Satellite mission discovers how 650-foot mega tsunami in 2023 left Earth shaking for 9 days

NASA and France's CNES (Centre National d'Études Spatiales) working on the international Surface Water and Ocean Topography (SWOT) satellite mission, recently captured the unique contours of a tsunami as it traveled through the steep walls of a fjord in Greenland.

The tsunami, triggered by a massive rockslide, unleashed a seismic resonance that echoed around the world for nine days.

"The international Surface Water and Ocean Topography (SWOT) satellite mission, a collaboration between NASA and France’s CNES (Centre National d’Études Spatiales), detected the unique contours of a tsunami that sloshed within the steep walls of a fjord in Greenland in September 2023. Triggered by a massive rockslide, the tsunami generated a seismic rumble that reverberated around the world for nine days. An international research team that included seismologists, geophysicists, and oceanographers recently reported on the event after a year of analyzing data," said the official statement.


A colossal landslide in Greenland in September 2023 triggered a series of unusual events, including a 200-meter-high tsunami and an enigmatic nine-day seismic signal that puzzled scientists across the globe. According to a new study published in the journal Science, the landslide was caused by the collapse of a glacier in Dickson Fjord, a remote part of eastern Greenland, setting off a mega-tsunami and generating a rare seismic signal that reverberated around the world.

What did SWOT discover?

The SWOT satellite collected water elevation measurements in Dickson Fjord on September 17, 2023, the day after the initial rockslide and tsunami. The data was compared with measurements made under normal conditions a few weeks prior, on Aug. 6, 2023.

The data suggests that water levels at some points along the north side of the fjord were as much as 4 feet (1.2 meters) higher than on the south, said NASA's press release.

“SWOT happened to fly over at a time when the water had piled up pretty high against the north wall of the fjord,” said Josh Willis, a sea level researcher at NASA’s Jet Propulsion Laboratory in Southern California. “Seeing the shape of the wave — that’s something we could never do before SWOT.”

In a paper published recently in Science, researchers traced a seismic signal back to a tsunami that began when more than 880 million cubic feet of rock and ice (25 million cubic meters) fell into Dickson Fjord. Part of a network of channels on Greenland’s eastern coast, the fjord is about 1,772 feet (540 meters) deep and 1.7 miles (2.7 kilometers) wide, with walls taller than 6,000 feet (1,830 meters).

Why did Earth shake?

As per the research, far from the open ocean, in a confined space, the energy of the tsunami’s motion had limited opportunity to dissipate, so the wave moved back and forth about every 90 seconds for nine days. It caused tremors recorded on seismic instruments thousands of miles away.

From about 560 miles (900 kilometers) above, SWOT uses its sophisticated Ka-band Radar Interferometer (KaRIn) instrument to measure the height of nearly all water on Earth’s surface, including the ocean and freshwater lakes, reservoirs, and rivers.

“This observation also shows SWOT’s ability to monitor hazards, potentially helping in disaster preparedness and risk reduction,” said SWOT program scientist Nadya Vinogradova Shiffer at NASA Headquarters in Washington.

It can also see into fjords, as it turns out.

“The KaRIn radar’s resolution was fine enough to make observations between the relatively narrow walls of the fjord,” said Lee-Lueng Fu, the SWOT project scientist. “The footprint of the conventional altimeters used to measure ocean height is too large to resolve such a small body of water.”

What was the impact?

The seismic signal from the event was so powerful that it was detected across the globe, with sensors as far as Antarctica picking up the vibrations within hours. While no human lives were lost, the tsunami wiped away centuries-old cultural heritage sites and caused damage to an empty military base in the region. Scientists noted that had a cruise ship been in the area, which is a commonly used route, "the consequences would have been devastating," according to the study’s authors.