The entire Earth vibrated for nine days after a climate-triggered mega-tsunami | The climate crisis

A landslide and mega-tsunami in Greenland in September 2023, triggered by the climate crisis, caused the entire Earth to vibrate for nine days, a scientific investigation has found.

The seismic event was detected by earthquake sensors around the world, but it was so completely unprecedented that researchers initially had no idea what caused it. Having now solved the mystery, scientists said it showed how global warming was already having impacts on a planetary scale and that major landslides were possible in places thought to be stable as temperatures rose rapidly.

The collapse of a 1,200-meter-high mountain peak in remote Dickson Fjord occurred on September 16, 2023, after the melting glacier below could no longer support the rock face. It set off an initial wave 200 meters high, and the subsequent splash of water back and forth in the twisting fjord sent seismic waves across the planet for more than a week.

The landslide and mega-tsunami were the first recorded in East Greenland. Arctic regions are affected by the most rapid global warming, and similar, albeit smaller seismic events, have been observed in western Greenland, Alaska, Canada, Norway and Chile.

Dr Kristian Svennevig of the Geological Survey of Denmark and Greenland, lead author of the report, said: “When we started this scientific adventure, everyone was puzzled and no one had the slightest idea what caused this signal. It was much longer and simpler than earthquake signals, which usually last minutes or hours, and was labeled a USO – an unidentified seismic object.

“It was also an extraordinary event because it is the first giant landslide and tsunami we have recorded in East Greenland. It certainly shows that East Greenland is online when it comes to landslides. The waves destroyed an uninhabited Inuit site at sea level that was at least 200 years old, indicating nothing of the kind for at least two centuries.

A large number of huts were destroyed at a research station on Ella Island, 70 km (45 mi) from the landslide. The site was founded by fur trappers and explorers two centuries ago and is used by scientists and the Danish military, but was empty at the time of the tsunami.

The fjord is also on a route commonly used by tourist cruise ships, and one carrying 200 people got stuck in the mud in Alpefjord, close to Dickson Fjord, last September. He was released just two days before the tsunami hit, avoiding waves estimated at four to six meters.

“It was pure luck that nothing happened to anyone here,” Svennevig said. “We’re in scientifically uncharted waters because we don’t really know what a tsunami does to a cruise ship.”

Dr Stephen Hicks of University College London, one of the leaders of the research team, said: ‘When I first saw the seismic signal I was completely baffled. Never before has such a long, globally traveling seismic wave containing only a single frequency of oscillation been recorded.”

The signal looked completely different from the multi-frequency noises and pings from the earthquakes. It took 68 scientists from 40 institutions in 15 countries to solve the mystery by combining seismic data, field measurements, ground and satellite imagery, and high-resolution computer simulations of tsunami waves.

The analysis, published in the journal Science, estimated that 25 cubic meters of rock and ice crashed into the fjord and traveled at least 2,200 meters along it. The direction of the landslide at 90 degrees to the length of the fjord, together with the steep parallel walls of the inlet and a 90 degree bend 10 km down, all contributed to keeping much of the landslide energy in the fjord and resonance so much time. .

The tsunami wave reduced to seven meters within minutes, the researchers calculated, and would have dropped to several centimeters in the following days when the Danish military visited and photographed the fjord. But this rumbling of a vast body of water continued to send seismic waves around the world.

Coincidentally, sensors measuring water depth were installed by scientists in the fjord two weeks before the landslide. “It was also pure luck,” Svennevig said. “They were sailing under this glacier and mountain that they didn’t know was about to collapse.”

A key part of determining the cause of the seismic event was modeling the tsunami and comparing it to measurements. “Our model predicted an oscillation with exactly the same period – 90 seconds – which is an amazing result, as well as the height of the tsunami, and the waves decayed in exactly the same way as the seismic signals. That was the eureka moment.”

Professor Anne Mangeney, a landslide modeler at the Institut de Physique du Globe de Paris in France, who was part of the team, said: “This unique long-lasting tsunami challenged the classical models we previously used to only simulate a few hours of Tsunami Propagation – we had to go to an unprecedented numerical resolution. This opens up new avenues for modeling tsunamis.”

Such events will become more frequent as global temperatures continue to rise. “Even more profoundly, for the first time, we can see quite clearly that this event, triggered by climate change, caused a global vibration under all our feet, all over the world,” Mangeney said. “Those vibrations traveled from Greenland to Antarctica in less than an hour. So we saw an impact of climate change that affected the whole world in just one hour.”

Humans’ impact on the planet has also recently been demonstrated by studies showing that reshaping the Earth through mass melting of polar ice is lengthening the length of each day and causing the north and south poles to shift. Other work has shown that carbon emissions shrink the stratosphere.