Greenland's 650-Foot Mega-Tsunami Lasted for Nine Days: What Caused the Wave, How Scientists Solved the Mystery. On September 16, 2023, a colossal landslide in Greenland’s remote Dickson Fjord triggered a mega-tsunami with waves reaching nearly 200 meters (650 feet), an event so powerful it sent seismic vibrations reverberating across the globe for nine days. Unlike typical tsunamis that dissipate within hours, this wave, trapped in the fjord’s steep, narrow walls, oscillated relentlessly, creating a rhythmic pulse that baffled scientists worldwide.
Through a combination of advanced satellite technology, seismic data, and interdisciplinary collaboration, researchers unraveled the mystery of this unprecedented event. The findings, driven by data from NASA and France’s CNES Surface Water and Ocean Topography (SWOT) satellite, not only revealed the mechanics of the tsunami but also underscored the growing threat of climate-driven instability in the Arctic. This article explores the causes of the mega-tsunami, the scientific detective work that solved the mystery, and the broader implications for a warming world.
The Catastrophic Trigger: A Climate-Driven Landslide
The mega-tsunami’s origin lies in a massive landslide that occurred on September 16, 2023, when approximately 25 million cubic meters of rock and ice—equivalent to the volume of 25 Empire State Buildings or 10,000 Olympic-sized swimming pools—plummeted from a 1,200-meter-high mountain peak into Dickson Fjord. This catastrophic collapse was not a random geological event but a direct consequence of climate change.
Decades of global warming had thinned the glacier at the base of the mountain, a process known as glacial debuttressing, where the retreat of ice removes the structural support for the rock above. As Greenland’s glaciers melt at an alarming rate—losing an estimated 30 million tonnes of ice per hour due to rising global temperatures—the slopes they once stabilized become increasingly prone to collapse.
The landslide itself was a cascading hazard, as described by Kristian Svennevig, a geologist at the Geological Survey of Denmark and Greenland (GEUS). The melting glacier destabilized the mountain, causing a rockslide that swept part of the glacier into the fjord. This rock-ice avalanche, traveling at a peak velocity of 42 meters per second, plunged into the water, displacing an immense volume and triggering the initial 200-meter-high wave.
The fjord’s steep walls, towering over 1,830 meters (6,000 feet), and its narrow width of 2.7 kilometers (1.7 miles) created a confined environment where the wave’s energy could not easily dissipate. Instead, it transformed into a seiche—a standing wave that oscillates back and forth like water sloshing in a bathtub—sustaining its motion for nine days.
The event’s scale was unprecedented in eastern Greenland, a region previously thought to be geologically stable. The landslide scoured vegetation from the fjord’s shores and left a visible sediment mark on the glacier, evidence of the wave’s extraordinary height. While no human lives were lost—owing to the remote location—the tsunami caused approximately $200,000 in damage to an unoccupied research station on Ella Island, 70 kilometers away. The event also highlighted the potential danger to Arctic cruise ships that frequent these fjords, raising concerns about future risks as climate change accelerates.
A Global Seismic Mystery
The landslide and tsunami would have been remarkable enough, but what truly captured the attention of the global scientific community was the seismic signal it produced. Beginning on September 16, 2023, seismometers worldwide, from the Arctic to Antarctica, detected a monotonous, low-frequency vibration oscillating every 90 seconds.
Unlike the complex, high-frequency patterns of earthquakes, which typically last minutes or hours, this signal—classified as a very long period (VLP) seismic event—was a single, rhythmic hum that persisted for nine days. Initially dubbed an “unidentified seismic object” (USO) by researchers, it defied all known patterns of seismic activity.
Stephen Hicks, a seismologist at University College London and co-author of the study published in Science, described the signal as “completely unprecedented.” The vibrations traveled globally within an hour, a testament to the event’s magnitude. Seismologists were initially baffled, with some suspecting their instruments were malfunctioning.
The signal’s consistency and duration suggested a source far different from typical geological events, prompting a global investigation involving 68 scientists from 41 institutions across 15 countries.
The seismic data alone could only narrow the source to eastern Greenland, but local reports of a tsunami in Dickson Fjord provided a crucial clue. The challenge was to connect the seismic signal to the physical processes in the fjord, a task that required integrating diverse data sources and advanced technology.
The SWOT Satellite: A Game-Changer in Observation
The breakthrough in solving the mystery came from the Surface Water and Ocean Topography (SWOT) satellite, a collaborative mission between NASA and France’s Centre National d’Études Spatiales (CNES), with contributions from the Canadian Space Agency and the UK Space Agency.
Launched in December 2022, SWOT is designed to measure the height of water surfaces worldwide using its Ka-band Radar Interferometer (KaRIn), which provides high-resolution data even in narrow bodies of water like fjords. On September 17, 2023, just one day after the landslide, SWOT passed over Dickson Fjord, capturing critical water elevation measurements.
The satellite data revealed a striking pattern: water levels on the northern side of the fjord were up to 1.2 meters (4 feet) higher than on the southern side, indicating a significant tilt caused by the oscillating wave. By comparing these measurements to baseline data taken on August 6, 2023, under normal conditions, researchers confirmed the presence of a seiche.
Josh Willis, a sea level researcher at NASA’s Jet Propulsion Laboratory, noted, “SWOT happened to fly over at a time when the water had piled up pretty high against the north wall of the fjord… Seeing the shape of the wave—that’s something we could never do before SWOT.” The KaRIn instrument’s ability to resolve water heights in the fjord’s narrow confines was pivotal, as previous satellites lacked the resolution to observe such phenomena.
A second landslide in the same area on October 11, 2023, produced a smaller tsunami and a weaker seismic signal, but SWOT’s timely pass provided additional data. This time, researchers estimated the seiche’s initial amplitude at approximately 7.9 meters (26 feet), with a maximum cross-channel slope of 1.37 meters per kilometer.
