A massive landslide in remote Greenland caused Earth to vibrate for nine days straight, releasing an enigmatic seismic signal that left scientists in search of answers. The landslide, which occurred in September of the previous year, triggered a massive tsunami in Dickson Fjord, resulting in puzzling tremors and a global “hum,” according to scientists. This hum, which was unlike typical earthquake activity, led to an international investigation to determine its origins and possible effects.
Researchers from University College London (UCL) and other institutions eventually traced the signal to a colossal rockslide that triggered a mega-tsunami, linking the event to the climate crisis. The landslide started when a 1.2km-high mountain peak fell into the fjord, generating a 200m-tall wave through the narrow waterway.
Seismic signal with a single steady frequency
The wave, initially 110m high, created vibrations detected by seismometers worldwide, from the Arctic to Antarctica. Dr. Stephen Hicks from UCL Earth Sciences, one of the study’s co-authors, expressed his initial confusion upon seeing the seismic signal.
He noted that although seismometers can record various surface sources, such a prolonged, globally traveling seismic wave with a single frequency had never been recorded before.
The seismic signal, differing from usual earthquake activity, consisted of a single steady frequency. This unusual “hum” led scientists to categorize it as a “USO” – an unidentified seismic object. It wasn’t until researchers received reports of a tsunami in Greenland that they started to piece together the puzzle.
A team of 68 scientists from 40 institutions then worked together to reconstruct the event. By using satellite imagery, field measurements, and advanced mathematical models, they showed that the vibrations were caused by water sloshing in the fjord, a phenomenon that lasted for nine days.
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Landslide was triggered by the thinning of a glacier
According to a study published in the journal Science, the landslide was triggered by the thinning of a glacier at the mountain’s base, which could no longer support the rock above. This was a direct consequence of the climate crisis, which has significantly weakened Greenland’s glaciers.
Previous studies have shown that the Greenland ice cap is losing an average of 30m tonnes of ice per hour due to the climate crisis, resulting from rapidly increasing global temperatures caused by carbon pollution from burning fossil fuels.
Dr. Hicks remarked that the event highlights the complex interactions between atmospheric climate change, glacier destabilization, water body movements, and Earth’s crust. He noted that this was the first time water sloshing was recorded as vibrations through Earth’s crust, traveling globally and lasting several days.
Dr. Kristian Svennevig from the Geological Survey of Denmark and Greenland, the lead author, indicated that this was the first recorded landslide and tsunami in eastern Greenland. He found it particularly interesting as it was the first-ever landslide and tsunami observed in this region, showcasing the significant impact of climate change.
Landslide challenged classical numerical models
The unique tsunami tested the limits of existing scientific models for such events. Co-author Anne Mangeney from Université Paris Cité, Institut de Physique du Globe de Paris, explained that the event challenged classical numerical models, requiring unprecedented numerical resolution to simulate the long-duration event, paving the way for advancements in tsunami modeling.
The tsunami reached up to 4m high, damaging a research base 70km away and destroying cultural heritage sites.
Although no cruise ships were near the fjord at the time, researchers caution that similar events could become more frequent in the future. They stress the importance of monitoring previously considered stable geological regions to provide early warnings of such massive landslide and tsunami events.
Co-author Thomas Forbriger from the Karlsruhe Institute of Technology acknowledged that the discovery and analysis of this significant event would not have been possible without global networks of high-fidelity broadband seismic stations.
