Sound of science
A lot of the time the Arctic Ocean is an underwater blackout – the sun never rises for most of the winter, and it’s dark under the ice all year round. As a result, many Arctic animals have adapted to use sound rather than sight as a crucial tool for communication, navigation and hunting. Narwhals hunt for fish up to mile below the ice using biosonar, emitting 1000 high-pitched clicks every second and listening to the reflected echos to ‘see by sound’ in the same way that bats do. Humpback whales communicate with each other over hundreds of miles with calls so loud they make your ribcage shake when you’re in the water with them. Male cod attract females with sound during their reproduction season, using low-pitched rumbles as love songs of the deep. The Arctic Mission science team is using specialist underwater microphones and loudspeakers to understand how these sounds travel through the water, and what impacts melting ice might have on the Central Arctic’s animal choir.
Aside from ongoing wildlife observations, acoustics is the most time consuming experiment being carried out during Arctic Mission. Whenever they get the chance, lead scientist Tim Gordon and his research assistent, Heather Bauscher, load up the dinghy with microphones, batteries, amplifiers, loudspeakers, and a paddle board. They then head out until they are one kilometre from the yachts, which is far enough away so that any noises from waves against the yacht’s hulls won’t interfere with their highly sensitive underwater microphones. Hanging their microphones off the paddle board, they record the sounds of the Central Arctic Ocean. Their particular interest is in understanding how melting ice affects background noise levels and whale song transmission. Playing a range of precisely calibrated artificial and natural sounds out of an underwater speaker, Tim and Heather use several different underwater microphones to understand how both pressure waves and particle movements associated with sound are impacted by ice melt.
With the air and water temperature both hovering around zero degrees, Tim and Heather sit shrouded by freezing fog, with 1000 metres of water below them. They must stay completely still in the dinghy because their hydrophones are so sensitive that they would pick up disturbances caused by their movements through the hull of the boat. Over a kilometer away, the Arctic Mission yachts turn off their engines, depth sounders and bilge pumps – more noises that might otherwise interfere with recordings. The dinghy and the boats keep track of each others’ positions in the mist using GPS, radar and handheld radios. After two hours of running experiments, Tim and Heather return to the yachts to warm up, download their data, pack away their microphones and prepare to run their next experiments on other aspects of Arctic ecology.