A new model suggests Antarctica’s Thwaites Glacier could contribute up to 30 millimeters to global sea-level rise by 2100—about twice previous projections. The projection comes from a study described in a ScienceDaily report published October 28 and published in Nature Communications. It remains a model result, not a prediction that the glacier will certainly lose that much ice. The report says the estimate holds even without additional global warming.
The researchers’ explanation centers on a zone beneath the ice that older models represented too simply. Where grounded glacier ice meets floating ice, the boundary is not always a narrow line. Satellite observations show that warm ocean water can reach several kilometers beneath ice that remains grounded on the seafloor. The researchers’ model represents this broader grounding zone, where water can melt ice from below.
The study was developed by researchers at the University of California, Irvine, and NASA’s Jet Propulsion Laboratory. Mattia Poinelli, identified in the report as lead author, was a UC Irvine postdoctoral scholar when the work was conducted. The paper’s listed authors also include Eric Rignot, Hélène Seroussi, Joshua Cuzzone, Tyler Pelle and Eric Larour.
Thwaites lies in the Amundsen Sea Embayment of West Antarctica, a region responsible for about one third of the Antarctic Ice Sheet’s total mass loss. The glacier has thinned and retreated in recent decades, while its ice has flowed faster. According to the report, conventional models struggled to reproduce the acceleration observed by satellites.
To test their approach, the team compared simulations with more than two decades of observations. They also analyzed synthetic aperture radar measurements from Finland’s ICEYE satellite constellation. Those measurements revealed fluctuations across several kilometers of the grounding zone along Thwaites’ main trunk. The report says the updated model reproduced historical changes from the 1990s to the present that were four times more pronounced than changes represented by conventional models.
The proposed process is tied to the movement of the ocean as well as the shape of the ice bed. Tides lift the ice and repeatedly expose its underside to warm, pressurized seawater. Ocean currents, which the report says have been altered by climate change, bring water to the Antarctic coast. The model accounts for how this water can penetrate beneath the grounded glacier and increase melting. It therefore offers an explanation for why earlier models may have underestimated the glacier’s retreat.
The potential consequences extend to Thwaites’ underwater supports. The glacier’s main trunk is temporarily stabilized by the Mouginot Ridge. The team’s simulations suggest that, with a grounding zone 4 to 6 kilometers wide, there is a 60 percent probability Thwaites will detach from that ridge by the end of the century. That is a conditional model estimate, not a certainty. If the ridge no longer holds the ice, the report says the glacier could retreat across a seabed that slopes down toward the next high point, South Ridge.
For people along coasts, the revised estimate matters because it suggests a larger potential contribution to rising seas than earlier projections indicated. Co-author Eric Rignot said the model’s closer match to the observed record points to greater coastal flooding risk and exposure than previously anticipated. The study does not establish the exact sea-level rise any particular coast will experience; it updates one glacier’s modeled contribution. Its central message is that representing the water and ice beneath Thwaites in more detail can change projections of how quickly this major Antarctic glacier may lose ice.