[g Fun Facts online explores advanced technological topics and their wide-ranging implications across various fields, from geopolitics and neuroscience to AI, and environmental conservation, from Hong Kong since April 2025].
Welcome to gFun Facts online. Today we're journeying to the vast frozen landscapes of Greenland. But our story isn't about what you can see on the surface. Beneath the silent icy waters of its majestic fjords, a hidden drama is unfolding. Colossal underwater waves, some as tall as skyscrapers, are secretly devouring the foundations of the island's mighty glaciers.
This is a newly discovered titan, a powerful and previously underestimated force driving the rapid decay of the Greenland ice sheet with profound consequences for us all. For years, we've known about two primary culprits, rising air temperatures melting the ice from above and warmer ocean water attacking it from below. But recent research has unveiled a shocking new mechanism, a violent feedback loop called the calving multiplier effect, where the very act of a glacier shedding ice into the ocean triggers a process that dramatically accelerates its own destruction.
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To understand this, we first need to look at the unique stage where this drama plays out, a Greenlandic fjord. These are not just any inlets. They are long, deep, and narrow canyons carved by glaciers over thousands of years. They are the battlegrounds where the fate of much of the world's frozen fresh water is decided.
During the summer, the water in these fjords separates into distinct layers. At the very top, you have a layer of cold, fresh water. This comes from the melting ice sheet and the countless rivers of melt water pouring in. Because it's fresh, it's less dense, so it floats.
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The sharp boundary between these two layers, the cold, fresh top and the warm salty bottom, is called a picnic line. Think of it like oil and vinegar in a salad
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Beneath this chilly surface layer lies a completely different body of water. A much warmer, saltier volume that is journeyed from the Atlantic Ocean. This warmer, denser Atlantic water settles in the deep parts of the fjord. The sharp boundary between these two layers, the cold, fresh top and the warm salty bottom is called a picnic line. Think of it like oil and vinegar in a salad dressing before you shake it. This stratification is the key. 2.10
While the fjorded surface might look perfectly calm, this hidden boundary can be disturbed, creating what scientists call internal waves. They are invisible from the air, but they carry immense energy through the depths.
For a long time, scientists thought these waves were mainly generated by tides and winds. But they were about to discover a far more violent trigger.
That trigger is the spectacular process of iceberg calving. The face of a glacier that meets the sea is a place of constant tension. When a huge chunk of ice, sometimes the size of a city block, breaks free and crashes into the ocean, the event is anything but quiet. The initial splash creates massive surface waves, sometimes called calving induced tsunamis that can surge for miles, a well-known danger to anyone nearby.
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Inuit hunters have long known to listen for the distant rumble of a cving glacier, knowing that destructive waves might follow. But the most significant impact happens beneath the surface. The immense energy released by that plunging iceberg acts like a giant paddle violently disturbing the stratified water column. This is what gives birth to the skyscraper sized internal waves.
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Immense energy released by that plunging iceberg acts like a giant paddle violently giving birth to skyscraper sized internal waves.
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A pioneering 2025 study published in Nature gave us our first detailed look. Researchers found that long after the surface tsunami has passed and the water appears still again, these massive internal waves continue to roll through the depths of the fjord. And their effect is profound. They act as powerful mixers, churning the water column with incredible force.
Here's an analogy. Imagine you have a glass of iced tea on a hot day. If you don't stir it, a thin layer of cold water forms around the ice cubes, insulating them from the warmer tea. The ice melts slowly, but if you stir the drink, you violently disrupt that cold layer, bringing the warm tea into direct contact with the ice and it melts much, much faster.
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The internal waves in a Greenlandic fjord are doing exactly the same thing, but on a monumental scale. They obliterate the protective layer of cold, fresh melt water that would normally insulate the glaciers submerged face. This brings a steady, renewed supply of that warmer, saltier Atlantic water into direct, sustained contact with the ice.
The result is a dramatic acceleration of underwater melting at the glaciers base. This creates a vicious feedback loop. The increased melting at the base undermines the towering ice cliff above, making it more unstable and more likely to calve again, more calving means more and larger internal waves, which in turn leads to even more melting. This is the calving multiplier effect, a significant amplifier of ice loss in Greenland that until recently we never even knew existed.
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So, how do you observe something so powerful yet so invisible in one of the most dangerous environments on Earth? You can't just drop sensors in front of a cving glacier. They would be destroyed instantly. This is where scientists on the Swiss Polar Institute's Green Fjord project turned to a revolutionary technology distributed acoustic sensing or DAS. In essence, DAS technology turns a standard fiber optic cable into a string of thousands of virtual microphones.
It works like this. An instrument sends pulses of laser light down the cable. Microscopic imperfections in the glass fiber cause a tiny fraction of that light to reflect back to the source. When the cable is stretched or compressed by even the tiniest amount due to vibrations from sound waves or seismic tremors, it changes the properties of that reflected light. By analyzing these changes, scientists can detect and pinpoint the location, intensity, and frequency of vibrations all along the cable's entire length in real time.
