Mohsen Badiey

Arctic acoustical oceanography

UD's Badiey among 225 researchers selected to share in $67.9 million in Department of Defense funding

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9:50 a.m., July 1, 2015--University of Delaware professor Mohsen Badiey is among 225 university researchers at 111 academic institutions selected to share in $67.8 million in new funding, according to a Department of Defense (DoD) news release

The awards will be made under the Defense University Research Instrumentation Program, which supports the purchase of state of the art equipment that augments current university capabilities or develops new capabilities to perform cutting edge defense research of importance to national defense. 

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Awardees were selected through a highly competitive proposal process conducted by three DoD research offices: the Army Research Office, Office of Naval Research (ONR) and Air Force Office of Scientific Research. 

The nearly $400,000 in new funding will enhance Badiey’s ongoing ONR-funded research to better understand and predict how acoustic signals will travel in the Arctic as the topography and oceanography change in the presence or absence of seasonal ice cover; variable oceanography and moving ice. 

Badiey, acting dean of the College of Earth, Ocean, and Environment (CEOE) and professor of physical ocean science in the School of Marine Science and Policy (SMSP), and Andreas Muenchow, an SMSP associate professor and Arctic oceanographer, received a separate $1 million ONR grant in March to study the upwelling on the Beaufort continental shelf-basin region in Alaska.

Partners in the UD effort include collaborators at the Applied Research Laboratory at the University of Texas, Austin; Woods Hole Oceanographic Institution; U.S. Naval Research Laboratory; the Canadian Defence Research Establishment and Scripps Institution of Oceanography. 

Listening in the Arctic

Research surrounding underwater acoustics in the Arctic region was popular for defense purposes, but faded in the early 1990s with the end of the Cold War era. Accelerated melting of Arctic sea ice and subsequent environmental changes in recent years have created new geopolitical challenges and economic opportunities, and may also have significant implications for defense. 

As scientists analyze changes there and consider implications for global weather and climate, there has been renewed interest in improving underwater acoustic studies in the region.

Badiey is an expert in ocean acoustics, or the study of sound transmission in the ocean, as well as acoustical oceanography, which is the use of sound waves to study the properties of the ocean. His research group has been very active in studying how oceanography affects sound propagation on the continental shelf of the United States, particularly in shallow-water or nearshore coastal environments.

Working in the shelf-slope region of the Beaufort Sea, the UD-led research team will focus on upwelling that may affect how sound moves between the deep Arctic basin and shallow shelf seas. The primary goal is to understand the effects of changing Arctic conditions on acoustic wave propagation and ambient noise. 

The reduction of polar ice thickness may have profound effects such as reduced sound intensity variability compared to that observed during earlier investigations.

Muenchow explained that upwelling occurs in the open ocean and along coastlines when winds blowing across the ocean surface are pushed due to wind, causing waters from beneath the surface to rise up. As mobile sea ice creates a rougher sea surface for sound transmission, upwelling of warmer Atlantic waters over the continental slope is changing the way that sound spreads, both in intensity and in direction. 

The UD team is trying to understand these dynamics using acoustic wave transmissions.

The researchers theorize that these upwelling events, which have increased in recent years, could be the result of global warming and may be the reason for accelerated melting of ice in the Arctic. The scientists will investigate how to predict coastal upwelling events and how their occurrence affects sound transmission.

“In deep water, sound waves can travel long distances without interruption. In shallow waters, however, sound waves can be interrupted by the sea surface and bottom, as well as oceanographic features in the water column, such the internal waves, causing changes in intensity, coherence and the direction of sound wave propagation, among other things,” Badiey said. 

During a pilot experiment this summer, Badiey and colleagues from Woods Hole Oceanographic Institution and the Scripps Institute of Oceanography will install a passive acoustic recorder to record background sounds coming from the deep water hundreds of kilometers away and verify the feasibility of sound transmission from deep to shallow water on the Arctic’s Beaufort shelf region. 

The marine recorder previously was used for long duration experiments in the Delaware Bay.

Future work includes fabricating a low frequency underwater sound projector that will be deployed in summer 2016 and a mooring system for long-term oceanographic measurement for a one-year experiment in the Arctic Beaufort continental shelf and slope region.

Badiey explained that seasonal temperature changes cause sea ice to break up and reform causing changes in flow, which, over time can affect how the sound waves transmit under ice. His research team is trying to pick up these spikes in temperature acoustically, and then monitor them to understand how it affects sound transmissions. 

Their results could have important implications for the design of underwater communication systems necessary for operation of undersea robots and autonomous underwater vehicles.

The researchers will use sensors to measure temperature, salinity, current profile, and ice thickness, while simultaneously recording sound transmissions. The equipment will measure environmental data related to how sound waves travel in the ocean while arrays of underwater microphones, called hydrophones, simultaneously measure the sound transmission. 

Establishing correlations between sound intensity and variations in the environment can help scientists leverage sound waves to monitor changes in the oceanographic conditions.

“Sound waves are the only means of long term communication under sea water because the electromagnetic waves used for terrestrial communication, like cell phones, do not travel under water,” Badiey said. 

“As the environment changes, it can be monitored in time using the background sounds in the ocean, so it is important to capture this information now. Having a baseline of sounds that are present throughout each season of the year will enable us to better communicate under water.”

This is the fourth major, multi-institutional and interdisciplinary grant awarded to Badiey over the last decade. Total funding for the work across all partners is approximately $6 million, with more than $1.4 million awarded directly to UD, including the latest DoD funding.

According to Badiey, collaboration between scientists, engineers, signal processors, mathematical modelers and others with unique but complementary scientific capabilities is key to finding solutions to large-scale problems. 

“We are thrilled that we have been selected to take part in this important and exciting research,” he said.

Article by Karen B. Roberts

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