Greenland's 650-foot tsunami in 2023 sent shockwaves across the globe, rattling sensors for 9 days—check out image

Greenland's 650-foot tsunami in 2023 sent shockwaves across the globe, rattling sensors for nine days (Image: Canva)

The world’s seismic stations picked up a strange beat. A quiet rhythm pulsed through the Earth for nine days straight. It was slow, deep, and felt nowhere—but recorded everywhere.

Scientists soon traced the cause to Greenland’s remote east. Dickson Fjord, a narrow inlet, had suffered a massive collapse. A towering section of mountain had broken free, changing the landscape forever.

On 16 September 2023, millions of tonnes of rock fell. The impact hurled up a wave 650 feet high. It raced down the fjord, smashed into cliffs, then reversed.

Water rocked back and forth for hours, creating a rare seiche. Instead of fading, the sloshing triggered waves that shook the planet’s crust. Scientists later built models to study the event’s force. One team estimated water levels jumped 8½ feet. Another believed the rise had been as much as 30 feet.

A satellite image of Dickson Fjord, featuring radar data from 11 October, highlights the recorded variations in water height. (Image: Thomas Monahan)

Though their calculations differed, their conclusion was the same: the collapse had sent ripples through the world’s seismic network.

Over 70 scientists worked to solve the puzzling signals. Teams studied the landscape, mapped new scars, and ran simulations. Kristian Svennevig, from Denmark’s geological survey, recalled their efforts. “Nobody knew what caused this pulse,” he said. “It took a huge team to connect the dots.”

Images revealed where the rock broke away. Supercomputers showed how water had moved after impact. Slowly, the team unravelled the mystery. Robert Anthony, of the US Geological Survey, called the research a triumph. “We needed people from many fields to piece it together.”

The SWOT satellite captured data on the fjord, just half a day after the 11 October tsunami began. (Image: Monahan et al., Nat. Commun., 2025)

Glacier ice once supported the fragile slopes above the fjord. But rising temperatures have melted away that natural shield. In 2017, another landslide caused a deadly tsunami nearby. Eleven homes were destroyed, and four lives were lost. Experts warn such events could become more frequent. Dickson Fjord lies near a growing Arctic cruise route. Its collapse was a reminder of the risks for travellers.

Authorities now explore ways to track these threats. Satellites and seismic monitors could offer new warning systems. New space missions promise sharper detail on remote waters. Thomas Monahan, from Oxford University, praised the power of next-generation satellites. “They give us a better view of ocean extremes,” he said.

Researchers will now search past seismic records for similar slow pulses. Each new discovery will improve forecasts and help protect high-latitude communities. Even the quietest corners of the world can teach us something. Sometimes, it takes listening closely to understand their warnings.

The study was published in Science and Nature Communications.