Study finds Thwaites Glacier sea-level contribution doubles in new models

A new study published in Nature Communications on October 12, 2026, reports that the sea-level contribution from Thwaites Glacier in West Antarctica could be approximately double previous projections. The research, led by Mattia Poinelli and colleagues, indicates that modeling the glacier’s grounding zone as a dynamic, melting region rather than a sharp boundary significantly alters future sea-level estimates.

Grounding Zones and Model Calibration

Thwaites Glacier is a major contributor to Antarctic mass loss. Previous ice-sheet models typically treated the grounding line—the transition where grounded ice becomes floating ice—as a sharp boundary. However, satellite observations from the ICEYE constellation have revealed that seawater penetrates several kilometers beneath grounded ice, creating a dynamic "grounding zone" where tidal cycles cause active flushing and melting.

The study utilized the Ice-sheet and Sea-level System Model (ISSM) to simulate the glacier's evolution from 1996 to 2023. The researchers found that models only successfully reproduced nearly three decades of observed retreat, thinning, and acceleration when grounding zones were represented as 2-5 km wide regions. "We have come to acknowledge a different arrangement beneath Earth’s major ocean-terminating glaciers," said Mattia Poinelli, the report’s lead author and a project scientist at UCLA. According to Poinelli, this arrangement allows relatively warm ocean water to penetrate "deep underneath the ice sheets and causing vigorous melting."

Projections for 2100

Using a calibrated model with a constant climate forcing baseline—effectively isolating the role of grounding-zone melting from future ocean-warming uncertainty—the study projects that Thwaites Glacier could contribute up to 30 ± 6 mm of global mean sea-level rise by 2100. This figure is approximately double previous projections. CNN reports this as up to 1.2 inches of sea-level rise by 2100.

The study highlights the role of the Mouginot Ridge, a bathymetric high that currently pins the glacier. The models suggest that grounding-zone processes govern the glacier’s detachment from this stabilizing ridge. Simulations with a 2–3 km grounding zone predict a ~45% probability of unpinning from the Mouginot Ridge by the end of the century. Simulations consistent with recent satellite-inferred grounding-zone extents (4–6 km) show a higher probability of ~60% of crossing the ridge by 2100, with unpinning occurring as early as 2038 in some scenarios.

Expert Reactions and Future Research

Eric Rignot, a report author and professor of Earth system science at UC Irvine, stated that the results "predict greater risk of and exposure for coastal flooding than anticipated in the coming decades." Rignot noted that while the world must cut planet-heating pollution to limit impacts, "even if we do, we can expect higher sea levels in the future resulting from the damage that has already been done."

Ted Scambos, a senior research scientist at the University of Colorado Boulder who was not involved in the research, described the findings as potentially "a real gamechanger for sea level forecasting from Thwaites." However, Robert Larter, a marine geophysicist at British Antarctic Survey, also not involved in the study, cautioned that more research is needed. "The reality is that there is a lot we still need to find out about grounding zone processes to be able to make confident predictions about how fast ice will be lost," Larter said.

Why it matters

Thwaites Glacier, often referred to as the "Doomsday Glacier," holds enough water to raise sea levels by more than 2 feet if it were to collapse entirely. It currently contributes around 4% to global sea-level rise. The doubling of projected contributions in this study underscores the urgency of understanding sub-glacial processes. The researchers plan to travel to the glacier in 2028 to deploy instruments that will document the flushing of seawater, aiming to refine these projections with direct observational data.

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Sources

• nature.com: Sea-level contribution from Thwaites Glacier doubles in an observation-constrained ice-sheet model | Nature Communications
• cnn.com: Scientists say Doomsday Glacier melting ‘aggressively’ | CNN

This article was drafted with AI assistance and checked against the sources above. Company claims are reported as claims. Cover image is AI-generated.