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in august 2023, søren rysgaard from aarhus university in denmark came to dickson fjord in northeastern greenland. dixon sound is sandwiched between steep cliffs thousands of meters high.together with other large and small fjords, it forms a winding and complex fjord system.。

photo credit: stephen hicks; kristian svennevig; alexis marbeouf

rysgaard is here to install a series of monitoring equipment on the mountain and underwater to complete the real-time subglacial marine environment monitoring network in northeast greenland. but just a few weeks after they left, on september 16,a huge landslide broke the calm sea. the equipment rysgaard installed happened to detect unusual fluctuations in sea levels—a tsunami occurred. then, centered on eastern greenland,an earthquake signal spread throughout the earth. and for the next nine days, this seismic wave continued to reverberate under the feet of everyone around the world.

satellite images before and after the landslide (image source: copernicus, sentinel-2, eo browser)

mysterious seismic waves

kristian svennevig, a researcher at the geological survey of denmark and greenland (geus), first noticed the signal at the request of the greenland and danish joint arctic command.investigate this landslide and tsunami event。

from the scene and satellite photos, you can clearly see what happened here: a mountaintop about 1,200 meters high above the fjord collapsed, triggering a landslide. the fallen mountain slid all the way along the glacier, carrying more ice and sediment, and fell into the fjord.the volume of collapsed mountain rock and ice reached 25 million cubic meters, enough to fill 10,000 olympic-sized swimming pools.

image source: original paper

the sudden impact triggered a violent tsunami in dickson sound,the first wave was 200 meters high——far higher than the wave height of the 2004 indonesian tsunami and the 2011 tsunami that hit the fukushima nuclear power plant in japan. and just 70 kilometers east of the fjord is the monitoring station ella ø. the wave height here still reaches 4 meters, and the sea water spreads 80 meters inland from the coastline. fortunately, no one works or lives in the monitoring station at this time.the tsunami only destroyed a lot of equipment here and caused no casualties.

mountain peaks and glaciers taken from the fjord before (left) and after (right) the landslide and tsunami. the yellow area in the picture is the fallen mountain top rock, and the red area is the area affected by the tsunami. (image credit: søren rysgaard, danish army)

at that same time, an online community gathered a large group of seismologists from around the world. what caught their attention was the same mysterious earthquake signal: just after the landslide and tsunami in dickson sound, from the arctic to the antarctic,highly sensitive seismic sensors around the world have detected a strange seismic wave.