For their groundbreaking study at the Ecolo Rutsit Kangilit Seriat Glacier in southern Greenland, researchers deployed a 10 kilometer long fiber optic cable on the seafloor right in front of the glaciers 3 km wide cving face. This single glacier releases a staggering 3.6 cub kilm of ice into the ocean every year.
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The DAS system allowed the science team to safely listen to the entire symphony of the glacier from the initial fracturing of the ice to the crash of the iceberg and crucially to the subsequent turmoil in the water column. For the first time, they could visualize the propagation of these massive internal waves and measure their impact. It was like having a thousand sensors directly beneath the chaos, revealing the hidden mechanism of destruction.
This discovery provides a key to understanding what's happening at many of Greenland's other major glaciers, the ones responsible for draining the vast interior ice sheet. Let's look at some of the big ones. First, there's Yakob Shavean Isra, often called Greenland's fastest moving glacier. Located on the west coast, it was responsible for about a millimeter of global sea level rise all on its own between 2000 and 2010. Its dramatic retreat has been linked to the arrival of warm ocean waters into its fjord.
The cving multiplier effect is almost certainly accelerating its melt even further.
Then there are the giants in the east, Kangerluswok and Helheim Glacier. Kangangeruswalk was stable for a long time, but between 2018 and 2021, it retreated 7 kilometers and doubled its ice discharge after an intrusion of warm Atlantic water. And at Helheim, scientists in 2018 filmed a single cving event where a 4-mile long iceberg broke away, a visceral demonstration of the immense scale of these processes.
The story is the same across Greenland. Of its more than 200 coastal glaciers, the vast majority are retreating. They're being eaten away by a warming atmosphere from above and an ever more aggressive ocean from below.
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And now we know that the ocean's attack is even more powerful than we thought, thanks to these cving driven internal waves. This isn't just a remote Arctic issue. The fate of Greenland's ice has profound global consequences. The Greenland ice sheet holds enough frozen water to raise global sea levels by more than 7 m or 23 ft if it were to melt entirely.
While a complete collapse isn't imminent, the current rate of melt is deeply concerning. Since 2002, Greenland has lost about 5900 billion tons of ice. This melt is currently responsible for about 20% of all observed global sea level rise. For every 360 gigatons of ice that melts, the global average sea level goes up by 1 millm.
The Intergovernmental Panel on Climate Change, the IPCC, projects that Greenland could contribute between 8 and 27 cm to sea level by the year 2011. But discoveries like the cving multiplier effect suggest that our current models may not be capturing the full speed of the process. The real numbers could be higher.
And it's not just about rising water levels. There's another equally serious threat. The massive influx of cold fresh water from Greenland's melting ice sheet could disrupt the Atlantic meridian overturning circulation or AMOC. You might know it as the Great Ocean Conveyor belt.
This vast system of currents which includes the Gulf Stream transports warm water from the tropics northward warming places like Europe and sends cold deep water southward. It is a critical regulator of the global climate. This entire circulation is driven by density.
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AMOC is currently weaker than it has been in the last 1,000 years. It could be approaching a tipping point.
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In the North Atlantic the warm salty water cools, becomes denser, and sinks driving the deep return flow. But the flood of fresh melt water from Greenland is less salty and therefore less dense. It doesn't sink as readily. This can act like a break on the entire system. Scientists have already observed that the AMOC is currently weaker than it has been in at least the last 1,000 years. There are serious concerns that it could be approaching a tipping point, a threshold beyond which it could slow dramatically or even collapse, which would have devastating consequences for climate patterns, especially in Europe and North America.
The question is no longer whether Greenland will contribute to sea level rise, but how much and how fast. Scientists are increasingly worried about irreversible tipping points.
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One of these is the melt elevation feedback. As the ice sheet melts, its surface gets lower in altitude. Lower altitudes are warmer, which accelerates melting, which lowers the surface even more in a self-reinforcing cycle.
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Melt elevation feedback. As the ice sheet melts, its surface gets lower in altitude, which is warmer, which accelerates melting, which lowers the surface even more in a self-reinforcing cycle.
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Climate models paint a stark picture of different futures for Greenland, depending entirely on our success in reducing greenhouse gas emissions. In a low emissions scenario where we meet the most ambitious goals of the Paris Agreement, the rate of ice loss would slow down, but it wouldn't stop. Greenland would still contribute to sea level rise. But under a high emissions business as usual trajectory, the melting would accelerate dramatically.
In that future, the entire ice sheet could become ice free within a millennium, committing the world to the full 7 plus meters of sea level rise. Some models predict Greenland could contribute over a meter and a half or 5 ft to sea levels by the year 2,200 in this worstc case scenario.
The discovery of the skyscraper sized internal waves adds a new layer of urgency to these projections. This powerful feedback loop hasn't been fully included in many older climate models, which means the ice sheet may be even more sensitive to warming than we understood.
The silent, invisible power of these underwater waves is a stark reminder of the complex and sometimes surprising ways our planet is responding to climate change. What happens in the hidden depths of Greenland's fjords will not stay there. It will be felt on coastlines around the world for centuries to come. The roaring crash of a calving iceberg is not just an end. It is the beginning of a process that is hastening the melt of our planet's great northern ice sheet.
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