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  • 1
    Online Resource
    Online Resource
    Conditions for Growth and Retreat of the Laurentide Ice Sheet
    Consortium Erudit ; 2008
    In:  Géographie physique et Quaternaire Vol. 41, No. 2 ( 2008-01-15), p. 279-290
    Details
    In: Géographie physique et Quaternaire, Consortium Erudit, Vol. 41, No. 2 ( 2008-01-15), p. 279-290
    Abstract: Die Ergebnisse eines dreidimensionalen numerischen Modells der nordamerikanischen Eisdecken entsprechend den Variationen der Sonneneinstrahlung in verschiedenen Breiten werden in Bezug auf die Bedingungen fur die Bildung und den Riickzug der Eisdecken untersucht. Die letzte Interglazialzeit ist eine klare Folge der vorhergehenden hohen sommerlichen Sonneneinstrahlungen und ist nicht sehr abhângig von den klimatischen Parametern. Der Umfang und die Dauer des letzten glazialen Maximums erlauben die klimatischen Parameter genau zu bestimmen. Zwischen diesen beiden Perioden war der Umfang des Vorrückens und Rückzugs der Eisdecke stark beeinflupt vom Umfang der Albedo-Parameter der Eisdecke. Die zeitlichen Wechsel der Sonneneinstrahlung, des Klimas, der Eisdecke und der Senkung des Landes sind nicht phasengleich, und so wird kein Gleichgewicht erreicht. Die Verteilung der Erdoberflächenerhebungen nimmt eine Schlüsselrolle ein in dër Verteilung des Wachsens der Eisdecke und den darauf folgenden Rückphasen, dem Zusammenwachsen und dem Rückzug. Es ist anzunehmen, dap die Art der Verteilung des Landes in der Grundmoräne eher das Anwachsen und die VorstoBphasen der Eisdecke spiegelt als ihre maximale Gestalt. Zuletzt entsprechen dem Modell nach die Zyklen der Vereisung während der letzten 500,000 Jahre dem Vorkommen extremer sommerlicher Sonneneinstrahlung entlang eines breiten Gùrtels von 40-80 o nördlicher Breite, infolge der Übereinstimmung von Neigungswinkel und Charakteristika der Sonnennähe, überlagert durch die Hysteresis-Wirkungen der Eisdecke.
    Type of Medium: Online Resource
    ISSN: 1492-143X , 0705-7199
    URL: Article
    DOI: 10.7202/032683ar
    Language: English
    Publisher: Consortium Erudit
    Publication Date: 2008
    detail.hit.zdb_id: 2035245-1
    SSG: 14
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  • 2
    Online Resource
    Online Resource
    Collapse and reorganisation of the Southern Ocean overturning under global warming in a coupled model
    American Geophysical Union (AGU) ; 2001
    In:  Geophysical Research Letters Vol. 28, No. 20 ( 2001-10-15), p. 3927-3930
    Details
    In: Geophysical Research Letters, American Geophysical Union (AGU), Vol. 28, No. 20 ( 2001-10-15), p. 3927-3930
    Abstract: This study investigates the long‐term behaviour of the thermohaline circulation (THC) in the CSIRO climate model, under a scenario of transient increase of atmospheric (equivalent) CO 2 concentration followed by a perpetual stabilisation at triple the initial level (3 × CO 2 ). The North Atlantic Deep Water Formation (NADWF) declines substantially and the Antarctic Bottom Water Formation (AABWF) essentially ceases by the time of CO 2 tripling. During the subsequent millennium of stable 3 × CO 2 , NADWF recovers slightly but the AABWF shows no sign of returning and the residual deep overturning dies away. Accelerating the convergence to equilibrium of the deep ocean under the 3 × CO 2 condition, the global THC eventually reaches a near‐stable state with the entire ocean warming by about 7°C, NADWF fully recovered and AABWF partly re‐established. This result shows a possible new quasi‐equilibrium of the ocean under long‐term global warming induced by the anthropogenic CO 2 increase.
