Mega-Tsunamis That Shook the World for 9 Days Revealed in New Satellite Images
Scientists have finally solved the mystery behind two strange events that shook the entire planet for nine days straight. Their findings close the book on a years-long effort to trace the seismic signals back to their source.
In September 2023, global seismometers detected something strange. The Earth was experiencing minor tremors every 90 seconds—and the shaking went on for nine days. One month later, it happened again. Scientists were baffled, as natural tectonic processes couldn't explain the anomalies.
After roughly a year of scientific sleuthing, two studies published in 2024 independently hypothesized that the shaking resulted from two huge landslides, setting off two 'mega-tsunamis' in the Dickson Fjord in East Greenland. These enormous standing waves—or seiches—sloshed back and forth inside the fjord and triggered small movements within the Earth's crust, they posited.
It was an intriguing possibility, and both studies presented compelling evidence to support their claims. But, 'there were some big uncertainties that made it difficult to fully corroborate that this was actually the root cause,' Thomas Monahan, a Schmidt AI in Science fellow at the University of Oxford, told Gizmodo.
So, Monahan and his colleagues set out to confirm whether this hypothesis was correct. In a study published today in the journal Nature Communications, they unveiled the first direct satellite observations of the seiches and definitively linked them to the seismic anomalies.
The researchers used data captured by NASA's Surface Water Ocean Topography (SWOT) satellite, which launched in December 2022 to map the height of water across 90% of Earth's surface. This type of data collection—known as satellite altimetry—works by transmitting radar pulses from a satellite to Earth's surface, and then measuring the time it takes for the signals to bounce off the surface and return to the satellite.
Conventional altimeters failed to capture evidence of the seiches due to long gaps between observations, according to an Oxford statement. As such, they generally struggle to gather data in fjord regions due to the complexity of the terrain, Monahan said. But SWOT is equipped with a cutting-edge altimeter instrument that uses two antennas to triangulate the return signals. This allows the satellite to take very high-resolution measurements of surface water levels.
'What we're able to get is essentially an incredibly high-resolution snapshot of what the elevation of the sea surface is doing in these complex regions,' Monahan said. These snapshots provided a more accurate picture of how the fjord's sea surface height changed during the 2023 seismic events, allowing his research team to calculate the slopes of the massive waves that had formed.
'We were able to essentially unearth the fact that there was a significant anomaly in the fjord exactly when we would expect this wave to occur,' Monahan said.
But determining that these seiches formed at the same time as the strange seismic signals still wasn't enough to prove the two events were linked. The researchers needed direct evidence to prove that these huge waves were capable of generating global tremors.
To that end, they linked the SWOT snapshots to small movements in the Earth's crust detected at seismic stations located thousands of miles away from the fjord. Coupling this continuous seismic data with the intermittent satellite observations allowed them to reconstruct the characteristics of the wave, even for periods that SWOT did not observe. The researchers also ruled out the possibility that the seismicity stemmed from weather or tidal conditions and ultimately determined that the seiches were the sources of the tremors.
These waves formed when a warming glacier collapsed in on itself, Monahan said. 'This created very large landslides, which—when they struck the fjord—produced massive mega-tsunamis on the order of 200 meters or 600 feet tall,' he explained.
'This was the first time that a mega-tsunami of that nature had occurred in Eastern Greenland,' Monahan said, adding that this type of event has been documented on the territory's west coast. To see this phenomenon spreading to other parts of the ice sheet 'is concerning,' he said, because it shows that climate change is accelerating in this region.
'I think what this study really emphasizes is that—well, it sounds silly to say—but climate change is a global phenomenon,' Monahan said.
'Some of the biggest and fastest changes are occurring in the Arctic and in remote regions where we may not see it every single day. But it's important to understand and quantify those changes as they will eventually come to impact us where we live,' he said. Indeed, the waves that shook the world offer a stark reminder of the sweeping impacts of rising global temperatures.
