How did scientists receive a real-time tsunami alert

Tsunamis are notoriously difficult to spot in the open ocean as they approach shore. But in the summer of 2025, scientists witnessed the development of one such tsunami in real time, reports Air forceIt was the most powerful earthquake in nearly 15 years. It struck the eastern coast of Russia's Kamchatka Peninsula in July 2025, a magnitude 8,8 quake that also triggered a tsunami with waves traveling at speeds of more than 400 mph (644 km/h).

Within minutes, alarms were raised in communities around the Pacific. Millions of people were ordered to evacuate in the tense hours that followed, including at least two million in Japan alone. But as the wave spread across the ocean, it caused more than just fear-it created ripples in the Earth's atmosphere.

The ocean's enormous up-and-down motions disrupted the atmosphere above it and disrupted global satellite navigation signals. It was this disruption that allowed scientists to detect the tsunami in near real time.

Coincidentally, the day before, NASA had added an artificial intelligence component to a disaster warning system called Guardian, which allows scientists to automatically alert them to major events. About 20 minutes after the Kamchatka earthquake, observers already knew that the waves were heading towards Hawaii - a full 30 to 40 minutes before they reached the coast.

Fortunately, fears of widespread destruction were unfounded. The waves that hit Hawaii were up to 1,7 meters high, causing only minor flooding and no serious damage. Most of the tsunami's energy dissipated in the open ocean, with the largest waves hitting uninhabited areas. But if the situation had been more severe, those extra minutes of warning could have been crucial.

The incident proved that NASA already has a system capable of detecting tsunamis long before they reach land under the right conditions-just by analyzing the radio signals used by global navigation satellites to communicate with ground stations. The same approach could even detect volcanic eruptions, missile launches, and underground nuclear weapons tests.

"They were able to say in almost real time, 'There's a tsunami,'" says Jeffrey Anderson, a data scientist at the U.S. National Center for Atmospheric Research who helped develop the Guardian system. He admits that when he first heard about the idea of ​​such a technology, it seemed "kind of crazy."

From an idea in the 70s to reality today

The idea of ​​using radio signals transmitted between ground-based receivers and satellites to detect tsunamis in near real time has been around for decades. As early as the 70s, a few academic papers discussed such a system, but it wasn't until the 2020s with the advent of Guardian that it became a reality. In 2022, Anderson and a team at NASA's Jet Propulsion Laboratory in California, USA, published a paper outlining key details about the system.

The reason that navigation satellites can detect tsunamis is because of the up-and-down motion of the sea. While a tsunami forms in the open ocean, its waves can initially be as small as 10-50 cm (4-20 inches) and almost invisible.

"A tsunami is almost imperceptible as it moves across the open ocean," says Yue Cynthia Wu, a marine engineering researcher at the University of Michigan who specializes in ocean wave dynamics.

But this movement is on a gigantic scale, carrying enormous amounts of water at once. It displaces the air above the ocean and disrupts the atmosphere, creating ripples in the layer of charged particles that make up the ionosphere, about 50 to 300 kilometers above the Earth's surface. These ripples change the number of electrons in different parts of the ionosphere.

Navigation satellites use dual frequencies to communicate with ground stations. When the number of electrons in the ionosphere increases, this leads to unusual delays in the arrival of signals. By measuring these delays, systems like Guardian can detect unusual phenomena in the ionosphere.

GPS engineers have long known that signals are distorted in this way, and they must correct for this "noise" to maintain navigation accuracy. But Earth scientists have realized that this noise can be used to detect tsunamis.

"These are smart people who think outside the box," Anderson commented.

In recent years, researchers have been able to identify the fingerprints of tsunamis and volcanoes in ionospheric data. Michael Hickey, a professor emeritus of physics at Embry-Riddle Aeronautical University in Daytona Beach, Florida, who has studied atmospheric waves for years, and his colleagues retrospectively analyzed the magnitude 9,1 earthquake that struck the northeastern coast of Japan in 2011 and triggered a tsunami. "We saw the rings," Hickey recalls, referring to the giant waves in the ionosphere over Japan, visualized by electron density data.

The huge volcanic eruption in Tonga in 2022 also left distinct traces in the ionosphere, which scientists later analyzed in detail.

But no major tsunami had been tracked in real time using this method until the Kamchatka earthquake this year. While predictions were made using the National Oceanic and Atmospheric Administration's DART tsunami detection system, which uses buoys anchored to the ocean floor, the Guardian system allowed waves to be tracked as they developed.

The atmosphere as radar: Guardian and the hopes for early tsunami detection

Atmospheric monitoring raises hopes that a system like Guardian could detect tsunamis in the open ocean before they reach great heights and crash into shores, allowing communities to receive earlier warnings and avoid false alarms.

The technology has the potential to be applied to phenomena other than earthquakes and volcanic eruptions. It could even help detect nuclear explosions. For example, waves in the ionosphere confirmed that North Korea had conducted underground nuclear weapons tests in 2009.

The minutes that save lives

Until now, tsunami monitoring systems have relied primarily on seismometers that analyze earthquakes around the world and ocean buoys that record sudden changes in wave height. But these tools do not provide as comprehensive and immediate a picture as ionospheric data.

"Minutes are critical in tsunami evacuation, so Guardian's early detections are an important advance for safety," said Harold Tobin, a seismologist at the University of Washington.

Anderson adds that monitoring the ionosphere, rather than just seismometers, could make it easier to detect tsunamis triggered by landslides.

A look into the future

Soon, Guardian may not be the only such tool.

"In Europe, we are developing our own version," says Elvira Astafieva, a senior researcher in geophysics and space sciences at the Paris Institute of Earth Physics.

She and her colleagues plan to test the system in the coming years, and the system could cover large areas - including the Indian Ocean, where France has territories. Hickey says it is also possible to detect tsunamis through auroras - faint glows in the atmosphere caused by large disturbances in the air.

But Guardian isn't finished yet. Anderson explains that future improvements will allow not only automatic detection, but also prediction of wave behavior.

"This would mean automated prediction of the size of the waves, where they will hit land, and when," he says. The system could generate new predictions every ten minutes or so as the tsunami develops.

But there are still some limitations. Diego Melgar, an expert on earthquakes, tsunamis and early warning systems at the University of Oregon, notes that the ionosphere reacts with a delay of several to tens of minutes. For communities close to the epicenter, that's too slow. For local warnings, that signal comes too late to be helpful.

But large tsunamis can cross entire ocean basins. In the Boxing Day disaster of 2004, which devastated coastlines around the Indian Ocean and killed an estimated 228,000 people, the waves reached Sri Lanka two hours after the earthquake off Indonesia, and the eastern coast of Somalia seven hours later.

Systems like Guardian can provide crucial early warnings to more remote communities during such disasters.

"If something will spread over a reasonable distance, then yes - it will save lives," Hickey concludes.