    Type of Medium: Online Resource
    ISSN: 0094-8276 , 1944-8007
    URL: Article
    DOI: 10.1029/2001GL013705
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2001
    detail.hit.zdb_id: 2021599-X
    detail.hit.zdb_id: 7403-2
    SSG: 16,13
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  • 3
    Online Resource
    Online Resource
    The tertiary creep of polycrystalline ice: experimental evidence for stress-dependent levels of strain-rate enhancement
    International Glaciological Society ; 2012
    In:  Journal of Glaciology Vol. 58, No. 208 ( 2012), p. 301-314
    Details
    In: Journal of Glaciology, International Glaciological Society, Vol. 58, No. 208 ( 2012), p. 301-314
    Abstract: Laboratory creep deformation experiments have been conducted on initially isotropic laboratory-made samples of polycrystalline ice. Steady-state tertiary creep rates, , were determined at strains exceeding 10% in either uniaxial-compression or simple-shear experiments. Isotropic minimum strain rates, , determined at ˜1 % strain, provide a reference for comparing the relative magnitude of tertiary creep rates in shear and compression through the use of strain-rate enhancement factors, E, defined as the ratio of corresponding tertiary and isotropic minimum creep rates, i.e. . The magnitude of strain-rate enhancement in simple shear was found to exceed that in uniaxial compression by a constant factor of 2.3. Results of experiments conducted at octahedral shear stresses of t o = 0.040.80 MPa indicate a creep power-law stress exponent of n = 3 for isotropic minimum creep rates and n = 3.5 for tertiary creep rates. The difference in stress exponents for minimum and tertiary creep regimes can be interpreted as a t 0 stress-dependent level of strain-rate enhancement, i.e. .The implications of these results for deformation in complex multicomponent stress configurations and at stresses below those used in the current experiments are discussed.
    Type of Medium: Online Resource
    ISSN: 0022-1430 , 1727-5652
    URL: Article
    DOI: 10.3189/2012JoG11J149
    Language: English
    Publisher: International Glaciological Society
    Publication Date: 2012
    detail.hit.zdb_id: 2140541-4
    SSG: 14
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  • 4
    Online Resource
    Online Resource
    Book Reviews
    Oxford University Press (OUP) ; 1981
    In:  Military Medicine Vol. 146, No. 3 ( 1981-03-01), p. 164-214
    Details
    In: Military Medicine, Oxford University Press (OUP), Vol. 146, No. 3 ( 1981-03-01), p. 164-214
    Type of Medium: Online Resource
    ISSN: 0026-4075 , 1930-613X
    URL: Article
    DOI: 10.1093/milmed/146.3.164
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 1981
    detail.hit.zdb_id: 2130577-8
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  • 5
    Online Resource
    Online Resource
    Ice-flow properties at Dome Summit South, Law Dome, East Antarctica
    International Glaciological Society ; 2002
    In:  Annals of Glaciology Vol. 35 ( 2002), p. 567-573
    Details
    In: Annals of Glaciology, International Glaciological Society, Vol. 35 ( 2002), p. 567-573
    Abstract: Ice-flow properties within a polar ice sheet are examined using the comprehensive data gathered from ice-core drilling by Australian National Antarctic Research Expeditions (ANARE) at Dome Summit South (DSS), on Law Dome, East Antarctica. Using the shear strain rates derived from borehole inclination measurements we demonstrate the need to modify the ice-flow relations to treat enhanced shear deformation deep within the ice sheet. We show that the relation between enhanced flow and the measured crystallographic properties is generally in accord with expectations, at least in the upper parts of the ice sheet, but it becomes clear that nearer to the bedrock the situation is more complicated. We also compare the observed shear strain-rate profile with results from a model that describes flow enhancement as a function of the applied stresses.
