Introduction: A Breakthrough View from Space
Satellite observations have unveiled a striking fact about storms: they can generate mega ocean waves that look like they reach the height of five giraffes stacked on top of each other. In late December 2024, during Storm Eddie, the French-US SWOT satellite captured measurements showing waves averaging nearly 20 meters in height—the largest recorded from space. This discovery not only captive astonishes but also expands our understanding of how storms transmit energy across oceans without making landfall.
How Satellites Measure Mighty Waves
Traditional ocean measurements relied on buoys and ships, but space-based radar and altimetry provide a broader, near-real-time view. SWOT, along with assets from SARAL, Jason-3, Copernicus Sentinel-3A/-3B, Sentinel-6 Michael Freilich, CryoSat, and CFOSAT, creates a high-resolution picture of sea surface height, wave height, and wind speed. The collaboration mentioned in the Storm Eddie case merged decades of data with SWOT’s imaging to map record swells radiating up to 24,000 km from the North Pacific to the Atlantic between late December 2024 and early January 2025.
What the Data Reveal About Wave Energy
One key finding is that long ocean swells carry significant energy, but the peak energy concentrates not in the longest swells but in the higher-energy, shorter waves generated directly by the storm winds. This nuance challenges earlier beliefs that swell length alone dictates energy transfer. In practical terms, coastal communities should heed both the presence of powerful swells and their frequency—the time between crests, or wave period—which indicates the storm’s hidden potential for damage. A typical 20-second period implies waves arriving in a steady, regular rhythm, amplifying water movement along shores far from the storm center.
Why This Matters for Forecasting and Resilience
Forecasting models now have richer data to refine predictions of where and when dangerous swells will strike. The SWOT mission’s detailed imaging, combined with long-term ESA Climate Change Initiative sea-state records, enables researchers to forecast coastal impacts with greater confidence. Improved forecasts support decision-making for infrastructure protection, emergency planning, and community preparedness as climate change drives more frequent extreme events.
Implications for Coastal Management
The European and U.S. space agencies’ partnership highlights the value of open-access satellite data in building resilient coastal systems. Beyond immediate protection, better understanding of energy transfer in storms informs building codes, shore protection projects, and insurance risk assessments. As storms intensify and sea levels rise, knowing how waves radiate energy outward helps communities anticipate swell-driven hazards even when storms do not directly threaten the coast.
Looking Ahead: A New Era of Remote Sensing
Copernicus Sentinel-6 now provides near-real-time measurements of significant wave height and wind speed for daily ocean forecasts, delivering tangible benefits for maritime safety, port operations, and coastal defense. The SWOT mission’s insights, supported by decades of satellite data, mark a pivotal leap in understanding the origins, scale, and impact of Earth’s wildest waves. As scientists continue to decode the complex dance between storms and swells, coastal populations gain better tools to anticipate, adapt, and endure the planet’s changing seas.
