Antarctica's "Doomsday Glacier" Is Melting Far Faster Than Scientists Feared

A Revised Reckoning for the World's Most Dangerous Glacier

One of Earth's most dangerous glaciers is emerging as a potentially greater driver of future sea-level rise than previously understood. A landmark new study published in Nature Communications has delivered a stark reassessment of Thwaites Glacier — the massive West Antarctic ice sheet that scientists have long called the "Doomsday Glacier." The new model projects that the melting of Thwaites will contribute up to 30 millimeters (1.2 inches) of sea level rise by 2100 — twice previous estimates — even without additional climate warming.

Thwaites holds enough ice to raise sea levels by more than 2 feet if it collapses, and it also helps hold back the wider Antarctic ice sheet — meaning its loss could ultimately contribute to around 10 feet of sea level rise. The new findings suggest the clock on that scenario may be ticking faster than the scientific community had realized.

What the Old Models Got Wrong

Glaciologists have long based their assumptions of ice sheet dynamics on the "grounding line" — a discrete, narrow, and mostly stable demarcation where ice leaves the land and begins floating on water. That assumption, it turns out, was dangerously incomplete. Rather than treating the grounding line as fixed and mostly stable, the new model represents it as a grounding zone, sometimes miles wide. Seawater moves in and out with the tides, lifting and lowering the ice in a process called tidal pumping — which can carry relatively warm water beneath the ice and intensify melting.

By adjusting the computer model of Thwaites to include the concept of a "grounding zone" instead of a "grounding line," researchers were able to reconstruct historical glacier change from the 1990s to the present that is four times more pronounced than traditional models. In other words, the old models weren't just slightly off — they were missing a fundamental physical process happening beneath the ice. Lead author Mattia Poinelli said satellite data confirmed this tidal movement, describing the water as reaching "deep underneath the ice sheets and causing vigorous melting."

A Critical Tipping Point as Early as 2038

The model also points to a specific weak spot: the glacier's fastest-moving section, its main trunk, is currently held back by the Mouginot Ridge, a bump in the seafloor a few kilometers across that sits about 950 meters below sea level. Grounding-zone processes govern the glacier's detachment from stabilizing seafloor ridges, enabling unpinning as early as 2038. Once that anchor is gone, there may be little stopping an accelerated collapse.

"Our new model with more complete physics is able to match the record and then produces projections that are twice as large as before," said Eric Rignot, a professor of Earth system science at UC Irvine and co-author of the study. Unlike most of its predecessors, the model also reproduces what satellites have actually watched the glacier do: retreat, thin, and speed up — all at once. That alignment between model and real-world observation is what gives this study its weight.

Why 1.2 Inches Is More Dangerous Than It Sounds

A sea level rise of 1.2 inches may not sound like much, but it's enough to greatly magnify dangers to coastal populations. Even modest increases in baseline sea levels dramatically amplify the reach and frequency of storm surges, flooding events, and coastal erosion — impacts felt most acutely by the hundreds of millions of people living in low-lying areas around the world. And this projection covers only Thwaites, only one source among many contributing to rising seas.

The researchers say more observations beneath the glacier are needed to improve forecasts. A UC Irvine-led investigation published in 2024 used satellite radar to document extensive seawater intrusion beneath Thwaites , and the new model builds directly on that evidence. As satellite technology improves and more data flows in from beneath the ice, scientists expect the picture to sharpen further — and the urgency to grow with it.