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  • 2015-2019  (2)
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  • 1
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    EGU General Assembly 2019
    In:  EPIC3EGU 2019, Vienna, Austria, 2019-04-07-2019-04-12EGU General Assembly 2019
    Publication Date: 2019-04-29
    Description: Crystal Orientation Fabric (COF) of c-axes in ice cores reveals information about deformation within ice sheets. While this is a well established analysis technique for deep ice cores from ice divides, information about COF in ice streams is just now becoming available: the EastGRIP ice core is situated inside the largest ice stream in Greenland, the North East Greenland Ice Stream (NEGIS). With the ongoing analysis of samples from the EastGRIP ice core, COF is now available down to 1714 m, revealing an extremely more rapid evolution of COF anisotropy with depth compared to all other ice cores. This enables us to study the ability of polarimetric radar measurements to infer an overall pattern of COF from measurements conducted at the surface. Depending on whether the COF is isotropic or anisotropic, a radar signal is reflected differently in terms of angle dependence and polarization. We conducted these polarimetric measurements around the EastGRIP drill site and we compare them to COF data obtained from 778 thin sections, prepared and measured at EastGRIP drill site. We investigate the hypothesis that the same pattern of COF can be retrieved from the polarimetric measurements as is available from the ice core. If confirmed, this would provide an addition constraint on the (an)isotropy at locations where no ice core is available. This would potentially provide quasi spatial coverage and greatly improve our understanding of the evolution of anisotropy over from ice divides to outlet glaciers.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
    Location Call Number Limitation Availability
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  • 2
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    In:  EPIC3IGS 2019 Five Decades of Radioglaciology, Stanford University, 2019-07-08-2019-07-12
    Publication Date: 2019-08-12
    Description: Deformation processes dominated by dislocation activity within ice sheets take place on small scale: ice crystals are effectively re-oriented to minimize resistance when deformation takes place. The analysis of Crystal Orientation Fabric (COF) of c-axes in ice cores is a well-established technique to investigate these processes within ice sheets. Due to the extensive infrastructure required for drilling and protracted analysis of ice cores, the amount of information of COF of the Antarctic and Greenland Ice Sheet is limited, both, in aerial coverage as well as in depth resolution. Indirect measurements, such as geophysical techniques, provide complementary information. Depending on whether the COF is isotropic or anisotropic, a radar signal is propagating differently in terms of angle of incidence and polarization, and, partially reflected when COF properties change along the direction of travel. We study the ability of phase-sensitive radar measurements to infer an overall pattern of COF by comparing our results to COF derived from the EastGRIP ice core, drilled into the North East Greenland Ice Stream (NEGIS). If radar measurements allow to reveal information about the COF as analyzed ice cores do, this would provide important additional information on the (an)isotropy at locations where no ice core is available. Furthermore, it has the ability to offer a quasi-continuous spatial coverage and to greatly improve our understanding of the evolution of anisotropy along ice-flow trajectories, from ice divides to the calving front of outlet glaciers.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
    Format: application/pdf
    Location Call Number Limitation Availability
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