Greenland Landslide Tsunami Sparks 9-Day Global Seismic Signal

In 2023, a massive rockslide in East Greenland, driven by glacial melt, triggered a towering tsunami and a rare global seismic signal that resonated for nine days, according to a new study. The study provides insights into how climate change-induced events like glacial thinning can lead to significant geophysical phenomena with impacts extending throughout the Earth system. Due to climate change, steep slopes are increasingly vulnerable to landslides. In Arctic regions - which are undergoing the most rapid warming globally - landslides can be driven by glacial debuttressing, permafrost degradation, and altered precipitation patterns. These landslides can trigger large and destructive tsunamis, particularly when they occur in confined water bodies like fjords. Such events have been recorded around the globe, including recently in West Greenland. Large tsunamigenic landslides produce long-period seismic waves, which can be detected remotely, and their tsunamis may create standing waves known as seiches, in which water sloshes back and forth at a specific resonant frequency. Seiches create long-period, monochromatic signals useful for studying energy transfer between the hydrosphere and the solid Earth. However, current observations of seiches have been limited to short-duration effects recorded by local seismometers. What's more, numerical modeling of tsunami-induced seiches is limited, leaving a gap in understanding of how climate change can cause cascading, hazardous feedbacks between the cryosphere, hydrosphere, and lithosphere. Here, Kristian Svnnevig and colleagues report data from a significant landslide event in East Greenland that occurred in September 2023, which produced a very-long-period seismic signal that was detected globally for nine days. The event, which was triggered by glacial thinning, led to a massive rock-ice avalanche into Dickson Fjord, generating a 200-meter-high tsunami. This tsunami stabilized into a 7-meter-high long-duration seiche with a 90-second period, which produced a 10.88 millihertz (mHz) global seismic signal that resonated for nine days. Using a variety of geophysical techniques, Svennevig et al. show that the observed seismic signal was driven by the seiche. The findings further reveal that seiches in narrow fjords can produce long-duration seismic signals without persistent external driving forces, like strong winds or storm events.