At a Glance
- In September and October 2023, a strange seismic signal repeating every 90 seconds puzzled scientists, who suspected it originated from trapped tsunami-like waves in a Greenland fjord.
- Researchers used the SWOT satellite’s advanced radar to detect high-resolution changes in water height, revealing back-and-forth wave motions consistent with seiches trapped inside the fjord.
- By correlating satellite water level data with global seismic signals, scientists confirmed the waves’ presence and ruled out other causes, such as weather or tides.
- This study provided the first solid observational evidence that fjord seiches can trigger widespread seismic effects, linking ocean dynamics to crustal movement thousands of miles away.
- Researchers emphasized the role of climate change in creating these extreme events and highlighted the power of new satellite tools in monitoring Earth’s most remote and dynamic environments.
In September 2023, a strange seismic signal was detected worldwide, occurring every 90 seconds for nine days. This unusual pattern was repeated a month later, prompting scientists to investigate its origin. Researchers proposed that the signal could be caused by mega-tsunamis triggered by massive landslides in an East Greenland fjord. These tsunamis trapped waves in the fjord, forming standing waves known as seiches. These waves move back and forth and could explain the seismic anomalies. However, until now, no direct observations have confirmed this theory.
In a new study published in Nature Communications, researchers from Oxford University used advanced satellite technology to gather data that could confirm the presence of these waves. The team utilized the Surface Water Ocean Topography (SWOT) satellite, launched in 2022, to measure the height of water across the Earth’s surface with remarkable precision. Unlike previous satellites, SWOT uses a cutting-edge radar instrument that provides highly detailed 2.5-meter resolution data over a 30-mile-wide area. By analyzing this data, researchers could map water levels in the Greenland fjord and detect clear, back-and-forth motion of the water, which aligned with the patterns expected from seiches.
The researchers were able to link these observations to small shifts in Earth’s crust measured by seismic data from thousands of miles away. This allowed them to reconstruct the properties of the waves, even during periods when the satellite did not capture the data. They also accounted for weather conditions and tidal movements, ruling out other potential causes such as wind or tides. This combination of satellite data and seismic information provided solid evidence for the seiche theory, offering a rare glimpse into this natural phenomenon.
Lead author Thomas Monahan, a DPhil student at Oxford, emphasized this research’s significance, highlighting how climate change is driving new, extreme events, particularly in remote areas like the Arctic. This study shows how new satellite technologies, such as SWOT, can be leveraged to study oceanic processes in regions where traditional methods struggle. Professor Thomas Adcock, co-author of the study, added that these advancements would provide new insights into extreme ocean events like tsunamis, storm surges, and freak waves. With further innovations in data analysis, researchers can continue to unlock the mysteries of our planet’s most extreme natural occurrences.
References
- Monahan, T., Tang, T., Roberts, S., & Adcock, T. A. A. (2025). Observations of the seiche that shook the world. Nature Communications, 16(1), 4777. https://doi.org/10.1038/s41467-025-59851-7
- University of Oxford. (2025, June 3). Greenland’s mega tsunamis: First direct observation of the trapped waves that shook the world. Phys.Org; University of Oxford. https://phys.org/news/2025-06-greenland-mega-tsunamis-shook-world.html
