A new view of the underside of Arctic sea ice

The Autosub-II autonomous underwater vehicle (AUV), operating off NE Greenland in August 2004, obtained the first successful swath sonar measurements under sea ice, showing in unprecedented detail the three-dimensional nature of the under-ice surface. The vehicle, operated from RRS James Clark Ross, obtained more than 450 track-km of under-ice multibeam data. We show imagery from first- and multiyear ice, including young ridges, old hummocks and undeformed melting ice. In addition, we show how the combination of other on-board sensors enabled the vehicle to obtain detailed information about seabed topography, water structure and current fields in an exploratory mode within a region which is seldom visited because of difficult year-round ice conditions. This included identification of a new current regime in the Norske Trough.