"When the floating ice shelf in front of Thwaite's glacier loses thickness, it can no longer act as a brake on the ice behind it. This buttressing is the only thing slowing the flow of the glacier into the sea. Thwaite's ice shelf has already lost between 30 and 40% of its buttressing strength in past decade. The world's most advanced simulations are underestimating how quickly the glacier is destabilizing. As soon as the ice shelf's back pressure weakens enough, the glacier's own weight starts to drive a runaway retreat. The process is not gradual. Once the critical buttressing is lost, the glacier can shift from a slow drain to a rapid collapse." READ & WATCH If This Glacier Collapses, 40 Million People Will Be Underwater, transcript below Feb 25 2026 [Earthline channel Joined YT Mar 15, 2021 4.16K subscribers 109 videos]
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In this video, we examine the growing instability of the so-called “Doomsday Glacier” and what scientists say could happen if it collapses. This isn’t just about melting ice; it’s about structural ice shelf failure, rising sea levels, and the chain reaction that could follow. We break down the science, the timeline uncertainties, and the real-world impact on coastal cities, infrastructure, and global migration. How close are we to a tipping point, and what would it actually mean If This Glacier Collapses, 40 Million People Will Be Underwater
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Thwaite's glacier is melting nearly twice as fast as scientists projected, exposing weaknesses the climate models missed. And under the right conditions, a rapid collapse could send a wall of water hurtling toward coastal cities like New York within hours. 40 million people live in the crosshairs, and not even the experts agree on how much time remains.
Just how close are we to disaster? And what would actually happen if this ticking glacier finally breaks?
Satellites measuring the mass of Antarctica have delivered a clear warning. The ice is vanishing much faster than climate models predicted. The Grace and Grace FO mission show that Antarctica lost 150 billion tons of ice each year from 2002 to 2023. Thwaite's glacier alone is shedding around 35 billion tons annually, a number that has only climbed in recent years. Yet, when scientists compare these hard measurements to the latest climate model outputs, a stark gap appears. The CMI P6 model ensemble which guides global risk assessments projects just 20 billion tons per year for Thwaite's. That is nearly half the observed rate. This is not a minor oversight.
Models that miss the mark by such a wide margin cannot be trusted to forecast the true pace of sea level rise. Eric Rignau of the University of California, Irvine says, "The recent acceleration in mass loss is far beyond what the latest generation of coupled climate ice models anticipate.
The numbers leave little room for comfort. Across West Antarctica, the observed melt rate is outpacing projections by a factor of two. The difference is not just academic. It means the world's most advanced simulations are underestimating how quickly the glacier is destabilizing. This growing mismatch between satellite records and model predictions has forced scientists to re-examine the physical processes at work. It is not just about missing a decimal point. The models are failing to capture key mechanisms that drive rapid ice loss, especially under the floating ice shelves and along the grounding line.
The next step is to look at exactly what those models are missing and why the glacier's mechanics are so much harder to predict than anyone hoped.
When the floating ice shelf in front of Thwaite's glacier loses thickness, it can no longer act as a brake on the ice behind it. This process is called buttressing and it is the only thing slowing the flow of the glacier into the sea.
Over the past decade, satellite and radar measurements have shown that the western ice shelf has already lost between 30 and 40% of its buttressing strength. The loss isn't uniform. Weak spots form where warm, deep ocean water carves channels into the shelf's base, creating hidden vulnerabilities right at the grounding zone.
Ted Scamos, a leading glaciologist, says the grounding line is retreating on a retrograde slope. And once that process reaches a critical threshold, models will severely underrepresent the ensuing collapse. This retrograde slope means the bedrock beneath the glacier actually gets deeper as you move inland.
With each kilometer, the grounding line retreats about 5 km since 2018 alone. Thicker and heavier ice is exposed to the ocean, accelerating melt. The bed drops from around -500 m at the current edge to depths near -1,500 m, just 75 km farther in. This is the classic setup for marine ice sheet instability.
As soon as the ice shelf's back pressure weakens enough, the glacier's own weight starts to drive a runaway retreat. The process is not gradual. Once the critical buttressing is lost, the glacier can shift from a slow drain to a rapid collapse with the retreat feeding on itself. Scientists have found that these mechanics are what most climate models have missed, underestimating both the pace and the risk of a large scale failure.
The physical structure of Thwaite's with its thinning shelf, its deepening bed, and its loss of friction creates a direct path to instability. Once the buttressing ice shelf gives way, the glacier's restraint vanishes almost instantly. British Antarctic survey models simulate what happens next. A surge front driven by gravity and the sudden release of pent up ice races outward at speeds near 20 km hour. In this scenario, a pulse of about 10 cm of meltwater and disintegrating ice barrels off the Antarctic coast. The ocean absorbs this shock, but the energy does not just fade, it travels. The resulting wave, though not a towering tsunami, is a rapid continent scale bulge in sea level that can cross the South Atlantic in less than a day.
