The eastern edge of Greenland, which was quiet, suddenly became the focus of global science in September 2023, when seismic stations around the world simultaneously recorded a strange signal lasting up to 9 days.
It is a slow, steady vibration, repeated for about 92 seconds at a time - too weak for humans to feel but strong enough to spread through the rock from North America to Oceania. This is not typical of any ordinary earthquake.
After analysis, scientists determined that the signal source was located at Dickson Fjord - a narrow bay in eastern Greenland, sandwiched between two cliffs nearly 900m high.
Satellite images show that a large mountainside has collapsed, leaving clear scars on the terrain. This event triggered an extremely large and rare tsunami.
Accordingly, on September 16, 2023, more than 19 million cubic meters of rock and ice - equivalent to about 10,000 Olympic swimming pools - suddenly plunged into the Dickson Fjord. The giant collision created a super tsunami nearly 198m high, erupting like a water wall in the narrow space of the bay.
The wave rolled along a corridor more than 3km long, hitting the bottom of the bay and then rebounding, causing damage of about 200,000 USD to an empty research station on Ella Island nearby.
The unusual thing is that after the first impact, the water surface did not quickly settle but began to fluctuate back and forth between the two cliffs - a phenomenon called "seiche".
Models show that the water level rises and then descends with an amplitude of about 2.5 to nearly 9m, rhythmically repeated like a giant piston pressing down to the bottom of the bay. This prolonged movement has created the "geological heartbeat" that global seismic stations record.
Unlike the chaotic signal of an earthquake, this earthquake graph appears smoothly, steadily and almost without weakening for more than a week. Never before has a seiche phenomenon been recorded creating such a persistent global earthquake fingerprint.
Although research groups differ in estimating the amplitude of fluctuations due to different bay shape assumptions, they all agree that the cause of the tsunami is landslides.
According to scientists, climate change plays a key role. Previously, the ice layer helped support the mountainside, but rising air temperature and sea level have weakened this ice layer, causing the rock mass to become unstable.
Dickson Fjord is located near the Arctic cruise route. Although there were no tourists at the time of the event, the incident sounded a warning bell about the increasing risks as maritime activities in the polar region increased.
Decoding this rare phenomenon has made an important contribution from the SWOT satellite - a new generation of satellites capable of mapping water surfaces with high resolution, especially effective in remote areas such as the Arctic.
Scientists believe that satellite data combined with real-time seismic data will help improve tsunami forecasting and bring valuable warning moments in the future.