By correlating these observations with seismic data from a station 1,300 kilometers away in Alert, Canada, the team reconstructed the wave’s dynamics, confirming that the seiche was responsible for the global vibrations.
The Role of the Fjord’s Geography
Dickson Fjord’s unique geometry was critical to the tsunami’s extraordinary duration. Measuring 1.7 miles wide and 1,772 feet deep, with walls exceeding 6,000 feet, the fjord acts as a natural resonance chamber. Unlike open-ocean tsunamis, which dissipate energy rapidly, the wave in Dickson Fjord was trapped, sloshing back and forth approximately every 90 seconds. This rhythmic motion, known as a seiche, generated the seismic vibrations detected globally. The fjord’s rounded bottom and complex, zigzag shape further reduced resistance, allowing the wave to persist with minimal energy loss.
Supercomputer simulations, conducted by researchers like Alice Gabriel from UC San Diego’s Scripps Institution of Oceanography, modeled the tsunami’s behavior with unprecedented resolution. These simulations matched the observed wave heights and oscillation periods, confirming that the seiche was the source of the seismic signal.
Anne Mangeney, a landslide modeler at the Institut de Physique du Globe de Paris, emphasized that the event challenged existing tsunami models, requiring new approaches to simulate such long-lasting phenomena.
Climate Change as the Underlying Culprit
The Dickson Fjord event is a stark reminder of climate change’s far-reaching impacts. The glacier’s thinning, driven by accelerated warming in the Arctic, destabilized the mountain, setting off a chain reaction: glacier retreat, landslide, tsunami, and seiche. Arctic regions are warming at a rate up to four times faster than the global average, making such events more likely. As permafrost thaws and glaciers recede, previously stable slopes become vulnerable, increasing the risk of landslides and tsunamis in Greenland, Alaska, Canada, and Norway.
Kristian Svennevig warned that while the Dickson Fjord event does not confirm a definitive trend, its scale underscores the need for further research. Previous incidents, such as the 2017 Karrat Fjord tsunami in western Greenland, which killed four people, highlight the potential for devastation. The absence of cruise ships in Dickson Fjord during the 2023 event was fortunate, but the fjord’s proximity to tourist routes raises concerns about future risks.
Scientific Collaboration and Technological Innovation
Solving the mystery required an extraordinary interdisciplinary effort. The team combined seismic data, satellite imagery from SWOT and Copernicus Sentinel-2, photographs from the Danish Navy, and field measurements. Supercomputer simulations reconstructed the landslide’s trajectory and the tsunami’s evolution, while Bayesian machine learning helped correlate satellite and seismic data. The collaboration, involving experts from seismology, geophysics, oceanography, and glaciology, demonstrated the power of integrating diverse datasets to understand complex natural phenomena.
The SWOT satellite’s role was particularly transformative. Its ability to measure water heights in narrow fjords provided insights unattainable with earlier technologies. Lee-Lueng Fu, SWOT’s project scientist, noted that the KaRIn instrument’s resolution was fine enough to capture the wave’s contours between the fjord’s steep walls. This capability not only solved the mystery but also highlighted SWOT’s potential for monitoring hazards in remote regions, aiding disaster preparedness.
Implications for the Future
The Dickson Fjord mega-tsunami is a wake-up call for the scientific community and policymakers. As climate change destabilizes Arctic landscapes, the frequency and scale of such events are likely to increase. Similar risks exist in other polar and mountainous regions, such as Alaska’s Barry Arm fjord, where unstable slopes threaten coastal communities. The 2023 event’s global seismic impact—vibrations detected from Greenland to Antarctica within an hour—underscores the interconnectedness of Earth’s systems and the far-reaching consequences of climate change.
Researchers advocate for enhanced monitoring of vulnerable regions using seismic networks and satellite technology. The global network of high-fidelity seismic stations proved invaluable in detecting the event, and SWOT’s success suggests that satellites can play a critical role in early warning systems. Paula Snook, a landslide geologist at the Western Norway University of Applied Sciences, emphasized that the Arctic is entering “uncharted waters,” requiring new scientific approaches to predict and mitigate these hazards.
The 2023 Dickson Fjord mega-tsunami, triggered by a climate-induced landslide, was a geological event of staggering scale and duration. Its 650-foot waves, sustained for nine days by the fjord’s unique geography, sent seismic ripples across the planet, challenging scientists to unravel a complex puzzle. The SWOT satellite, combined with seismic data and international collaboration, provided the key to understanding this unprecedented phenomenon. Beyond its scientific significance, the event serves as a stark warning of climate change’s destabilizing effects on Arctic landscapes. As glaciers continue to melt and slopes weaken, the risk of similar disasters grows, urging the global community to invest in monitoring, research, and preparedness to mitigate future threats.
Event Details
Date: September 16, 2023
Location: Dickson Fjord, East Greenland
Trigger: Landslide of 25 million cubic meters of rock and ice
Wave Height: Up to 200 meters (650 feet) initially, with seiche amplitude of ~7.9 meters
Duration: Nine days of oscillation (seiche)
Seismic Impact: Very long period (VLP) signal detected globally every 90 seconds
Damage: $200,000 to an unoccupied research station on Ella Island
Key Technology: SWOT satellite (NASA/CNES) with KaRIn instrument
Lead Researchers: Kristian Svennevig (GEUS), Stephen Hicks (UCL), Alice Gabriel (Scripps), Josh Willis (JPL)
Publication: Science (September 2024)
Sources:
NASA Jet Propulsion Laboratory
Science journal
BBC News
The Guardian
Smithsonian Magazine
Nature Communications.
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