Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Mariana Trench: 7 miles deep, the ocean is still a noisy place

03.03.2016

For what may be the first time, scientists have eavesdropped on the deepest part of the world's oceans and instead of finding a sea of silence, they discovered a cacophony of sounds both natural and caused by humans.

For three weeks, a titanium-encased hydrophone recorded ambient noise from the ocean floor at a depth of more than 36,000 feet in a trough known as Challenger Deep in the fabled Mariana Trench near Micronesia. The team of researchers from the National Oceanic and Atmospheric Administration, Oregon State University and the U.S. Coast Guard expected to hear little. They were surprised.


The Mariana Trench and surrounding terrain is seen in this graphic.

Credit: Center for Coastal and Ocean Mapping - Joint Hydrographic Center

"You would think that the deepest part of the ocean would be one of the quietest places on Earth," said Robert Dziak, a NOAA research oceanographer and chief scientist on the project. "Yet there really is almost constant noise from both natural and man-made sources.

The ambient sound field at Challenger Deep is dominated by the sound of earthquakes, both near and far was well as the distinct moans of baleen whales and the overwhelming clamor of a category 4 typhoon that just happened to pass overhead.

"There was also a lot of noise from ship traffic, identifiable by the clear sound pattern the ship propellers make when they pass by," added Dziak, who has a courtesy appointment in Oregon State's College of Earth, Ocean, and Atmospheric Sciences. "Guam is very close to Challenger Deep and is a regional hub for container shipping with China and The Philippines."

The project, which was funded by the NOAA Office of Ocean Exploration and Research, was designed to establish a baseline for ambient noise in the deepest part of the Pacific Ocean. Anthropogenic, or human-caused noise has increased steadily over the past several decades and getting these first recordings will allow scientists in the future to determine if the noise levels are growing.

Getting those first sounds wasn't easy.

The bottom of the Challenger Deep trough is roughly seven miles below the ocean's surface. In fact, you could put the world's tallest peak - Mount Everest - in the trench and its top would still be more than a mile from the surface.

The pressure at that depth is incredible, said Haru Matsumoto, an Oregon State ocean engineer who along with NOAA engineer Chris Meinig helped to develop a hydrophone capable of withstanding such pressure. In the average person's home or office, the atmospheric pressure is about 14.7 pounds per square inch; at the bottom of the Mariana Trench, it is more than 16,000 PSI.

"We had never put a hydrophone deeper than a mile or so below the surface, so putting an instrument down some seven miles into the ocean was daunting," Matsumoto said. "We had to drop the hydrophone mooring down through the water column at no more than about five meters per second. Structures don't like rapid change and we were afraid we would crack the ceramic housing outside the hydrophone."

Partnering with the U.S. Coast Guard, the researchers deployed the hydrophone from the Guam-based cutter Sequoia in July 2015. It took more than six hours for the instrument package to free-fall to the bottom of the Mariana Trench. Its recordings filled the flash drive in about 23 days, but the researchers had to wait until November to retrieve the hydrophone because of ships' schedules and persistent typhoons.

Once back on site, they recovered the hydrophone mooring by sending an acoustic signal from the ship above, triggering its release from the seafloor. Attached floats allowed it to gradually ascend to the surface.

"It is akin to sending a deep-space probe to the outer solar system," Dziak said. "We're sending out a deep-ocean probe to the unknown reaches of inner space."

For the past several months, Dziak and his colleagues have been analyzing the sounds and differentiating natural sounds from ships and other human activities.

"We recorded a loud magnitude 5.0 earthquake that took place at a depth of about 10 kilometers (or more than six miles) in the nearby ocean crust," Dziak said. "Since our hydrophone was at 11 kilometers, it actually was below the earthquake, which is really an unusual experience. The sound of the typhoon was also dramatic, although the cacophony from big storms tends to be spread out and elevates the overall noise for a period of days."

Matsumoto said the hydrophone also picked up a lot of noise from the surface of the ocean - some seven miles above - including waves and winds disturbing the surface.

"Sound doesn't get as weak as you think it does even that far from the source," he said.

Another OSU co-investigator on the project, Joe Haxel, will lead a planned return to Challenger Deep in 2017, where the researchers will deploy the hydrophone for a longer period of time and attach a deep-ocean camera.

Dziak, Matsumoto and Haxel are affiliated with the Acoustics Program in the NOAA/Pacific Marine Environmental Laboratory and work at OSU's Hatfield Marine Science Center in Newport, Ore. The project in Challenger Deep is one of a number of projects in which the U.S. Coast Guard partners with NOAA to sponsor scientific research.

###

Note to Editors: Images, video and sound files are available to help illustrate this story at: http://bit.ly/1QSb8Mv. See the "descriptions" icon for cutline and credit information.

Bob Dziak | EurekAlert!

Further reports about: Atmospheric Mariana Trench Matsumoto Ocean deep-ocean earthquake

More articles from Earth Sciences:

nachricht NASA looks to solar eclipse to help understand Earth's energy system
21.07.2017 | NASA/Goddard Space Flight Center

nachricht Scientists shed light on carbon's descent into the deep Earth
19.07.2017 | European Synchrotron Radiation Facility

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: 3-D scanning with water

3-D shape acquisition using water displacement as the shape sensor for the reconstruction of complex objects

A global team of computer scientists and engineers have developed an innovative technique that more completely reconstructs challenging 3D objects. An ancient...

Im Focus: Manipulating Electron Spins Without Loss of Information

Physicists have developed a new technique that uses electrical voltages to control the electron spin on a chip. The newly-developed method provides protection from spin decay, meaning that the contained information can be maintained and transmitted over comparatively large distances, as has been demonstrated by a team from the University of Basel’s Department of Physics and the Swiss Nanoscience Institute. The results have been published in Physical Review X.

For several years, researchers have been trying to use the spin of an electron to store and transmit information. The spin of each electron is always coupled...

Im Focus: The proton precisely weighted

What is the mass of a proton? Scientists from Germany and Japan successfully did an important step towards the most exact knowledge of this fundamental constant. By means of precision measurements on a single proton, they could improve the precision by a factor of three and also correct the existing value.

To determine the mass of a single proton still more accurate – a group of physicists led by Klaus Blaum and Sven Sturm of the Max Planck Institute for Nuclear...

Im Focus: On the way to a biological alternative

A bacterial enzyme enables reactions that open up alternatives to key industrial chemical processes

The research team of Prof. Dr. Oliver Einsle at the University of Freiburg's Institute of Biochemistry has long been exploring the functioning of nitrogenase....

Im Focus: The 1 trillion tonne iceberg

Larsen C Ice Shelf rift finally breaks through

A one trillion tonne iceberg - one of the biggest ever recorded -- has calved away from the Larsen C Ice Shelf in Antarctica, after a rift in the ice,...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Closing the Sustainability Circle: Protection of Food with Biobased Materials

21.07.2017 | Event News

»We are bringing Additive Manufacturing to SMEs«

19.07.2017 | Event News

The technology with a feel for feelings

12.07.2017 | Event News

 
Latest News

Ultrathin device harvests electricity from human motion

24.07.2017 | Power and Electrical Engineering

Scientists announce the quest for high-index materials

24.07.2017 | Materials Sciences

ADIR Project: Lasers Recover Valuable Materials

24.07.2017 | Materials Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>