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  • 1
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    Online Resource
    Surface topography and ice flow in the vicinity of the EDML deep-drilling site, Antarctica
    International Glaciological Society ; 2007
    In:  Journal of Glaciology Vol. 53, No. 182 ( 2007), p. 442-448
    Details
    In: Journal of Glaciology, International Glaciological Society, Vol. 53, No. 182 ( 2007), p. 442-448
    Abstract: Interpretation of ice-core records requires accurate knowledge of the past and present surface topography and stress–strain fields. The European Project for Ice Coring in Antarctica (EPICA) drilling site (75.0025° S, 0.0684° E; 2891.7 m) in Dronning Maud Land, Antarctica, is located in the immediate vicinity of a transient and forking ice divide. A digital elevation model is determined from the combination of kinematic GPS measurements with the GLAS12 datasets from the ICESat. Based on a network of stakes, surveyed with static GPS, the velocity field around the drilling site is calculated. The annual mean velocity magnitude of 12 survey points amounts to 0.74 m a –1 . Flow directions mainly vary according to their distance from the ice divide. Surface strain rates are determined from a pentagonshaped stake network with one center point close to the drilling site. The strain field is characterized by along-flow compression, lateral dilatation and vertical layer thinning.
    Type of Medium: Online Resource
    ISSN: 0022-1430 , 1727-5652
    URL: Article
    DOI: 10.3189/002214307783258512
    Language: English
    Publisher: International Glaciological Society
    Publication Date: 2007
    detail.hit.zdb_id: 2140541-4
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  • 2
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    Converging flow and anisotropy cause large-scale folding in Greenland's ice sheet
    Springer Science and Business Media LLC ; 2016
    In:  Nature Communications Vol. 7, No. 1 ( 2016-04-29)
    Details
    In: Nature Communications, Springer Science and Business Media LLC, Vol. 7, No. 1 ( 2016-04-29)
    Abstract: The increasing catalogue of high-quality ice-penetrating radar data provides a unique insight in the internal layering architecture of the Greenland ice sheet. The stratigraphy, an indicator of past deformation, highlights irregularities in ice flow and reveals large perturbations without obvious links to bedrock shape. In this work, to establish a new conceptual model for the formation process, we analysed the radar data at the onset of the Petermann Glacier, North Greenland, and created a three-dimensional model of several distinct stratigraphic layers. We demonstrate that the dominant structures are cylindrical folds sub-parallel to the ice flow. By numerical modelling, we show that these folds can be formed by lateral compression of mechanically anisotropic ice, while a general viscosity contrast between layers would not lead to folding for the same boundary conditions. We conclude that the folds primarily form by converging flow as the mechanically anisotropic ice is channelled towards the glacier.
    Type of Medium: Online Resource
    ISSN: 2041-1723
    URL: Article
    DOI: 10.1038/ncomms11427
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2016
    detail.hit.zdb_id: 2553671-0
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  • 3
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    Automated identification of vulnerable devices in networks using traffic data and deep learning
    Inderscience Publishers ; 2021
    In:  International Journal of Information Privacy, Security and Integrity Vol. 5, No. 1 ( 2021), p. 1-
    Details
    In: International Journal of Information Privacy, Security and Integrity, Inderscience Publishers, Vol. 5, No. 1 ( 2021), p. 1-
    Type of Medium: Online Resource
    ISSN: 1741-8496 , 1741-850X
    URL: Article
    DOI: 10.1504/IJIPSI.2021.119166
    Language: English
    Publisher: Inderscience Publishers
    Publication Date: 2021
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  • 4
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    Forward Modeling of the Internal Layers in Radio Echo Sounding Using Electrical and Density Measurements from Ice Cores
    American Chemical Society (ACS) ; 1997
    In:  The Journal of Physical Chemistry B Vol. 101, No. 32 ( 1997-08-01), p. 6201-6204
    Details
    In: The Journal of Physical Chemistry B, American Chemical Society (ACS), Vol. 101, No. 32 ( 1997-08-01), p. 6201-6204
