A slower collapse is paradoxically harder to reverse
Photographs taken by a Navy photographer over Antarctica in 1966 have become the foundation of a discovery that reframes how humanity understands its coastal future. Researchers at the University of Copenhagen, analyzing those archival images alongside modern satellite data, have determined that it is warm ocean water eroding ice from below — not atmospheric heat from above — that drives the collapse of Antarctic ice shelves. The process unfolds more slowly than feared, yet this offers no comfort: a gradual collapse is harder to reverse, and once the ice brake fails, glaciers surge freely toward the sea, carrying with them the potential for meters of sea level rise that would reshape the geography of human civilization.
- Decades-old aerial photographs have overturned a foundational assumption in climate science — the primary engine of Antarctic ice shelf collapse is warm seawater eating upward from below, not surface melting from a warming sky.
- The Wordie Ice Shelf's 30-year disappearance, now reconstructed in three dimensions, is a proof of concept for far larger shelves like Ronne and Ross, whose collapse could raise global sea levels by five meters.
- A slower collapse sounds reassuring, but scientists warn it is paradoxically more dangerous — the longer the process runs, the more entrenched and irreversible it becomes, with glaciers accelerating freely once their ice brake is gone.
- Gravitational dynamics mean Antarctic melting strikes Northern Hemisphere coastlines — including Denmark's — harder than anywhere else, turning a distant southern crisis into an immediate northern emergency.
- The findings reframe the urgency of emissions cuts: the window to prevent collapse is not a future problem to be solved later, but is being determined by the carbon released today into warming oceans.
In November 1966, a Navy photographer aboard an American aircraft captured the Antarctic Peninsula below — and unknowingly documented the beginning of the end of the Wordie Ice Shelf. Those images, dormant for decades, have become the foundation of a discovery that is reshaping how scientists understand one of the gravest threats to coastal cities in the Northern Hemisphere.
Researchers at the University of Copenhagen analyzed those archival photographs alongside modern satellite data, reconstructing Wordie's slow-motion collapse in unprecedented detail. Their finding overturned years of assumption: the culprit was not a warming atmosphere or surface meltwater pools, but warm ocean water eroding the ice shelf from below, at the boundary where floating ice meets the sea. This distinction fundamentally changes the calculus of when and how ice shelves fail.
Wordie itself is modest in scale — its disappearance over thirty years raised sea levels by only millimeters. But it was a proof of concept. The two largest Antarctic ice shelves, Ronne and Ross, hold enough ice to account for five meters of sea level rise. For countries like Denmark, this is not abstract: gravitational effects cause Antarctic melting to raise sea levels more sharply in the Northern Hemisphere than elsewhere on Earth.
Using a technique called structure-from-motion photogrammetry, the team extracted three-dimensional data from overlapping aerial images, measuring ice thickness, flow velocity, and structural integrity across decades. They identified what they call 'pinning points' — anchors of structural stability that can now serve as early-warning diagnostics for other vulnerable shelves.
Lead author Mads Dømgaard noted that collapse unfolds more gradually than earlier models suggested — seemingly reassuring. But colleague Anders Anker Bjørk offered a sobering counterpoint: a slower collapse is paradoxically harder to reverse. Once the ice shelf begins to fail, it becomes entrenched. The shelf acts as a brake on interior glaciers; when that brake fails, glaciers surge freely into the ocean. The longer the process runs, the more irreversible it becomes.
The photographs from 1966 are not merely a record of the past. Every ton of carbon released today warms the oceans that will drive the slow, inexorable failure of ice shelves that have existed for millennia. The collapse of Wordie took thirty years. The collapse of Ronne or Ross could take far longer — and by the time it is complete, the sea level rise it triggers will have permanently redrawn the map of human settlement.
In November 1966, a Navy photographer aboard an American aircraft pointed his camera down at the Antarctic Peninsula and captured something that would not be fully understood for decades: the beginning of the end of the Wordie Ice Shelf. That single frame, and the dozens that followed over the next few years, have become the foundation of a discovery that is reshaping how scientists think about one of the most consequential threats to coastal cities in the Northern Hemisphere.
Researchers at the University of Copenhagen recently published their analysis of those archival photos alongside modern satellite data, revealing the slow-motion collapse of Wordie in unprecedented detail. What they found overturned assumptions that had guided climate science for years. The culprit was not, as long believed, a warming atmosphere or the formation of meltwater pools on the ice surface. Instead, it was warm ocean water eating away at the ice shelf from below, at the boundary where floating ice meets the sea. This distinction matters because it changes the entire calculus of how and when ice shelves fail.
