Why Thwaites Glacier Is Melting and What It Means for Sea Levels

What is Thwaites Glacier?

Thwaites is a broad glacier in West Antarctica that flows toward the Amundsen Sea. It is an important source of Antarctic ice loss and a major uncertainty in projections of future sea-level rise. ²³

The nickname “Doomsday Glacier” reflects concern about the consequences of its retreat, but it is not a scientific forecast that the glacier will suddenly collapse. The available sources describe ongoing loss and uncertain future behavior, not a precisely timed catastrophe. ²³

Why is Thwaites Glacier melting?

The main driver described in the research is ocean-driven melting. Ocean water reaches the glacier's underside near the grounding line, where ice that rests on the seabed transitions toward floating ice. ²³

The 2026 study focuses on the grounding zone: a several-kilometer-wide area where seawater can intrude beneath grounded ice. The authors found that representing this actively melting zone was necessary for their model to reproduce nearly three decades of observed retreat, thinning and acceleration. ²

What did the 2026 Thwaites study find?

Many ice-sheet models treat the transition from grounded to floating ice as a sharp boundary. The study's model instead represented the grounding zone as a region 2 to 5 kilometers wide, where seawater intrusion and melting can occur. ²

With that process included, the model better matched past changes in Thwaites and produced higher future sea-level estimates than earlier projections. It also suggested the glacier could become detached from stabilizing seafloor ridges as early as 2038. That is a model result, not a confirmed date for an event. ²

How much could Thwaites raise sea levels?

The study estimates that Thwaites could contribute up to 30 ± 6 millimeters to global mean sea level by 2100, approximately double previous projections. This estimate comes from one model that includes grounding-zone processes; it should not be read as a guaranteed amount. ²

Global mean sea level is an average across the world's oceans. The figure does not tell a reader exactly how much sea level will change at a particular shore, and the sources do not provide local forecasts. The researchers say their estimate is possible even without additional climate warming, within the study's model setup. ²

Will Thwaites keep melting if oceans cool?

A report on separate computer modeling says Thwaites could continue losing ice for at least 150 years even under a scenario with extremely cool oceans. That scenario was described as unrealistic, so the finding is best understood as a model stress test rather than a likely forecast. ³

This result does not mean ocean temperatures no longer matter. The sources identify ocean-driven melting as a major cause of present ice loss, while the modeling suggests that cooling alone may not quickly reverse the glacier's retreat. ²³

What is still uncertain about Thwaites?

The new projection depends on how the model represents seawater intrusion, melting and the glacier's contact with seafloor ridges. The result improves the fit to past observations, but it remains a projection of future behavior rather than a direct observation of what will happen. ²

The sources do not establish the precise timing or extent of future retreat, nor how any change would translate into sea-level change at a specific location. They also describe a possible wider loss of West Antarctic ice if Thwaites collapses, but do not make that outcome certain. ²³