NJIT mathematician to help map Earth's last frontier with Navy grant

(Press-News.org) We’ve mapped nearly all of Mars’ surface from orbit, yet we know less about Earth’s ocean floor — almost 75% remains unmapped in high resolution.

This terrestrial blind spot is driving NJIT Mathematics Professor Eliza Michalopoulou’s latest research, funded by the Office of Naval Research (ONR). The project aims to improve how scientists explore the vast, uncharted ocean floor through sound.

“Mapping the seabed is a challenging endeavor due to the extreme conditions,” said Michalopoulou, chair of NJIT’s Department of Mathematical Sciences. “The immense pressure is crushing at depths like the Pacific’s Mariana Trench, for example, where it reaches over 1,000 times sea-level atmospheric force, making it difficult and costly to deploy submersibles for exploration. The remarkably low temperatures further complicate efforts.”

Rather than sending equipment into such depths, Michalopoulou’s research harnesses underwater sound waves to study the ocean remotely.

“By ‘listening’ to the ocean, we can analyze its properties and characteristics without the need to physically deploy extensive equipment into the depths of the vast underwater world,” she added.

Michalopoulou is currently investigating a fundamental mathematical question crucial to both ocean exploration and naval defense operations — how do physical properties of the ocean shape the way sound travels beneath the surface?

Her field, called geoacoustic inversion, uses mathematical models to transform underwater sound waves into detailed information about stretches of the seafloor, revealing everything from bathymetry (depth) to sediment density and sub-bottom layering. It can also help scientists explore the habitats and migration patterns of marine life.

“The process relies on underwater microphones, called hydrophones, that capture sound waves,” Michalopoulou explained. “We integrate this acoustic data with mathematical models to understand how sound interacts with the seabed. This helps us predict how signals — like those from submarines — travel through water and what they should ‘look’ like when received.”

However, Michalopoulou says there’s a challenge — different methods for analyzing this acoustic data often paint conflicting pictures of the same seafloor.

“Different methods can point to completely different structures in the seabed layers,” she explained. “Understanding the properties of the seabed is pivotal for things like defense operations and environmental conservation, but we need to understand why these methods disagree to be confident in our data.”

These variations arise from the fundamental complexity of mathematical modeling. “Some approaches assume oceanographic conditions, like currents and their influence on sound speed, are known,” Michalopoulou said. “Others treat both ocean processes and sediment properties as unknowns, which can lead to significantly different interpretations of the same data.”

Real-world factors further complicate the picture. Ship traffic and marine life create acoustic interference that can distort measurements. To understand these variations, Michalopoulou is applying modeling simulations that can help reveal the true properties of the ocean floor below.

“The problem is that the ocean floor is largely a mystery, and we usually don’t know the true properties of the seabed, so it is difficult to assess how well a given method performs in mapping it accurately,” said Michalopoulou. “With advanced mathematical models, we can now create realistic simulations where the true environmental conditions are known. This allows us to evaluate different mapping methods and understand their variability.

“In three years, we expect to have thoroughly analyzed a wide range of approaches, assessing their accuracy, inherent uncertainty and potential for real-time application,” she added. “The insights and conclusions drawn from this research will contribute to high-fidelity seabed exploration, ultimately enhancing the effectiveness of anti-submarine warfare strategies.”

Michalopoulou’s project is underway amid other global efforts like the Seabed 2030 project and UNESCO’s Ocean Decade, contributing to broader initiatives to map and explore Earth’s ocean floor.

Since Michalopoulou joined NJIT in 1994, the ONR has supported her leading research efforts in the fields of underwater acoustics and signal processing. In 2022, she was named Distinguished Lecturer by the Institute of Electrical and Electronics Engineers’ Oceanic Engineering Society and has also been named Fellow of the Acoustical Society of America, among many other distinctions.

Michalopoulou’s project, “A Simulation Study for Assessing Accuracy, Uncertainty, and Consistency in Geoacoustic Inversion Across Methodologies,” recently commenced under ONR’s Basic and Applied Scientific Research program.

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