Autonomous submarines track ocean sounds for marine life research
Image credit: uea
Autonomous submarines are being used by scientists to listen to the ocean in order to gain a greater understanding of weather patterns and marine life.
Developed by researchers at the University of East Anglia (UEA), the vehicles are silent when in operation so that the only sounds recorded are those of the ocean itself.
The submarines are about the same size as a human diver, but can reach depths of 1,000m and travel the ocean for months, covering thousands of kilometres. They communicate by satellite with their pilot to build an underwater soundscape of the world’s oceans.
Autonomous underwater vehicles are becoming increasingly popular amongst scientists. Last month, a team started automatically collecting and archiving seawater samples in order to track and study ocean microbes in unprecedented detail.
Pierre Cauchy, a researcher from UEA’s School of Environmental Sciences, has been using one of these autonomous submarines for five years, recording underwater noises in the Mediterranean Sea and the North Atlantic and Southern oceans.
The recordings can be used to measure sea-surface wind speed and monitor storms as well as eavesdropping on marine life.
At an upcoming conference, Cauchy will demonstrate how the robot - called a Seaglider - can measure the wind speed, listen in to the sounds made by fishes and whales and pick up human activities, such as marine traffic and seismic surveys.
By recording sounds in remote locations where there are no permanent weather stations, the robots provide valuable information on wind or storm patterns, which can help to fine-tune climate models.
“As an acoustician, it is fascinating to listen in to underwater life such as long-finned pilot whales in the North Atlantic, but also to hear the echoes of what is happening in the skies above,” Cauchy said.
While pilot whales make whistles, buzzes and clicks, pods of hunting dolphins create high-pitched echo-location clicks and larger species such as sperm whales make louder, slower clicks.
High winds raise the background noise level, but seismic surveys’ intense pulses are unique and easily identifiable, while marine vessels are clearly identified by low-frequency rumbles.
The Seaglider weighs just over 50kg and is 1.5m tall. It is remotely controlled by a pilot and is silent, so records only sound from the ocean without adding its own tones.
Cauchy said: “Now that they have been shown to be useful for modelling climate, monitoring storms or protecting marine life, I hope that other researchers will integrate the silent robot divers into their work and their use will broaden.”
Modelling such as this is becoming increasingly important due to changes in the ocean weather.
A new study released this week has found that that the frequency of marine heatwaves has increased by more than a third globally between 1925 and 2016.
Scientists have expressed alarm at the phenomenon and have said it is a direct result of human-induced climate change.
During this time the length of each recorded heatwave event rose by 17 per cent. Overall, there had been a 54 per cent increase in the number of global “marine heatwave days” occurring each year.