September 13, 2024
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‘Unidentified seismic object’ shook the Earth for 9 days. Now we know what it is
Scientists have traced the baffling, monotonous planetary hum that lasted nine days to the Greenland ice sheet.
Dixon Fjord (before August 2023) (left) and thereafter (September 2023) (right) Landslide.
Søren Rysgaardleft); Danish Army (right)
The following article is reprinted with permission from: 
conversationAn online publication covering cutting-edge research.
Earthquake scientists detected an unusual signal on a monitoring station used to detect seismic activity in September 2023. We saw it on sensors everywhere from the North Pole to the South Pole.
We were baffled. The signal was unlike anything recorded before. Instead of the rich frequency of the typical earthquake, it was a monotonous hum, with only one vibration frequency. Even more baffling was that the signal lasted for nine days.
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Initially classified as a “USO”, the signal’s source, an unidentified seismic object, was eventually traced back to a massive landslide in Greenland’s remote Dickson Fjord. Enough rock and ice to fill 10,000 Olympic swimming pools crashed into the fjord, generating a 200-meter-high mega-tsunami and a phenomenon known as a seisy. A seisy is a wave that continues to rock back and forth in the ice fjord approximately 10,000 times over a nine-day period.
To put the tsunami in context, that 200m wave was twice the height of Big Ben in London and several times higher than anything recorded since the 2004 Boxing Day tsunami in Indonesia or the 2011 Fukushima tsunami in Japan. It was probably the highest wave ever recorded on Earth. Since 1980.
Planet Labs satellite images before (30 minutes before) and after (7 minutes after) the landslide occurred.
Our findings have now been published in the journal scienceIt relied on collaboration with 66 other scientists from 40 institutions in 15 countries. Like investigating an airplane crash, solving this mystery required gathering a treasure trove of evidence, from seismic data to satellite imagery, water level monitors in the fjord, and detailed simulations of how tsunami waves evolved.
All of this highlighted a catastrophic chain of events that lasted from decades to seconds before the collapse. The landslide traveled along a very steep glacier in a narrow canyon before crashing into a narrow, confined fjord. But ultimately, decades of global warming had thinned the glacier by tens of meters, making it no longer able to support the mountain that towered above it.
Unknown sea
But beyond the strangeness of this scientific wonder, the incident highlights a deeper, more disturbing truth: that climate change is altering our planet and our scientific method in ways we are only just beginning to understand.
It is a sobering reminder that we are sailing in uncharted waters. Just a year ago, the idea that a hurricane could last nine days would have been dismissed as absurd. Likewise, a century ago, the idea that warming could destabilize the Arctic slopes, leading to massive landslides and tsunamis that occur almost every year would have been considered absurd. But these once unthinkable events are now a reality in our new reality.
As we move deeper into this new era, we can expect to witness more phenomena that defy our previous understanding, because our experience does not encompass the extremes we are now facing. We have discovered nine-day waves that no one could have imagined before.
Before and after landslides and tsunamis.
Søren Rysgaardleft); Danish Army (right)
Traditionally, discussions of climate change have focused on looking upward and outward, at changing weather patterns and rising sea levels in the atmosphere and oceans. But Dickson Fjord forces us to look downward, at the crust beneath our feet.
Perhaps the first time climate change has triggered an earthquake with global consequences, a landslide in Greenland caused the Earth to shake, creating seismic waves that traveled around the globe within an hour of the event. The ground beneath our feet was not immune to these tremors, metaphorically opening up cracks in our understanding of these events.
This will happen again
Landslide-tsunamis have been recorded before, but the September 2023 landslide-tsunami was the first to occur in eastern Greenland, a region that seemed immune to such catastrophic climate change-induced phenomena.
This certainly won’t be the last landslide-megatsunami. As permafrost on steep slopes continues to warm and glaciers continue to thin, we can expect to see more such events. More often and on a larger scale Unstable slopes have recently been identified across polar and mountainous regions around the world. West Greenland and Alaska A clear example of an impending disaster.
As we face these extreme and unexpected events, it is becoming clear that our existing scientific methods and toolkits may need to be fully retooled to handle them. We did not have a standard workflow for analyzing the 2023 Greenland event. We also need to adopt a new way of thinking, because our current understanding was shaped by a previously stable climate that is now largely extinct.
As we continue to change the Earth’s climate, we must prepare for unexpected phenomena that challenge our current understanding and require new ways of thinking. The ground beneath us is shaking, literally and figuratively. The scientific community must adapt and pave the way for informed decision-making, but it is up to decision-makers to act.
This article was originally published on: conversation. Read it Original article.
