See NASA’s GUARDIAN Catch a Tsunami

NASA's Jet Propulsion Laboratory spent years building a tsunami early warning system that runs on signals most people have never thought about. On July 29, 2025, it had to work. It did.

When a magnitude 8.8 earthquake struck off Russia's Kamchatka Peninsula that morning, it sent a tsunami racing across the Pacific at over 500 miles per hour. The wave was heading for Hawaii. GUARDIAN — short for GNSS Upper Atmospheric Real-time Disaster Information and Alert Network — flagged it within eight minutes of the quake, and confirmed the approaching wave off the coast of Kauai 32 minutes before landfall, ahead of the tide gauges at that location.

The timing was notable for another reason: JPL had activated GUARDIAN's AI detection layer and prototype alerting system one day before the earthquake.

The system works by repurposing an existing global network. All day, every day, GPS and other positioning satellites transmit navigation signals to ground stations around the world. Before those signals arrive, they pass through the ionosphere — a charged layer of the upper atmosphere. When a tsunami moves across the ocean, it displaces massive volumes of water in near-unison, pushing pressure waves upward that travel through the atmosphere and perturb ionospheric plasma. GUARDIAN treats those perturbations as signal, not noise.

JPL's GUARDIAN system currently scours data from more than 350 GNSS ground stations distributed around the Pacific Ring of Fire, where the ocean's deadliest waves originate. In favorable geometry — a GNSS station within range of a tsunami — the system can provide up to an hour and 20 minutes of warning to coastal communities, according to JPL.

The core design advantage over existing infrastructure is geographic coverage. Deep-ocean pressure sensors — the current gold standard for detection — are expensive, require maintenance, and are sparsely deployed. Coverage gaps remain, especially in the southern Pacific and Indian Ocean, where no seafloor sensors exist at all. GUARDIAN's value in those regions is not that it outpaces individual seafloor instruments, but that it provides a detection layer where none currently exists, using infrastructure already built and already running. "NASA's GUARDIAN can help fill the gaps," said Christopher Moore, director of the National Oceanic and Atmospheric Administration Center for Tsunami Research, who noted the system "provides one more piece of information, one more valuable data point, that can help us determine, yes, we need to make the call to evacuate."

Bill Fry, chair of the United Nations technical working group for tsunami early warning in the Pacific, called it part of a technological "paradigm shift" — moving from sea-surface inference to direct observation of ocean dynamics from space.

That said, GUARDIAN is still experimental. Near-real-time outputs currently require trained analysts to interpret. The system is not yet wired into automated alert chains. JPL developer Camille Martire said it "functioned to its full extent" during the Kamchatka event, which caused minimal damage and casualties — but the physics does not care whether the next event is also benign. The infrastructure for turning GUARDIAN's signals into public warnings is still being built.

The Kamchatka event also validated that the system can detect tsunamis not generated by earthquakes. Volcanic eruptions, underwater landslides, and certain meteorological conditions can also produce the atmospheric pressure signatures GUARDIAN monitors. That breadth matters: historical warning systems were largely calibrated around seismic triggers, and non-seismic tsunamis have historically arrived with less warning.

GUARDIAN is being developed by JPL's Global Differential GPS project with support from NASA's Space Geodesy Project.