Extreme ocean waves once dismissed as maritime folklore are now being captured in precise detail from space and the latest satellite data are prompting new concerns among scientists and shipping operators.
Recent observations show individual waves in the Pacific reaching heights of up to 35 metres taller than a 10-storey building even in the absence of so-called “super hurricanes.” Researchers say these measurements suggest that dangerous sea states may be developing under conditions previously considered routine.
For decades, rogue waves were treated as exaggerated sea tales. That perception began to shift in the 1990s when radar altimeters aboard European and American satellites started systematically recording wave heights across the globe.
Today, agencies including the National Oceanic and Atmospheric Administration define rogue waves as walls of water at least twice the height of surrounding waves steep, sudden and capable of inflicting serious damage on large vessels.
Early evidence from the European Space Agency confirmed that such waves occur more frequently than previously assumed. More recently, the French-US Surface Water and Ocean Topography (SWOT) mission recorded extreme sea states during a major North Pacific storm in December 2024.
Analysis led by oceanographer Fabrice Ardhuin found average wave heights exceeding 19 metres during the system’s peak, with some individual crests likely reaching or surpassing 35 metres the highest levels yet documented from space. The findings were published in the Proceedings of the National Academy of Sciences.
Extreme Waves Without Extreme Hurricanes
What is particularly concerning, researchers note, is that some of these extreme wave readings are emerging outside the most intense tropical cyclone systems.
Shipping records over recent years show instances of unexplained hull damage and container losses during what had been forecast as manageable storm conditions. In several cases, satellite archives later revealed brief but intense spikes in local wave height along major Pacific trade routes.
Modern route planning increasingly integrates near real-time satellite wave data with traditional wind and swell forecasts. Some operators now deliberately adjust courses even at the cost of longer travel times to avoid narrow corridors where wave anomalies are detected.
Warming Ocean, A More Energetic Surface
Climate scientists caution that the issue extends beyond maritime safety. More than 90 percent of excess heat from global warming is absorbed by the oceans. Rising ocean temperatures alter wind patterns, current interactions and storm dynamics all of which influence wave formation.
Long-term satellite analyses of significant wave height indicate clustering of extreme events in certain Pacific belts, particularly in regions experiencing surface warming of one to two degrees Celsius. Steeper waves enhance mixing at the ocean surface, accelerating exchanges of heat and moisture between sea and atmosphere processes that can influence future storm intensity and marine heatwaves.
Implications for Coasts and Infrastructure
The impact of extreme waves does not remain offshore. Long-period swells generated in distant storms can travel thousands of kilometres, reaching coastlines as powerful surf capable of accelerating erosion and stressing harbour infrastructure.
Satellite systems that detect wave extremes are also used to refine sea-level rise models and coastal flood maps, tools that increasingly underpin urban planning, port upgrades and insurance assessments.
While 35-metre waves remain rare, scientists warn that the statistical boundaries of “extreme” appear to be shifting. What was once considered a once-in-a-century anomaly may now be closer to a once-in-a-decade event along certain corridors.
The emerging satellite record does not suggest an ocean in constant chaos. Rather, it reveals a more complex and energetic system than traditional safety margins anticipated. As global temperatures rise and Pacific conditions evolve, researchers say continuous monitoring will be critical.
The ocean has not changed its laws overnight but the range of possibilities within those laws appears to be expanding.