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Dr. Robert Dziak on How the Sound of the Deep Sea Gives Clues About the Health of Our Oceans
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Dr. Robert Dziak on How the Sound of the Deep Sea Gives Clues About the Health of Our Oceans

Robert Dziak is an oceanographer and the Acoustics Program Manager at the National Oceanic and Atmospheric Administration. His job is to listen to the deep sea, collecting clues about the health of our planet. In this episode, he will share his findings from the deepest known point in the oceans called Challenger Deep.

Podcast Transcript

Intro: I view the work we’re doing at challenger deep, similar to what astronomers and astrophysicists do in deep space, sending probes out to investigate the deepest regions of our solar system. We are putting a deep-ocean probe into the far reaches of deep inner space, getting a new view of how our planet works.”

Eva (The Y Circus): “Hi, everyone, and welcome back to another episode of The Y Circus podcast. The intro, which you have just heard, featured Robert Dziak, Senior Research and acoustics Program Manager at the National Oceanic and Atmospheric Administration. His job is to listen to the deep sea, collecting clues about the health of our oceans. He does that with the help of so-called hydrophones pressure-resistant underwater microphones. In this episode, he will share his findings from the deepest known point in the oceans called Challenger Deep. So yeah, I hope you enjoy this episode.”

Robert Dziak: “Challenger Deep is the deepest location in the world’s oceans. It’s like you said, it’s 11 kilometers deep. We initially thought that the Mariana Trench or the challenger deep would be a very quiet place, you know, acoustically isolated and one of the quietest places on earth because it’s so deep. At times it is, but it also turns out it can also be a pretty noisy place. And there’s a wide range of sources. One Mariana Trench is an active earthquake zone. Some marine mammals would be sailing over the top of the hydrophone, which was kind of interesting. Also, we could hear lots of ship traffic. So human-made noise is kind of prevalent. Marine animals use sound to navigate, communicate and find food. So if you’re introducing noise into that environment, it’s probably having a negative effect on them.”

Photo by Rod Long

Eva: “An analysis of more than 10,000 academic papers published in the journal Science in February concludes that noise pollution is stressing marine fauna far more than previously understood. Therefore, sound research in this area is vital to better understand the extent of its impact on marine wildlife. Another important area of Dziaks’ research is recording the cracking noise of melting glaciers in Antarctica that will assemble clues about climate change.”

Robert Dziak: “In 2016, we recorded the sound of the Nansen ice shelf. It’s located in the Ross Sea. We recorded a significant calving event where a big chunk broke free and produced two large icebergs, and sailed out to the Southern Ocean, South Pacific. Research shows that it was a likely influx of warm water that weakened the ice shelf. We recorded the ice shelf breaking free initially with cracking sounds that we picked up on the hydrophones.

Eva: “Usually scientists rely on Satellite images to measure glacial retreat, but the images don’t present a complete picture.   especially when it’s cloudy, foggy, raining, or snowing the information scientists can get has its limits.Given that glaciers are typically difficult to reach, collecting data remotely is key. Hydrophones, on the other hand, can record underwater in all these conditions.”

Ziak and his colleagues published their research in a scientific paper where they describe that On April 7, 2016, the Nansen ice shelf front calved into two icebergs, the first large-scale calving event in over 30 years. Three hydrophone moorings were deployed seaward of the Nansen ice shelf in December 2015 and over the following months recorded hundreds of short-duration cracking sounds. The majority of these icequakes occurred between January and early March 2016, several weeks prior to the calving observed by satellite on April 7. 

Robert Dziak: “It didn’t move until a big storm blew the ice shelf out at sea. So our work showed that we didn’t know that the ice shelf failed catastrophically until we saw it on the satellite image but the sound files give an idea that it happened much earlier. So it was an interesting insight that weather-related processes play a big role as well as climate change.”

Eva: “Dziak says that the icebergs breaking free can reach sizes of cities and small islands.”

Robert Dziak: “And when they’re floating around Antarctica, they will sometimes come back, and impact the continental shelf, the underwater part of the continent, and their keel. The iceberg will hit that and start scraping on the seafloor, and that scraping sound makes a huge sound. It’s equivalent to the level of giant earthquakes. So that sound gets into the ocean and propogates all way far north, all the way up to the equator.

Eva: “Dziak’s colleagues also use hydrophones to get insights into the behavior of migratory whales. They reach places so far offshore that visual surveys aren’t possible. So recording the sound of waves is a great tool to track them, like the example of the research on the endangered North Atlantic Right Whale shows”:

Report NOAA: “Marine biologists track their migratory routes of North America for the spring and fall, but the wintering grounds for much of the Right Whale population are unknown. Using hydrophones, scientists reported whale calls in the waters between Greenland and Iceland from July to December 2007. A hydrophone is simply a microphone designed to capture underwater sounds. North Atlantic Right Whale calls sound like screen bangs in rows. After deciphering 1000s of these new recordings, there was evidence of right whales calling nearby many times. This area was thought to be an abandoned habitat, but this discovery confirms that it continues to be used.”

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Eva: “I hope you enjoyed this episode. And to learn more about Robert Dziak’s research, you find all the relevant links in the show notes below. Thanks so much for listening and bye-bye

Further Information:

Hydroacoustic, Meteorologic and Seismic Observations of the 2016 Nansen Ice Shelf Calving Event and Iceberg Formation

National Oceanic and Atmospheric Administration

Hearing the under-sea whispers of a warming climate

Noise Pollution Impacting Marine Animals Worse Than Previously Thought

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