In September 2023, something very unusual happened in a remote fjord in East Greenland. Scientists around the world picked up a strange signal—like a slow, steady heartbeat—coming from the Earth itself. This signal lasted for nine days, and then, a month later, it appeared again for another week. No one had ever seen anything quite like it.
The story begins with two enormous landslides that crashed into the Dickson fjord, each one sending a huge wave, or tsunami, racing through the water. But these tsunamis did more than just splash the fjord’s shores. They set off a rare and mysterious phenomenon called a seiche (pronounced “say-sh”). A seiche is a standing wave that rocks back and forth in a closed or partly closed body of water, like the sloshing you see when you shake a bathtub or a bowl of soup.
Scientists had long suspected that the strange signals were caused by a seiche, but proving it was difficult. The fjord is remote, and there were no instruments in the water to record what happened. Instead, researchers had to rely on computer models and distant earthquake sensors. These gave clues, but not direct proof.
Everything changed when a new satellite, called SWOT (Surface Water Ocean Topography), passed over Greenland. This satellite can measure the height of water surfaces with amazing detail, even in narrow fjords. When SWOT flew over Dickson fjord soon after the landslides, it captured clear snapshots of the water’s surface. The images showed the fjord’s water tilted from side to side, just like a giant, slow-moving wave was rocking back and forth—exactly what you would expect from a seiche.
This was the first time anyone had directly observed such a long-lasting seiche after a mega-tsunami. The satellite’s data matched what scientists had predicted and confirmed that the mysterious signals were indeed caused by a seiche.
This discovery is more than just a scientific curiosity. As climate change brings more extreme events to remote places, satellites like SWOT will be vital for spotting and understanding rare phenomena that would otherwise go unseen. By using space technology, scientists can now monitor even the most hidden corners of our planet, helping us prepare for the unexpected in a changing world.
