The Thwaites Glacier, often called the “doomsday glacier,” is not expected to fully collapse this century, but it is already losing roughly 50 billion tons of ice per year more than it gains from snowfall. Its floating ice shelf will likely break apart within the next decade, while the glacier itself is projected to keep retreating through the 2100s and 2200s, with the potential for a broader collapse of the West Antarctic Ice Sheet over that timeframe.
That timeline matters because Thwaites holds enough ice to raise global sea levels by about 3 meters (nearly 10 feet) if it melts entirely, and its position in West Antarctica means its loss could destabilize the much larger ice sheet behind it.
Why It’s Called the Doomsday Glacier
Thwaites stretches roughly the size of Great Britain and sits in a deep submarine basin in West Antarctica. Scientists have described it as a “cork in the bottle” because its massive size and central position mean that if it goes, the surrounding ice sheet could follow. The nickname traces back to glaciologist Terry Hughes, who titled a research paper “Deluge II and the continent of doom” decades ago. The name stuck because the stakes are real: a full collapse of just Thwaites could redraw coastlines worldwide, and if the rest of the West Antarctic Ice Sheet followed, total sea level rise could reach far higher.
Cities like Shanghai, New York, Tokyo, and Bangkok sit on coastal plains or river deltas that would face severe flooding from even a fraction of that rise. Even the current rate of ice loss from Thwaites accounts for roughly 4 to 5 percent of global sea level rise each year.
What’s Happening Right Now
The Thwaites Eastern Ice Shelf, a floating extension covering about half of the glacier’s 120-kilometer-wide front, is the most immediate concern. Fractures have intensified along its shear zones and near the grounding line (the point where the glacier lifts off the bedrock and begins to float). This cracking has created a feedback loop: more fractures lead to faster ice flow, which opens more fractures. The International Thwaites Glacier Collaboration, a joint U.S.-British research effort that studied the glacier from 2018 to 2024, concluded this ice shelf is likely to break up and drift away within the coming decade.
Headlines in late 2021 warned the shelf might “shatter like a car windscreen” within five years. That dramatic prediction hasn’t played out on that exact schedule, but the shelf’s structural integrity continues to weaken.
How Warm Water Attacks From Below
The primary force driving Thwaites’ retreat isn’t warm air. It’s warm ocean water. Deep currents carry relatively warm water beneath the glacier’s floating ice, where it reaches the grounding line with more than enough heat to melt ice. Researchers who sent instruments beneath the ice shelf found water temperatures holding roughly 1.8°C above the freezing point of ice near deep crevasses.
This warm water doesn’t melt the ice evenly. It carves into sloped surfaces and steep crevasse walls, sculpting the underside of the ice into terraces. The meltwater produced along these steep faces rises and creates a layered effect that actually suppresses melting along flat surfaces nearby. The result is an uneven, increasingly unstable ice base. As the grounding line retreats further inland into deeper bedrock, more of the glacier’s underside gets exposed to this warm water, which is why scientists worry about runaway melting once the retreat reaches a certain point.
The Ice Cliff Question
One of the biggest fears about Thwaites involves a process called marine ice cliff instability. The idea is straightforward: if the floating ice shelf breaks away, it could expose tall cliffs of ice at the glacier’s edge. If those cliffs exceed about 80 meters above the waterline, the ice may not be strong enough to support its own weight and could begin to crumble. If each collapse exposes another equally tall cliff behind it, the process could become self-sustaining, like dominoes falling.
Early models incorporating this mechanism projected dramatic outcomes: up to 1 meter of sea level rise from Antarctica alone by 2100, and over 15 meters by 2300 under high-emission scenarios. Those projections were later revised downward to about 0.35 meters by 2100 and 9 meters by 2300, but they still represented a worst case.
More recent research has been cautiously reassuring on this front. A 2024 study published in Science Advances found that Thwaites is unlikely to experience runaway cliff collapse this century. In model simulations, when the grounding line retreated to expose taller cliffs, the ice thinned and sped up in ways that actually reduced the calving rate, stabilizing the cliff before it could trigger a chain reaction. That said, the glacier sits over a basin that gets deeper further inland, meaning cliffs taller than 200 meters could eventually be exposed as retreat continues over the coming centuries. At those heights, stabilization becomes much harder.
The Realistic Timeline
The most current scientific consensus, drawn from the ITGC’s six years of fieldwork and modeling, breaks the timeline into phases. The floating ice shelf will likely disintegrate in the next decade or so. When it does, the grounded glacier behind it will speed up, but only modestly at first, on the order of a 10 percent increase in flow speed. That’s a less dramatic near-term acceleration than many feared.
The medium and long-term picture is grimmer. Even without the ice cliff mechanism, models predict continuing rapid ice loss through this century that will accelerate further through the next. A general collapse of the West Antarctic Ice Sheet over the next one to two centuries cannot be ruled out. The ITGC has described the medium-term outlook for Thwaites as “grim,” noting that while the process won’t be sudden, it appears irreversible with current warming trends.
In practical terms, this means Thwaites won’t disappear overnight or even in a single decade. But the ice it loses each year will keep growing, contributing an increasing share of global sea level rise through the 2100s. The full 3 meters of sea level rise locked in Thwaites’ ice would likely play out over one to three centuries, depending heavily on how much the ocean continues to warm.
What 3 Meters of Sea Level Rise Means
Three meters doesn’t sound like much until you consider how many people live near sea level. That amount of rise would put large sections of coastal cities underwater, including parts of Miami, New York, Shanghai, Bangkok, and Tokyo. Low-lying island nations would lose most of their habitable land. River deltas that support hundreds of millions of people, from the Mekong to the Ganges, would be reshaped.
And 3 meters is the contribution from Thwaites alone. If its collapse triggers the broader West Antarctic Ice Sheet to destabilize, the total could be substantially higher. Combined with ice loss from Greenland and thermal expansion of warming oceans, some long-term projections put total sea level rise in the range of several meters by 2300. The pace matters as much as the total: faster rise gives coastal communities less time to adapt, build barriers, or relocate.