On December 21, 2024, the satellite SWOT (Surface Water and Ocean Topography), a collaboration between NASA and CNES, captured a wave in the North Pacific with a significant height of 19.7 meters, equivalent to a six-story building. It is the largest wave ever measured from space in the open sea.
The phenomenon was generated by Tropical Storm Eddie, an extratropical cyclone of exceptional intensity that crossed the North Pacific and caused damage from Canada to Peru.
The significant wave height represents the average of the largest waves recorded over a given period. Although individual crests of up to 35 meters were estimated, the officially validated value was 19.7 meters.
Before SWOT, about 15 satellites had measured waves since 1991, but no observation had exceeded 18.5 meters. The difference lies in that SWOT crossed the heart of Storm Eddie at the moment of peak intensity.
Energy traveling thousands of kilometers
The generated waves transformed into swell capable of traveling great distances. In this case, they traveled 24,000 kilometers, crossing the Drake Passage between South America and Antarctica until reaching the tropical Atlantic in January 2025.
This finding allowed for the correction of models that overestimated the energy transported by long waves by up to 20 times. The new calculations, based on SWOT analysis, improve the reliability of extreme wave predictions.
Risks and applications
Waves of this size pose a direct risk to:
- Cargo ships.
- Marine energy platforms.
- Submarine cables.
- Ports and coastal structures.
Accurately monitoring where and how they form allows for adjusting maritime routes, reviewing engineering standards, and reducing tragedies.
Climatic context
The European Space Agency reminded that swells act as “messengers” of storms: even if they do not make landfall, their energy can travel thousands of kilometers. An example was Storm Hercules in 2014, which generated 23-meter waves in the Atlantic.
An open question is whether megastorms like Eddie are becoming more frequent due to climate change. Warmer oceans store more energy, fuel more intense storms, and favor winds that generate extreme waves.
More than a curious record, the nearly 20-meter wave captured from space demonstrates that part of the ocean’s force escaped traditional measurements.
Now, invisible phenomena in remote areas are transformed into concrete data for science, navigation, and maritime safety, reinforcing the need for satellite monitoring on a planet increasingly exposed to extreme events.