    Type of Medium: Online Resource
    ISSN: 0260-3055 , 1727-5644
    URL: Article
    DOI: 10.3189/172756402781816924
    Language: English
    Publisher: International Glaciological Society
    Publication Date: 2002
    detail.hit.zdb_id: 2122400-6
    SSG: 14
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  • 6
    Online Resource
    Online Resource
    Meteoric and marine ice crystal orientation fabrics from the Amery Ice Shelf, East Antarctica
    International Glaciological Society ; 2010
    In:  Journal of Glaciology Vol. 56, No. 199 ( 2010), p. 877-890
    Details
    In: Journal of Glaciology, International Glaciological Society, Vol. 56, No. 199 ( 2010), p. 877-890
    Abstract: The northwestern sector of the Amery Ice Shelf, East Antarctica, has a layered structure, due to the presence of both meteoric ice and a marine ice layer resulting from sub-shelf freezing processes. Crystal orientation fabric and grain-size data are presented for ice cores obtained from two boreholes ˜70 km apart on approximately the same flowline. Multiple-maxima crystal orientation fabrics and large mean grain sizes in the meteoric ice are indicative of stress relaxation and subsequent grain growth in ice that has flowed into the Amery Ice Shelf. Strongly anisotropic single-maximum crystal orientation fabrics and rectangular textures near the base of the ˜200 m thick marine ice layer suggest accretion occurs by the accumulation of frazil ice platelets. Crystal orientation fabrics in older marine ice exhibit vertical large circle girdle patterns, influenced by the complex stress configurations that exist towards the margins of the ice shelf. Post-accumulation grain growth and fabric development in the marine ice layer are restricted by a high concentration of brine and insoluble particulate inclusions. Differences in the meteoric and marine ice crystallography are indicative of the contrasting rheological properties of these layers, which must be considered in relation to large-scale ice-shelf dynamics.
    Type of Medium: Online Resource
    ISSN: 0022-1430 , 1727-5652
    URL: Article
    DOI: 10.3189/002214310794457353
    Language: English
    Publisher: International Glaciological Society
    Publication Date: 2010
    detail.hit.zdb_id: 2140541-4
    SSG: 14
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  • 7
    Online Resource
    Online Resource
    Modelled stress distributions at the Dome Summit South borehole, Law Dome, East Antarctica: a comparison of anisotropic ice flow relations
    International Glaciological Society ; 2015
    In:  Journal of Glaciology Vol. 61, No. 229 ( 2015), p. 987-1004
    Details
    In: Journal of Glaciology, International Glaciological Society, Vol. 61, No. 229 ( 2015), p. 987-1004
    Abstract: In this study we compare the anisotropic flow relations for polycrystalline ice of Azuma and Goto-Azuma (1996), Thorsteinsson (2002), Placidi and others (2010) and Budd and others (2013). Observations from the Dome Summit South (DSS) ice-coring site at Law Dome, East Antarctica, are used to model the vertical distribution of deviatoric stress components at the borehole site. The flow relations in which the anisotropic rheology is parameterized by a scalar function, so that the strain-rate and deviatoric stress tensor components are collinear, provide simple shear and vertical compression deviatoric stress profiles that are most consistent with laboratory observations of tertiary creep in combined stress configurations. Those flow relations where (1) the anisotropy is derived from the magnitude of applied stresses resolved onto the basal planes of individual grains and (2) the macroscopic deformation is obtained via homogenization of individual grain responses provide stress estimates less consistent with laboratory observations. This is most evident in combined simple shear and vertical compression flow regimes where shear is dominant. Our results highlight the difficulties associated with developing flow relations which incorporate a physically based description of microdeformation processes. In particular, this requires that all relevant microdeformation, recrystallization and recovery processes are adequately parameterized.
