Warm seawater is reaching deep beneath Antarctica’s Thwaites Glacier, and new research suggests the process could make its contribution to global sea-level rise roughly twice as large as earlier models projected.
A study published October 12 in Nature Communications estimates that the West Antarctic glacier could add about 1.2 inches (3 centimeters) to global sea levels by 2100 under one set of modeling assumptions. That is approximately double the average projection from an earlier international modeling comparison, even without assuming additional climate warming.
The findings suggest that a critical melting process beneath the glacier has been underestimated, potentially affecting predictions of how quickly Antarctic ice will contribute to rising oceans.
Scientists Discover How Seawater Is Accelerating Ice Loss
For decades, scientists have studied how warmer ocean water melts Antarctica’s glaciers from below. But the new research suggests that many computer models have failed to fully capture what happens where a glacier meets the ocean floor.
Traditionally, models have represented this boundary as a relatively narrow grounding line, separating ice resting on bedrock from ice floating on seawater.
Satellite observations, however, reveal a more complicated process. Ocean tides can push seawater several kilometers beneath ice that would otherwise remain grounded, creating a wider grounding zone where melting occurs.
Researchers led by Mattia Poinelli, a scientist affiliated with UCLA and NASA’s Jet Propulsion Laboratory, incorporated this process into a revised ice-sheet model.
Using satellite measurements collected between 1996 and 2023, the team tested whether the model could reproduce the glacier’s observed retreat, thinning and acceleration.
The results showed that models incorporating actively melting grounding zones approximately 2 to 5 kilometers (1.2 to 3.1 miles) wide were much more successful at reproducing the historical observations.
When the researchers extended their simulations to 2100, a model with a grounding zone about 5 kilometers wide projected roughly 30 millimeters of global mean sea-level rise from Thwaites, compared with an average of approximately 15 millimeters in the earlier modeling comparison under comparable climate assumptions.
Thwaites Glacier Could Lose Contact With a Stabilizing Ridge
Another important finding concerns the underwater landscape supporting parts of Thwaites Glacier.
The glacier’s main ice stream remains partly stabilized by Mouginot Ridge, an elevated section of the seabed that helps resist its inland retreat.
As seawater penetrates beneath the grounded ice, it can weaken that contact.
In simulations representing grounding zones between 4 and 6 kilometers wide, approximately 60% of the model runs showed the glacier losing contact with Mouginot Ridge before 2100. Some simulations placed that separation as early as 2038.
Such a development would allow the grounding line to retreat farther inland toward another underwater elevation known as South Ridge.
Thwaites is the widest glacier on Earth, stretching approximately 120 kilometers (75 miles) across. Its drainage basin covers around 192,000 square kilometers (74,000 square miles), an area comparable to Senegal.
According to the International Thwaites Glacier Collaboration, ice loss from the glacier already accounts for about 4% of current global sea-level rise.
If all the land-based ice associated with Thwaites were eventually lost, global sea levels could rise by approximately 65 centimeters (26 inches). That is a much longer-term possibility, not the outcome projected by the new study for 2100.
Another Study Finds Thwaites May Keep Losing Ice for 150 Years
The latest findings follow separate research by scientists from the British Antarctic Survey, suggesting that part of Thwaites’ ongoing ice loss may already be difficult to reverse.
In a study published in Geophysical Research Letters in July 2026, researchers used three independent ice-sheet models to explore what would happen if ocean-driven melting beneath the floating ice shelves were completely eliminated.
The results revealed a marked difference between two major West Antarctic glaciers.
Pine Island Glacier began thickening and advancing toward its former position. Thwaites, however, continued losing ice throughout the 150-year simulations, although the rate of loss gradually declined.
The researchers concluded that Thwaites is still responding to earlier changes in ocean conditions, with past retreat continuing to influence its present behavior.
Why Antarctic Ice Loss Matters for Greece and the Mediterranean
Although Thwaites Glacier lies thousands of kilometers from Europe’s coastlines, its loss of land-based ice contributes to changes in sea levels worldwide.
The additional rise projected in the new study would form part of the global total alongside contributions from other glaciers, ice sheets and the thermal expansion of warming seawater.
The Mediterranean is already experiencing rising sea levels. The United Nations’ Intergovernmental Panel on Climate Change (IPCC) projects further increases throughout the 21st century, raising risks of coastal flooding, erosion and saltwater intrusion.
For Greece, these changes matter particularly in low-lying coastal areas, ports and communities dependent on beaches and coastal tourism.
The IPCC has identified the Thessaloniki coastal plain as an area where land subsidence can compound the effects of rising seas. Similar coastal risks exist elsewhere in the Mediterranean, although their severity varies with local geography and infrastructure.
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