SAN DIEGO — A report published today revealed that two UC San Diego seismologists were among an international team of scientists who set out to investigate a mysterious nine-day seismic event in Greenland that triggered a “mega-tsunami.”
Alice Gabriel and Carl Ebeling of UCSD’s Scripps Institution of Oceanography were puzzled like scientists around the world when, in September 2023, the seismic waves continued for more than a week.
The culprit was a mountaintop collapsing into the sea in a Greenland fjord, a body of water often surrounded by steep cliffs. The resulting wave topped 650 feet and ricocheted back and forth in the narrow fjord for nine days, keeping up the seismic signal baffling scientists. A wave in a partially enclosed body of water is called a seiche.
The research was published in Thursday’s edition of Science.
“When we set out on this scientific adventure, everybody was puzzled and no one had the faintest idea what caused this signal,” said Kristian Svennevig, a geologist at the Geological Survey of Denmark and Greenland and the study’s lead author. “All we knew was that it was somehow associated with the landslide. We only managed to solve this enigma through a huge interdisciplinary and international effort.”
The massive, rebounding waves did not hurt anyone but destroyed around $200,000 in research equipment at an empty scientific camp on an island.
According to the scientists, climate change spurred the glacier melt at the foot of the mountain, causing the landslide. It displaced more than 25 million cubic meters, enough to fill 10,000 Olympic-sized swimming pools. The authors of the study believe a warming climate could cause more large-scale landslides.
“Climate change is shifting what is typical on Earth, and it can set unusual events into motion,” said Gabriel, whose work on this study was supported by the European Research Council, Horizon Europe, the National Science Foundation and NASA.
While scientists were at first baffled by the unusual seismic readings, ultimately, it was tracked down to the landslide on Sept. 16 in Dickson Fjord, in the remote eastern portion of Greenland.
The team, comprised of 68 scientists from 41 research institutions, compared seismic readings globally and was able to reconstruct the events with computer simulations.
“It was a big challenge to do an accurate computer simulation of such a long-lasting, sloshing tsunami,” Gabriel said.
While nobody was harmed in the seismic event, the fjord is near a cruise ship route and could portend more catastrophic things to come if it were to happen in a populated area — like in 2017, when a smaller landslide in western Greenland’s Karrat Fjord triggered a tsunami that flooded the village of Nuugaatsiaq, destroying 11 houses and killing four people.
Gabriel said the results have sparked interest in examining old seismic records for similar events not known before.
“This shows there is stuff out there that we still don’t understand and haven’t seen before,” said Ebeling, who co-authored the study with support from NSF and helped manage a network of seismic sensors that detected the seiche’s vibrations. “The essence of science is trying to answer a question we don’t know the answer to — that’s why this was so exciting to work on.”
