Sea-level contribution from Thwaites Glacier doubles in an observation-constrained ice-sheet model.

Modeling grounding zones as 2-5 km wide regions is essential to accurately reproduce Thwaites Glacier’s observed retreat, thinning, and acceleration over three decades.

• Why it matters: Understanding the processes driving glacier retreat is critical for predicting future sea-level rise, yet most models neglect the role of kilometer-scale seawater intrusions at grounding zones.
• What they did: The study used an observation-constrained ice-sheet model incorporating active melting grounding zones, calibrated to nearly 30 years of data, and extended projections to 2100.
• The result: Grounding-zone processes may cause Thwaites Glacier to unpin from seafloor ridges as early as 2038, leading to up to 30 ± 6 mm of global sea-level rise by 2100—about twice previous estimates without additional warming.