Canadian researcher completes rare achievement at Mariana Trench

A Canadian researcher has completed a rare achievement, sending a hi-tech machine designed at Nova Scotia’s Dalhousie University to the world’s deepest ocean depths.

David Barclay, an oceanographer and Canada Research Chair at Dalhousie, worked with a team that lowered the Deep Acoustic Lander (DAL) to the bottom of the Mariana Trench. Barclay says part of the expedition’s success in the West Pacific, in April, was the fact his research equipment survived the plunge to a depth of almost 11,000 metres.

“There was only a half-expectation that we’d get the equipment back,” Barclay said with a chuckle. “Because it’s just such a risky proposition sending it down there.”

Barclay’s research was centred at a section of the Mariana Trench called the Challenger Deep. At 11 kilometres down, water pressure is so intense there it would destroy many normal scientific instruments. His lander is one of few to successfully complete the research, using sensors to measure water temperature, salt content and sound.

“We wanted to measure the water properties throughout the entire range of ocean depth.”

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The lander captured only the second audio recordings ever from the Challenger Deep. Some of the early sounds were unnerving: shards of glass, chipping off from a section of the lander.

At the very bottom, there was almost total silence. Scientists consider the Challenger Deep one of the quietest underwater locations on the planet. Barclay says the only sound was the ripples of waves breaking, tens of thousands of metres above.

“One of the most interesting things is actually making that entire profile, measuring the sound from the surface, all the way to the bottom, and thinking about the different sources that contribute to what you’re receiving.”

Barclay says the mission came about after he developed a working relationship with American explorer Victor Vescovo, who took his submersible to the Challenger Deep in 2019, breaking the world record for deepest dive in history. Vescovo’s ship, the DSSV Pressure Drop, served as a support ship back on the surface.

Barclay’s lander was recovered, data intact, providing Barclay and his colleagues with an opportunity to analyze its findings.

“To understand, how does the human use of the ocean impact the acoustic environments of the open ocean?”

Barclay says he’s already begun developing a model that can predict ocean properties far beneath the surface — findings that could lead to better nautical charts for mariners, and a more detailed map of the seafloor itself.