SWOT observed water levels in Dickson Fjord on September 17, 2023, just a day after the rockslide initiated the tsunami. This data was compared to normal water measurements taken a few weeks earlier on August 6, 2023.
"SWOT happened to fly over at a time when the water had piled up pretty high against the north wall of the fjord," explained Josh Willis, a NASA Jet Propulsion Laboratory sea level researcher. "Seeing the shape of the wave - that's something we could never do before SWOT."
This seismic event began as over 880 million cubic feet (25 million cubic meters) of rock and ice fell into the fjord, which reaches depths of approximately 1,772 feet (540 meters) and spans 1.7 miles (2.7 kilometers) in width. The fjord's towering 6,000-foot (1,830-meter) walls created a confined space where the tsunami's energy had minimal room to dissipate, causing waves to oscillate every 90 seconds for over a week. Seismic instruments recorded tremors from the event thousands of miles away.
Orbiting at around 560 miles (900 kilometers) above Earth, SWOT uses advanced Ka-band Radar Interferometer (KaRIn) technology to measure the height of nearly all surface water bodies, including oceans, lakes, and rivers. According to Nadya Vinogradova Shiffer, SWOT program scientist at NASA Headquarters, "This observation also shows SWOT's ability to monitor hazards, potentially helping in disaster preparedness and risk reduction."
Furthermore, SWOT's KaRIn radar displayed fine enough resolution to capture water height fluctuations within the fjord's narrow walls. "The footprint of the conventional altimeters used to measure ocean height is too large to resolve such a small body of water," noted Lee-Lueng Fu, the SWOT project scientist.
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