In September 2023, seismic stations worldwide began detecting an unusual, rhythmic signal repeating every 92 seconds. The faint yet persistent pulse, which lasted for nine days and briefly reappeared a month later, puzzled scientists across the globe. Though imperceptible to humans, the signal was strong enough to be recorded from Alaska to Australia — an uncommon pattern for traditional earthquakes.
After weeks of investigation, researchers pinpointed the origin of the mysterious tremor to East Greenland’s remote Dickson Fjord — a narrow waterway flanked by towering 3,000-foot cliffs.
The Hidden Catastrophe
Recent satellite imagery revealed a dramatic change in the landscape: a fresh scar on a mountainside, where a vast section of rock had disappeared. The discovery led scientists to uncover a colossal natural disaster that struck the fjord on September 16, 2023.
On that day, more than 25 million cubic yards of rock and ice — enough material to fill around 10,000 Olympic-sized swimming pools — collapsed into the fjord. The immense impact generated a mega tsunami, with waves towering up to 650 feet high. The surging water traveled along the two-mile-long fjord, crashing into cliffs and reverberating back, creating a phenomenon known as a seiche — a sustained, oscillating wave motion within an enclosed body of water.
Unlike typical tsunamis that move outward in a single direction, seiches cause water to slosh back and forth repeatedly, sending low-frequency seismic waves through the Earth’s crust for days on end.
Solving the Seismic Puzzle
The breakthrough in understanding this event came thanks to data from the Surface Water and Ocean Topography (SWOT) satellite — a collaborative mission launched in 2022 by NASA and the French space agency. The satellite detected subtle water level changes in the fjord, with slopes of up to two metres that matched the oscillating patterns expected from seiches.
To fill in the gaps and model the event more accurately, scientists employed machine learning techniques to simulate the wave dynamics over time.
“It was exciting to be working on such a puzzling problem with an interdisciplinary and international team of scientists,” said Robert Anthony of the US Geological Survey. “Ultimately, it took a plethora of geophysical observations and numerical modeling from researchers across many countries to put the puzzle together and get a complete picture of what had occurred.”
The study highlights the importance of advanced satellite technology and global scientific collaboration in understanding complex natural phenomena that ripple through the planet — sometimes in ways we can’t immediately see or feel.
