HR: 0800h
AN: C11B-0429    [Abstracts]
TI: Three Dimensional Mapping of the Sea Ice Underside From AUVs
AU: * Wadhams, P
EM: p.wadhams@damtp.cam.ac.uk
AF: Dept. of Applied Mathematics and Theoretical Physics, University of Cambridge, Wilberforce Road, Cambridge, CB3 0WA, United Kingdom
AU: Doble, M J
EM: doble@obs-vlfr.fr
AF: Dept. of Applied Mathematics and Theoretical Physics, University of Cambridge, Wilberforce Road, Cambridge, CB3 0WA, United Kingdom
AU: Wilkinson, J P
EM: jpw28@sams.ac.uk
AF: Scottish Association for Marine Science, Dunstaffnage Marine Laboratory, Oban, PA37 1QA, United Kingdom
AB: In August 2004 the Autosub-II 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. The Gavia imagery shows the morphological distinctions between first-year (FY) and multi-year (MY) ice undersides, the contrast between the shapes of FY and MY ridges, and the appearance of refrozen leads. Ice drafts were validated by drilling, and it was found that ridge slope statistics and local probability density functions (PDFs) of draft could be derived with high precision.
DE: 0700 CRYOSPHERE (4540)
DE: 0750 Sea ice (4540)
DE: 1621 Cryospheric change (0776)
DE: 4207 Arctic and Antarctic oceanography (9310, 9315)
DE: 4540 Ice mechanics and air/sea/ice exchange processes (0700, 0750, 0752, 0754)
SC: Cryosphere [C]
MN: 2007 Fall Meeting