One of Earth’s most dangerous glaciers is emerging as a potentially greater driver of future sea-level rise than previously understood.

A team of glaciologists at the University of California and NASA’s Jet Propulsion Laboratory developed a new ice sheet model to come up with a more accurate projection of the melting of Thwaites Glacier in West Antarctica. The findings, published in Nature Communications, estimate that the glacier could contribute up to 1.2 inches (30 millimeters) of sea level rise by 2100, even without additional climate warming.

The study highlights an even greater risk of coastal flooding in the coming decades than previously estimated.

Also known as the Doomsday Glacier, Thwaites has undergone a profound transformation in recent decades, thinning, accelerating, and retreating inland as warm ocean water eats away at its floating ice shelves from below.

For decades, glaciologists have relied on the concept of the “grounding line” to understand ice-sheet dynamics: a distinct boundary where ice transitions from resting on bedrock to floating on the ocean, traditionally treated as a relatively narrow and stable feature.

Scientists use computer models to predict how glaciers flow towards the ocean and how quickly they lose ice. Meanwhile, satellite observations measure how quickly ice moves across Antarctica. The predictions and the real-world observations, however, don’t fully agree.

Thwaites is particularly important because its ice rests on bedrock that deepens inland in many areas. As warm ocean water melts ice near its grounding zone, the glacier can retreat into deeper water, potentially allowing more ice to flow into the ocean.

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