A landslide east of Greenland generated a mega-tsunami which vibrations were recorded around the world for nine days. The cause: global warming, which is weakening the Arctic.
Somewhere in a remote, uninhabited Arctic fjord, 25 million m3 of rock and ice collapse, triggering a 110-metre-high mega-tsunami. As the wave spread across the fjord, a 4-metre-high wall of water hit a research station 70km away. On a planetary scale, the shock was recorded in the form of oscillations that shook the Earth, from the Arctic to the Antarctic, for nine days.
This story could have been taken from one of those Hollywood disaster movies, but it’s not. The event is very real and took place in Greenland in September 2023. At least, that’s what a multi-disciplinary team of researchers reports, with results published on 12 September in the publication Science.
But what really happened? In September 2023, a huge pile of rock collapsed into Dickson Fjord. The 25 million m3 of rock and ice tumbled down the 1 200 metres separating them from the waters of the fjord. The impact is violent. Water splashes up to 200 metres high, and the landslide triggers a mega-tsunami with waves up to 110 metres high.
In the minutes that followed, the wave travelled 10 km across the fjord, losing height to reach a height of seven metres. Continuing its course, the wave reached and damaged a research station located 70 km from the initial landslide, on Ella Island. Other cultural and archaeological heritage sites along the fjord will also be destroyed.
In the days that followed, the wave was reduced to a few centimetres. Trapped in a narrow, winding fjord, it nevertheless retained enough energy to continue moving back and forth. This oscillating movement, known as seiche, which occurs at regular 90-second intervals, will then generate vibrations in the Earth’s crust, recorded by seismometers.
In the form of a monotonous-sounding hum, far from the usual rumbles and pings characteristic of earthquakes, the vibrations recorded intrigued scientists determined to find an explanation for the phenomenon: “When I first saw the seismic signal, I was completely baffled.”, says Dr. Stephen Hicks of UCL Earth Sciences, in a press release issued by University College London on 13 September. “Even though we know seismometers can record a variety of sources happening on Earth’s surface, never before has such a long-lasting, globally travelling seismic wave, containing only a single frequency of oscillation, been recorded. This inspired me to co-lead a large team of scientists to figure out the puzzle.”
Global warming is to blame
To reconstruct the event, a multidisciplinary international team was set up. Sixty-eight scientists from 40 institutions in 15 different countries joined forces to explain the phenomenon. Using a detailed mathematical model, and taking into account the topography of the site and the angle of the collapse, the research team was able to reconstruct the landslide by combining seismometric and infrasound data, field measurements, on-the-ground and satellite imagery, and simulations of tsunami waves.
And for scientists, there’s no doubt that the landslide and tsunami are linked to global warming. Thinned by rising temperatures, the glacier at the foot of the mountain could no longer support the rock face above it. The rock then collapsed, generating this major landslide. The first observed in this part of Greenland: “As a landslide scientist, an additional interesting aspect of this study is that this is the first-ever landslide and tsunami observed from eastern Greenland, showing how climate change already has major impacts there.”, said Dr Kristian Svennevig, lead author of the study and member of the Geological Survey of Denmark and Greenland (GEUS) in the same press release issued by UCL.
The Arctic is particularly hard hit by climate change, which is causing temperatures to rise and could well lead to further events of this kind. With potentially dramatic consequences. Despite its vast, isolated expanses, the Arctic is nonetheless an inhabited and frequented region. Dickson Fjord, for example, is on the itinerary of expedition cruises, and the toll could have been much higher had a ship been close by.
In addition, there are several villages and buildings in the fjords. Damage to the scientific station on Ella Island, located 70 km from the landslide site, already gives an idea of the damage such phenomena could inflict on local populations and infrastructure. Hence the need, according to the study’s authors, for close monitoring of Arctic regions to provide early warnings of landslides and mega-tsunamis.
Link to article: Kristian Svennevig et al, A rockslide-generated tsunami in a Greenland fjord rang Earth for 9 days.Science385,1196-1205(2024).DOI:10.1126/science.adm9247
Mirjana Binggeli, Polar Journal AG
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