Thwaites Glacier in West Antarctica could contribute up to 30 millimeters, or approximately 1.2 inches, to global mean sea-level rise by 2100, according to research published in October 2026. Scientists from the University of California, Irvine, and NASA’s Jet Propulsion Laboratory developed an ice-sheet model that accounts for melting across a wider zone where the glacier meets the ocean. Their results suggest that this process could produce roughly twice the sea-level contribution estimated in earlier projections used for comparison in the study.
The findings highlight a challenge in predicting future sea levels: small differences in how scientists represent the interaction between ocean water and Antarctic ice can significantly affect long-term forecasts. Thwaites, one of the major contributors to Antarctic ice loss, is retreating as relatively warm ocean water melts ice near its base. The researchers found that incorporating a more realistic grounding zone helped their model reproduce nearly three decades of observed retreat, thinning and acceleration. The projection remains model-based, and the glacier’s contribution is only one part of future global sea-level rise.
Key Takeaways
- Up to 1.2 inches by 2100: The model projects a contribution of 30 ± 6 millimeters to global mean sea-level rise from Thwaites Glacier.
- Roughly double earlier projections: The study’s estimate is approximately twice the previous projections used for comparison.
- A wider melting zone matters: Scientists modelled a grounding zone approximately 2–5 kilometers wide rather than treating the boundary as a sharp line.
- Potential unpinning by 2038: The model suggests the glacier could detach from stabilizing seafloor ridges as early as 2038.
- No additional warming assumed: The researchers report the projected contribution even without additional climate warming beyond the model’s baseline assumptions.
- Not the total global sea-level forecast: Other glaciers, ice sheets and warming oceans also contribute to rising seas.
- Better models are essential: The findings show how accurately representing ice-ocean interactions can change long-term projections.
What Is Thwaites Glacier and Why Does It Matter?
Thwaites Glacier is a large glacier in West Antarctica that flows toward the Amundsen Sea. It is closely watched by climate scientists because it is losing ice and contributes to rising global sea levels.
Its importance extends beyond the amount of ice it currently releases. The glacier is connected to the wider West Antarctic Ice Sheet, where parts of the ice rest on bedrock below sea level. Changes in the glacier’s grounding zone can influence how quickly ice moves toward the ocean and how much additional melting occurs.
Scientists have described Thwaites as a particularly important source of uncertainty in projections of future Antarctic ice loss. Its behavior depends on several interacting factors, including the shape of the bedrock beneath it, the movement of ocean water, ice thickness and the stability of floating ice.
The glacier’s potential contribution to sea-level rise is therefore a major focus of research. However, estimates vary depending on the models, observations and future conditions scientists use. The new study does not establish an exact date for a complete collapse; it examines how improved modelling of the grounding zone changes the projected contribution through 2100.
How Much Could Thwaites Glacier Raise Sea Levels?
The new model projects up to 30 millimeters, with an uncertainty range of approximately 6 millimeters in either direction, of global mean sea-level rise from Thwaites Glacier by 2100.
| Measurement | Study finding |
|---|---|
| Projected contribution by 2100 | Up to 30 mm |
| Equivalent in inches | Approximately 1.2 inches |
| Reported uncertainty | ±6 mm |
| Comparison with earlier projections | Approximately double |
| Potential timing of unpinning | As early as 2038 |
| Modelled grounding-zone width | 2–5 km |
The central estimate of 30 millimeters is approximately 1.18 inches, commonly rounded to 1.2 inches. The reported uncertainty means the model’s estimate is not a single guaranteed outcome.
It is also important to understand what this number represents. The projection concerns the contribution from Thwaites Glacier to global mean sea level, not the total amount that sea levels will rise worldwide by 2100.
Global sea levels respond to several processes. These include the melting of glaciers and ice sheets, as well as the expansion of seawater as it warms. The new research focuses on improving estimates for one glacier rather than replacing broader climate projections.
Why Did Scientists Revise the Projection?
The main change concerns how the model represents the grounding zone, the region where a glacier transitions from ice resting on the seabed to ice floating in the ocean.
Many traditional ice-sheet models approximate this transition as a relatively sharp boundary called the grounding line. However, observations show that the interaction between ice, bedrock and ocean water can extend across a much wider area.
The new research represents the grounding zone as a region several kilometers wide. This allows the model to account for melting and seawater intrusion over a broader area as the glacier retreats.
How ocean water melts ice beneath the glacier
Warm ocean water can enter beneath parts of the glacier and melt ice near its base. As the glacier thins, the grounding line can move inland, changing the area exposed to ocean water and altering the forces that control the glacier’s movement.
The study found that actively melting grounding zones were needed to reproduce nearly three decades of observed retreat, thinning and acceleration. Models that treated the grounding line as a sharp boundary did not reproduce those observations as successfully.
When the researchers incorporated the wider zone into their model and projected the glacier’s future behavior, the estimated sea-level contribution increased substantially.
