Some discoveries start like in Hollywood movies, with a scientist detecting a strange signal on the screen and his gesture breaking down. Something similar happened to Kristian Svennevig and his team at the Geological Survey of Denmark and Greenland (GEUS) when in September 2023 they discovered a seismic signal of unknown origin. It was a completely different recording from those left by earthquakes or volcanic eruptions, containing only a single vibration frequency, like a monotonous hum that lasted nine days.
Several months of work later, and after involving 68 scientists from 40 institutions in 15 countries, the researchers were able to reconstruct the data to discover the source of the signal, which was recorded by highly sensitive sensors around the planet, from the Arctic to Antarctica. The conclusion is that what happened was the consequence of a disaster that occurred on September 16 in Greenland and that there were no deaths, by chance.
That day, the summit of a 1,200-metre mountain in Dickson Fjord collapsed, causing a colossal avalanche of rock and ice that carried away more than 25 million cubic metres and raised a 200-metre tsunami when it hit the water. The vibration could be detected all over the planet. Its origin? The erosion of the base of the glaciers due to global warming.
The fjord is located on a route commonly used by tourist cruises, but fortunately that day there were none in this region of Greenland. Scientists are calling for vigilance in the face of possible situations of this type that put people’s lives at risk and that will become increasingly frequent due to the increase in temperatures.
A “world bell”
In a book published this Thursday in the magazine ScienceThe researchers describe how the material gained strength as it was channeled through the ravine and, when it hit the waters, produced an initial 200-metre wave that reverberated across the fjord, where high waves lasted as if they were nine days of someone shaking the inside of a bathtub (known in geology as a seiche).
“The signal was very strange and lasted nine days,” Esteban Chaves, a researcher at the Volcanological and Seismological Observatory of Costa Rica (OVSICORI-UNA) and co-author of the work, told elDiario.es. “We started looking at other stations nearby and it was also seen; we extended the distance and we continued to see each other. It is observed not only in Greenland, but also in Europe, the United States, Costa Rica and even Antarctica.
The impact was not only recorded on seismographs around the world, the researchers also obtained data from a ship that sailed several kilometres from the area. They also found evidence that four-metre-high tsunami waves damaged the research base on the island of Ella Ø, 70 km away, and destroyed cultural and archaeological heritage sites throughout the fjord system.
“The next step was to look for satellite images and go out there to observe the area with a drone,” Chaves says. “What we saw was very clear. It’s like you have a mountain made of earth and ice and you cut it in two. “It just disappeared.”
It’s like you have a mountain made of dirt and ice and you cut it in two. It just disappeared.
Esteban Chaves
— OVSICORI-UNA researcher and co-author of the work
The scientists themselves could have been there at the time of the collapse, as they visit the area from time to time. “We sailed to Dickson Fjord last year to set up instruments right in front of the mountain a few weeks before it collapsed,” says Søren Rysgaard of Aarhus University and co-author of the study. “It’s strange to think that the entire fjord was flooded by such a giant wave shortly afterward. Fortunately, our instrument survived and we were able to follow the events in real time.”
culprit: global warming
Evidence collected by the team shows that the slide was caused by the thinning of glaciers at the base of the mountain in recent decades, ultimately triggered by climate change. Numerical simulations, data from the local oceanographic sensor network and satellite images confirm that the resulting megatsunami is one of the largest in recent history.
Never before, anywhere on Earth, have we directly recorded a multi-day water oscillation caused by a single event.
Stephen Hicks
— Researcher at University College London and co-author of the study
“This is the first landslide and tsunami observed in East Greenland, which shows that climate change is already having significant impacts there,” says Svennevig. “Never before, anywhere on Earth, have we directly recorded a multi-day water oscillation caused by a single event that lasted only a few minutes, in this case a landslide and an ice slide,” he adds. Stephen Hicksresearcher at University College London and co-author of the study.
“When the thaw occurs, these fluids infiltrate the ground and produce fractures that serve as channels through which they move from the most superficial to the deepest part of the mountain,” explains Esteban Chaves. “This landslide marks a before and after. Now we have to pay attention to the polar ice caps, but also closer to the tropics, where extreme rains can cause the same effect.”
The study concludes that with the rapid acceleration of climate change, it will be more important than ever to characterize and monitor regions previously considered stable and provide early warning of massive landslides and tsunamis.
We must be vigilant
For geologist and popularizer Nahúm Méndez Chazarra, the article is very interesting because it is able to establish a clear link between global warming and the appearance of potentially very dangerous geological disasters. “They are capable of causing tsunamis that can reach, as in this case, 200 meters high, because the fjords serve as a funnel that amplifies it, potentially causing a lot of damage, even deaths.”
This is not the first time this has happened, the specialist recalls. “In 2017, on the west coast of Greenland, the municipality of Nuugaatsiaq had to be abandoned after a landslide caused a tsunami reaching 100 metres high and killing four people,” he says. “What can we learn as a lesson? “We need to focus on monitoring this type of phenomenon, because if global warming accelerates as predicted, these types of events will become more and more common.”
It is likely that we will see more of this type of phenomenon due to warming in Greenland. We will have to be vigilant.
Raul Perez
— Geologist IGME-CSIC
Raúl Pérez, a geologist at the Geological and Mining Institute of Spain (IGME-CSIC), particularly appreciates the collaboration of dozens of experts that this work required to follow the signal. “They only pulled a tiny thread and were faced with a phenomenon of global change for which we are largely responsible,” he says. “It is likely that we could see more phenomena of this type if warming continues in Greenland due to increasingly frequent atmospheric rivers. We will have to be vigilant,” he concludes.
