Fabric beats in radar data across the NEGIS ice stream
Eisen, Olaf ORCID: https://orcid.org/0000-0002-6380-962X,
Jansen, Daniela ORCID: https://orcid.org/0000-0002-4412-5820,
Franke, Steven ORCID: https://orcid.org/0000-0001-8462-4379,
Paden, John,
Weikusat, Ilka ORCID: https://orcid.org/0000-0002-3023-6036,
Ershadi, Mohammadreza,
Drews, Reinhard,
Steinhage, Daniel ORCID: https://orcid.org/0000-0003-4737-9751,
Lilien, David,
Yan, Jie-Bang,
Humbert, Angelika,
Rückamp, Martin ORCID: https://orcid.org/0000-0003-2512-7238,
Wilhelms, Frank ORCID: https://orcid.org/0000-0001-7688-3135,
Dahl-Jensen, Dorthe,
Grindsted, Aslak,
Hvidberg, Christine S. and
Miller, Heinrich
;
Contact
Olaf.Eisen [ at ] awi.de
Abstract
Crystal anisotropy of ice causes slight birefringence for electromagnetic waves. At the same time,
the mechanical anisotropy amounts to several orders of magnitude, thus making fabric properties
highly-relevant for internal deformation. To date, bulk anisotropy of glaciers and ice sheets can be
determined by geophysical methods, such as polarimetric radar, or direct sampling from ice cores.
A shortcoming has been so far that changes of bulk anisotropy could mainly be inferred at single
point observations, but less so as continuous profiles. Here, we exploit the effect of birefringence
caused by bulk anisotropy in co-polarized airborne radar data to determine the horizontal
anisotropy across the North-East Greenland Ice Stream. We base our analysis on the fact that
birefringence causes a second-order effect on radar amplitudes, which leads to a beat frequency in
the low and medium frequency range (O(100 kHz)), which is proportional to the horizontal
anisotropy. Complementing our radar analysis with direct fabric and dielectric property
observations we can constrain the range of all three fabric eigenvalues as a function of space
across and along the ice stream. Finally, we assess the effect of the inferred fabric distribution on
the overall ice rheology in the context of ice stream dynamics and compare it with numerical model
results. Our overall approach has the advantage that it can be applied to co-polarized radar
systems, as commonly used in profiling surveys, and does not require dedicated cross-polarized
radar set-up. This provides the opportunity to revisit older data, especially from Greenland and
Antarctica, to map fabric anisotropy in ice-dynamically interesting regions.
Item Type
Conference
(Talk)
Authors
Eisen, Olaf ORCID: https://orcid.org/0000-0002-6380-962X,
Jansen, Daniela ORCID: https://orcid.org/0000-0002-4412-5820,
Franke, Steven ORCID: https://orcid.org/0000-0001-8462-4379,
Paden, John,
Weikusat, Ilka ORCID: https://orcid.org/0000-0002-3023-6036,
Ershadi, Mohammadreza,
Drews, Reinhard,
Steinhage, Daniel ORCID: https://orcid.org/0000-0003-4737-9751,
Lilien, David,
Yan, Jie-Bang,
Humbert, Angelika,
Rückamp, Martin ORCID: https://orcid.org/0000-0003-2512-7238,
Wilhelms, Frank ORCID: https://orcid.org/0000-0001-7688-3135,
Dahl-Jensen, Dorthe,
Grindsted, Aslak,
Hvidberg, Christine S. and
Miller, Heinrich
;
Divisions
Primary Division
Programs
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Publication Status
Published
Event Details
24th Alpine Glaciology Meeting, 25 Mar 2021 - 26 Mar 2021, online.
Eprint ID
53897
Cite as
Eisen, O.
,
Jansen, D.
,
Franke, S.
,
Paden, J.
,
Weikusat, I.
,
Ershadi, M.
,
Drews, R.
,
Steinhage, D.
,
Lilien, D.
,
Yan, J. B.
,
Humbert, A.
,
Rückamp, M.
,
Wilhelms, F.
,
Dahl-Jensen, D.
,
Grindsted, A.
,
Hvidberg, C. S.
and
Miller, H.
(2021):
Fabric beats in radar data across the NEGIS ice stream
,
24th Alpine Glaciology Meeting,
online,
25 March 2021 - 26 March 2021
.
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