This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: A new ice sheet model developed by glaciologists at the University of California, Irvine and NASA's Jet Propulsion Laboratory projects that the melting of Thwaites Glacier in West Antarctica will contribute up to 30 millimeters (1.2 inches) of sea level rise by 2100—twice previous estimates—even without additional climate warming. In a paper published in Nature Communications, the researchers explained that by adjusting a computer model of Thwaites to include the concept of a "grounding zone" instead of a "grounding line," they were able to reconstruct historical glacier change from the 1990s to the present that is four times more pronounced than traditional models.
"Glaciologists have long based their assumptions of ice sheet dynamics on the 'grounding line,' a discrete, narrow and mostly stable demarcation where ice leaves the land and begins floating on water," said lead author Mattia Poinelli, who was a UC Irvine postdoctoral scholar in Earth system science when this study was conducted. "We have come to acknowledge a different arrangement beneath Earth's major ocean-terminating glaciers. Satellite observations demonstrate the existence of a 'grounding zone,' sometimes kilometers wide, where warm ocean water is reaching deep underneath the ice sheets and causing vigorous melting." Thwaites Glacier is in the Amundsen Sea Embayment sector of West Antarctica, which accounts for roughly one-third of the mass loss from the Antarctic Ice Sheet.
In recent decades, Thwaites has undergone rapid retreat and thinning, but scientists have been struggling to reconcile ice sheet models that show slower movement with satellite observations that show substantial ice flow acceleration. The UC Irvine-led team worked to calibrate ice sheet models against observations spanning more than 20 years. Using synthetic aperture radar readings from the Finnish ICEYE satellite constellation, the researchers have been able to detect kilometer-scale fluctuations in the grounding zone along the main trunk of Thwaites.
The data indicate that seawater penetrates several kilometers beneath grounded ice and lifts it during tidal cycles, flushing the ice with pressurized, warm seawater being pushed to the Antarctic coastline by currents that have been altered by climate change. According to Poinelli, a NASA JPL research affiliate who is now a project scientist at UCLA, this study showed that grounding zone processes are causing accelerated detachment of Thwaites Glacier from stabilizing ridges, leading to more rapid ice flow and deterioration. "The Thwaites main trunk is being temporarily stabilized by the Mouginot Ridge," he said.
"Once that ridge is unpinned, the glacier will continually retreat across a predominantly retrograde seafloor toward its next topographic high, the South Ridge." Poinelli said that computer simulations that factor in a 4–6-kilometer grounding zone (2.5–3.7 miles) predict a 60% probability of unpinning the Mouginot Ridge by the end of the century. "When you factor in key physical processes and calibrate against historical observations, you gain a reliable pathway for narrowing uncertainty in projections," he said. "We have documented and quantified the impacts of climate change on our planet's sensitive ice sheets for decades, but a mounting realization gained in recent years of what is happening on the undersides of glaciers like Thwaites is leading to an even greater sense of alarm," said co-author Eric Rignot, UC Irvine professor of Earth system science.
"Most projections to date have struggled to match the rapidity of the mass loss because of missing physics; our new model with more complete physics is able to match the record and then produces projections that are twice as large as before. These results predict greater risk of and exposure to coastal flooding than anticipated in the coming decades." Mattia Poinelli et al., Sea-level contribution from Thwaites Glacier doubles in an observation-constrained ice-sheet model, Nature Communications (2026). DOI: 10.1038/s41467-026-77976-1 Journal information: Nature Communications Provided by University of California, Irvine Bachelor's in mathematical biology, Master's in creative writing.
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