-penetrating radar observations, and by the timing of mid-winter warming events in stable-isotope ratios, which demonstrate significantly better than 1 year accuracy in the last 20 years. Dating precision to ±1 month is demonstrated by the occurrence of summer nitrate peaks and stable-isotope ratios in phase with nssSO42–, and winter-time sea-salt peaks out of phase, with phase variation of <1 month. Dating precision and accuracy are uniform with depth, for at least the last 100 years.
Snow chemistry across Antarctica
Authors: Bertler N. , Mayewski P.A. , Aristarain A. , Barrett P. , Becagli S. , Bernardo R. , Bo S. , C. Xiao , Curran M. , D. Qin , Dixon D. , Ferrona F. , Fischer H. , Frey M. , Frezzotti M. , Fundel F. , Genthon C. , Gragnani R. , Hamilton G. , Handley M. , Hong S. , Isaksson E. , J. Kang , J. Ren , Kamiyama K. , Kanamori S. , Kärkäs E. , Karlöf L. , Kaspari S. , Kreutz K. , Meyerson E. , Kurbatov A. , Ming Y. , M. Zhang , Motoyama H. , Mulvaney R. , Oerter H. , Osterberg E. , Proposito M. , Pyne A. , Ruth U. , Simões J. , Smith B. , Sneed S. , Teinilä K. , Traufetter F. , Udisti R. , Virkkula A. , Watanabe O. , Williamson B. , Winther J-G. , Y. Li , Wolff E. , Z. Li , Zielinski A. 
Published: November 2007

AbstractAn updated compilation of published and new data of major-ion (Ca, Cl, K, Mg, Na, NO3, SO4) and methylsulfonate (MS) concentrations in snow from 520 Antarctic sites is provided by the national ITASE (International Trans-Antarctic Scientific Expedition) programmes of Australia, Brazil, China, Germany, Italy, Japan, Korea, New Zealand, Norway, the United Kingdom, the United States and the national Antarctic programme of Finland. The comparison shows that snow chemistry concentrations vary by up to four orders of magnitude across Antarctica and exhibit distinct geographical patterns. The Antarctic-wide comparison of glaciochemical records provides a unique opportunity to improve our understanding of the fundamental factors that ultimately control the chemistry of snow or ice samples. This paper aims to initiate data compilation and administration in order to provide a framework for facilitation of Antarctic-wide snow chemistry discussions across all ITASE nations and other contributing groups. The data are made available through the ITASE web page (http://www2.umaine.edu/itase/content/syngroups/snowchem.html) and will be updated with new data as they are provided. In addition, recommendations for future research efforts are summarized.
ENSO variability in the deuterium-excess record of a coastal Antarctic ice core from the McMurdo Dry Valleys, Victoria Land
Authors: Patterson N.G. , Bertler N.A.N. , Naish T.R. , Morgenstern U. 
Published: November 2007

AbstractThe El Niño–Southern Oscillation (ENSO) signal in coastal Antarctic precipitation is evaluated using deuterium-excess data measured from an ice core located at Victoria Lower Glacier (VLG) Dome, McMurdo Dry Valleys. Recent studies suggest that interannual variations in the intensity and position of the Amundsen Sea low, a low-pressure centre that controls moisture flux in the West Antarctic sector, is modulated by the ENSO. Deuterium-excess values from the VLG ice core, which serve as a proxy for changes in regional moisture flux, exhibit oscillations of equivalent duration to those observed in the Southern Oscillation Index (SOI). Results of cross-spectral analyses show that temporal fluctuations in deuterium excess and the SOI covary and are coherent at ~4.9, 3.6, 3.0, 2.6, 2.4 and 2.0 year frequencies between 1950 and 2000. We ascribe this covariance to shifts in the source and transport pathway of precipitation that is deposited in coastal Victoria Land as a consequence of ENSO’s influence. High values of deuterium excess are consistent with increased meridional flow carrying warm, moist air southward across the Ross Sea when the low-pressure centre is positioned to the north of the Ross Ice Shelf (La Niña mode). Low deuterium-excess values, which reflect a more westerly to southerly flow across the West Antarctic ice sheet and Ross Ice Shelf leading to cooler and drier en-route conditions, occur when the low-pressure centre is positioned above the Amundsen Sea (El Niño mode).
Observed surface snowmelt at high elevation in theSouthern Alps of New Zealand
Authors: Cutler Eryn S. , Fitzharris Blair 
Published: November 2007

AbstractSnowmelt is measured over a 34 day summer period at 2440ma.s.l. on Tasman Glacier (>500m above the equilibrium-line altitude) using a tipping-bucket lysimeter and an array of ten ablation stakes. A degree-day factor for snowmelt is calculated using a linear relationship between combined measured melt and the number of degree-days. The slope of the regression line for these data points provides an estimate of the degree-day factor for use in runoff models. Average snowmelt is 17.8 mmd–1, but varies between 0 and 78 mmd–1. Melt occurs in a series of distinct cyclical events or pulses, each of which lasts 5–8 days. These correspond to the eastward passage of anticyclones, then troughs over the Southern Alps. When all days with northwest airflow across the Southern Alps are excluded, the melt factor is 3.4 mm˚C–1 d–1. Northwest days belong to a different population with a much higher average melt factor of 9.1 mm˚C–1 d–1, but more measurements are required to better understand key processes.
Surface melting on Larsen Ice Shelf, Antarctica
Authors: Sergienko Olga , Macayeal Douglas R. 
Published: November 2007

