A seismic signal heard across the world last September for nine days has been traced back to a trapped tsunami triggered by a landslide in the remote fjords of Greenland. Climate scientists say that the collapse seems to have been set off by melting glaciers – a phenomenon that is more and more common in the face of the man-made climate crisis.
Did you feel the Earth move beneath your feet last September? For nine days, sensors across the world registered the same rhythmic shudder, every 90 seconds, regular as a heartbeat.
Scientists standing by their sensors were baffled. The seismic signal didn’t seem like an earthquake – and besides, what kind of tremor pounds the earth in minute-and-a-half intervals for more than a week?
Soon, researchers across the world were sharing theories in a global group chat. A team in Denmark had a lead – reports of a landslide in the far-off fjords of Greenland. Satellite images soon showed what looked like a cloud of dust hanging over a gully in the remote Dickson Fjord.
Read moreMelting ice caps slow Earth's spin, lengthening days at 'unprecedented' rate
A look at pictures taken before and after the event told the full story. Twenty-five million cubic metres of rock had slid down the mountain into the icy water, sending a 200-metre wave roaring across the fjord. Trapped in the twists and turns of the watercourse, the mega-tsunami, now a seven-metre-high standing wave, had slammed back and forth between the bare rock walls for nine long days, triggering the seismic contortions that had set off sensors on the other side of the Earth.
University College London’s Stephen Hicks, one of the scientists involved in the months-long investigation, told the BBC that landslides of this nature were becoming more and more common as melting glaciers buckled beneath the weight of the mountains they supported.
“We’ve never seen such a large-scale movement of water over such a long period,” he said. “That glacier was supporting this mountain, and it got so thin that it just stopped holding it up. It shows how climate change is now impacting these areas.”
Julienne Stroeve, professor of polar modelling and observation at University College London, said that 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 glacier collapse, tsunamis can also be triggered,” she said. “Here in Chamonix where I’m currently living, glacier melting is leading to loss of life from avalanches, seracs falling down … glacier lakes that form may also burst, causing flooding downstream.”
Read moreRising water levels threaten Indonesia's Jakarta
Remnants of the Earth’s last ice age, when sheets of ice covered swathes of the globe, the world’s glaciers retreated to the frigid polar regions around 10,000 years ago. Over the past few decades, the rate in which these glaciers are shrinking has accelerated dramatically – one of the most visible consequences, climate scientists say, of rising global temperatures triggered by the man-made climate crisis.
“Glaciers play an important role for water resources around the world, and today all glaciers are retreating in response to climate change,” Stroeve said. “In Greenland and Antarctica, glaciers discharge land ice into the oceans that contributes to sea level rise. Thus, loss of glacier mass impacts communities around the world that rely on them for freshwater and further raises global sea level, impacting coastal communities.”
Since the end of the 20th century, the amount of ice loss reported from the dozens of glaciers monitored by climate scientists has been measured in feet rather than inches. Relative to 1970, glaciers in this reference network have lost a little more than 26 feet of water equivalent as of 2023 – the equivalent of slicing 94 feet off the top of each glacier.
Stroeve said that the increasing rate in which the world’s glaciers were shrinking, fragmenting or disappearing altogether was yet another reminder of the urgent need to curb carbon emissions.
“Of course we need to reduce greenhouse gas emissions, as that is the main driver behind ice melting all around the world these days,” she said. “That will require strong political leadership which the world still seems to lack.”
