3D EM modelling of Antarctic sea ice pressure ridges

Julian Vrbancich; James Reid; David Annetts; Andreaus Pfaffling; Tony Worby

doi:10.1071/ASEG2004ab150

ISSN: 2202-0586
E-ISSN:

oa 3D EM modelling of Antarctic sea ice pressure ridges
Authors Julian Vrbancich^a, James Reid^b, David Annetts^c, Andreaus Pfaffling^d and Tony Worby^e
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^a Defence Science & Technology Organisation,, Australia, [email protected] ^b University of Tasmania,, Australia, [email protected] ^c CSIRO Exploration & Mining, [email protected] ^d AWI, Bremerhaven,, Germany, [email protected] ^e Antarctic CRC & Australian Antarctic Division,, Australia, [email protected]
Publisher: Australian Society of Exploration Geophysicists
Source: ASEG Extended Abstracts, Volume 2004, Issue ASEG2004 - 17th Geophysical Conference, Dec 2004, p. 1 - 4
DOI: https://doi.org/10.1071/ASEG2004ab150
- Published online: 01 Dec 2004

Abstract

The use of airborne electromagnetic (AEM) surveys to measure Antarctic sea ice thickness is being investigated as a regional mapping tool to aid global climate studies. Undeformed sea ice floes are modelled as ID structures. However, sea ice pressure ridge sails (in air) and keels (undersea) form convenient 2D and 3D targets. In order to use AEM techniques to study the distribution of ice thickness, it is first necessary to test if realistic sea ice structures can be modelled electromagnetically.

Pressure ridge structures from drillhole sampling can in some cases be constructed from simple block models. Finite element and integral equation 3D EM modelling programs can then be applied to these structures to test for agreement, and to predict the AEM response, including topography (sails). EM modelling of frequency domain systems shows that good agreement is obtained at certain frequencies and that a vertical coaxial (VCX) transmitter-receiver coil configuration laterally resolves the ice keel better than a horizontal coplanar (HCP) configuration. Cross-sectional dimensions of the sails and keels are relatively small and mesh design is critical in order to avoid discretisation errors. Software and hardware constraints may limit successful EM modelling of multiple keels that combine sub-metre structures and coarser structures. For a given mesh, discretisation errors may lead to noisy EM response profiles depending on the frequency, coil geometry, and component (in-phase or quadrature). Adaptive mesh structures may be required to minimise discretisation errors.

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References

Haas, C, 1998, Evaluation of ship-based electromagnetic-inductive thickness measurements of summer sea-ice in the Bellingshausen and Amundsen Seas, Antarctica: Cold Regions Science and Technology, 27, 1-16.
Haas, C, Gerland, S., Eicken, H, and Miller, H, 1997, Comparison of sea ice thickness measurements under summer and winter conditions in the Arctic using a small electromagnetic induction device: Geophysics, 62, 749-757.
Kovacs, A., Valleau, N. C, and Holladay, J. S, 1987, Airborne EM sounding of sea ice thickness and sub-ice bathymetry: Cold Regions Science and Technology, 14, 289-311.
Prinsenberg, S. J., Peterson, I. K., and Holladay, J. S., 1996, Comparison of airborne electromagnetic ice thickness data with NOAA/AVHRR and ERS-1/SAR images: Atmosphere-Ocean, 34, 185-205.
Raiche, A., 1999, Accurate EM modelling for appropriate levels of geological and system complexity: 61st EAGE Conference, Helsinki.
Reid, J. E., and Vrbancich, J., 2004a, A comparison of the inductive-limit footprints of airborne electromagnetic configurations: accepted for publication in Geophysics.
Reid, J. E., and Vrbancich, J., 2004b, Footprints of AEM systems over ID earths: ASEG 17th Geophys. Conference.
Reid, J.E., Vrbancich, J., and Worby, A.P., 2003, A comparison of shipborne and airborne EM methods for Antarctic sea ice thickness measurements: Exploration Geophysics, 34, 46-50.
Reid, J.E., Worby, A.P., Vrbancich, J., and Munroe, I.S., 2003, Ship-borne measurements of Antarctic sea ice thickness: Geophysics, 68, 1537-1546.
Worby, A. P., Griffin, P. W., Lytle, V. I., and Massom, R. A., 1999, On the use of electromagnetic induction sounding to determine winter and spring sea ice thickness in the Antarctic: Cold Regions Science and Technology, 29, 49-58.

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Article Type: Research Article

Keyword(s): AEM; Antarctica; EM modelling; sea ice

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