Three major cities face flooding risk if Antarctic glacier collapses, scientists warn

Deep in the Antarctic wilderness, a massive force of nature is quietly reshaping the future of our planet. Scientists around the world are closely monitoring a catastrophic scenario that could fundamentally alter coastlines across three continents, displacing millions of people and redrawing the world map as we know it. The implications of this unfolding crisis extend far beyond what most people imagine, touching every aspect of modern civilization from economics to geopolitics.

The Looming Antarctic Crisis

The scientific community has been increasingly alarmed by developments surrounding what researchers have dubbed the “Doomsday Glacier”—a name that, while dramatic, accurately reflects the catastrophic potential of this Antarctic behemoth. The Thwaites Glacier, larger than the entire state of Florida, has earned this ominous nickname because its breach would allow warmer ocean waters to melt the West Antarctic Ice Sheet and raise sea levels by nearly 11 feet.

More than 2 kilometers (1.2 miles) thick in places, Thwaites has been likened to a cork in a bottle. Were it to collapse, sea levels would rise by 65 centimeters (26 inches). But the true terror lies not in the glacier’s immediate impact, but in its role as a gateway to something far more devastating.

The Thwaites is one of a line of glaciers sitting along the marine-facing rim of the West Antarctic Ice Sheet (WAIS)—a massive bowl of ice nearly three times the size of Texas. The only bulwarks that prevent the ocean from filling the basin and melting or dislodging the ice are the glaciers. Should Thwaites fail in its role as guardian, the consequences would be felt in major population centers thousands of miles away.

The Cities in the Crosshairs

Three major metropolitan areas stand at the epicenter of this potential catastrophe, each representing different aspects of human civilization that would be irrevocably altered by the glacier’s collapse. London, New York, and Bangkok—cities that collectively house millions of people and represent trillions of dollars in economic activity—face the prospect of being partially or completely submerged beneath rising seas.

London: A Historic Capital Under Threat

London, one of the world’s most iconic cities and a global financial center, sits at a particularly vulnerable elevation. The Thames Barrier, constructed in the 1980s as a flood defense system, was designed to protect against storm surges and high tides—not against the kind of permanent sea level rise that would accompany Thwaites’ collapse. If Thwaites were to collapse completely, it could raise sea levels by more than 10 feet, a scenario that would overwhelm the city’s existing flood defenses.

The city’s underground transport system, the London Underground, would be among the first casualties. Many of the network’s tunnels run below current sea level and are kept dry only by constant pumping. A permanent rise in water levels would make entire sections of the system uninhabitable, paralyzing transportation for millions of commuters.

Historic landmarks that have stood for centuries would face an existential threat. The Tower of London, Westminster Abbey, and the Houses of Parliament—all located near the Thames—would find themselves fighting a losing battle against the encroaching waters. The cultural and historical losses would be incalculable, representing the erasure of centuries of human heritage.

New York: The Economic Capital at Risk

New York City, America’s most populous urban center and its economic heart, faces perhaps the most complex challenges from rising sea levels. Already, many cities are at sea level, like Shanghai, New York and London. If sea levels rise by even a couple of feet, millions of people might have to move.

Manhattan, built on an island, would be particularly vulnerable. The subway system, which carries over 5 million passengers daily, would face catastrophic flooding. Wall Street, the nerve center of global finance, sits at an elevation that would put it directly in the path of rising waters. The economic disruption would ripple through global markets, affecting everything from pension funds to international trade.

The city’s airports—JFK, LaGuardia, and Newark—are all located at low elevations and would be among the first major infrastructure casualties. The Port of New York and New Jersey, one of the busiest cargo ports in the United States, would cease to function, disrupting supply chains that serve the entire northeastern United States.

Bangkok: A Sinking City’s Final Battle

Bangkok faces a uniquely dire situation because it’s already sinking. The Thai capital sits barely above sea level and has been subsiding at a rate of 1-2 centimeters per year due to groundwater extraction and the weight of urban development. The problem? Rising waters can damage infrastructure, like roads and bridges, leading to big costs for repairs. Not to mention, it can hurt ecosystems living along the coast.

The city’s 10 million residents would face displacement on a scale unprecedented in modern history. The Chao Phraya River, which flows through the heart of Bangkok, would become a highway for rising seas to penetrate deep into the urban core. The city’s famous floating markets, temples, and cultural sites would disappear beneath the waves.

Thailand’s agricultural heartland, the Central Plains, would also be inundated, affecting rice production that feeds not just Thailand but much of Southeast Asia. The country’s tourism industry, which depends heavily on coastal attractions, would be decimated.

