A bizarre global seismic signal was observed in September 2023, repeating every 90 seconds over nine days. The phenomenon reappeared a month later. Recently, two scientific studies proposed that the cause of these seismic anomalies were two mega tsunamis triggered by landslides in an unnamed East Greenland fjord.
The waves became trapped in the fjord system, forming standing waves (or seiches) that undulated back and forth, causing the mystery signals. However, no observations of these seiches existed to confirm this theory.
Researchers at the University of Oxford used novel analysis techniques to interpret satellite altimetry data from the Surface Water Ocean Topography (SWOT) satellite. This satellite measures the height of the Earth’s surface by recording radar pulses and has unprecedented accuracy up to 2.5 meters resolution.
The researchers created elevation maps of the Greenland Fjord at various time points following the two tsunamis, showing clear cross-channel slopes with height differences of up to two metres. The data showed that water moved backwards and forwards across the channel.
To prove their theory, the researchers linked these observations to small movements of the Earth’s crust measured thousands of kilometres away. This connection enabled them to reconstruct the characteristics of the wave, even for periods which the satellite did not observe. They also reconstructed weather and tidal conditions to confirm that the observations could not have been caused by winds or tides.
The study highlights the potential of next-generation satellite earth observation technologies to study oceanic processes in remote areas. “SWOT is a game changer for studying oceanic processes,” said lead author Thomas Monahan. The research team aims to use machine learning and knowledge of ocean physics to interpret new results and gain insights into ocean extremes such as tsunamis, storm surges, and freak waves.
Source: https://www.eurekalert.org/news-releases/1085450