Thwaites Glacier melting faster, could double sea-level rise

Revised sea-level projections

New research published in Nature Communications indicates that Antarctica's Thwaites Glacier is melting far more rapidly than previously understood, with the massive ice formation potentially contributing roughly 30 millimeters to global sea-level rise by the end of the century, according to the peer-reviewed findings. Researchers estimate this contribution could occur even without additional warming beyond recent conditions, roughly doubling earlier conventional ice-sheet models that projected a 15-millimeter increase by 2100. The findings suggest the glacier — nicknamed the Doomsday Glacier because of the potentially severe consequences of its collapse — is responding to ocean warming more sensitively than previously recognized.

Thwaites covers around 192,000 square kilometers in West Antarctica — roughly the size of Senegal and larger than the US 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.

Tidal pumping mechanism

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, but researchers instead modeled a broader zone where tides repeatedly lift and lower the ice, allowing warm seawater to penetrate several kilometers farther underneath than earlier assumptions allowed. 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.

Warm ocean water driven beneath the ice is considered a key factor in the accelerated melting. Human-caused climate change, particularly warming linked to fossil fuel emissions, is raising ocean temperatures and increasing pressure on glaciers worldwide, pushing warm water into cavities beneath the ice sheet. Scientists have closely monitored the glacier since discovering in the 1980s that it was retreating rapidly.

Implications for coastal communities

The new modeling raises concerns that Thwaites could lose contact with the underwater Mouginot Ridge, which currently helps restrain its movement and slow its flow into the ocean. 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, according to the study. 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.

The loss of the ridge constraint could trigger a more rapid collapse of the ice formation, fundamentally altering projections for global sea-level rise within decades and threatening low-lying coastal regions. The study underscores the vulnerability of West Antarctica's ice sheet to ocean warming and the potential for unexpected acceleration in ice loss as atmospheric and oceanic warming continues.