Sound as measuring instrument

The Arctic Ocean is larger than Europe and several thousand meters deep. It is covered by meter-thick ice in the winter, while increasingly large areas open up in the summer. The Arctic Ocean is challenging to explore, as it is a large area far from people and difficult to access. The Nansen Center uses sound to take the temperature of the Arctic Ocean. Using loudspeakers anchored in the water column, we send sound several thousand kilometers across the Arctic Ocean. The travel time gives us the speed of the sound, which we can use in turn to calculate the temperature of the water through which the sound has passed. Ocean currents and smaller movements in the water can also be researched using sound. Sound can not only be used as a tool to measure conditions in the sea, but also to collect data from installations on the seafloor or instruments that drift in the water column. By sending out sound from speakers in known positions under the ice, we can calculate the position of various instruments that move under the ice, such as e.g., gliders and drift buoys. This way we know where data has been obtained, also in periods where the presence of sea ice has meant that the measuring instruments have not been able to go to the surface to retrieve the GPS position from satellites.