Study Details How a Massive Tsunami in East Greenland Reverberated Across the Globe
A recent study led by Kristian Svennevig and a team of international researchers reveals that a massive rockslide in East Greenland in September 2023 triggered a tsunami that sent seismic waves ringing around the globe for nine days. Published in Science, the research uncovers how a rock-ice avalanche plunged into Dickson Fjord, generating a 200-meter-high tsunami that evolved into a long-duration seiche—an oscillating wave trapped in the fjord. This event was so powerful that it produced a unique, 92-second very-long-period (VLP) seismic signal detectable worldwide.
The team, comprising experts from Denmark, Germany, and the United States, used satellite imagery, field data, and numerical simulations to reconstruct the sequence of events that began with a climate change-induced rockslide and ended with a tsunami-driven seiche. Their findings shed light on the complex interactions between glaciers, landslides, and ocean systems in a rapidly warming Arctic.
A Tsunami Born of Ice and Rock
The event began on September 16, 2023, when a 25-million-cubic-meter section of rock, destabilized by glacial thinning, broke away from a mountain peak 1,200 meters above Dickson Fjord. The rockslide triggered a rock-ice avalanche, as massive chunks of ice were torn from the glacier, and plunged into the fjord. The impact created a tsunami with an initial wave height of 200 meters, one of the highest ever recorded in Greenland.
This tsunami caused widespread damage, including the destruction of historical sites and research stations in the region. Simulations suggest that the tsunami stabilized into a 7-meter-high seiche, an oscillating wave that persisted in the fjord for days, producing a continuous seismic signal that was recorded as far as 10,000 kilometers away.
Seismic Signals and Climate Change’s Ripple Effects
What makes this event particularly significant is the seismic signature it left behind. The long-period seismic waves were monochromatic, meaning they had a single, consistent frequency of 10.88 millihertz, which persisted for nine days. This type of seismic signal is rare and provided scientists with an unprecedented opportunity to study how oceanic processes, like seiches, can generate global seismic activity.
Climate change played a critical role in this event. As glaciers retreat and ice thins, slopes that were once stabilized by ice become prone to collapse, triggering landslides that can have far-reaching consequences. This study highlights the cascading effects of climate change in the Arctic, where warming temperatures are increasingly setting off hazardous chain reactions involving the Earth’s cryosphere, hydrosphere, and lithosphere.
Understanding Seiches: A Rare Phenomenon
The study provides new insights into the phenomenon of seiches, which are long-duration waves that form in enclosed or semi-enclosed water bodies. The team’s simulations show that the seiche formed in Dickson Fjord had a frequency of 11.45 millihertz, close to the seismic signal’s 10.88 millihertz frequency. The research demonstrated how this wave’s oscillation, driven by the fjord’s unique geometry, was responsible for the prolonged seismic activity.
By using high-resolution bathymetric data, the scientists were able to model the tsunami’s impact and the subsequent seiche, revealing how the confined nature of the fjord amplified the event’s effects. The results underscore the importance of understanding fjord dynamics in assessing the risks posed by landslides and tsunamis in polar regions.
Implications for Future Hazards in Polar Regions
This research has profound implications for the future of Arctic regions as climate change accelerates. The findings highlight the need for increased monitoring of glacial and mountainous regions in Greenland and other polar areas, where landslides and tsunamis could become more frequent. With glaciers receding at unprecedented rates, the risks of further rockslides and associated tsunamis are likely to rise.
The team calls for the installation of high-sampling-rate sea-level gauges and seismic sensors in fjords and other vulnerable areas to detect these events in real-time. Better monitoring could help mitigate the risks posed by such natural disasters, protecting both local communities and vital infrastructure.
Conclusion: A Global Signal from the Arctic’s Melting Ice
The September 2023 rockslide-tsunami event in East Greenland is a stark reminder of the cascading effects of climate change in the polar regions. As glaciers retreat and permafrost melts, the stability of the surrounding landscapes is increasingly threatened. This study not only offers a new understanding of the interactions between rockslides, tsunamis, and seiches but also underscores the global reach of these seemingly localized events.
With seismic signals from the Arctic ringing the Earth for days, the message is clear: the impacts of climate change in the polar regions are not confined to the poles but can reverberate across the entire planet.
Source: A rockslide-generated tsunami in a Greenland fjord rang Earth for 9 days