ON THE MAP
Massive “scours” caused by drifting icebergs scar the Arctic seabed ( image 3). Some ruts are more than 25 metres wide and kilometres long, and may be hundreds of years old. Other images reveal phenomena such as large areas covered in pockmarks ( background image) — possibly caused by gas deposits — reminiscent of a lunar landscape. In August 2014, a team of scientists, engineers and navy personnel from Defence Research and Development Canada (the research arm of Canada’s Department of National Defence) captured these sonar images of nearly 30 square kilometres of seabed in the central Canadian Arctic’s Victoria Strait, a remote and often icecovered underwater environment that has never been seen, far less charted. The researchers, part of the 2014 Victoria Strait Expedition searching for Sir John Franklin’s lost ships HMS Terror and Erebus, used the aptly named Arctic Explorer, a torpedo-shaped autonomous underwater vehicle carrying the latest in military R&D equipment — a state-of-theart synthetic aperture sonar (SAS) system. Originally designed to detect and classify underwater mines, it is able to survey for more than 18 hours before recharging, and creates ultra-high-resolution imagery over very large areas. DRDC produced these first images of a previously unmapped zone near the place where Franklin’s ships were abandoned almost 170 years ago. Erebus, of course, was later found southeast of Victoria Strait, in Queen Maud Gulf, but what Arctic Explorer captured seems to conjure up an extraterrestrial world. In addition to huge scours and other geological formations, the team observed interesting physical phenomena involving internal waves of fresh water from melting sea ice, which travel slowly down through the salt water, causing sound to bend in such a way that the fresh water creates ghostly ripples in the sand. The frigid -1.5 C water of the Arctic Archipelago creates an ideal environment for sound propagation, contributing to unparalleled sonar image quality and range. There is potential that these images and accompanying bathymetric data, which meets t he standards of t he International Hydrographic Organization, could be used with other data to create the first detailed charts of the area. The 2014 Victoria Strait Expedition highlighted the need to map and explore these waters, part of an Arctic region in which human activity is increasing. These challenges are inspiring Canadian industry, government and academia to develop technologies that can operate in one of the most difficult environments known to humankind.
How an innovative sonar technology may help map parts of Canada’s previously uncharted Far North