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Underwater robots key to measuring ocean sounds

Thursday, January 9, 2020

Underwater robotics is a popular extracurricular activity in the Warrenton-Hammond School District and others in the state.

An underwater robotic glider is the key for real-world research conducted through a joint effort of Oregon State University and the National Oceanic and Atmospheric Administration. Researchers have developed an effective method to measure sound levels on the ocean floor.

“Healthy marine ecosystems need to have noise levels within particular ranges,” said Joe Haxel, an assistant professor in the College of Earth, Ocean and Atmospheric Sceinces at OSU. “As an analogy for humans, it’s the difference between living in the country or living in the city or somewhere really loud.”

Haxel is based at the Hatfield Marine Science Center in Newport.

Ocean sound was listed as an essential ocean variable due to its importance for marine life and seagoing humans and because it’s used to monitor and locate everything from earthquakes to tsunamis to nuclear explosions.

Traditionally, scientists have measured ocean sound by attaching hydrophones, or underwater microphones, to fixed moorings in the water. The problem is scientists only get data from that single location.

Ocean sound also can be measured from a research ship, but those are expensive to operate and create a lot of noise themselves, which disturbs marine animals and fish that are sensitive to sound.

Attaching a hydrophone to a glider solves the problems because gliders operate autonomously, are relatively quiet and can cover hundreds of miles over several weeks.

The glider used by Haxel and his team is about 5 feet long and weighs 120 pounds. The glider traveled for 18 days between Grays Harbor, Wash., and Brookings, about 285 miles.

The glider operated along the continental shelf break about 30 miles off the coast where the ocean depth begins to drop more steeply. The shelf break is a key migratory path for marine animals.

Researchers were able to cross-reference data collected during the 18-day glider trip with historical data from hydrophones attached to moorings along the route.

It was shocking how closely the data sets aligned, Haxel said. The team concluded that the gliders are an effective and valuable asset for measuring underwater ocean sound.

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