Data from space shows water tilting up toward the north side of the Dickson Fjord as it sloshed from south to north and back every 90 seconds for nine days after a 2023 rockslide.
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.
The SWOT satellite collected water elevation measurements in Dickson Fjord on Sept. 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.
In the data visualization (above), colors toward the red end of the scale indicate higher water levels, and blue colors indicate lower-than-normal levels. 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.
“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).
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.”
More About SWOT
Launched in December 2022 from Vandenberg Space Force Base in California, SWOT is now in its operations phase, collecting data that will be used for research and other purposes.
The SWOT satellite was jointly developed by NASA and CNES, with contributions from the Canadian Space Agency (CSA) and the UK Space Agency. NASA’s Jet Propulsion Laboratory, managed for the agency by Caltech in Pasadena, California, leads the U.S. component of the project. For the flight system payload, NASA provided the KaRIn instrument, a GPS science receiver, a laser retroreflector, a two-beam microwave radiometer, and NASA instrument operations. CNES provided the Doppler Orbitography and Radioposition Integrated by Satellite (DORIS) system, the dual frequency Poseidon altimeter (developed by Thales Alenia Space), the KaRIn radio-frequency subsystem (together with Thales Alenia Space and with support from the UK Space Agency), the satellite platform, and ground operations. CSA provided the KaRIn high-power transmitter assembly. NASA provided the launch vehicle and the agency’s Launch Services Program, based at Kennedy Space Center in Florida, managed the associated launch services.
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