In September 2023, scientists detected a mysterious global seismic signal unlike anything seen before. Every 90 seconds, Earth rumbled—continuously—for nine days. A similar signal followed just weeks later. Now, new satellite data has finally confirmed the source: a massive megatsunami trapped in a remote fjord in East Greenland.
The seismic waves were caused by a rare phenomenon called a seiche—a standing wave that sloshes back and forth in a confined body of water. In this case, the event unfolded in Dickson Fjord, triggered by two enormous landslides from a melting glacier. The impact created giant waves up to 7.4 to 8.8 meters high (24.3 to 28.9 feet), reverberating within the fjord for days.
Until now, no one had directly observed the phenomenon. Not even a military ship that arrived three days into the event noticed it. But satellites captured what the human eye missed.
Using data from NASA’s Surface Water and Ocean Topography (SWOT) satellite—launched in 2022—researchers obtained precise sea-surface height measurements. The satellite’s Ka-band Radar Interferometer recorded clear changes in water elevation, revealing the presence of a 2-meter (6.6-foot) standing wave inside the fjord.
“This is the first time we’ve seen something like this in action,” said ocean engineer Thomas Adcock of the University of Oxford. “It’s a perfect example of how next-generation satellite technology can uncover natural events that would otherwise go undetected.”
By comparing SWOT data with global seismic recordings, researchers confirmed that the seiche was indeed the source of the tremors. Their analysis ruled out other possible causes and allowed them to reconstruct the events in detail—including the times when no satellite coverage was available.
“This discovery is a game changer,” said study co-author Thomas Monahan, also from the University of Oxford. “As climate change accelerates, we’re seeing new and extreme events in remote places like the Arctic. Traditional monitoring methods often can’t reach these areas, but satellites like SWOT give us the tools to observe and understand them in unprecedented detail.”
This breakthrough not only confirms the link between seiches and global seismic signals but also marks a significant step forward in monitoring climate-driven ocean phenomena like tsunamis, storm surges, and extreme waves—especially in remote, data-scarce regions.