    Type of Medium: Online Resource
    ISSN: 1520-6106 , 1520-5207
    URL: Article
    DOI: 10.1021/jp963218+
    RVK:
    VA5430.B
    Language: English
    Publisher: American Chemical Society (ACS)
    Publication Date: 1997
    detail.hit.zdb_id: 1357799-2
    detail.hit.zdb_id: 2006039-7
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  • 5
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    On the evolution of an ice shelf melt channel at the base of Filchner Ice Shelf, from observations and viscoelastic modeling
    Copernicus GmbH ; 2022
    In:  The Cryosphere Vol. 16, No. 10 ( 2022-10-10), p. 4107-4139
    Details
    In: The Cryosphere, Copernicus GmbH, Vol. 16, No. 10 ( 2022-10-10), p. 4107-4139
    Abstract: Abstract. Ice shelves play a key role in the stability of the Antarctic Ice Sheet due to their buttressing effect. A loss of buttressing as a result of increased basal melting or ice shelf disintegration will lead to increased ice discharge. Some ice shelves exhibit channels at the base that are not yet fully understood. In this study, we present in situ melt rates of a channel which is up to 330 m high and located in the southern Filchner Ice Shelf. Maximum observed melt rates are 2 m yr−1. Melt rates inside the channel decrease in the direction of ice flow and turn to freezing ∼55 km downstream of the grounding line. While closer to the grounding line melt rates are higher within the channel than outside, this relationship reverses further downstream. Comparing the modeled evolution of this channel under present-day climate conditions over 250 years with its present geometry reveals a mismatch. Melt rates twice as large as the present-day values are required to fit the observed geometry. In contrast, forcing the model with present-day melt rates results in a closure of the channel, which contradicts observations. The ice shelf experiences strong tidal variability in vertical strain rates at the measured site, and discrete pulses of increased melting occurred throughout the measurement period. The type of melt channel in this study diminishes in height with distance from the grounding line and is hence not a destabilizing factor for ice shelves.
    Type of Medium: Online Resource
    ISSN: 1994-0424
    URL: Article
    DOI: 10.5194/tc-16-4107-2022
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2022
    detail.hit.zdb_id: 2393169-3
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  • 6
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    Basal melting at the Ekström Ice Shelf, Antarctica, estimated from mass flux divergence
    International Glaciological Society ; 2012
    In:  Annals of Glaciology Vol. 53, No. 60 ( 2012), p. 294-302
    Details
    In: Annals of Glaciology, International Glaciological Society, Vol. 53, No. 60 ( 2012), p. 294-302
    Abstract: We characterize the basal mass balance of the Ekström Ice Shelf, Dronning Maud Land, Antarctica, using interferometrically derived surface velocities and ice thickness measurements from radio-echo sounding (RES). The surface velocities are based on data from European Remote-sensing Satellites-1 and -2 (ERS-1/2) during 1994–97. The ice thickness grid consists of 136 RES profiles acquired between 1996 and 2006. Mass fluxes are calculated along selected RES profiles where possible, to reduce uncertainties from ice thickness interpolation. Elsewhere large-scale mass fluxes are calculated using interpolated ice thickness data. Themass flux into the Ekström Ice Shelf from the main grounded drainage basins is estimated to be 3.19±0.4Gt a –1 . The mass flux near the ice shelf front is 2.67±0.3Gt a –1 . Assuming steady state, and based on the equation of continuity, we interpret the residual mass flux as a combined effect of snow accumulation and subglacial melting/refreezing. Using net snow accumulation rates from previous studies, we link the mass flux divergence in irregular-shaped polygons to processes beneath the ice shelf. The highest subglacial melt rates of ~1.1ma –1 are found near the grounding zone of two main inflow glaciers, and around the German station Neumayer III. The detection of unlikely refreezing in a small area ~15 km west of Neumayer III is attributed to both dataset inaccuracies and a (possibly past) violation of the steady-state assumption. In general, the method and input data allow mapping of the spatial distribution of basal melting and the results are in good agreement with several previous studies.