For the eastern United States, the numbers are stark. That water mass, once released, could reach the shores of New York in as little as 8 hours. The models track the wave's progress as it moves up the continental shelf, compressing against the shallow margins and amplifying local tides. The initial surge is measured not just in centimeters, but in the suddenness of its arrival, enough to overwhelm coastal defenses designed for storms, not for a global scale pulse.
Scientists emphasize that this rapid collapse scenario represents the outer edge of what is physically possible, not the expected outcome. Yet the mechanics are clear. A critical breach at Thwaite's does not unfold over centuries, but can send immediate shock waves across the world's oceans.
The numbers 20 km hour, 10 cub km of water, 8 hours to New York are not just theoretical. They are the product of physical law and they define the urgency facing every low-lying coastline on the Atlantic rim. Global sea level rise is not measured in single events, but in decades and centuries of change.
The Intergovernmental Panel on Climate Change in its sixth assessment report lays out a range of futures based on greenhouse gas emissions under the low emission scenario known as SP 1-2.6. Thwaite's is projected to add about 0.3 m to global seas by the year 2100. If emissions follow a high-end path SSP 5-8.5, the median estimate rises to 0.5 m. Yet, these numbers only tell part of the story. The same report warns that upperbound outcomes, which account for the possibility of rapid unstable collapse, could see Thwaite's alone push sea levels more than 1 meter higher within the next century. This upperbound scenario draws from the concept of marine ice sheet instability where the loss of buttressing and the retreat of the grounding line create a feedback loop that accelerates ice loss.
If this process takes hold, the pace of sea level rise could jump well beyond what most coastal defenses are built to withstand. The difference between 0 0.3 m and 1 meter is not just a matter of inches. It is the difference between a city's flood barrier holding the line or being overtopped in a single storm cycle. Policy timelines rarely account for the full spectrum of risk. Most adaptation plans are built around the IPCC central projections, but the physics of Thwaite's leaves open the chance of far more dramatic outcomes.
Scientists like Eric Rigno and Ted Scamos caution that the true upper limits are not yet known and that current models may still be underestimating how quickly the glacier could destabilize.
The lasting impact is measured not just in centimeters but in the fate of entire coastal regions over the coming century. Roughly 40 million people live in coastal areas that would be exposed if Thwaite's glacier contributes just 1 meter to sea level rise. Major cities including New York, Miami, Boston, New Orleans, London, and Rotterdam sit on the front lines. The economic stakes are staggering. The United States Army Corps of Engineers estimates that a 1 m rise could inflict between $400 billion and $800 billion in direct damages to American coastal infrastructure alone.
The ripple effects extend far beyond flooded streets. Insurance markets could collapse under the strain of repeated payouts, forcing entire neighborhoods into uninsurability. Supply chains that depend on ports and rail lines near sea level would face chronic disruption, threatening food and fuel deliveries. In some regions, the only option may be organized retreat as local governments weigh the cost of defending every block against the reality of rising tides. For millions, the question is not just when the water arrives, but where they will go when it does.
City planners and federal agencies are racing to close the gap between risk and readiness. In New York, the Big U project aims to wrap lower Manhattan with a barrier of BMS and seaw walls, while Miami's adaptation plan calls for raising roads and installing powerful pump stations. Since 2020, FEMA has funneled over $200 million into coastal resilience grants for vulnerable communities. The Department of Homeland Security has staged multi-day drills simulating a sudden Atlantic surge testing the limits of emergency response.
On the scientific front, the National Science Foundation and NASA are funding fleets of autonomous floats and ice penetrating radars to monitor Thwaite's in real time. International teams, including the US Army Corps of Engineers and the British Antarctic Survey, assess defenses from Boston Harbor to the Tempame's estuary. Yet, each new study reveals just how much remains uncertain, forcing governments to prepare for a future that is both urgent and unpredictable. Scientists warns is melting faster than models predicted, raising real risk for millions living on vulnerable coasts. Governments weigh evacuation plans, sea walls, and retreat. But uncertainty remains. The next move isn't just science. It's how we act on warnings we can no longer afford to ignore. What's your perspective? *** WATCH If This Glacier Collapses, 40 Million People Will Be Underwater
https://www.youtube.com/watch?v=9UKLFdfQnrw
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What climate scientists found on Thwaite's Glacier- "It represents a couple of feet of sea level rise; in computer models, it just unravels itself" Amanpour and Company 13-min Feb 17 report w transcript at DIYH on a Heating Planet blog
"Thwaites Glacier breach can send immediate shock waves across the world's oceans"; Earthline channel 12-min Feb 25 report W TRANSCRIPT at DIYH on a Heating Planet blog [Pt 2 of 3]
"When the floating ice shelf in front of Thwaite's glacier loses thickness, it can no longer act as a brake on the ice behind it. This buttressing is
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unday, March 1, 2026
Thwaite's 3 of 3 "Seismic Quakes Explode as Antarctica’s Doomsday Ice Starts to Fail! Glacier breaking fast"; w Transcript- Climate Watch 13-min Feb 24 at DIYH on a Heating Planet blog
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