The glacier is not just melting up, but melting out
At the bottom of the world, a glacier the size of Florida is quietly unraveling — not in the ways science had long assumed, but through hidden fractures and underwater staircases that funnel warm ocean water deep into the ice. New research from the International Thwaites Glacier Collaboration has revealed that Thwaites, already responsible for 4 percent of annual sea level rise, is being hollowed from within at rates that challenge prior models and compress the timeline of potential collapse. What happens in this remote Antarctic expanse is not a distant abstraction — it is a slow-moving reckoning with consequences that will reshape coastlines and communities across the entire human world.
- Scientists discovered that Thwaites is not melting evenly from below but is being carved apart by warm seawater forcing through deep crevasses and staircase-like underwater terraces — a mechanism far more destabilizing than flat-surface melt models had predicted.
- Though melting rates on flat sections of the ice shelf were slower than expected, the glacier is still retreating rapidly, suggesting even modest ice loss is enough to push the system dangerously out of balance.
- A 2021 study warned the ice shelf could shatter within five years, and the new findings reinforce that urgency — the fractures doing the most damage were invisible to researchers until a torpedo-shaped robot named Icefin descended nearly 2,000 feet beneath the ice.
- If Thwaites collapses entirely, it could unlock the rest of West Antarctica's ice, driving global sea levels up by roughly ten feet — enough to redraw coastlines and displace coastal populations worldwide.
- Researchers say the findings sharpen sea level projections and underscore that the transformation is already underway, accelerating through pathways that only became visible when scientists looked directly into the cracks.
Antarctica's Thwaites Glacier — roughly the size of Florida and long nicknamed the 'Doomsday Glacier' — has been shedding billions of tons of ice into the ocean each year, contributing about 4 percent of global sea level rise annually. Its ice shelf acts as a natural brake on the glacier's slide toward the sea, but that brake is weakening. If Thwaites collapsed entirely, sea levels would rise more than two feet on their own — and by potentially ten feet if the surrounding West Antarctic ice followed. New research published in Nature has now revealed that the glacier is deteriorating through mechanisms far more complex and dangerous than scientists had previously modeled.
In late 2019, a joint American and British team from the International Thwaites Glacier Collaboration drilled nearly 2,000 feet through the ice and deployed Icefin, a torpedo-shaped underwater robot, into the cavity below. The robot transmitted images and data about water temperature, salinity, and ocean currents from regions that had never before been directly observed. What it found upended assumptions in two significant ways.
The first surprise was that melting beneath the flat sections of the ice shelf was slower than models had predicted — a layer of colder, fresher water was partially suppressing the melt. But this offered little comfort: the glacier was still retreating rapidly, meaning even modest ice loss was enough to destabilize the system. The second finding was more alarming. The underwater terrain was dominated by deep crevasses and staircase-like terraces, and warm, salty ocean water was funneling through these fractures, widening them and accelerating melt dramatically. The glacier, researchers found, was not simply melting from below — it was being hollowed from within.
These findings close a critical gap in scientific understanding. Prior models had focused on flat-surface melting; the new research reveals that fracture-driven melt may be the primary mechanism driving the ice shelf toward collapse — and potentially on a much shorter timeline than the centuries some projections had assumed. One researcher noted that despite Thwaites' remoteness, its fate will be felt by everyone. The data now available will help refine sea level projections and inform coastal protection planning — but it also carries an unmistakable message: the changes are not coming. They are already here.
Antarctica holds a glacier the size of Florida, and it is coming apart in ways scientists did not fully understand until recently. The Thwaites Glacier, named the "Doomsday Glacier" because its collapse could trigger catastrophic sea level rise, sits in West Antarctica with an ice shelf jutting into the ocean that acts as a natural brake, holding the massive ice mass back from sliding into the sea. But that shelf is weakening as the ocean warms, and new research published in Nature reveals the glacier is melting through mechanisms far more complex and dangerous than previous models suggested.
Every year, Thwaites sheds billions of tons of ice into the ocean, accounting for roughly 4 percent of the world's annual sea level rise. If the glacier collapsed entirely, global sea levels would rise more than two feet. But the real threat extends beyond Thwaites itself. The glacier acts as a dam holding back the rest of West Antarctica's ice. Scientists estimate that if Thwaites gave way completely, the surrounding ice could follow, pushing global sea levels up by roughly ten feet—enough to reshape coastlines and devastate communities worldwide. The process could unfold over centuries, or it could accelerate dramatically. A 2021 study suggested the ice shelf could shatter within five years.
