Global Seismic Mystery Resolved
On September 16, 2023, the world was startled by a peculiar seismic signal that reverberated with a relentless rhythm every 90 seconds for a full nine days. Following this, an almost identical signal returned a month later and persisted for another week before vanishing. Now, scientists have uncovered that these seismic anomalies were the result of two monumental landslides in a remote fjord in East Greenland.
The Genesis of Mega-Tsunamis
These landslides unleashed rock-ice avalanches, generating mega-tsunamis that surged to heights of up to 200 meters, even causing damage to an unoccupied military base in the area. The phenomenon of interest was identified as a “seiche” (pronounced "saish"), which are standing waves that oscillate back and forth in a body of water, producing long, resonating signals akin to a drum.
Interestingly, a Danish military vessel conducting research in Dickson Fjord just three days after the first seismic event failed to observe any such wave, leading researchers to rely primarily on analytical and numerical models until now.
Next-Gen Satellite Confirmation
In a recent breakthrough study published in Nature Communications, researchers utilized state-of-the-art satellite technology data from the Surface Water Ocean Topography (SWOT) satellite to confirm the presence of these standing waves, revealing fluctuations in water levels by as much as two meters.
According to Thomas Monahan, a PhD student in the Department of Engineering Science at the University of Oxford and the study's lead author, "These extremes are changing the fastest in remote areas, such as the Arctic, where our ability to measure them using physical sensors is limited. This study illustrates how emerging satellite Earth observation technologies can effectively study these processes. ”
Innovations in Satellite Measurements
The SWOT satellite, launched in December 2022, employs a cutting-edge Ka-band Radar Interferometer that allows for unprecedented accuracy in measuring ocean and surface water levels over a wide area. The technology surpasses conventional satellite altimeters, which weren't sensitive enough to detect subtle standing waves. This advancement has allowed the research team to construct detailed elevation maps of the Greenland fjord.
These maps revealed opposing cross-channel slopes, indicating that water was moving back and forth across the channel, confirming the presence of the seiches.
Understanding Climate Change Impacts
These findings signal not only a resolution to a scientific mystery but also a stark reminder of the rapidly changing dynamics caused by climate change. With ongoing ice melt from Greenland’s glaciers, the frequency of glacier-related landfalls and subsequent tsunamis is likely to increase, posing new risks.
As co-author Professor Thomas Adcock emphasized, "This study exemplifies how next-generation satellite data can address phenomena that have remained enigmatic. Insights into ocean extremes, such as tsunamis and storm surges, can be gleaned through these innovative technologies, but we must also employ machine learning and physics to fully interpret the results."
Looking to the Future
The implications of this research stretch far beyond understanding past seismic events. It highlights the urgent need for investments in satellite technologies to monitor and respond to the evolving threats posed by climate change. As we enter an era of unprecedented change in the Arctic, continuous observations will be essential for safeguarding environments and communities against the new extremes borne from a warming planet.
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