650-foot tsunami in Greenland fjord creates waves that last 9 days, scientists

Summary

The tsunami, one of the largest ever recorded, was the result of a series of rare, cascading events set in motion by melting ice.

After seismologists detected unusual vibrations, they determined that a 650-foot tsunami had hit Greenland.
The tsunami was the result of melting glacial ice, which caused a landslide that displaced water in a fjord in Greenland.
The waves it created bounced back and forth across the fjord for nine days.

Last September, seismologists around the world detected the opposite tremor from what they had previously picked up. A monotonous hum seemed to emanate from Greenland. It will continue for nine days.

“It turned out to be a very strange signal that I’ve never seen before at some of our stations up north,” said seismologist Carl Ebling of the University of California, San Diego’s Scripps Institution of Oceanography.

Shortly after the tremors began, a cruise ship sailing near the fjords in Greenland spotted a landmark on remote Ella Island – used for scientific research and by the Danish military for sled dog patrols. Base – has been destroyed.

These events drew seismologists, the Danish military and an international group of oceanographers to the mystery: What hit the island, and where did it come from?

On Thursday, the researchers published their findings in the journal Science. They said the island was hit by one of the largest tsunamis ever recorded, with waves that left a water mark about 650 feet high.

It was the result of a series of rare, cascading events set in motion by climate change.

The researchers found that the initial trigger occurred when a thin glacier tongue collapsed due to rising temperatures. It destabilized a steep hill, sending a rock and avalanche crashing into Greenland’s deep Dixon Fjord. This displaced a large volume of water, so a large wave swept across the narrow fjord, which is about 1.5 miles wide.

Tsunami waves – some at least as high as the Statue of Liberty – were rushing up the steep rock walls on the fjord. Because the mudslide hit the waterway at about a 90-degree angle, waves bounced back and forth over it for nine days — a phenomenon scientists call a seiche.

“No one had ever seen anything like this,” said Kristian Svenvig, lead author of the study and senior researcher at the Geological Survey and the Geological Survey of Denmark and Greenland.

Before and after photos show the location where the rockfall and glacier ice suddenly collapsed into Dixon Fjord. Scientists determined that the landslide was caused by climate change, and it generated a tsunami wave of about 650 feet.

The findings are the result of a complex, year-long investigation. The team determined that Ella Island — about 45 miles from the landslide — was hit by a tsunami at least 13 feet high. Tourists occasionally visit the island.

“Just a few days before the event, the cruise ships were there and they were on the beach,” Svennevig said. “It was really, really lucky that no one was there when it happened.”

This is the longest observation scientists have ever made. Previously, landslide-triggered tsunamis typically generated waves that dissipated within a few hours.

“It’s really a confluence of events and it hasn’t been observed before,” said Alice Gabriel, co-author of the study. “Earth is a very dynamic system and right now, we’re at a stage where climate change is causing this very delicate balance to be disrupted quite violently.”

Tsunamis caused by landslides are more common than many people realize and are dangerous for people living or working in the Arctic and some subarctic regions.

In 2017, four people were killed and 11 houses destroyed in a tsunami-induced landslide in the village of Nugatsiak in West Greenland. The wave was at least 300 feet high. Two villages were evacuated after the incident as further landslides are likely. Svennevig said hundreds of people are homeless.

Brett Wood “Hugh” Higman, an Alaskan geologist who studies landslide tsunamis but was not involved in the new study, said he has compiled evidence that suggests landslide tsunamis are a growing phenomenon. problem, although further studies are needed.

“I’m pretty sure we’re seeing these events become more common,” he said. “Exactly how often these events are happening and can we predict the future? We’re not there.”

Hugman said he thinks the researchers behind the Greenland study “nailed it” with their analysis and that it’s a prime example of how dangerous these landslide tsunamis can be.

Arctic and subarctic regions are warming two to three times faster than the rest of Earth because as the ice melts, the dark surfaces that are exposed absorb more sunlight. Hageman said warming is creating three dynamics that could make landslides more common in glacial regions.

The first is that higher temperatures are causing permafrost within rock formations to melt, which can weaken slopes and make them more likely to collapse. Second, warming means thinning of the glaciers that sometimes grip the rocky slopes. Removing this snow can cause a sudden collapse. Third, climate change increases the likelihood of heavy rainfall, which is the greatest risk factor for landslides because saturated rocks and soils are more prone to sliding.

Hugman is listing Alaskan slopes at risk of landslides that could cause tsunamis. He said there were dozens of sites he was concerned about that needed further investigation. Some are close to populated areas and could cause havoc if they slip.