Seismologists detected an unusual signal at monitoring stations used to detect seismic activity in September 2023. They saw it with sensors everywhere, from the Arctic to the Antarctic.
We were puzzled because the signal was different from any other signal recorded before: instead of the rich vibrational tone typical of earthquakes, this was a monotonous hum, containing only a single vibrational frequency. Even more puzzling, the signal continued for nine days.
Initially classified as a “USO” (Unidentified Seismic Object), the signal was eventually traced back to a massive landslide in Dikson Fjord, on the remote edge of Greenland. A massive amount of rock and ice, the equivalent of 10,000 Olympic-sized swimming pools, slid into the fjord, triggering a 200-metre-high megatsunami and a phenomenon known as a seiche, where the waves in the ice-covered fjord rock back and forth about 10,000 times over a nine-day period.
To put the tsunami into context, the 200 metre wave was twice the height of London’s Big Ben tower and many times higher than the 2004 Indonesian undersea earthquake (Boxing Day tsunami) and the 2011 Fukushima tsunami in Japan (Fukushima nuclear plant tsunami). It was probably the tallest wave ever recorded on Earth. Since 1980.
Our findings have now been published in the journal Sciencewas the collaboration of 66 scientists from 40 institutions in 15 countries. As with any plane crash investigation, solving this mystery required pulling together a wide range of evidence, from a treasure trove of seismic data to satellite imagery, water-level monitors in the fjord, and detailed simulations of how the tsunami waves evolved.
All this highlights a series of catastrophic events that began decades before the collapse, right up to the seconds before. The landslides slid down the very steep glacier in a narrow canyon and into a narrow, enclosed fjord. But finally, decades of global warming thinned the glacier by tens of metres, and it could no longer support the mountain towering above it.
Uncharted territory
But beyond the strangeness of this scientific marvel, the incident highlights a deeper, more disturbing truth: Climate change is transforming our planet and the scientific method in ways that we are only just beginning to understand.
This is a stark reminder that we are navigating uncharted waters. Just a year ago, the idea that a seiche could last nine days would have been dismissed as absurd. Similarly, a century ago, the idea that a warming climate would destabilize the Arctic slopes, causing massive landslides and tsunamis almost every year would have seemed unrealistic. Yet these once unthinkable events are now becoming commonplace. new reality.
Something “once unthinkable” is sending ripples around the world.
As we move deeper into this new era, we expect to see more phenomena that defy our understanding because our experience does not include the extreme conditions we are currently facing. We have discovered nine-day waves that no one could have ever imagined existed.
Traditionally, discussions of climate change have focused on looking upwards and outwards to the atmosphere and oceans with changing weather patterns and rising sea levels, but Dikson Fjord challenges us to look downwards, to the very crust beneath our feet.
Perhaps for the first time, climate change has triggered an earthquake with global impact. The Greenland landslide sent vibrations across the globe, shaking the Earth and setting off seismic waves that traveled across the planet within an hour of the event. No piece of land beneath our feet was safe from these vibrations, metaphorically opening a fissure in our understanding of these events.
This will happen again
While landslide-induced tsunamis have been recorded before, the September 2023 tsunami was the first to be observed in East Greenland, an area thought to be immune to catastrophic events caused by climate change.
This will not be the last such landslide-induced megatsunami: more such events are expected as the permafrost on steep slopes continues to warm and the glaciers continue to thin. More frequently and on a larger scale Unstable slopes have recently been identified in polar and mountainous regions around the world. West Greenland and Alaska These are clear examples of impending disaster.
Gabe Wolken/USGS
In the face of such extreme and unexpected events, it is becoming clear that existing scientific methods and toolkits may need to be adequately equipped to deal with them. There was no standard workflow for analyzing the 2023 Greenland event. And because our current understanding is shaped by a once-stable, but now-near-extinct, climate, we need to embrace new ways of thinking.
As Earth’s climate continues to change, we must prepare for unexpected phenomena that will challenge our current understanding and demand new ways of thinking. The ground is shaking beneath our feet, literally and figuratively. The scientific community must adapt and pave the way to make informed decisions, but it is up to decision makers to act.
The authors discuss their findings in further detail.
Stephen Hicks He is a researcher in computational seismology. London University Cricket Ground and Christian Svennevig Senior Researcher in the Cartography and Mineral Resources Department. Geological Survey of Denmark and Greenland
This article is reprinted from conversation Published under a Creative Commons license. Original article.
