Scientists have finally solved the mystery behind two strange events that shook the entire planet for nine days straight.
Their findings close the book on a years-long effort to trace the seismic signals back to their source.
The researchers used data captured by NASA’s Surface Water Ocean Topography (SWOT) satellite, which launched in December 2022 to map the height of water across 90% of Earth’s surface.
But determining that these seiches formed at the same time as the strange seismic signals still wasn’t enough to prove the two events were linked.
Indeed, the waves that shook the world offer a stark reminder of the sweeping impacts of rising global temperatures.
Researchers have finally figured out what caused two odd occurrences that rocked the world for nine days in a row. Their conclusions bring an end to a multi-year endeavor to locate the origin of the seismic signals.
Seismometers around the world noticed something odd in September 2023. For nine days, there were slight tremors going through the Earth every ninety seconds. It occurred again a month later. Natural tectonic processes were unable to account for the anomalies, leaving scientists perplexed.
A year or so of scientific investigation led to two separate studies in 2024 that independently postulated that the shaking was caused by two massive landslides that triggered two “mega-tsunamis” in East Greenland’s Dickson Fjord. They hypothesized that these massive standing waves, also known as seiches, sloshed back and forth inside the fjord and caused tiny movements in the crust of the Earth.
The possibility was intriguing, and both studies provided strong evidence to back up their assertions. Thomas Monahan, a Schmidt AI in Science fellow at the University of Oxford, told Gizmodo that “there were some big uncertainties that made it difficult to fully corroborate that this was actually the root cause.”.
Monahan and his associates therefore set out to verify the validity of this theory. In a study that was published today in the journal Nature Communications, they established a clear connection between the seismic anomalies and the first direct satellite observations of the seiches.
The researchers mapped the height of water over 90% of the Earth’s surface using data from NASA’s Surface Water Ocean Topography (SWOT) satellite, which launched in December 2022. This kind of data collection, called satellite altimetry, involves sending radar pulses from a satellite to the surface of the Earth and timing how long it takes for the signals to return to the satellite after bouncing off the surface.
According to an Oxford statement, long intervals between observations prevented conventional altimeters from recording evidence of the seizures. Because of the intricacy of the terrain, they typically have trouble collecting data in fjord regions, according to Monahan. The state-of-the-art altimeter instrument that SWOT has, however, triangulates the return signals using two antennas. This enables the satellite to measure surface water levels at extremely high resolution.
The elevation of the sea surface in these intricate areas can be seen in a snapshot that is extremely high-resolution, according to Monahan. His research team was able to determine the slopes of the enormous waves that had formed because these photos gave a more precise image of how the fjord’s sea surface height changed during the 2023 seismic events.
“We basically discovered that there was a big irregularity in the fjord at the precise moment we anticipated this wave to happen,” Monahan said.
Even if it was established that these seiches occurred concurrently with the odd seismic signals, this did not establish a connection between the two occurrences. For the researchers to demonstrate that these enormous waves could cause tremors around the world, they needed concrete proof.
In order to do this, they connected the SWOT images to minute alterations in the Earth’s crust that were picked up at seismic stations thousands of miles from the fjord. By combining this ongoing seismic data with the sporadic satellite observations, they were able to reconstruct the wave’s characteristics, even during times when SWOT did not observe them. After ruling out the possibility that the seismicity was caused by tidal or weather conditions, the researchers concluded that the tremors were coming from the seiches.
According to Monahan, these waves were created when a glacier that was warming collapsed in on itself. According to him, “this produced very large landslides, which when they struck the fjord—produced massive mega-tsunamis on the order of 200 meters or 600 feet tall.”.
“This was the first time that a mega-tsunami of that kind had happened in Eastern Greenland,” Monahan stated, noting that similar occurrences have been recorded on the west coast of the region. He stated that the fact that this phenomenon is spreading to other ice sheet regions “is concerning” because it indicates that climate change is accelerating in this area.
“This study, in my opinion, really highlights the fact that—well, that may sound ridiculous, but climate change is a worldwide phenomenon,” Monahan stated.
Some of the most significant and rapid changes are taking place in the Arctic and other isolated areas where we might not notice them every day. However, he added, “it’s critical to comprehend and measure those changes because they will eventually affect us where we live.”. It is true that the world-shaking waves serve as a clear reminder of the far-reaching effects of warming temperatures.
