Unprecedented Seismic Waves Detected Following Greenland Landslides

Global Seismic Activity Traced to Greenland's Dickson Fjord

In September 2023, a remarkable seismic event captured the attention of researchers worldwide. An ultra-low frequency vibration, detected at 10.88 millihertz, persisted for nine days and was later traced back to Dickson Fjord in East Greenland. This event was triggered by two substantial landslides that unleashed tsunamis and initiated an unusual, long-lasting seiche—a standing wave phenomenon.

Understanding the Origin of Seismic Vibrations

Seismic sensors across the globe registered this very-long-period (VLP) seismic signal, which returned a month later, prompting further investigation. Using advanced tools, researchers were able to identify that the primary source of these vibrations was indeed a seiche oscillating within the fjord itself. This groundbreaking discovery marks the first time that scientists have directly observed a fjord seiche through satellite imaging, employing data from NASA’s Surface Water and Ocean Topography (SWOT) mission.

Innovative Research Methodology

The research team from the University of Oxford amalgamated satellite data, seismic records, and Bayesian machine learning techniques to validate a natural occurrence that previous models had only hypothesized. A seiche, which characteristically forms in enclosed basins such as fjords, lakes, or harbors, is typically shorter in duration; however, the one observed in this incident lasted significantly longer, producing seismic signals strong enough to be detected internationally.

Instrumental Measurements Post-Landslide

Following the first landslide on September 16, 2023, the SWOT satellite conducted several passes over Dickson Fjord, including a key pass approximately 12 hours post-event. The satellite’s Ka-band Radar Interferometer (KaRIn) captured detailed measurements of the water’s surface, revealing subtle yet consistent tilts that align with the characteristics of a standing wave.

• The maximum cross-channel slope was estimated at approximately 1.83 ± 0.59 m per km, correlating with earlier analytical predictions.
• The initial amplitude of the observed seiche was approximated at 7.9 m (26 feet).

Weeks later, in October, a subsequent, smaller landslide occurred in the same region, once again activating the seiche and producing a weaker seismic signal detected by SWOT, further validating the team’s conclusions and solidifying their findings.

Examining Alternative Explanations

In their thorough investigation, the researchers ensured that the observed wave motion was not merely a result of tidal action or local wind. By analyzing tidal models and local weather data, they conclusively ruled out these influences, enhancing their argument that the observed water motions were definitively characteristic of a seiche.

Implications for Future Ocean Studies

One of the major breakthroughs from this research is the realization that satellite altimetry, typically reserved for monitoring gradual oceanic shifts, can also effectively capture rapid, localized events in coastal systems. Professor Thomas Adcock, a co-author of the study, described this discovery as a game-changer for understanding extreme ocean phenomena. He emphasized the necessity of integrating machine learning and oceanic physics knowledge to harness the full potential of these next-generation satellite observations.

Conclusion

This unprecedented observation not only provides a clearer understanding of the events at Dickson Fjord but also opens new avenues for research into ocean dynamics in remote regions. The insights gained could enhance our understanding of extreme oceanic occurrences, from tsunamis to sudden storm surges, crucial for future monitoring and disaster preparedness.