    Type of Medium: Online Resource
    ISSN: 0260-3055 , 1727-5644
    URL: Article
    DOI: 10.3189/2012AoG60A167
    Language: English
    Publisher: International Glaciological Society
    Publication Date: 2012
    detail.hit.zdb_id: 2122400-6
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  • 7
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    Investigating small-scale variations of the recent accumulation rate in coastal Dronning Maud Land, East Antarctica
    International Glaciological Society ; 2007
    In:  Annals of Glaciology Vol. 46 ( 2007), p. 14-21
    Details
    In: Annals of Glaciology, International Glaciological Society, Vol. 46 ( 2007), p. 14-21
    Abstract: The accumulation rate on Potsdam Glacier, East Antarctica, and its spatial and temporal variations are examined using ground-penetrating radar, snow samples and firn-core studies. Physical properties in snow samples and along firn cores provide distributions of density with depth, showing only small spatial variation. Counting of peaks in δ 18 O along the firn cores yields an age–depth distribution that is transferred to the stratigraphy of isochronal internal layers observed with radar. From two radar horizons we determine the spatial accumulation pattern, averaged over the periods 1970–80 and 1980–2004. The shape of internal layers indicates an ablation area at the eastern margin of the investigation area. Accumulation rates show a very high spatial variability, with a mean value of 141 kgm –2 a –1 for the period 1970–2004 and a standard deviation of almost 50%. Mean temporal variation of only a few per cent throughout the investigated area for the observed time interval is much less than the spatial variations. The mean accumulation values are somewhat less than values reported before from this region. Accumulation pattern and surface topography are linked in a way indicating that wind-borne redistribution of snow significantly contributes to the observed spatial variations of accumulation rates. The accumulation data and their variability complement and validate present and future satellite studies of Antarctica’s mass balance.
    Type of Medium: Online Resource
    ISSN: 0260-3055 , 1727-5644
    URL: Article
    DOI: 10.3189/172756407782871756
    Language: English
    Publisher: International Glaciological Society
    Publication Date: 2007
    detail.hit.zdb_id: 2122400-6
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  • 8
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    Surface accumulation in Northern Central Greenland during the last 300 years
    Cambridge University Press (CUP) ; 2020
    In:  Annals of Glaciology Vol. 61, No. 81 ( 2020-04), p. 214-224
    Details
    In: Annals of Glaciology, Cambridge University Press (CUP), Vol. 61, No. 81 ( 2020-04), p. 214-224
    Abstract: The internal stratigraphy of snow and ice as imaged by ground-penetrating radar may serve as a source of information on past accumulation. This study presents results from two ground-based radar surveys conducted in Greenland in 2007 and 2015, respectively. The first survey was conducted during the traverse from the ice-core station NGRIP (North Greenland Ice Core Project) to the ice-core station NEEM (North Greenland Eemian Ice Drilling). The second survey was carried out during the traverse from NEEM to the ice-core station EGRIP (East Greenland Ice Core Project) and then onwards to Summit Station. The total length of the radar profiles is 1427 km. From the radar data, we retrieve the large-scale spatial variation of the accumulation rates in the interior of the ice sheet. The accumulation rates range from 0.11 to 0.26 m a −1 ice equivalent with the lowest values found in the northeastern sector towards EGRIP. We find no evidence of temporal or spatial changes in accumulation rates when comparing the 150-year average accumulation rates with the 321-year average accumulation rates. Comparisons with regional climate models reveal that the models underestimate accumulation rates by up to 35% in northeastern Greenland. Our results serve as a robust baseline to detect present changes in either surface accumulation rates or patterns.