    Type of Medium: Online Resource
    ISSN: 0022-1430 , 1727-5652
    URL: Article
    DOI: 10.3189/2015JoG14J198
    Language: English
    Publisher: International Glaciological Society
    Publication Date: 2015
    detail.hit.zdb_id: 2140541-4
    SSG: 14
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  • 8
    Online Resource
    Online Resource
    Response of the antarctic circumpolar current transport to global warming in a coupled model : ACC TRANSPORT UNDER GLOBAL WARMING
    American Geophysical Union (AGU) ; 2002
    In:  Geophysical Research Letters Vol. 29, No. 24 ( 2002-12), p. 26-1-26-4
    Details
    In: Geophysical Research Letters, American Geophysical Union (AGU), Vol. 29, No. 24 ( 2002-12), p. 26-1-26-4
    Type of Medium: Online Resource
    ISSN: 0094-8276
    URL: Article
    DOI: 10.1029/2002GL015919
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2002
    detail.hit.zdb_id: 2021599-X
    detail.hit.zdb_id: 7403-2
    SSG: 16,13
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  • 9
    Online Resource
    Online Resource
    Impact of transient increases in atmospheric CO 2 on the accumulation and mass balance of the Antarctic ice sheet
    International Glaciological Society ; 1997
    In:  Annals of Glaciology Vol. 25 ( 1997), p. 137-144
    Details
    In: Annals of Glaciology, International Glaciological Society, Vol. 25 ( 1997), p. 137-144
    Abstract: The response of the Antarctic ice sheet to climate change over the next 500 years is calculated using the output of a transient-coupled ocean-atmosphere simulation assuming the atmospheric CO 2 value increases up to three times present levels. The main effects on the ice sheet on this time-scale include increasing rates of accumulation, minimal surface melting, and basal melting of ice shelves. A semi-Lagrangian transport scheme for moisture was used to improve the model’s ability to represent realistic rates of accumulation under present-day conditions, and thereby increase confidence in the anomalies calculated under a warmer climate. The response of the Antarctic ice sheet to the warming is increased accumulation inland, offset by loss from basal melting from the floating ice, and increased ice flow near the grounding line. The preliminary results of this study show that the change to the ice-sheet balance for the transient-coupled model forcing amounted to a minimal sea-level contribution in the next century, but a net positive sea-level rise of 0.21 m by 500 years. This new result supercedes earlier results that showed the Antarctic ice sheet made a net negative contribution to sea-level rise over the next century. However, the amplitude of the sea-level rise is still dominated In the much larger contributions expected from thermal expansion of the ocean of 0.25 m for 100 years and 1.00 m for 500 years.
    Type of Medium: Online Resource
    ISSN: 0260-3055 , 1727-5644
    URL: Article
    DOI: 10.3189/S0260305500013938
    Language: English
    Publisher: International Glaciological Society
    Publication Date: 1997
    detail.hit.zdb_id: 2122400-6
    SSG: 14
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  • 10
    Online Resource
    Online Resource
    Laboratory studies of the flow rates of debris-laden ice
    International Glaciological Society ; 2003
    In:  Annals of Glaciology Vol. 37 ( 2003), p. 108-112
    Details
    In: Annals of Glaciology, International Glaciological Society, Vol. 37 ( 2003), p. 108-112
    Abstract: Ice-sheet basal ice is warmer than that above because of the heat from the Earth’s interior. The stresses acting on the basal ice are greatest. In addition, the basal ice often contains debris consisting of silt and small stones picked up from the rock over which the ice flows. Because the base is the warmest part of an ice sheet and the stress there is greatest, flow rates in the basal ice are large and often contribute most of the ice movement. It is therefore important, for accurate modelling of the ice sheets, to know whether the debris within the basal ice enhances or retards the flow of the ice. In this paper, we describe laboratory deformation tests in uniaxial compression and in simple shear, on sand-laden ice. We find no significant dependence of flow rate on sand content (up to 15% volume) in the stress range 0.13–0.5 MPa and temperature range –0.02 to –18.0°C. Further work needs to include laboratory tests on debris-laden ice extracted from the polar ice sheets. This work is underway.
    Type of Medium: Online Resource
    ISSN: 0260-3055 , 1727-5644
    URL: Article
    DOI: 10.3189/172756403781815537
    Language: English
    Publisher: International Glaciological Society
    Publication Date: 2003
    detail.hit.zdb_id: 2122400-6
    SSG: 14
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