A massive landslide caused by a melting glacier in September of last year in Greenland resulted in a megatsunami that reached a height of 650 feet. Subsequently, there was an unexplainable tremor that rocked the earth for nine days.
Numerous scientists from all over the world have been attempting to identify this signal for the past year.
According to a recent study published in the journal Science, they now have an explanation, and it serves as yet another caution that as global temperatures rise due to human activity, the Arctic is moving into "uncharted waters."
According to University College London seismologist Stephen Hicks, a co-author of the study, when seismologists began to feel vibrations through the ground back in September, some of them believed their instruments were broken.
He described it as more of a monotonous hum than the rich orchestra of high pitches and rumbles you might expect with an earthquake. The normal duration of an earthquake signal is a few minutes; this one lasted for nine days.
It was "completely unprecedented," he said, and he was perplexed.
The signal was traced to eastern Greenland by seismologists, but they were unable to pinpoint its exact location. They thus got in touch with colleagues in Denmark, who had learned of a tsunami that had been caused by landslides in the isolated Dickson Fjord area of the region.
In order to solve the mystery, 68 scientists from 15 different countries worked together for almost a year, sifting through data from satellites, on the ground, seismic activity, and tsunami wave simulations.
According to Svennevig, what transpired is known as a "cascading hazard," and it all began with climate change brought on by humans.
Like many glaciers in the rapidly warming Arctic, the one at the foot of a massive mountain rising nearly 4,000 feet above Dickson Fjord had been melting for years.
The mountain grew more unstable as the glacier receded and ultimately fell on September 16 of last year, spilling enough debris and rock into the water to fill 10,000 Olympic-sized swimming pools.
One of the biggest tsunamis in recent memory, the one that followed, caused a wave that was trapped in the crooked fjord for over a week, sloshing back and forth every 90 seconds.
The term "seiche" describes a phenomenon where a wave moves rhythmically in a confined space, resembling the sound of water splattering back and forth in a cup or bathtub. A scientist even attempted to replicate the impact in their own bathtub, but was unsuccessful.
Although seiches are well known, their prolonged duration was previously unknown to scientists.
"People would have laughed at me a year ago if I had suggested that a seiche could last for nine days. It's not possible," Svennevig said, comparing the revelation to discovering a new color in a rainbow out of nowhere.
The scientists discovered that the seismic energy present in the Earth's crust originated from this seiche.
According to Hicks, this may be the first time that scientists have seen the effects of climate change "on the ground beneath our feet." And nowhere was safe; he said the signal took about an hour to travel from Greenland to Antarctica.
The tsunami destroyed an abandoned military base and carried away centuries-old cultural heritage sites, but no one was hurt. However, this area of water is on a frequently traveled cruise ship route. The authors of the study stated that "the consequences would have been devastating" if one had been present at the time.
According to Svennevig, a landslide and tsunami of this magnitude had never before occurred in Eastern Greenland. According to him, it indicates that more regions of the Arctic are "coming online" for these kinds of climate events.
Landslide-triggered mega-tsunamis may become more frequent and deadly as the Arctic continues to warm; over the past few decades, the region has warmed four times faster than the rest of the world.
Four people lost their lives and houses were destroyed in northwest Greenland in June 2017 due to a tsunami. According to Svennevig, the threat is not limited to Greenland; fjords with a similar shape can be found in Alaska, some parts of Canada, and Norway.
Paula Snook, a landslide geologist at the Western Norway University of Applied Sciences who was not involved in the study, said that what happened in Greenland last September "once again demonstrates the ongoing destabilization of large mountain slopes in the Arctic due to amplified climate warming."
She told that recent rock avalanches in the Alpine and Arctic regions are "an alarming signal." "The ground we are thawing has been frozen and frigid for many thousands of years."
Lena Rubensdotter, a researcher at the Geological Survey of Norway who was not involved in the study, cautioned that there is still much to be learned about rock avalanches, which are also impacted by natural processes.
She did, however, note that it is "logical to assume that as the climate warms in Arctic regions, we will see more frequent rock collapses in permafrost slopes."
According to Svennevig, the discovery of natural phenomena acting in ways that appear out of the ordinary illustrates how this region of the world is changing in ways that are not anticipated.
"This indicates that these systems are being forced into unfamiliar territory by climate change."
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