In September 2023, scientists around the world noticed something odd. Every 90 seconds, the Earth shook slightly—but this repeated for nine days straight before stopping. A month later, the same pattern happened again.
Strange Earthquakes Without a Cause: How SWOT Helped Solve the Mystery
These small tremors were picked up by sensitive earthquake detectors globally, but no one could explain their source. There were no explosions, volcanic activity, or known earthquakes nearby, making the cause a true mystery.
The mystery began to clear thanks to data from NASA’s SWOT satellite. Researchers used SWOT’s advanced radar technology to study a remote fjord in East Greenland, where two massive landslides had recently occurred due to glacier melting from rising temperatures. These landslides triggered huge tsunamis that didn’t simply fade away. Instead, the waves bounced back and forth inside the fjord as seiches—standing waves powerful enough to shake the Earth’s crust and cause the strange seismic signals detected worldwide.
SWOT’s wide-area, high-resolution measurements were crucial because traditional satellites could not capture these trapped waves. By analyzing SWOT data, scientists made the first direct observations of these seiches and confirmed their link to the global seismic signals. Without SWOT’s detailed imaging and surface height measurements, this unusual climate-driven natural event might have remained unexplained.
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A Satellite That Sees the Invisible
Even though scientists suspected that seiches were the cause, there was one big problem: no one had actually seen them happen. No cameras were watching, and the few ships nearby didn’t report anything strange. Without proof, it was still just a theory.
That changed thanks to a new satellite called SWOT, short for Surface Water and Ocean Topography. This satellite, developed by space agencies to study Earth’s water bodies, has a special tool onboard called the Ka-band Radar Interferometer, or KaRIn for short. Unlike older satellites that take narrow, straight-line measurements, SWOT scans wide areas—about 50 kilometers wide—and does so in high detail. It can detect tiny changes in water surface height, accurate to about 2.5 meters.
When researchers looked at SWOT’s data over the East Greenland fjord, they found what they had been searching for. The satellite showed something amazing: the water in the fjord had tilted in opposite directions at different times. One side would rise while the other fell, then the pattern would reverse. These tilting water surfaces are the fingerprints of seiches—standing waves that go back and forth without leaving the container they’re in.
Older satellites had missed this entirely because they couldn’t see the whole picture at once. SWOT’s unique imaging method made it possible to finally spot the hidden waves. And although a Danish military ship had been in the fjord during the events and noticed nothing unusual, SWOT captured what no human eye or older instrument could.
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From Glacier to Global Tremors
The chain of events started with a warming glacier in a little-known part of East Greenland. As the ice melted, it loosened the land around it. Eventually, large pieces of mountain rock broke off and plunged into the fjord below. This sudden movement displaced a massive amount of water, like a child jumping into a full bathtub. The result was a mega-tsunami—an enormous wave caused by the falling land.
But unlike ocean tsunamis that race across seas, these waves had nowhere to go. Trapped inside the fjord’s narrow, steep walls, they began to bounce back and forth. These were not just small ripples. They were strong enough to create pressure against the walls and floor of the fjord, shaking the Earth’s crust in a regular pattern. That’s what caused the 90-second intervals picked up by earthquake detectors around the globe.
Scientists were able to match the seismic data with the exact times the satellite saw the fjord water tilting. This clear connection ruled out other possible explanations like wind, tides, or nearby human activity. The mystery signals from September and October 2023 could now be confidently traced back to a rare chain of natural events driven by climate change: glacier melting, landslides, tsunamis, and trapped waves.
These findings show that Earth is full of surprises—and that sometimes, the answers to strange global signals are hiding in faraway places no one is watching. But with the right tools, like NASA’s SWOT satellite, scientists can uncover the hidden stories written in the planet’s water and land.
