Using sound to ‘see’ the structure of the ocean
June 26, 2024 | by Nicole Crozier
The depths of the ocean can be a dark and noisy place. While the darkness can make it difficult to extract visual information, the noise can be used to help us learn more about the ocean’s physical structure. UVic professor emeritus Ross Chapman has dedicated his career to developing methods to turn noise into information and put it to good use. He was recently awarded the Walter Munk Medal by The Oceanography Society in recognition of his contributions to oceanography over the course of his career.
“Walter Munk was an amazing, very intelligent individual who had a major impact on ocean science. To receive an award associated with his name is a significant honour to me. I’m very pleased to receive the award, and thankful to the Oceanography Society and those who supported the nomination.”
- Ross Chapman, professor emeritus in the School of Earth and Ocean Sciences
The Walter Munk Medal is a lifetime achievement award presented every two years by The Oceanography Society, a professional associated founded to advance oceanographic research, technology and education. The medal recognizes extraordinary accomplishments and novel insight contributing to the advancement or application of physical oceanography, ocean acoustics or marine geophysics. This award has only been given out 14 times over the last 30 years, and has now twice been won by faculty members from UVic’s School of Earth and Ocean Sciences; David Farmer received the medal in 1994.
Chapman has dedicated his career to understanding the ocean through the use of sound. The ocean is full of noise, and since sound carries information about the medium it has travelled through, all that noise contains useful information that can help us understand the physical structure of the ocean. However, in order to extract that information, we need to understand how sound propagates in the ocean, and how sound interacts with boundaries, such as the surface of the ocean and the various sediments, rocks, etc. on the ocean’s bottom. Chapman’s research has focused on untangling sound waves using complex physics to extract useful information. He has developed theoretical models and various statistical inference methods to do this work. His methods have been widely used and served as the foundation for the work of many other ocean acousticians.
“Ross has made diverse and profound contributions to the study of underwater sound. Over his career, his research has involved fundamental work in a number of different areas—ocean-acoustic propagation modelling, ambient noise measurements, acoustic signal processing and inversion, and the detection and characterization of gas-hydrate deposits in marine sediments. His award of the Walter Munk Medal by the Oceanography Society is well deserved!”
- Stan Dosso, professor and former Director of the School of Earth and Ocean Sciences
One example of Chapman’s work is the study of methane hydrates off Vancouver Island. 25 years ago, methane hydrates were discovered on the sea floor in Barkley Canyon, just off the coast of Ucluelet, after a trawler ran over a piece of the hydrate, broke it off and pulled it up to the sea surface where it bubbled and fizzed. Using acoustic data, Chapman was able to study these hydrates and determine where they were, what depth they were at, how much hydrate was present and in what form. Chapman also had the opportunity go out to sea to find the physical specimens of the hydrates using remotely operated submersibles. The large deposits of methane hydrate in Barkley Canyon continue to be studied by other research groups internationally.
Chapman’s impact goes beyond his research findings and published papers. Throughout his career, he has supervised dozens of students, and demonstrated a strong commitment to excellence in advising and mentoring the next generation of ocean acousticians. Many of his graduate students have gone on to academic or industry positions focused on ocean acoustics. Current SEOS professor Stan Dosso got his introduction to ocean acoustics in Chapman’s class and subsequently, his research lab. David Hannay, the Chief Scientific Officer at JASCO Applied Sciences, a consulting company that is widely considered a world leader in underwater acoustics, completed his MSc with Chapman, and JASCO continued to regularly hire students from Chapman’s lab until his retirement.
“As the first graduate student that Ross supervised at UVic, back in the 1980s, I can attest to the influence his mentorship and support have had throughout my own career. I know that the same is true for many others. Ross’s training, encouragement and inspiration of a generation of ocean-acoustic scientists in Canada is a legacy that will enrich the field for years to come.”
- Stan Dosso
Chapman started his career as a defence scientist with the Ocean Acoustics Group at Defence Research Establishment Pacific, working there for almost 20 years before coming to UVic. He served as director of the former Centre for Earth and Ocean Research for six years. He is a Fellow of the Acoustical Society of America and the Institute of Electrical and Electronic Engineers and was Editor-in-Chief of the IEEE Journal of Oceanic Engineering.
Chapman’s achievements were celebrated at the Oceanography Society’s Honors Breakfast this year, and he delivered the Walter Munk Medal Lecture in May. His lecture was titled "Inference of geoacoustic model parameters from acoustic field data: Perspectives on geoacoustic inversion”.