An autonomous submarine equipped with upward-facing sonar has been used to measure thickness of Antarctic floes

Sonar-equipped robot measures Antarctic ice with unprecedented precision

A submersible robot equipped with upward-looking sonar has been used to measure thickness of Antarctic ice floes.

The technology, used to create high-resolution 3D maps, provided scientists with more accurate data than they had been able to obtain previously using other approaches including satellite measurements.

The project, carried out by the British Antarctic Survey, seeks to assess the changes of polar ice caps caused by global warming.

"The AUV missions have given us a real insight into the nature of Antarctic sea ice – like looking through a microscope,” said British Antarctic Survey scientist Jeremy Wilkinson.

“We can now measure ice in far greater detail and were excited to measure ice up to 17 metres thick."

The 2m-long autonomous underwater vehicle (AUV), known as SeaBED, was sent below the floes, reaching 20 to 30 metre depths. It’s upward-facing sonar then measured the thickness of the ice by sending sound signals towards the surface and detecting the returning sound waves reflected by the floes.

"Putting an AUV together to map the underside of sea ice is challenging from a software, navigation and acoustic communications standpoint,” said Hanumant Singh, from Woods Hole Oceanographic Institution in Massachusetts, the USA, a member of a team that built and operated the robot.

"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."

The research, recently reported in the journal Nature Geoscience, was one of the pioneering experiments assessing the viability of autonomous robots for oceanographic research.

The team was satisfied with the results, saying it greatly simplifies the ice-monitoring procedures.

While satellites usually provide good overview information, details are sometimes difficult to obtain due to snow coverage on top of the icebergs. To overcome such shortcomings, scientists would have to visit some of the sites in person, drilling holes into the ice and measuring the thickness directly.

"This new paper presents important results obtained from a novel underwater vehicle that radically change our concepts of the structure of Antarctic sea ice, and the processes that influence it,” said Professor Mike Meredith, deputy director of science at the British Antarctic Survey.

“Such understanding is key to improving our models of how sea ice will change into the future."

Thawing of ice in the polar regions and the ensuing changes to the ecosystems caused by the rising temperatures threaten to wreak havoc with the global climate. Especially the larger Antarctica, which presents considerable challenges to the scientific community when it comes to the understanding of the ongoing processes due to its size and geographical variability.

Autonomous submarines are becoming an increasingly popular tool for the oceanographic community to collect data about the changes, offering a simpler and cheaper alternative to costly expeditions aboard polar ships.

Earlier this month, American researchers reported results of an experiment that relied on robotic dolphins to study ocean currents distributing warm water along the coast of Antarctica.

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