To understand what was actually happening beneath the ice, a team of American and British scientists from the International Thwaites Glacier Collaboration traveled to the glacier in late 2019. Using a hot water drill, they bored nearly 2,000 feet down through the ice and lowered instruments into the cavity below, including a torpedo-shaped robot called Icefin that could navigate the underwater landscape and transmit images and data about water temperature, salinity, and ocean currents. The robot gave researchers access to areas that had been nearly impossible to study before.
What they found was surprising in two ways. First, the melting rate beneath much of the flat ice shelf was slower than models had predicted—between 2 and 5.4 meters per year. A layer of colder, fresher water at the base of the glacier was suppressing the melt. But this discovery did not mean the glacier was stable. Despite the relatively modest melting in flat areas, the glacier was still retreating rapidly, suggesting that even small amounts of ice loss could push it out of balance.
The second finding was more alarming. The underwater landscape was far more complex than expected, dominated by staircase-like terraces and deep crevasses cutting all the way through the ice shelf. Warm, salty ocean water was funneling through these cracks and widening them, causing melting to accelerate dramatically in these areas. The researchers found that melting along the sloped ice of the cracks and terraces, rather than across flat surfaces, may become the primary trigger for the ice shelf to collapse. As one researcher put it, the glacier was not just melting up but melting out—being hollowed from within by water working through its fractures.
These findings fill in gaps in the scientific understanding of how Thwaites is changing. Researchers have known for years that the glacier was melting, that ocean temperatures were rising, and that the atmosphere was warming. What was missing was a precise picture of the mechanisms driving the collapse. The new research provides that picture, revealing a system far more vulnerable to rapid destabilization than the flat-surface melting models had suggested. The ice shelf could disintegrate much sooner than the centuries-long timescale some projections had assumed, potentially triggering an unstoppable retreat of the glacier itself.
The implications reach far beyond Antarctica. One oceanographer involved in the research emphasized that despite Thwaites' remoteness, what happens there will affect everyone. Better understanding of how the glacier is melting allows scientists to make more accurate projections about sea level rise, information that can inform efforts to mitigate climate change and protect coastal communities. But the research also carries an urgent message: the changes are happening now, and they are accelerating through pathways that were not fully visible until scientists looked closely at the cracks.
Notable Quotes
The glacier is still in trouble. Despite small amounts of melting there is still rapid glacier retreat, so it seems that it doesn't take a lot to push the glacier out of balance.— Peter Davis, oceanographer at the British Antarctic Survey
Despite it being so remote, the consequences of what happens on Thwaites will impact everybody.— Peter Davis
The Hearth Conversation Another angle on the story
Why does it matter that the melting happens through cracks rather than across flat surfaces?
Because cracks are like highways for warm water. Once water gets inside and starts widening them, the process feeds itself—more cracks mean more access, more melting, more instability. Flat surfaces melt slowly. Cracks can trigger collapse.
The study found less melting than expected in some areas. Doesn't that suggest the glacier is more stable than we thought?
No. That's the counterintuitive part. The glacier is retreating rapidly even though the flat-surface melting is slower than predicted. It means you don't need massive melting everywhere to destabilize it. A little bit of melting in the right places—the cracks, the terraces—is enough to push it past the point of no return.
How did they even get data from under the ice shelf?
They drilled down nearly 2,000 feet and sent a robot called Icefin through the hole. It's like sending a submarine into a cavity beneath the ice. The robot could swim around, take pictures, measure water temperature and salinity. It gave them access to places that were basically impossible to study before.
If the glacier collapses, what actually happens to the rest of West Antarctica?
Thwaites is acting like a cork in a bottle. It's holding back the ice behind it. If it fails, that ice starts flowing toward the ocean. Scientists estimate the total sea level rise could reach ten feet if the whole system goes.
Ten feet seems abstract. What does that mean for actual people?
Coastal cities get flooded. Not gradually—depending on how fast it happens, you could see rapid inundation of low-lying areas. Miami, New Orleans, parts of New York, cities in Bangladesh, the Netherlands. Entire regions become uninhabitable.
The research says this could take hundreds of years. Why the urgency?
Because one study suggested the ice shelf could shatter within five years. And once it starts, the retreat might be irreversible. We don't know the exact timeline, but the window for action is closing.