Underwater robot captures images of Antarctic sea ice
A team of scientists from the UK, USA and Australia have used an autonomous underwater vehicle (AUV) to capture 'detailed, high-resolution 3D maps' of Antarctic sea ice and provide accurate ice thickness measurements in areas previously too difficult to access.
Oceanographic survey instruments are typically designed to map features on the seafloor, but the team kitted out an AUV with an upward-facing sonar to accurately measure and map the underside of sea ice floes.
"Sea ice in Antarctica is hard to measure. This project was aimed at making 3D measurements of the thickness of sea ice by using an AUV to map the underside of ice floes while simultaneously mapping the surface," said Hanumant Singh, an engineering scientist at the Woods Hole Oceanographic Institution (WHOI) whose laboratory designed, built and operated the AUV.
The two metre long AUV, known as the SeaBED, is based on a dual-hulled concept designed to give it enhanced stability for low-speed photographic surveys. It was operated in a 'lawnmower pattern' at depth of between 20 and 30 metres to collect data, which Singh says was merged to create high-resolution 3D bathymetric surveys of the underside of the ice. The results of the survey, which included scientists from the WHOI, as well as the British Antarctic Survey and the Institute of Marine and Antarctic Studies in Australia, were published last November in the journal Nature Geoscience.
"Unlike most AUVs, the SeaBED is not torpedo shaped, which allows it to hover and work in extremely rugged terrain," said Singh.
"The standard SeaBED model uses sensors that face down at the seafloor. For working under-ice we had to mount all our sensors looking up. There were also significant challenges associated with navigation under sea ice which was moving, translating and rotating quite fast with respect to vehicle velocity," he added.
Since 2002, a total of 10 SeaBED AUV systems have been built for use around the world and, according to Singh, have proved themselves to be 'extremely robust' in a variety of applications. They are currently being used for habitat and fisheries work in the US, as well as by the University of Puerto Rico for Coral Reef Characterization and the Australian Center for Field Robotics for work associated with repeat surveys for observatories.
"They are also used by our group at Woods Hole for Archaeology, Sea Ice, Oil Spill Characterisation and other applications. Other SeaBED vehicles are also being deployed by a consortium in Mississippi and in Taiwan," said Singh.
"In Europe we are excited about the possibilities of working with a number of groups associated with oil spill mitigation and mapping under ice," he added.
By Andrew Williams
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