It started with a melting glacier that triggered a massive landslide, triggering a 650-foot mega-tsunami in Greenland last September. Then something inexplicable happened: a mysterious vibration that shook the planet for nine days.
Over the past year, dozens of scientists around the world have been trying to figure out what the signal was.
Now they have an answer, according to a new study in the journal Science, providing yet another warning that the Arctic is entering “uncharted waters” as humans push global temperatures ever higher. .
Some seismologists thought their instruments had broken when they started picking up vibrations from the ground in September, said study co-author Stephen Hicks, a seismologist at University College London.
It wasn’t the full orchestra of high pitches and commotion you might expect with an earthquake, but more of a monotonous harmony. Earthquake signals last for minutes. It lasted for nine days.
He was surprised, it was “completely unprecedented,” he said.
Seismologists traced the signal to East Greenland, but could not pinpoint a specific location. So they contacted their colleagues in Denmark, who had received reports of a landslide-triggered tsunami in a remote area called Dixon Fjord.
The result was a nearly year-long collaboration between 68 scientists from 15 countries, who worked through seismic, satellite and ground-based data, as well as tsunami wave simulations, to solve the puzzle.
What happened is called a “collapsing hazard,” Svenvig said, and it all started with human-caused climate change.
For years, the glacier at the base of a huge mountain about 4,000 feet above Dixon Fjord had been melting, as many glaciers do in the rapidly warming Arctic.
As the glacier thinned, the mountain became increasingly unstable before it collapsed on September 16 last year, sending enough rock and debris into the water to fill 10,000 Olympic-sized swimming pools.
The ensuing mega-tsunami — one of the largest in recent history — unleashed a wave that stuck in the twisting, narrow fjord for more than a week, rolling back and forth every 90 seconds.
The phenomenon, called “sicche,” refers to the rhythmic motion of a wave in an enclosed space, like water splashing back and forth in a bathtub or cup. One of the scientists tried (and failed) to recreate the effect in his own bathtub.
Although sechs are famous, scientists had no idea they could last so long.
“If I had suggested a year ago that a sitch could last for nine days, people would have shook their heads and said it was impossible,” said Svennevig, who attributed the discovery to a sudden new color in the rainbow. Likened to doing.
Scientists found that it was Seshe that generated seismic energy in the Earth’s crust.
Hicks said it may be the first time scientists have seen the effects of climate change “on the ground beneath our feet.” And no place was safe. He added that the signal travels from Greenland to Antarctica in about an hour.
No one was injured in the tsunami, although it washed away centuries-old cultural heritage sites and damaged an empty military base. But this stretch of water is in the path of a commonly used cruise ship. If someone had been there at the time, “the consequences would have been catastrophic,” the study authors wrote.
East Greenland had never experienced such landslides and tsunamis before, Svennevig said. He added that it shows that new areas of the Arctic are coming “on-line” for these types of climate events.
As the Arctic warms — over the past few decades, the region has warmed four times faster than the rest of the world — landslide-triggered mega-tsunamis could become more common and with deadly consequences.
In June 2017, a tsunami killed four people and washed away houses in northwestern Greenland. Svennevig said the threat extends beyond Greenland. Similar-shaped fjords exist in other regions, including Alaska, parts of Canada, and Norway.
Landslide geologist Paula Snook of the Western Norway University of Applied Sciences said that what happened in Greenland last September “shows once again the ongoing instability of large mountain slopes in the Arctic that has increased in climate.” is”.
Lena Rubensdotter, a researcher at the Geological Survey of Norway, cautioned that there is still much to be done on rock avalanches, which are also influenced by natural processes.
However, he added, “it is logical to assume that we will see more frequent rockfalls in permafrost slopes as Arctic regions warm.”
The discovery of natural phenomena behaving in seemingly unnatural ways highlights how this part of the world is changing in unexpected ways, Svennevig said.
“This is a sign that climate change is pushing these systems into uncharted waters.”