This does not mean scientists have discovered that the glacier suddenly began melting twice as fast in October 2026. Rather, the research suggests that earlier modelling approaches may have underestimated how certain physical processes affect its long-term evolution.
Could Thwaites Glacier Become Unstable by 2038?
The study suggests that grounding-zone processes could allow Thwaites Glacier to detach from stabilizing seafloor ridges as early as 2038.
These ridges can help slow the retreat of grounded ice. If the glacier loses contact with such a feature, the resistance that helps restrain its movement may weaken, potentially allowing retreat to progress.
The model identifies this possible transition as an important factor in the glacier’s future behavior. It also suggests that accurately representing the grounding zone is necessary to capture when and how such changes could occur.
However, 2038 should not be interpreted as a confirmed date for collapse. It is a modelled possibility, not a scheduled event or a precise prediction that the entire glacier will disappear at that time.
The glacier’s response depends on complex physical processes, and uncertainty remains about how those processes will evolve. Continued observations and improved models will be needed to assess the likelihood and timing of future changes.
Does the Projection Depend on Further Global Warming?
One notable finding is that the researchers project a contribution of up to 30 millimeters by 2100 even without additional climate warming in the scenario described by the study.
This matters because it suggests that some future ice loss may be driven by the glacier’s existing dynamics and the way its grounding zone evolves, rather than depending entirely on additional warming.
It does not mean climate change is irrelevant or that future warming would have no effect. Ocean temperatures, atmospheric conditions and other environmental factors remain important to Antarctic ice loss.
The result instead highlights a distinction between two questions: how future climate conditions influence a glacier, and how the glacier responds to the conditions and physical processes already affecting it.
Better modelling of those processes can improve projections under different climate scenarios. It can also help scientists understand how much uncertainty arises from the physics of the glacier itself.
What the Findings Mean for Coastal Communities
Rising sea levels increase the risks faced by low-lying coastal areas. Depending on local geography and other conditions, higher sea levels can worsen coastal flooding, erosion and the effects of storm surges.
The new Thwaites projection does not mean that every coastline will experience exactly 1.2 inches of additional water from this glacier by 2100. The figure represents a contribution to global mean sea level, while actual changes at a particular location can differ because of ocean circulation, land movement, gravity and regional conditions.
Nevertheless, improving projections of Antarctic ice loss is important for long-term coastal planning. Governments, infrastructure operators and communities use sea-level estimates to evaluate flood exposure, design protective infrastructure and assess future risks.
The study offers a more detailed estimate of one component of the problem. Its findings can help researchers refine wider assessments of Antarctic contributions to sea-level rise, although local planning still requires regional projections that include other sources of change.
The Bigger Picture
Thwaites Glacier illustrates why climate projections depend not only on collecting more observations but also on representing the underlying physics accurately. A model that treats the grounding line as a narrow boundary may miss processes occurring across several kilometers beneath the ice. Accounting for those processes can change estimates of retreat and the glacier’s contribution to sea-level rise.
The new study does not eliminate uncertainty, but it provides evidence that grounding-zone dynamics deserve greater attention in ice-sheet modelling. As satellite observations and other measurements improve, researchers can continue testing whether their models reproduce real-world changes and refine projections for the decades ahead. The broader lesson is that credible climate forecasts must reflect both changing environmental conditions and the complex mechanisms through which glaciers respond.
What Happens Next?
Researchers will continue comparing ice-sheet model results with observations of glacier movement, thinning and grounding-zone behavior. Additional measurements and independent modelling studies will help determine how robust the revised projection is and how the glacier may respond under different ocean and climate conditions. The possible unpinning date of 2038 and the projected contribution by 2100 should be treated as model outputs that may change as the evidence develops.
For coastal planners and policymakers, the immediate implication is to use updated scientific assessments when evaluating long-term sea-level risks rather than relying on a single estimate. Thwaites Glacier is only one contributor to global sea-level rise, so its projected impact must be considered alongside other Antarctic and Greenland ice loss, mountain glaciers and ocean warming. Continued research will be important for narrowing uncertainty and preparing for a range of possible future outcomes.
Frequently Asked Questions
1. How much could Thwaites Glacier raise sea levels by 2100?
The new model projects a contribution of up to 30 millimeters, or approximately 1.2 inches, to global mean sea-level rise by 2100. The researchers report an uncertainty of ±6 millimeters.
2. Why is the new estimate higher than earlier projections?
The model represents the grounding zone as a region several kilometers wide, accounting for melting and seawater intrusion across a wider area than models that treat the grounding line as a sharp boundary.
3. Will Thwaites Glacier collapse in 2038?
The study suggests that the glacier could detach from stabilizing seafloor ridges as early as 2038. This is a modelled possibility, not a confirmed date for a complete collapse.
4. Does the 1.2-inch estimate represent total global sea-level rise?
No. It represents the projected contribution from Thwaites Glacier alone. Global sea levels are also affected by other glaciers and ice sheets, as well as the expansion of seawater as the oceans warm.
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