What Greenland’s nine-day mega tsunami tells us about climate change

PARIS (France 24) – Did you feel the Earth moving beneath your feet in September 2023? For nine days, sensors around the world recorded the same rhythmic tremor, every 90 seconds, as regular as a heartbeat.

The scientists standing at their sensors were baffled. The seismic signal did not look like an earthquake, and what kind of tremor hits the earth at minute-and-a-half intervals for more than a week?

Soon, researchers around the world were swapping theories in a global group chat. A team from Denmark had a lead: reports of a landslide in the remote fjords of Greenland. Satellite images soon showed what looked like a cloud of dust hanging over a ravine in the remote Dickson Fjord.

A look at the photos taken before and after the event explained it all. 25 million cubic metres of rock had slid down the mountain into the icy water, sending a 200-metre wave roaring across the fjord.

Caught in the twists and turns of the waterway, the mega-tsunami, now a seven-metre-high wave, had pounded again and again between the bare rock walls for nine long days, triggering seismic contortions that had activated sensors on the other side of the Earth.

What climate experts say

Stephen Hicks, from University College London and one of the scientists involved in the months-long research, told the BBC that landslides of this nature were becoming more frequent as melting glaciers gave way under the weight of the mountains.

“We have never seen such a large-scale movement of water over such a long period of time,” he said. “That glacier was holding up this mountain and it weakened so much that it no longer held it up. It shows how climate change is now affecting these areas.”

Julienne Stroeve, professor of polar modelling and observation at University College London, said the plight of the world’s glaciers was having deadly consequences.

“If large glaciers collapse and fall into the ocean, or in this case a landslide caused by a glacier collapse, then tsunamis can also be triggered,” he explained. “Here in Chamonix, where I currently live, the melting of glaciers is causing loss of life through avalanches, seracs (fragmented ice blocks)… the glacial lakes that form can also burst, causing flooding downstream.”

Remnants of the Earth’s last ice age, when ice sheets covered swathes of the globe, the world’s glaciers retreated to the frigid polar regions about 10,000 years ago. In recent decades, the rate of shrinkage of these glaciers has accelerated dramatically, one of the most visible consequences, according to climate scientists, being the rise in global temperatures caused by the man-made climate crisis.

“Glaciers play an important role in water resources around the world, and today all glaciers are retreating in response to climate change,” said Stroeve. “In Greenland and Antarctica, glaciers discharge land ice into the oceans that contribute to sea level rise. So the loss of glacier mass impacts communities around the world that depend on them for fresh water and further raises global sea level, affecting coastal communities.”

Climate change, the cause

Since the late 20th century, ice loss recorded at the dozens of glaciers monitored by climate scientists is measured in feet, not inches. Relative to 1970, the glaciers in this reference network will have lost just over 26 feet of water by 2023 — equivalent to cutting 94 feet (about 28 meters) off the top of each glacier.

Stroeve said the accelerating rate at which the world’s glaciers are shrinking, fragmenting or disappearing is yet another reminder of the urgent need to curb carbon emissions.

“Of course we need to reduce greenhouse gas emissions, as they are the main driver of ice melting around the world these days,” he said. “That will require strong political leadership which the world still seems to lack.”