Underwater robot sheds new light on thick Antarctic sea ice

Researchers, including one of Indian-origin, have used an underwater robot to develop the first detailed, high-resolution 3-D maps of Antarctic sea ice.
The new technology provides accurate ice thickness measurements from areas that were previously too difficult to access, researchers said.
While most oceanographic survey instruments look down at the seafloor, the Autonomous Underwater Vehicle (AUV) known as SeaBED, was fitted with an upward-looking sonar in order to measure and map the underside of sea ice floes.
The AUV operated at a depth of 20 to 30 metres and was driven in a lawnmower pattern. These lines of data were merged to form high-resolution 3D bathymetric surveys of the underside of the ice.

The yellow SeaBED robot, which is approximately two meters long and weighs nearly 200 kg, has a twin-hull design that gives the robot enhanced stability for low-speed photographic surveys.
"Putting an AUV together to map the underside of sea ice is challenging from a software, navigation and acoustic communications standpoint," said Hanumant Singh, an engineering scientist at the Woods Hole Oceanographic Institution (WHOI) whose lab 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.
"It would have been tough to do many of the missions we did, especially under the conditions we encountered, with some of the larger vehicles," Singh said.

"The full 3-D topography of the underside of the ice provides a richness of new information about the structure of sea ice and the processes that created it," said co-author Dr Guy Williams from Institute of Antarctic and Marine Science in Tasmania.
"This is key to advancing our models particularly in showing the differences between Arctic and Antarctic sea ice," Williams said.
The data from SeaBED, combined with airborne measurements of sea-ice surface elevation, ice coring surveys, and satellite observations, vastly improves scientists' estimates of ice thickness and total sea ice volume.
"The AUV missions have given us a real insight into the nature of Antarctic sea ice - like looking through a microscope. We can now measure ice in far greater detail and were excited to measure ice up to 17 metres thick," said co-author Dr Jeremy Wilkinson from British Antarctic Survey (BAS).

The results were published in the journal Nature Geoscience.