From 500 miles above Earth, NASA's SWOT satellite peers down at the ocean with unprecedented clarity—but until now, hidden underwater waves have been blurring the view. Florida State University researchers have just solved that problem, developing a framework that filters out the interference from kilometer-scale internal tides and delivers ocean circulation data that is about 60% more accurate than before.
The breakthrough matters because understanding the ocean's fine-scale currents and eddies is essential to tracking how much heat and carbon the water absorbs from the atmosphere. These small features are precisely what SWOT was designed to observe, yet internal tides—underwater waves that travel beneath the surface—have historically obscured them. Scientists long assumed this interference was too chaotic to predict or correct, a stubborn limitation that would have compromised the satellite's most important measurements.
Yadidya Badarvada, lead author of the study published in Science Advances and a researcher at FSU's Center for Ocean-Atmospheric Prediction Studies, explains the challenge clearly: "Internal tides mimic the very features we are trying to observe." What the team discovered is that this interference, while appearing random, is actually predictable—once you have an ocean model sophisticated enough to track the system's changing state.
The solution relies on HYCOM, the Hybrid Coordinate Ocean Model, a three-dimensional operational U.S. Navy forecasting system developed over decades by researchers across institutions, including FSU. HYCOM works by continuously blending physics-based ocean simulations with real-time observational data through a technique called data assimilation. Every day, the model ingests measurements from orbiting satellites tracking sea surface height and temperature, robotic floats drifting through ocean depths, moored buoys, and ship-based instruments. This constant stream of information keeps the model's simulation as close to the true state of the ocean as possible.
What makes HYCOM particularly powerful is that it explicitly simulates the forces driving tides, including their interactions with seafloor ridges and seamounts. Internal tides emerge directly from the model's own physics rather than being estimated separately. By decomposing HYCOM's internal tide predictions into predictable and chaotic components, Badarvada's team could identify and remove both from SWOT's measurements. Because SWOT data were never fed into HYCOM, the comparison was a genuinely independent test—and the result was a 59% improvement over the best correction method previously available.
The implications extend far beyond cleaner satellite images. An ocean observation this precise helps scientists verify models used to project future warming and track the ocean's capacity to buffer rising temperatures. Without accurate space-based measurements of global ocean circulation, researchers cannot fully understand how the ocean transports heat and nutrients across vast distances or how it functions as a whole system.
"We can't deploy buoys across the entire globe," Badarvada notes. "The information from SWOT fills a huge gap in our understanding of the physics and dynamics that govern the ocean." By repurposing a tool built for naval navigation to sharpen humanity's most advanced ocean satellite, the team has given the world a clearer window into one of Earth's most critical systems.