A rockslide-generated tsunami in a Greenland fjord rang Earth for 9 days
Kristian Svennevig, Stephen P. Hicks, Thomas Forbriger, Thomas Lecocq, Rudolf Widmer-Schnidrig, Anne Mangeney, Clément Hibert, Niels J. Korsgaard, Antoine Lucas, Claudio Satriano, Robert E. Anthony, Aurélien Mordret, Sven Schippkus, Søren Rysgaard, Wieter Boone, and
53 more authors
Science, 2024.
Climate change is increasingly predisposing polar regions to large landslides.
Tsunamigenic landslides have occurred recently in Greenland (Kalaallit Nunaat),
but none have been reported from the eastern fjords. In September 2023, we detected
the start of a 9-day-long, global 10.88-millihertz (92-second) monochromatic
very-long-period (VLP) seismic signal, originating from East Greenland.
In this study, we demonstrate how this event started with a glacial thinning–induced
rock-ice avalanche of 25 × 10^6 cubic meters plunging into Dickson Fjord,
triggering a 200-meter-high tsunami. Simulations show that the tsunami stabilized
into a 7-meter-high long-duration seiche with a frequency (11.45 millihertz)
and slow amplitude decay that were nearly identical to the seismic signal.
An oscillating, fjord-transverse single force with a maximum amplitude of 5 × 10^11
newtons reproduced the seismic amplitudes and their radiation pattern relative
to the fjord, demonstrating how a seiche directly caused the 9-day-long
seismic signal. Our findings highlight how climate change is causing cascading,
hazardous feedbacks between the cryosphere, hydrosphere, and lithosphere.