Satellite spots planet-rumbling Greenland tsunami

The SWOT satellite, a joint project of NASA and France’s CNES, discovered the shape of a tsunami in a fjord in Greenland in September 2023. This tsunami was caused by a large rockslide, creating a seismic shock that could be felt worldwide for nine days.

An international team of scientists studied this event for a year. The SWOT satellite measured the water levels in Dickson Fjord the day after the tsunami and compared them to normal levels recorded a few weeks earlier.

In the data visualization, lighter colors show higher water levels, while darker colors indicate lower levels. The data reveals that water levels on the north side of the fjord were up to 4 feet (1.2 meters) higher than on the south side.

Josh Willis, a sea level researcher at NASA, noted that the SWOT satellite captured the wave’s shape when the water had built up significantly against the north wall of the fjord. This kind of observation was not possible before the SWOT mission.

In this study, researchers traced a seismic signal to a tsunami caused by a massive fall of over 880 million cubic feet (25 million cubic meters) of rock and ice into Dickson Fjord. This fjord is about 1,772 feet (540 meters) deep and 1.7 miles (2.7 kilometers) wide, with steep walls over 6,000 feet (1,830 meters) high.

The tsunami’s energy couldn’t dissipate efficiently since the fjord was closed off from the ocean. As a result, the wave moved back and forth every 90 seconds for nine days, creating tremors detected by seismic instruments located thousands of miles away.

From about 560 miles (900 kilometers) above the Earth, the SWOT satellite uses a special instrument called the Ka-band Radar Interferometer (KaRIn) to measure the height of almost all water on the planet. This includes oceans, freshwater lakes, reservoirs, and rivers.

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

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

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