Accurate sea ice measurement is essential for understanding climate change. Satellites can measure large-scale thickness, but data interpretation is difficult due to snow cover on the ice. Additional information can be gathered by drilling holes and making visual observations from ships. What was missing was the view from underwater.
Enter SeaBED, an Autonomous Underwater Vehicle (AUV) that uses upward-looking sonar to measure and map sea ice floes. SeaBED operated at up to 30 metres, trawling the sea ice in a ‘lawnmower’ pattern, and was deployed from the British Antarctic Survey’s RRS James Clark Ross while another AUV worked from the Australian icebreaker the RSV Aurora Australis.
‘Putting an AUV together to map the underside of sea ice is challenging from a software, navigation and acoustic communications standpoint,’ says Hanumant Singh, an engineering scientist at the Woods Hole Oceanographic Institution (WHOI) whose laboratory designed, built and operated the AUV.
‘SeaBED’s manoeuvrability and stability made it ideal for this application where we were doing detailed floe-scale mapping and deploying, as well as recovering in close-packed ice conditions’ adds Singh. ‘It would have been tough to do many of the missions, especially under the conditions we encountered, with some of the larger vehicles.’
Scientists will now carry out large-scale robotic surveys that can be compared to observations from aircraft and satellites.