Huge tsunami triggered by thinning glacier creates seismic event for nine days

'Unidentified Seismic Object' Rocked the Earth for Nine Days – Now We Know What It Was

TO Stephen Hicks, Christian Svennevig & US Conversation

The following essay is reprinted with permission. TalkAn online publication covering the latest research.

Earthquake scientists have detected an unusual signal at monitoring stations used to detect seismic activity in September 2023. We've seen it on sensors everywhere from the Arctic to Antarctica.

We were puzzled – the signal was unlike any previously recorded. Instead of the frequency-rich hum typical of earthquakes, it was a monotonous hum containing only one oscillation frequency. Even more puzzling was the fact that the signal lasted for nine days.

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Initially classified as a “USO” — an unidentified seismic object — the source of the signal was eventually traced to a massive landslide in the remote Dikson Fjord in Greenland. A staggering volume of rock and ice, enough to fill 10,000 Olympic swimming pools, collapsed into the fjord, triggering a 200-meter megatsunami and a phenomenon known as a seiche: a wave in the ice fjord that continued to slosh back and forth, some 10,000 times over nine days.

To put the tsunami in context, this 200-metre wave was twice as high as the tower that houses Big Ben in London, and many times higher than anything recorded after the massive undersea earthquakes in Indonesia in 2004 (the Boxing Day tsunami) or Japan in 2011 (the tsunami that hit the Fukushima nuclear power plant). It was possibly the tallest wave on Earth. since 1980.

Our discovery is now published in the journal Sciencerelied on collaboration with 66 other scientists from 40 institutions in 15 countries. Like investigating an air crash, solving the mystery required piecing together a wealth of evidence, from a trove of seismic data to satellite images, fjord water level monitors and detailed modeling of how the tsunami wave evolved.

All of this highlighted the catastrophic cascading chain of events, from decades to the seconds before the collapse. The landslide descended a very steep glacier in a narrow gully before plunging into a narrow, enclosed fjord. Ultimately, it was decades of global warming that thinned the glacier by a few dozen meters, meaning the mountain towering above it could no longer hold up.

Uncharted Waters

But beyond the strangeness of this scientific miracle, the event highlights a deeper and more troubling truth: climate change is changing our planet and our scientific methods in ways we are only beginning to understand.

It’s a stark reminder that we’re navigating uncharted waters. Just a year ago, the idea that a seiche could persist for nine days would have been dismissed as absurd. Likewise, a century ago, the idea that warming could destabilize slopes in the Arctic, leading to the massive landslides and tsunamis that occur almost annually would have been considered far-fetched. Yet these once-unthinkable events are now becoming ours new reality.

As we move deeper into this new era, we can expect to see more phenomena that challenge our previous understanding, simply because our experience does not cover the extreme conditions we are currently experiencing. We have discovered a nine-day wave that no one could have previously imagined.

Traditionally, discussions of climate change have focused on us looking up and out, at the atmosphere and oceans with changing weather patterns and rising sea levels. But Diksonfjord forces us to look down, to the very crust beneath our feet.

For perhaps the first time, climate change has caused a seismic event with global consequences. A landslide in Greenland sent vibrations through the Earth, shaking the planet and generating seismic waves that spread around the world within an hour of the event. No patch of ground beneath our feet was immune to these vibrations, metaphorically opening up cracks in our understanding of these events.

It will happen again.

Although landslides and tsunamis have been recorded before, the September 2023 tsunami was the first to hit East Greenland, a region that was thought to be immune to these climate-change-induced catastrophic events.

This certainly won't be the last such megatsunami landslide. As the permafrost on steep slopes continues to warm and glaciers continue to thin, we can expect these events to occur more often and on an even larger scale polar and mountainous regions worldwide. Recently identified unstable slopes in West Greenland and in Alaska are clear examples of impending disasters.

As we face these extreme and unexpected events, it becomes clear that our existing scientific methods and toolkits may need to be fully equipped to cope with them. We had no standard workflow for analyzing the 2023 Greenland event. We also need to adopt a new way of thinking, since our current understanding is shaped by a now nearly vanished, previously stable climate.

As we continue to change our planet’s climate, we must be prepared for unexpected phenomena that challenge our current understanding and require new ways of thinking. The ground beneath us is shaking, both literally and figuratively. While the scientific community must adapt and pave the way for informed decision-making, it is up to decision makers to act.

This article was originally published on Talk. Read original article.