A 200-meter-high mega-tsunami in Greenland shook seismometers around the world for 9 days

In the remote Dickson Fjord, In north-east Greenland, a catastrophic event occurred that resonated globally. The top of a mountain collapsed causing a massive landslide that generated a mega-tsunami. The waves, up to 200 meters high continued to swing inside the fjord for nine days, recording a seismic signal never observed before.

The contemporaneity of the two events has pushed researchers from numerous research institutions and universities around the world to collaborate to try to understand if there was actually a cause-effect relationship. Italy also took part in the research through the National Institute of Geophysics and Volcanology (INGV), the University of Catania and the University of Padua.

“Our search began in September 2023, when a mysterious 9-day-long seismic signal was discovered in recordings from seismic stations around the world, from the Arctic to the Antarctic.“, explains Flavio Cannavò, researcher at INGV and co-author of the study. “We immediately noticed, however, that the signal appeared completely different from the seismic signals that are recorded in the event of an earthquake: in fact, it contained a single vibration frequency, similar to a monotonous-sounding buzz.“.

The multidisciplinary team then analyzed seismic and infrasound data, field measurements, data from the local network of oceanographic sensors, live and satellite images, and numerical simulations of tsunami waves, managing to reconstruct the extraordinary cascade of events triggered in September last year. The result, “A rockslide-generated tsunami in a Greenland fjord rang the Earth for 9 days” published in the prestigious journal “Science”, saw the collaboration of 68 scientists from 40 institutions in 15 countries.

“When we started this scientific adventure we were all quite perplexed and none of us had the faintest idea of ​​what had caused that particular seismic signal: we only knew that it was somehow associated with the landslide.“, racconta Kristian Svennevig, del Geological Survey of Denmark and Greenland (GEUS)first author of the article. “This was the first landslide and tsunami due to melting ice ever observed in eastern Greenland, demonstrating that climate change is already having a strong impact on that area too.“.

The results of the reconstruction carried out by the researchers showed that, Inside the fjord, the water followed an oscillatory motion repeated every 90 seconds, the same oscillation period recorded by seismic waves. The correspondence of the two phenomena has highlighted how the force of the mass of moving water was able to generate seismic energy. propagated in the Earth’s crust. The oscillatory motion continued for 9 days, before losing intensity and strength.

“It is astonishing that what began as a routine check of a Belgian gravity sensor has turned into a global, multidisciplinary collaboration, with virtual exchanges online 24/7, spanning multiple time zones. In total, more than 8,000 messages were exchanged. In summary, they amount to more than 1 million typed characters: the length of a 900-page detective novel.“, racconta Thomas Lecocq, del Royal Observatory of Belgium (ROB) and co-author of the research.

“It is extraordinary how, nowadays, it is possible to easily assemble an international team with heterogeneous skills to solve complex problems and manage to explain phenomena never documented before in a short time”explains Andrea Cannata, researcher at the University of Catania and co-author of the study. “In particular, it was discovered that The landslide that started it all was caused by the collapse of over 25 million cubic meters of rock and ice into the fjordan amount sufficient to fill 10,000 Olympic-sized swimming pools. The collapse, in turn, was caused by the thinning, which occurred over the decades, of the ice at the base of the mountain overlooking the fjord, a clear expression of the effects of climate change.“.

“Multidisciplinary data analyses confirmed that The mega-tsunami resulting from the landslide was one of the highest ever recorded in recent history, reaching 200 meters of waves inside the fjord. About 70 kilometers away, tsunami waves reached 4 meters high, damaging a research base on the island of Ella Ø
“, adds Piero Poli, researcher at the University of Padua and co-author of the study.”The movement of such a mass of water was able to generate vibrations through the Earth, with seismic waves that, radiating from the Arctic to the Antarctic, generated an anomalous global seismic signal. This event underlines the importance of creating special systems for monitoring seismic data at a global scale, which allow the rapid identification and characterization of new and increasingly frequent signals associated with surface processes, such as landslides and rapid movements of ice or fluids, associated with climate change.o”.

“As is known, the melting of the polar ice caps, which we have identified as the ‘latent’ cause of the incredible sequence of events recorded in Dickson Fjord last year, is due to climate change The rapid acceleration of this phenomenon in recent years requires us to pay ever greater attention to the characterization and monitoring of those regions considered ‘stable’ until a few years ago, as well as to the development of systems capable of providing early warning in the event of landslides and tsunamis.“, concludes Flavio Cannavò.