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  • 2000-2004  (14)
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  • 1
    Publication Date: 2021-07-28
    Description: We review the historical, geological, tide-gauge, GPS and gravimetric evidence advanced in favour of or against continuing land uplift around Hudson Bay, Canada. After this, we reanalyse the tide-gauge and GPS data for Churchill using longer time series than those available to previous investigators. The dependence of the mean rate of relative sea-level change obtained on the length and mid-epoch of the observation interval considered is investigated by means of the newly developed linear-trend analysis diagram. For studying the shorter-period variability of the tide-gauge record, the continuous-wavelet transform is used. The mean rate of land uplift obtained from GPS is based on a new analysis using IGS solutions of GFZ. Furthermore, sea-level indicators from the Churchill region representing the relative sea-level history during the past 8000 a are included. Finally, the four types of observable are jointly inverted in terms of mantle viscosity. The optimum values are 3×10^20 Pa s and 1.6 × 10^22 Pa s for the upper- and lower-mantle viscosities, respectively.
    Language: English
    Type: info:eu-repo/semantics/report
    Format: application/pdf
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  • 2
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    In:  Planetary and Space Science
    Publication Date: 2020-02-12
    Keywords: 550 - Earth sciences
    Type: info:eu-repo/semantics/article
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  • 3
    Publication Date: 2020-02-12
    Description: The solution to the sea-level equation describing the redistribution of glacial melt water in the oceans is implemented in conjunction with the spectral-finite element method (Martinec, 2000) of modelling glacial-isostatic adjustment (GIA). The main feature of this method is that it solves the field equations governing GIA in the time domain, where a radially symmetric, self-gravitating, incompressible earth model consisting of a fluid core, a Maxwell-viscoelastic lower and upper mantle, and an elastic lithosphere has been adopted in the present study. The additional contribution to sea-level caused by the variation of the Earth's rotation due to the ice-water mass redistribution is determined by means of the Liouville equation. For predicting the GIA-induced sea-level change, three different global models of the Pleistocene deglaciation and several viscosity stratifications are used. We compare the predicted postglacial sea-level change induced by the Pleistocene deglaciation with a set of globally distributed sea-level index points and evaluate the acceptability of the underlying earth and ice models. The best-fitting models are employed to remove the GIA-induced contribution to the recent sea-level change recorded by a set of Fennoscandian tide-gauge stations. In future studies, the reduced tide-gauge trends may serve as a datum when studying the relation between recent ice-mass change and absolute sea-level rise. Martinec,Z., 2000. Spectral-finite element method approach to three-dimensional viscoelstic relaxation in a spherical earth. Geophys. J. Int., 142, 117-141.
    Keywords: 550 - Earth sciences
    Type: info:eu-repo/semantics/conferenceObject
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  • 4
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    In:  Geophysical Research Abstracts ; Vol. 5, 02586, 2003
    Publication Date: 2020-02-12
    Keywords: 550 - Earth sciences
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  • 5
    Publication Date: 2020-02-12
    Keywords: 550 - Earth sciences
    Type: info:eu-repo/semantics/article
    Format: application/pdf
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  • 6
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    In:  Journal of Geophysical Research
    Publication Date: 2020-02-12
    Description: Numerous examples of fault slip that offset late Quaternary glacial deposits and bedrock polish support the idea that the glacial loading cycle causes earthquakes in the upper crust. A semianalytical scheme is presented for quantifying glacial and postglacial lithospheric fault reactivation using contemporary rock fracture prediction methods. It extends previous studies by considering differential Mogi-von Mises stresses, in addition to those resulting from a Coulomb analysis. The approach utilizes gravitational viscoelastodynamic theory and explores the relationships between ice mass history and regional seismicity and faulting in a segment of East Antarctica containing the great Antarctic Plate (Balleny Island) earthquake of 25 March 1998 (Mw 8.1). Predictions of the failure stress fields within the seismogenic crust are generated for differing assumptions about background stress orientation, mantle viscosity, lithospheric thickness, and possible late Holocene deglaciation for the D91 Antarctic ice sheet history. Similar stress fracture fields are predicted by Mogi-von Mises and Coulomb theory, thus validating previous rebound Coulomb analysis. A thick lithosphere, of the order of 150–240 km, augments stress shadowing by a late melting (middle-late Holocene) coastal East Antarctic ice complex and could cause present-day earthquakes many hundreds of kilometers seaward of the former Last Glacial Maximum grounding line.
    Keywords: 550 - Earth sciences
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  • 7
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    In:  EOS, Transactions, American Geophysical Union, Suppl. ; Vol. 81, F326, 2000
    Publication Date: 2020-02-12
    Keywords: 550 - Earth sciences
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  • 8
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    In:  Geophysical Research Abstracts ; Vol. 4, 00061, 2002
    Publication Date: 2020-02-12
    Keywords: 550 - Earth sciences
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  • 9
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    In:  EOS, Transactions, American Geophysical Union, 85(17), Suppl.
    Publication Date: 2020-02-12
    Description: The intepretation of sea-level indicators (SLIs) in terms of glacial-isostatic adjustment (GIA) has usually been based on neighbouring SLIs grouped into a single sea-level curve, which is then assumed to represent the Holocene sea-level change in that region. In this method, the nominal height and age of a particular SLI are the only characteristics considered in the inference of the former sea-level height. However, only isolation basins yield a narrow range for sea level, whereas SLIs based on samples, such as flotsam, shells or peat, only allow the determination of an upper or lower bound or a range for it. To use also these types of sample properly, we have developed a classification scheme based on Fuzzy logic. After the defintion of appropriate membership functions, this method leads to a more systematic and realistic interpretation of the large amount of SLIs available. We apply this method to SLIs from several regions in Canada and demonstrate how it modifies the inference of GIA for a particular region and, thus, the determination of mantle viscosity.
    Keywords: 550 - Earth sciences
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  • 10
    Publication Date: 2020-02-12
    Description: We review the history of analyses of the tide-gauge record for Churchill, Manitoba, and advance a new analysis of the record using a longer time series than that available to Tushingham (1992). The sensitivity of the mean rate of relative sea-level change obtained to the averaging procedure employed is demonstrated by calculating rates for sliding observation intervals of variable widths. After that, the 'best' mean rate of relative sea-level rise is compared with estimates of the mean rate of land uplift and the mean rate of gravity change based on GPS and absolute gravimetry data, respectively. As an additional type of observation, the postglacial relative sea-level change obtained from paleo-shoreline evidence in the Churchill region is also included. Assuming that the governing process is glacial-isostatic adjustment, a joint inversion of the four types of data return upper- and lower-mantle viscosities of about $3 imes 10^{20}$ Pa s and $〉 5 imes 10^{21}$ Pa s, respectively.
    Keywords: 550 - Earth sciences
    Type: info:eu-repo/semantics/conferenceObject
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