‘It sounded kind of crazy’: How ripples in the high atmosphere warned scientists of a tsunami in real time – BBC

Lead

In July 2025 an 8.8 magnitude earthquake struck off the far eastern coast of Russia’s Kamchatka Peninsula and spawned a fast-moving tsunami that propagated across the Pacific. Within minutes authorities issued evacuations across the basin, including orders affecting at least two million people in Japan. As waves raced at more than 400mph (644 km/h) toward distant shores, scientists noticed a different signal: tiny disturbances high in the atmosphere that revealed the tsunami almost in real time. That detection, enabled by a NASA system called Guardian with a newly added AI component, provided observers up to 30 to 40 minutes of extra warning for places such as Hawaii.

Key takeaways

• The earthquake off Kamchatka in July 2025 measured magnitude 8.8 and produced ocean waves moving at roughly 400mph (644 km/h).
• NASA’s Guardian system, with an AI filter added the day before, flagged ionospheric disturbances about 20 minutes after the quake, giving Hawaii 30 to 40 minutes of advance notice.
• Waves that reached Hawaii peaked at about 5ft (1.7m), causing minor flooding but no major structural damage.
• Tsunami-driven ocean motion perturbed the ionosphere 30 to 190 miles above Earth, altering electron densities and delaying dual-frequency GNSS signals used by satellites.
• Guardian complements existing tools such as NOAA’s DART buoys and seismic networks by providing a near-real-time, basin-scale view under favourable conditions.
• The technique can also register large volcanic eruptions, rocket launches and has previously helped identify ionospheric signatures from underground nuclear tests.
• Limitations remain: the ionosphere responds on a minutes-to-tens-of-minutes timescale, making the method less useful for communities very close to an epicentre.

Background

For decades engineers and scientists have known that signals from global navigation satellite systems are affected by the ionosphere, the charged layer of the upper atmosphere. Navigation teams routinely correct for that interference to preserve positioning accuracy, and early academic work in the 1970s speculated that those same effects might carry signatures of large geophysical events. In the 2010s and early 2020s, researchers began to document retrospective ionospheric traces of major disturbances, including the 2011 Tohoku earthquake and tsunami (magnitude 9.1) and the 2022 Tonga eruption.

NASA and academic groups developed monitoring approaches that measure tiny delays between the dual frequencies used by GNSS satellites and ground receivers; those delays track changes in electron content above. In 2022, scientists including members of NASA’s Jet Propulsion Laboratory published results that helped turn the concept into an operational capability. The Guardian system was designed to integrate GNSS observations, physics-based interpretation and, more recently, automated analysis driven by machine learning.

Main event

On the morning of the Kamchatka quake, seismic alarms and NOAA DART buoy readings produced the conventional tsunami forecasts used by warning centers. Shortly after, the Guardian system identified coherent perturbations in the ionosphere consistent with a large, basin-scale ocean disturbance. Roughly 20 minutes after the earthquake, analysts received automated flags indicating outward-propagating ionospheric ripples that matched the expected arrival path to Hawaii.

Those ionospheric ripples form because an ocean moving up and down over thousands of kilometres displaces the air above it, setting acoustic-gravity waves that reach the ionosphere. The motions change electron concentrations in that layer and therefore the travel time of satellite radio signals. By measuring and mapping those delays across many receiver-satellite links, Guardian reconstructed a picture of a spreading wave front above the ocean in near real time.

When the tsunami reached Hawaii, local observations showed maximum wave heights of about 5ft (1.7m), producing limited flooding and no major damage to infrastructure. Most of the tsunami’s destructive energy dissipated in the open ocean or struck sparsely populated coastlines. Experts say that the extra tens of minutes of lead time provided in this instance would have been valuable had the coastal impacts been larger or targeted more densely populated areas.

Analysis & implications

Scientifically, the episode is a milestone: it demonstrates that an atmospheric channel can be used operationally to monitor tsunamis as they travel across ocean basins. That capability expands the toolkit beyond seismic records and ocean-bottom pressure sensors, offering a complementary, wide-area perspective. Where DART buoys and coastal gauges sample only specific points, GNSS-based ionospheric sensing leverages the global satellite constellation and dense ground networks to fill spatial gaps.

Operationally, the technique excels for transoceanic tsunamis that travel long distances and where minutes of extra warning can change evacuation outcomes. For example, the 2004 Indian Ocean tsunami took up to two hours to reach Sri Lanka from its Indonesian epicentre, and in that context basin-scale early detection could provide crucial decision time. Conversely, for communities within tens of kilometres of an epicentre, the ionospheric response is too slow to substitute for local seismic and coastal monitoring, because the signal takes minutes to develop.

There are further benefits beyond tsunamis. The same ionospheric measurements can detect volcanic explosions, large rocket launches and even aid verification of underground nuclear tests by flagging the atmospheric disturbances they create. That versatility may attract cross-agency investment and international collaboration, speeding the rollout of complementary systems in Europe and elsewhere.

Comparison & data

These figures illustrate why an ionospheric channel matters most for basin-scale tsunamis: when travel times are measured in hours, an automated detection tens of minutes earlier can materially improve preparedness for distant shorelines. The table is not exhaustive but shows the range of magnitudes and societal impacts that motivate improved detection networks.

Reactions & quotes

Scientists involved in Guardian and outside experts emphasised both the promise and the limits of the approach. Below are representative statements with context.

The team reported that, in this instance, they could say in close to real time that a tsunami was underway.

Jeffrey Anderson, data scientist, US National Center for Atmospheric Research

Anderson helped develop Guardian and noted that when he first heard proposals for ionospheric monitoring years earlier, he thought the idea sounded ‘kind of crazy.’ His perspective changed as model-data comparisons and retrospective studies validated the approach.

Minutes really matter for tsunami evacuation, so the Guardian early detections seem to me to be a really important advance for tsunami safety.

Harold Tobin, seismologist, University of Washington

Tobin, who studies seismic early warning and tsunami hazards, underlined that the method complements rather than replaces existing buoy and seismic networks, especially for communities remote from the epicentre.

Unconfirmed

• Precise timing and scope of the AI component being added to Guardian is reported as occurring the day before the quake; independent confirmation of that schedule is limited in public sources.
• The degree to which Guardian alone would have averted any casualties in a worse-impact scenario is hypothetical and depends on local response and infrastructure readiness.
• Claims that the approach can reliably forecast final coastal wave heights in every case remain under development and require further validation.

Bottom line

The Kamchatka episode in July 2025 shows that the ionosphere can act as a rapid, basin-scale sensor for tsunamis, offering tens of minutes of extra lead time for distant shorelines under favourable conditions. Guardian’s near-real-time flags complemented NOAA’s DART buoy forecasts and seismic analysis, demonstrating a practical, operational pathway from research to warning systems.

While the method will not replace local seismic and coastal gauges for near-field warnings, it strengthens the global network of hazard monitoring and could save lives when transoceanic waves threaten distant populations. Continued testing, international coordination and integration with established warning centres will be essential to move from a promising demonstration to routine, trusted use.

Sources

• BBC Future (press)
• NOAA Center for Tsunami Research – DART buoys (official/agency)
• National Center for Atmospheric Research (research institute)
• NASA Jet Propulsion Laboratory (research/agency)
• Encyclopaedia Britannica on the 2004 Indian Ocean tsunami (reference)