Wordie itself is relatively modest in size. Its eventual disappearance, which occurred roughly three decades after that 1966 photograph, raised sea levels by only millimeters. But Wordie was a proof of concept. The two largest ice shelves in Antarctica—Ronne and Ross—contain enough ice to account for five meters of sea level rise if they collapse. For countries like Denmark, which sits far from Antarctica, this is not an abstract concern. Due to gravitational effects, the melting of Antarctic ice causes sea levels to rise more sharply in the Northern Hemisphere than elsewhere on Earth. A collapse in the Southern Ocean becomes a crisis on northern coasts.
The researchers used a technique called structure-from-motion photogrammetry to extract three-dimensional data from the overlapping aerial photographs. By analyzing the subtle differences in perspective between images, they could measure ice thickness, extent, surface structure, and flow velocity with remarkable accuracy across decades. This allowed them to watch Wordie's collapse unfold frame by frame, identifying what they call "pinning points"—locations where the ice shelf's structural integrity is anchored. These pinning points serve as a diagnostic tool: by monitoring them in other ice shelves, scientists can now assess how far advanced a collapse has progressed and predict which shelves are most vulnerable.
Mads Dømgaard, the lead author of the study published in Nature Communications, emphasized that the dataset revealed something unexpected about the pace of collapse. The process unfolds more gradually than earlier models had suggested. This finding initially seems reassuring—there is more time to observe, to prepare, to adapt. But his colleague Anders Anker Bjørk offered a sobering counterpoint. A slower collapse, he explained, is paradoxically harder to reverse. Once the ice shelf begins to fail, it becomes a protracted process that, once initiated, cannot easily be halted. The ice shelf acts as a brake on glaciers flowing from the interior of the continent toward the sea. When that brake fails, the glaciers accelerate and begin to float freely into the ocean, melting more rapidly. The longer this process takes, the more entrenched it becomes, and the harder it is to stop.
This realization carries an urgent implication. The window for preventing Antarctic ice shelf collapse is not measured in decades of gradual warming that might be reversed with future action. It is measured in the emissions we produce now. Every ton of carbon released today contributes to the ocean warming that will drive the slow, inexorable failure of ice shelves that have existed for millennia. The photographs from 1966 show not just the past, but a warning about the present. The collapse of Wordie took thirty years to complete. The collapse of Ronne or Ross, should it begin, could take far longer. And by the time it is complete, the sea level rise it triggers will have reshaped the geography of human settlement across the globe.
Notable Quotes
The primary driver of Wordie's collapse is rising sea temperatures, which have generated the melting beneath the floating ice shelf— Mads Dømgaard, lead author, University of Copenhagen
Ice shelf collapse may be slower than we thought, but this longer process will make it harder to reverse the trend once it has started. This is an unambiguous signal to prioritize halting greenhouse gas emissions now rather than sometime in the future— Anders Anker Bjørk, Assistant Professor, University of Copenhagen
The Hearth Conversation Another angle on the story
Why does it matter that the collapse is slower than we thought? Doesn't that give us more time?
It seems that way, but it's actually the opposite. A slower collapse means the process becomes harder to interrupt once it starts. The ice shelf is like a brake on the glaciers behind it. Once that brake begins to fail, it fails for decades or longer. You can't just reverse it.
So the warm water underneath—that's the real problem, not the air temperature?
Yes. Everyone assumed the atmosphere was warming the ice from above, or that meltwater pools on the surface were destabilizing it. But the photographs showed the ocean itself was doing the work, melting the ice from below where it floats. That's a different mechanism entirely.
How does knowing the "pinning points" help us now?
It gives us a diagnostic tool. We can look at other ice shelves and see where they're anchored, where they're vulnerable. We can watch for the same signs of failure that Wordie showed. It's like learning to read the early symptoms of a disease.
If Wordie only raised sea levels by millimeters, why does it matter so much?
Because Wordie was small. The Ross and Ronne ice shelves are enormous. If they collapse the way Wordie did, we're talking about meters of sea level rise. And because of gravity, that rise hits the Northern Hemisphere harder. Denmark will feel it more than places closer to Antarctica.
What's the message to policymakers?
Stop emissions now, not later. The collapse process is so slow and so hard to reverse once it starts that waiting for future technology or future action won't work. The time to act is today.