Satellite Reveals Epic Tsunami That Shook Earth for 9 Days Last Year

A satellite flying over Greenland last year captured an aerial view of a tsunami that roiled a fjord in the country, and now researchers have published their analysis of the remarkable visuals.

Satellite images can reveal what was previously unseeable and provide new perspectives on old sights. From atmospheric phenomena to the slow creep of death in a forest and huge piles of trash, images from the air and near-Earth orbit can help scientists better understand the planet.

The tsunami happened in Dickson Fjord in September 2023, and was triggered by a rockslide that caused Earth to mysteriously shake for nine days. Every 90 seconds over that week-and-change, the waters in the fjord sloshed to and fro, bound by the 6,000-foot (1,830-meter) walls of the channel. Researchers published an analysis of the seismic event in Science in September, recounting how that 880 million cubic feet (25 million cubic meters) of ice, rock, and sediment caused an extended tsunami. With nowhere for the energy to dissipate, the fjord tsunami shook the Earth for over a week.

As the tsunami was rocking the fjord, the Surface Water and Ocean Topography satellite, or SWOT, was passing overhead. Operated by NASA and France’s Centre National d’Études Spatiales (CNES), SWOT was able to study how the tsunami changed water levels in the 1,772-foot-deep (540-meter-deep) fjord.

“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 a laboratory release. “Seeing the shape of the wave—that’s something we could never do before SWOT.”

The fjord is 1.7 miles (2.7 kilometers) wide. Based on SWOT data, the team found that the tsunami caused water levels on one side of the fjord (its north side) to be up to four feet (1.2 meters) higher than water levels on its south side.

SWOT collected this data using its interferometer, a device that uses interference patterns to measure the distance between objects. Interferometry can be done with extreme precision, making it a go-to tool for scientists taking very exact measurements to measure things like the rippling of spacetime’s fabric.

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

The tsunami caused about $200,000 worth of damage, as reported in our original coverage of the research. But the SWOT image adds a compelling new dimension to the anomalous tsunami—it shows the havoc from above.