    Type of Medium: Online Resource
    ISSN: 0260-3055 , 1727-5644
    URL: Article
    DOI: 10.1017/aog.2020.30
    Language: English
    Publisher: Cambridge University Press (CUP)
    Publication Date: 2020
    detail.hit.zdb_id: 2122400-6
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  • 9
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    Origin of englacial stratigraphy at three deep ice core sites of the Greenland Ice Sheet by synthetic radar modelling
    Cambridge University Press (CUP) ; 2022
    In:  Journal of Glaciology Vol. 68, No. 270 ( 2022-08), p. 799-811
    Details
    In: Journal of Glaciology, Cambridge University Press (CUP), Vol. 68, No. 270 ( 2022-08), p. 799-811
    Abstract: During the past 20 years, multi-channel radar emerged as a key tool for deciphering an ice sheet's internal architecture. To assign ages to radar reflections and connect them over large areas in the ice sheet, the layer genesis has to be understood on a microphysical scale. Synthetic radar trace modelling based on the dielectric profile of ice cores allows for the assignation of observed physical properties’ variations on the decimetre scale to radar reflectors extending from the coring site to a regional or even whole-ice-sheet scale. In this paper we rely on the available dielectric profiling data of the northern Greenland deep ice cores: NGRIP, NEEM and EGRIP. The three records are well suited for assigning an age model to the stratigraphic radar-mapped layers, and linking up the reflector properties to observations in the cores. Our modelling results show that the internal reflections are mainly due to conductivity changes. Furthermore, we deduce fabric characteristics at the EGRIP drill site from two-way-travel-time differences of along and across-flow polarized radarwave reflections of selected horizons (below 980 m). These indicate in deeper parts of the ice column an across-flow concentrated c -axis fabric.
    Type of Medium: Online Resource
    ISSN: 0022-1430 , 1727-5652
    URL: Article
    DOI: 10.1017/jog.2021.137
    Language: English
    Publisher: Cambridge University Press (CUP)
    Publication Date: 2022
    detail.hit.zdb_id: 2140541-4
    SSG: 14
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  • 10
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    Small-scale spatio-temporal characteristics of accumulation rates in western Dronning Maud Land, Antarctica
    International Glaciological Society ; 2008
    In:  Journal of Glaciology Vol. 54, No. 185 ( 2008), p. 315-323
    Details
    In: Journal of Glaciology, International Glaciological Society, Vol. 54, No. 185 ( 2008), p. 315-323
    Abstract: Spatio-temporal variations of the recently determined accumulation rate are investigated using ground-penetrating radar (GPR) measurements and firn-core studies. The study area is located on Ritscherflya in western Dronning Maud Land, Antarctica, at an elevation range 1400–1560 m. Accumulation rates are derived from internal reflection horizons (IRHs), tracked with GPR, which are connected to a dated firn core. GPR-derived internal layer depths show small relief along a 22 km profile on an ice flowline. Average accumulation rates are about 190 kg m −2 a −1 (1980–2005) with spatial variability (1 σ ) of 5% along the GPR profile. The interannual variability obtained from four dated firn cores is one order of magnitude higher, showing 1 σ standard deviations around 30%. Mean temporal variations of GPRderived accumulation rates are of the same magnitude or even higher than spatial variations. Temporal differences between 1980–90 and 1990–2005, obtained from two dated IRHs along the GPR profile, indicate temporally non-stationary processes, linked to spatial variations. Comparison with similarly obtained accumulation data from another coastal area in central Dronning Maud Land confirms this observation. Our results contribute to understanding spatio-temporal variations of the accumulation processes, necessary for the validation of satellite data (e.g. altimetry studies and gravity missions such as Gravity Recovery and Climate Experiment (GRACE)).
    Type of Medium: Online Resource
    ISSN: 0022-1430 , 1727-5652
    URL: Article
    DOI: 10.3189/002214308784886243
    Language: English
    Publisher: International Glaciological Society
    Publication Date: 2008
    detail.hit.zdb_id: 2140541-4
    SSG: 14
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