A huge landslide triggered by climate change rocked the Earth for 9 days
In September 2023, a massive landslide in Greenland generated a mysterious seismic signal that was detected worldwide for nine days. A volume of 25 million m³ of rock and ice collapsed in the isolated Dickson Fjord in eastern Greenland, triggering a 200 metre high tsunami.
This tsunami caused the fjord to oscillate for several days, forming a phenomenon known as “seiche”. The movements of these masses of water generated unusual seismic waves, recorded all over the world, from Greenland to Antarctica, emitting a curious harmonic hum.
Surprised by these signals, the seismologists collaborated with researchers from different disciplines. An international team in which the IPGP is involved (see below), made up of 68 scientists from 40 institutions and 15 countries, was set up to investigate this event. They combined various sources of data: seismic recordings, infrasound sensors, satellite images and tsunami simulations. Photographs of the region taken by the Danish army a few days after the collapse were also used to assess the damage.
The investigation revealed that the collapse of the mountain, which was once 1.2 km high, was due to glacial retreat caused by climate change. The volume of collapsed rock was titanic, equivalent to 10,000 Olympic swimming pools or 220,000 semi-trailers – a line of lorries stretching 3,700 km! The resulting tsunami was one of the most impressive seen in recent years. Seventy kilometres from the site of the collapse, four-metre waves damaged a research base and destroyed several archaeological and cultural sites.
Dickson Fjord, usually frequented by cruise ships, was fortunately deserted at the time of the tsunami. The findings of this study highlight the link between natural events occurring in isolated areas and their repercussions on a global scale. They also highlight the central role of climate change in such disasters, reminding us of the importance of better anticipating these events to protect populations and ecosystems.
The IPGP fully involved
The involvement of the IPGP in this study is crucial on multiple levels. As the organization responsible for the GEOSCOPE seismic network, the IPGP played a key role in identifying the atypical signal.
The rock avalanche phase was meticulously studied through satellite observations and in-situ imaging, allowing the teams from PSS, GEE, and seismology to characterize the terrain’s morphology and obtain high-resolution topography. Numerical simulations then confirmed the inversions of seismic signals in collaboration with the University of Strasbourg.
Numerous tsunami simulations were also carried out at the IPGP, particularly to identify the triggering factors behind the observed phenomenon. This work was further enriched by a sensitivity analysis on bathymetry, also conducted by IPGP members.
Meanwhile, members of the seismology team modeled the seismic signal generated by the seiche in the fjord, contributing to a more in-depth understanding of the process.
Ref: Kristian Svennevig et al., A rockslide-generated tsunami in a Greenland fjord rang Earth for 9 days. Science 385, 1196-1205 (2024). DOI: 10.1126/science.adm924
