In August 2004 the Autosub-II autonomous underwater vehicle (AUV), operating off NE Greenland, carried out the first multibeam digital terrain mapping of the sea ice underside, using a Kongsberg EM2000 sonar. We show some of the high-quality imagery from the experiment, and discuss its implications for ice thickness mapping and other applications. In April 2007 the second such mapping experiment took place, but this time using a small ice-launched Gavia AUV, equipped with a GeoSwath 500 kHz interferometric sonar system. Gavia could be launched and recovered manually through 3 x 1 m holes while Autosub required a ship and a crane. The greater range of Autosub is contrasted with the greater flexibility of Gavia in multisensor programs. We discuss how AUV techniques can be applied to problems such as mapping rubble fields around drilling platforms, oil containment by sea ice, and other topics of interest to the offshore industry.

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