Through-ice AUV deployment: Operational and technical experience from two seasons of Arctic fieldwork

Detailed sea ice draft mapping was recently accomplished in the Beaufort Sea, north of Alaska, in 2007 and in the Lincoln Sea, north of Canada's Ellesmere Island, in 2008 using a small (3 m long, 20 cm diameter), man-handleable Gavia AUV incorporating an inertial navigation system and a 500 kHz phase-measuring swath sonar. The topography of specific ice features was mapped across 80 m-wide swaths by performing repeated runs in the vicinity of access holes drilled in the sea ice. The paper discusses the technical and operational developments undertaken to successfully accomplish the missions, including test deployments in a frozen Canadian lake prior to each Arctic deployment. Example data are shown and accuracy issues discussed.