The Science Behind the Catastrophe

The mechanism driving this potential disaster is more complex and terrifying than simple surface melting. A team of glaciologists led by researchers at the University of California, Irvine used high-resolution satellite radar data to find evidence of the intrusion of warm, high-pressure seawater many kilometers beneath the grounded ice of West Antarctica’s Thwaites Glacier.

The findings suggest that existing climate models are underestimating the impact of ocean and ice interactions in future sea level rise projections. This represents a fundamental shift in our understanding of how glaciers behave and how quickly they can change.

The process is insidious and accelerating. Circumpolar deep water is salty and has a lower freezing point. While freshwater freezes at zero degrees Celsius, saltwater freezes at minus two degrees, and that small difference is enough to contribute to the “vigorous melting” of basal ice.

Through images Icefin beamed back, they discovered the glacier is melting in unexpected ways, with warm ocean water able to funnel through deep cracks and “staircase” formations in the ice. This discovery has fundamentally changed how scientists understand glacier dynamics and has made their predictions far more alarming.

The Hidden Lakes: An Unexpected Accelerant

Recent discoveries have revealed that the Thwaites Glacier contains hidden lakes beneath its surface—bodies of water that could dramatically accelerate the melting process. After studying the glacier since 2018, the International Thwaites Glacier Collaboration (ITGC) found that rapid ice loss is set to accelerate this century to such an extent that the whole glacier could collapse within 200 years.

Professor Noel Gourmelen, lead author of a March 2025 study and member of the ITGC, explained the significance of these hidden water bodies: “We expected that water draining from the underside of the ice sheet plays a role in modulating ocean melting, the sheer magnitude of this lake drainage gave us the opportunity to finally observe and quantify its impact. The lake outflow took place in a key sector impacting Thwaites’ stability, the drainage in effect momentarily turbo-charged Thwaites’ ocean-driven retreat.”

These subsurface lakes act as lubricants, allowing massive sections of ice to slide more easily toward the ocean. When these lakes drain, they create channels that warm ocean water can exploit, creating a feedback loop that accelerates the melting process exponentially.

The Accelerating Timeline

What makes the current situation particularly alarming is the speed at which conditions are deteriorating. The volume of water flowing into the sea from the Thwaites and its neighboring glaciers has doubled from the 1990s to the 2010s.

Scientists found that at some point in the past two centuries, the base of the glacier dislodged from the seabed and retreated at a rate of 1.3 miles (2.1 kilometers) per year. That’s twice the rate that scientists have observed in the past decade or so.

The hotter than expected 2025 in the Southern Hemisphere has particularly worried scientists and is believed to have sped up the process. University of South Florida’s Dr. Alastair Graham warned: “If Thwaites Glacier collapses it would cause a rise of around 65cm (25 inches) in sea level. This year is really different. It’s very difficult to recover from this in one season. The game has changed.”

The International Response

Since 2018, a team of scientists forming the International Thwaites Glacier Collaboration, has been studying Thwaites — often dubbed the “Doomsday Glacier” — up close to better understand how and when it might collapse. This unprecedented international effort involves over 100 scientists from multiple countries, using cutting-edge technology to monitor every aspect of the glacier’s behavior.

They sent a torpedo-shaped robot called Icefin to Thwaites’ grounding line, the point at which the ice rises up from the seabed and starts to float, a key point of vulnerability. The data collected by these missions has revolutionized our understanding of glacial dynamics and painted an increasingly grim picture of the glacier’s future.

The collaboration represents one of the most ambitious scientific endeavors in climate research, involving not just glaciologists but also oceanographers, atmospheric scientists, and geologists. Their work has revealed that the Thwaites is already in a phase of fast retreat and accounts for 4% of sea level rise on Earth, losing 50 billion tons of ice each year.

The Broader Implications

The collapse of Thwaites would trigger what scientists call a “tipping point”—a critical threshold beyond which changes become irreversible and self-reinforcing. A tipping point is when crossing a critical threshold—in this case, atmospheric and oceanic warming—leads to large, accelerating, and irreversible changes.

The melting of the Thwaites Glacier would lead to the collapse of the West Antarctic Ice Sheet which would in turn cause irreversible sea level rise that could endanger millions of people and accelerate warming of other ice.

The economic implications are staggering. The problem? Rising waters can damage infrastructure, like roads and bridges, leading to big costs for repairs. Insurance companies are already beginning to withdraw coverage from coastal areas, and real estate values in vulnerable locations are starting to reflect the long-term risks.

Migration and Human Displacement

The human cost of Thwaites’ collapse would be unprecedented in modern history. Low-lying countries like the Marshall Islands and Tuvalu could be submerged entirely. The displacement of populations would create refugee crises that dwarf current migration challenges.