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We all know someone with a fast metabolism. Or at least we think we do. They have a voracious appetite and yet never seem to put on weight. Is it that some people genetically are predisposed to be fatter than others? Perhaps our hormones are to blame, the type of foods we eat, even our gut health. There are certainly lots of competing theories for why some of us pile on the pounds, with corresponding diet advice. And all of them are a distraction, at least according to Prof Keith Frayn, one of the world's leading experts on metabolism. Having spent over 50 years studying metabolic health, he thinks we've made it all more complicated than it needs to be. Instead of cutting out carbs, drinking kefir, or avoiding low-fat/full-fat (depending on which influencer guru you prefer), he wants us to strip our thinking right back to basics: calories in, calories out. 'Arguments against this energy balance model are simply distracting us from what must be done,' says the emeritus professor of human metabolism at the University of Oxford. 'I'm not denying there are genetic effects on body weight, but as far as we can tell they act by changing how much you eat. Not how much you burn off. I think people have to understand that.' His book, A Calorie is a Calorie: The Inescapable Science that Controls our Body Weight is a rigorous account of the science of energy balance, in which he dispels the myth that some people have faster metabolism than others. If it's an excuse you've ever used yourself, then that probably isn't what you want to hear. As Prof Frayn adds: 'I know this is probably an unpopular view, but I've come at it as a scientist. Not as a celebrity influencer.' The energy balance model asserts that if we take in more energy than we expend, we will store the rest. Conversely if we expend more than we take in, our energy stores will be depleted, and hence our weight will fall. However the theory has become unpopular. 'People say it can't be that simple, or else we wouldn't be where we are,' says Prof Frayn. This suspicion that the cause of the obesity epidemic must be more complicated than calories in and calories out has led scientists – and a host of social media influencers – to posit alternative theories. We're often told to ditch the white bread and give rice a wide berth if we want to lose weight. The reasoning being that they quickly convert to sugar, which is then stored as fat. This so-called carbohydrate-insulin model has been widely promoted in recent years. Hence many of us worry about blood sugar spikes and follow-low carb diets. However, Prof Frayn says: 'I'm not convinced that spikes of blood sugar are bad for you. I don't think there's a lot of evidence for that, other than they make you hungry again more quickly. Whereas if you eat more unrefined fruit and vegetables they're going to take longer to be processed and keep you full for longer.' So it is not that carbohydrates are more likely to be laid down as fat, but rather they encourage you to eat more calories overall, affecting energy balance. 'A review of published studies has confirmed that low-carbohydrate diets help with weight loss because of reduced calorie intake rather than any specific effects of the lowering of carbohydrates,' he says. Popularised by the late Dr Michael Mosley whose 5:2 diet proved immensely popular as a method for losing weight, the suggestion being that it would encourage a period of fat burn. However research suggests that alternate-day fasting is about as effective as a typical low-calorie diet for weight loss. 'Time-restricted eating, intermittent fasting – so many of these ideas are just ways of altering energy intake: they do not change the underlying principle of energy balance,' says Prof Frayn. Related to the concept of intermittent fasting is the idea that our gut microbiome influences our weight. Prof Tim Spector has also popularised the idea of giving your gut a rest so that it can work more efficiently. There are clear observations to be made when you compare obese and lean people by looking at the microorganisms in their faeces, they have rather different populations. If obese people lose weight, it changes towards what we see in lean people. 'You can interpret that to say that the bacteria are causing them to become obese, but there is no proof of that,' says Prof Frayn. 'We don't have any experiment that would show that it is the different families of bacteria causing changes in body weight. It probably is so in mice, but mice are very different from humans.' Can dieting damage your metabolism? If you believe in weight set point theory then you might believe that it does. 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He cites the example of his two friends Bobby and Alex (names have been changed). Alex is large-framed and muscular, while Bobby is petite. When they talk about food, it seems that Bobby is the one who is continuously eating. Does it mean he has a fast metabolism? The answer, says Prof Frayn is, no. The truth is that Alex is under-reporting his true calorie intake. This is a problem that has confounded generations of scientists trying to study energy. Recent studies are finally showing just how unreliable we are at recording our own diets. 'You can find people who appear to eat very different amounts and yet they weigh the same. But when you bring them into the lab and study them it all disappears. It has to come down to the fact we're not getting the information right about what they're eating.' When it comes to calories, some foods are denser than others. In 1992 when British explorer Sir Ranulph Fiennes and his companion Dr Mike Stroud attempted to reach the North Pole, they needed food that packed a calorific punch for its weight. 'They knew they would spend months pulling these heavy sledges and they knew they'd be expending a lot of energy and that they had to carry what they were taking. So it was 'how do we maximise the amount of energy in those rations?'' They did it by adding butter. To everything. 'If you add fat to things you will add energy to things without much weight. It creates very calorific foods,' explains Prof Frayn. It means that if you want to lose weight, clearly trying to cut fat out of your diet might be useful. Take the example of muesli, which Prof Frayn has for his breakfast. 'If you look at the nutrition label on muesli and compare it to granola, you've added a good 50 calories with the latter [because of the added oils]. You're just adding calories in the form of fat.' One might argue it makes it tastier. 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