One of the world’s largest glaciers is melting much faster than previously understood and could contribute about twice as much to global sea-level rise by the end of the century as earlier projections suggested.
New research published this week in Nature Communications found that Antarctica’s Thwaites Glacier is rapidly losing mass as warm ocean water pushes several kilometers beneath it and melts the ice from below.
Researchers estimate the process could cause Thwaites to contribute up to 30 millimeters (1.2 inches) to global sea-level rise by 2100, even without additional warming beyond recent conditions.
In previous conventional ice-sheet models, scientists estimated that the Thwaites Glacier would contribute roughly 15 millimeters to global sea-level rise by the year 2100.
Nicknamed the Doomsday Glacier because of the potentially severe consequences of its collapse, Thwaites covers around 192,000 square kilometers (74,000 square miles) in West Antarctica – roughly the size of Senegal and larger than the U.S. state of Florida.
It forms part of the much larger West Antarctic Ice Sheet and, together with glaciers including Pine Island, acts as a barrier holding back vast quantities of inland ice.
Thwaites currently accounts for around 4% of global sea-level rise and has lost more than 1 trillion tons of ice since 2000, with losses continuing at roughly 50 billion tons annually.
Scientists have closely monitored the glacier since discovering in the 1980s that it was retreating rapidly.
Warm ocean water driven beneath the ice is considered a key factor. Human-caused climate change, particularly warming linked to fossil fuel emissions, is raising ocean temperatures and increasing pressure on glaciers worldwide.
The latest study focused on Thwaites’ "grounding zone,” where ice resting on bedrock begins to float on the sea.
Previous models often treated the grounding line as a fixed boundary. Researchers instead modeled a broader zone where tides repeatedly lift and lower the ice, allowing warm seawater to penetrate farther underneath.
Lead author Mattia Poinelli, a project scientist at UCLA, said this "tidal pumping” enables warm water to reach deep beneath the ice and cause vigorous melting.
The new modeling also raises concerns that Thwaites could lose contact with the underwater Mouginot Ridge, which currently helps restrain its movement.
Simulations consistent with recent observations indicated around a 60% chance of the glacier becoming detached from the ridge by 2100, potentially as early as the late 2030s.
Researchers warned that such a shift could accelerate the glacier's retreat and expose coastal communities worldwide to greater sea-level rise and flooding risks than previously projected.