AbstractThe disintegration of Larsen A and B ice shelves in 1995 and 2002, respectively, was preceded by intense surface melting during the summer of ice-shelf collapse and previous summers. To understand the transition of the ice-shelf surface from dry to wet conditions, we developed a one-dimensional model, describing the mass, heat and force balances of water and firn within the ice-shelf surface layer. The model is run using atmospheric data from an automatic weather station on Larsen C ice shelf (World Meteorological Organization station ‘Larsen Ice Site’) located south of Larsen A and B. The model’s derived melting rate is greater than melting predicted by the positive degree-day (PDD) approach, common in studies of ablating ice sheets, such as Greenland. The model shows that the years of ice-shelf break-up (1995 and 2002) are distinguished from previous years by local maxima in the number of melting days. When the PDD approach is considered, however, a maximum in the number of positive degree-days appears in the 2002 break-up year, but not in 1995.
Localized basal motion of a polythermal Arctic glacier:McCall Glacier, Alaska, USA
Authors: Pattyn Frank , Nolan Matt , Rabus Bernhard , Takahashi Shuhei 
Published: November 2007

AbstractWe analyzed the ice flow of McCall Glacier, Alaska, USA, by numerical glacier modeling and radio-echo sounding (RES). Model experiments were carried out with a higher-order numerical ice-flow model, and results were validated with measurements of annual ice velocities and compared with previous estimates of ice-flow dynamics. During the 2003 summer campaign, detailed RES measurements were carried out along the central flowline of the ablation area with a 5 MHz (central frequency) ice-penetrating radar, where 10m ice temperatures are approximately –7.5˚C. The bed reflection power (BRP) beneath this central flowline abruptly increases at one location area, followed by a slow decrease down-glacier. The model experiments show that basal sliding (<50%) is necessary to match the observed annual mean surface velocities in the area that is characterized by high BRP values. However, when thermomechanical effects are taken into account, a temperate basal ice layer is apparent in the ablation area, which locally softens the ice and can explain to a certain extent the anomalous flow field. The model results confirm that the present temperature field is a remnant of a larger glacier geometry that was near steady state before the onset of enhanced surface thinning in the 1970s.
Incorporation of particulates into accreted ice above subglacial Vostok lake, Antarctica
Authors: Royston-Bishop George , Priscu John C. , Tranter Martyn , Christner Brent , Siegert Martin J. , Lee Victoria 
Published: November 2007

AbstractThe nature of microscopic particulates in meteoric and accreted ice from the Vostok (Antarctica) ice core is assessed in conjunction with existing ice-core data to investigate the mechanism by which particulates are incorporated into refrozen lake water. Melted ice samples from a range of ice-core depths were filtered through 0.2 μm polycarbonate membranes, and secondary electron images were collected at ×500 magnification using a scanning electron microscope. Image analysis software was used to characterize the size and shape of particulates. Similar distributions of major-axis lengths, surface areas and shape factors (aspect ratio and compactness) for particulates in all accreted ice samples suggest that a single process may be responsible for incorporating the vast majority of particulates for all depths. Calculation of Stokes settling velocities for particulates of various sizes implies that 98% of particulates observed could ‘float’ to the ice–water interface with upward water velocities of 0.0003 ms–1 where they could be incorporated by growing ice crystals, or by rising frazil ice crystals. The presence of particulates that are expected to sink in the water column (2%) and the uneven distribution of particulates in the ice core further implies that periodic perturbations to the lake’s circulation, involving increased velocities, may have occurred in the past.
Ice crystal properties of amber ice and strain enhancement at the base of cold Antarctic glaciers
Authors: Samyn Denis , Svensson Anders , Fitzsimons Sean J. , Lorrain Reginald D. 
Published: November 2007

AbstractTo improve our understanding of the deformation properties of cold-based polar glaciers, we examine here some of the factors leading to the localization of strain within the amber ice facies. We present a crystallographic case study of amber ice (a fine-grained bubbly ice containing a relatively high impurity content) sampled at the base of two Antarctic glaciers. The crystal fabrics and textures of amber ice were computed by application of a recently developed automated method. To date, it was tedious and awkward to determine amber ice facies accurately because of the sub-millimetric crystal size and relatively high debris content of this facies. The authomatic analytical method applied in this study allows not only for improving analytical accuracy in this task but also for considerably reducing the time of analysis. Our investigations reveal highly homogeneous crystallographic properties for the studied amber ice. The ice crystals are mainly polygonal, equant and sub-millimetric, and show a strong lattice-preferred orientation. These properties, beside the relatively high impurity content, are likely to exert a major control on strain enhancement in amber ice when this facies is present at the base of cold glaciers.
Surface strain anomaly induced by the storage and drainage of englacial water in Koryto glacier, Kamchatka, Russia
Authors: Sugiyama Shin , Naruse Renji , Murav’yev Yaroslav D. 
Published: November 2007

AbstractTo investigate short-term flow-pattern variations of a temperate glacier, longitudinal surface strain was measured with a wire strainmeter in the ablation area of Koryto glacier, Kamchatka, Russia. Strain-rate anomalies were observed in late summer 2000 that were triggered by a water overflow from a moulin near the measurement site followed by the drainage of accumulated water. The strain event started with (compressive) strain rates of >–10–3 d–1 lasting for 6 hours, which then became tensile. Similar strain-rate variations were observed again on the next day. During the event, basal sliding speed measured at the margin in the lower reach of the glacier fluctuated by about ±50% of the daily mean. Smaller and larger sliding speeds corresponded to the compressive and tensile surface strains, respectively. These measurements suggest that the storage and sudden drainage of water caused spatially non-uniform water-pressure fluctuations along the glacier, changing the sliding regime over short time periods.