The three-dimensional modelling program MARCO_AIR has been used to calculate the response of idealized sea-ice pressure ridge models to practical airborne and shipborne electromagnetic systems. The model results clearly show the superior lateral resolution of the horizontal coplanar shipborne system compared to higher-altitude airborne measurements. However, sea-ice keel thicknesses estimated via one-dimensional inversion of shipborne single-frequency electromagnetic data are strongly dependent on relatively small variations in survey altitude. One-dimensional inversion of synthetic helicopter electromagnetic data over three-dimensional pressure ridge models shows that the maximum ice keel thickness is consistently underestimated, although airborne EM methods yield reliable thickness estimates over level ice. The vertical-coaxial coil survey geometry offers excellent lateral resolution of multiple targets, but the anomalies of typical Antarctic sea-ice pressure ridges would be too small to be reliably detected in practical surveys using an HEM system with a transmitter-receiver separation of 2?3 m. For an HEM system with a coil separation of 8 m, the vertical coaxial responses are larger, and lateral resolution of the vertical coaxial measurements at a flight height of 20 m is superior to a close-coupled horizontal coplanar system flown at an altitude of 10 m. © 2003, CSIRO. All rights reserved.

Item Type:	Refereed Article
Research Division:	Earth Sciences
Research Group:	Geophysics
Research Field:	Electrical and Electromagnetic Methods in Geophysics
Objective Division:	Expanding Knowledge
Objective Group:	Expanding Knowledge
Objective Field:	Expanding Knowledge in the Earth Sciences
Author:	Reid, JE (Dr James Reid)
Author:	Worby, AP (Professor Anthony Worby)
ID Code:	28039
Year Published:	2003
Web of Science® Times Cited:	5
Deposited By:	Earth Sciences
Deposited On:	2003-08-01
Last Modified:	2009-06-23
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