Thwaites Glacier Sea Level Rise Projections Double as Warm Ocean Water Seeps Under Antarctic Ice

A massive sheet of ice in Antarctica known as the Doomsday Glacier is melting faster than previously thought because warm ocean currents are creeping deep beneath its base. Scientists studying the frozen continent have discovered that seawater is pushing several miles underneath the frozen belly of the glacier, carving out hollow spaces and melting the ice from below. This hidden underbelly melt means coastal cities around the world could face far higher water levels much sooner than earlier scientific forecasts predicted.

The giant block of ice, officially named the Thwaites Glacier, is roughly the size of the American state of Florida or the entire island of Great Britain. It sits in West Antarctica and acts like a massive cork holding back a giant bottle of ice. Because it blocks other surrounding glaciers from sliding freely into the open ocean, glaciologists keep a constant eye on its stability. If Thwaites were to ever fully collapse, the ice trapped behind it could eventually raise global sea levels by more than two feet, permanently flooding coastal plains and harbor communities across the globe.

The findings were published on Monday, October 12, 2026, in the scientific journal Nature Communications. A research team led by glaciologists at the University of California and NASA’s Jet Propulsion Laboratory built a more advanced computer model to simulate how the ice behaves when it meets moving ocean tides. Their updated calculations reveal that the glacier could contribute up to 1.2 inches, or 30 millimeters, to global sea levels by the year 2100 on its own, which is twice the amount predicted by older climate models.

For a long time, traditional scientific models assumed that glaciers touch the ocean along a sharp, simple dividing boundary called a grounding line. On one side of this boundary, the ice was thought to sit firmly on solid rock, while on the other side, it floated on the water. In those older mathematical calculations, scientists assumed that seawater could not travel past that contact point. Because those older formulas ignored the water slipping past the boundary, they significantly underestimated how much warm water was attacking the ice from underneath.

High-resolution satellite radar pictures showed that the real world works quite differently. Instead of meeting at a narrow border line, the ice and ocean interact across a wide, shifting territory known as the grounding zone. This dynamic band stretches between two and five kilometers wide. When ocean tides rise and fall twice every day, the massive weight of the glacier lifts slightly off the seabed. That movement creates giant pressure pockets that suck relatively warm, salty ocean water deep into the cracks beneath the grounded ice.

Once the warm seawater finds its way inside, it starts melting the ice at rapid speeds, dissolving up to 120 meters of ice thickness every single year. This hidden melting hollows out the underbelly of the glacier, leaving the top layers unsupported. The water also lubricates the contact area between the bottom of the glacier and the bedrock below, turning rough ground into a slippery surface that makes the ice slide toward the sea much faster.

The computer simulations also revealed another serious problem regarding an underwater obstacle called the Mouginot Ridge. This giant underwater rock wall currently acts like a natural brake, pinning the glacier in place and slowing its forward slide into the sea. The new model indicates a sixty percent chance that the glacier will detach from this anchor point before the end of the century. If the ice slips off that ridge, the seafloor behind it slopes downward into a deep inland bowl, leaving no other major underwater barriers to stop the ice from accelerating into the ocean.

Scientists stress that this doubling of sea level contribution could happen even without additional atmospheric warming, simply because existing warm ocean water is already actively driving the process. While thirty millimeters of sea level rise might sound small on a ruler, adding that volume of water to every ocean on the planet creates devastating high tide floods, ruins freshwater drinking supplies, and makes normal storm surges far more destructive for millions of coastal residents.

Research teams plan to gather more direct measurements by sending robotic exploration submarines into the dark water channels beneath the ice shelf. For leaders and urban planners designing seawalls and flood defenses, the message is clear: coastal communities must prepare for higher water and faster changes than standard climate handbooks anticipated.