Scientists predict that its collapse could contribute to 65 centimeters, or roughly 26 inches in sea level rise, but this is just the beginning. The follow-on effects from the broader West Antarctic Ice Sheet collapse could displace hundreds of millions of people globally.

Coastal megacities around the world would face impossible choices: spend trillions on flood defenses that may ultimately prove inadequate, or begin the process of managed retreat—essentially abandoning centuries of urban development to the sea.

The Race Against Time

A key unanswered question is whether the loss of Thwaites Glacier is already irreversible. Heavy snowfalls, for example, regularly occur in the Antarctic and help replenish ice loss. However, the problem though is that we have this imbalance: There is more ice loss occurring than snowfall can compensate for.

Increased moisture in the planet’s atmosphere, caused by global warming evaporating ocean waters, could result in more Antarctic snow—at least for a while. At a certain point, though, that’s expected to switch over to rain and surface melting on the ice, creating a situation where the glacier is melting from above and below.

The scientific consensus is becoming increasingly alarming. “Towards the end of this century, or into the next century, it is very probable that we will see a rapid increase in the amount of ice coming off of Antarctica,” said Dr. Ted Scambos, a glaciologist at the University of Colorado. “The Thwaites is pretty much doomed.”

Technological Solutions and Geoengineering

Faced with the magnitude of the threat, some scientists are exploring radical solutions. With the fate of the Thwaites still uncertain, some scientists and engineers are turning to controversial ideas on how to alter the environment to slow glacier melt.

These geoengineering proposals range from building underwater barriers to artificially cooling the ocean waters that contact the glacier. However, such interventions would be unprecedented in scale and cost, potentially requiring international cooperation on a level never before achieved.

The technological challenges are immense. Any intervention would need to withstand the harsh Antarctic environment, operate continuously for decades, and avoid unintended consequences that could make the situation worse. Even if such solutions were technically feasible, the cost would likely exceed the GDP of most nations.

The Uncertainty Factor

Despite decades of research, significant uncertainties remain about the exact timeline and mechanism of Thwaites’ collapse. Eric Rignot, a glaciologist at the University of California, Irvine and part of the International Thwaites Glacier Collaboration said: “While progress has been made, we still have deep uncertainty about the future. I remain very worried that this sector of Antarctica is already in a state of collapse.”

Marine physicist Robert Larter, in a statement: “There is a consensus that Thwaites Glacier retreat will accelerate sometime within the next century. However, there is also concern that additional processes revealed by recent studies, which are not yet well enough studied to be incorporated into large scale models, could cause retreat to accelerate sooner.”

This uncertainty makes planning extremely difficult. Should cities like London, New York, and Bangkok begin immediate preparations for scenarios that might not occur for decades? Or should they wait for more certainty, risking being caught unprepared if the collapse happens sooner than expected?

The Point of No Return

Their findings, set out across a collection of studies, provide the clearest picture yet of this complex, ever-changing glacier. The outlook is “grim,” the scientists said in a report published Thursday, revealing the key conclusions of their six years of research.

They found rapid ice loss is set to speed up this century. Thwaites’ retreat has accelerated considerably over the past 30 years. The glacier that once seemed like a distant threat has become an immediate concern for planners and policymakers worldwide.

The window for preventing the worst-case scenarios is rapidly closing. How fast that happens depends in part on nations’ progress to slow climate change, but even aggressive action to reduce greenhouse gas emissions may not be enough to prevent Thwaites’ eventual collapse.

Living with the New Reality

As the scientific evidence mounts, the three cities most at risk—London, New York, and Bangkok—are beginning to grapple with a new reality. The question is no longer whether sea levels will rise, but how quickly and by how much. The collapse of the Doomsday Glacier represents not just a scientific curiosity or distant threat, but an immediate challenge that will define the future of human civilization.

Co-author Christine Dow, professor in the Faculty of Environment at the University of Waterloo in Ontario, Canada, said, “Thwaites is the most unstable place in the Antarctic and contains the equivalent of 60 centimeters of sea level rise. The worry is that we are underestimating the speed that the glacier is changing, which would be devastating for coastal communities around the world.”

The cities that have thrived for centuries as centers of commerce, culture, and human achievement now face an uncertain future. The decisions made in the coming years—about flood defenses, urban planning, and climate action—will determine whether these great metropolises can adapt to a world with dramatically higher sea levels, or whether they will join the ranks of lost cities claimed by the sea.

The story of the Doomsday Glacier is ultimately the story of humanity’s relationship with the planet we call home. It serves as a stark reminder that even the most stable-seeming features of our world—massive glaciers that have existed for millennia—can change with shocking speed when the delicate balance of natural systems is disrupted. The race is now on to understand, prepare for, and hopefully prevent the most catastrophic outcomes of this unfolding crisis.