Thwaites Glacier Model Doubles Its Sea Level Rise by 2100

Jeff's Daily Pick. A UC Irvine and NASA JPL model says Antarctica's Thwaites Glacier could add up to 30 mm (about 3 cm, 1.2 inches) to global sea level by 2100, about double earlier projections, even with no further warming (Nature Communications).

In the United States, glaciologists at the University of California, Irvine and NASA's Jet Propulsion Laboratory published a study in Nature Communications on October 12, 2026 on Thwaites Glacier in West Antarctica, often called the Doomsday Glacier. Lead author Mattia Poinelli, now at UCLA, and coauthor Eric Rignot of UC Irvine changed how a computer model handles the place where the ice lifts off the seafloor.

From a line to a zone

Most ice sheet models treat the grounding line, where grounded ice starts to float, as a sharp boundary. Radar images from the ICEYE satellite constellation show something else on Thwaites: seawater pushes several kilometers under the grounded ice and lifts it with each tide, flushing warm water underneath. The team built this grounding zone into the ISSM ice sheet model and tested it against the observed retreat, thinning and speedup of the glacier from 1996 to 2023. The model matched the record only when the zone was 2 to 5 km wide. Runs without a grounding zone were four times less likely to reproduce it.

The numbers, read carefully

With a 5 km zone, close to what satellites show today, the model gives 30.1 mm of sea level rise from Thwaites by 2100, plus or minus 5.7 mm. That is twice the 15.2 mm average of the ISMIP6 group of models under the same constant climate. With a 3 km zone, the most likely value in the calibration, it gives 19.4 mm. With no grounding zone, 8.3 mm. Ocean conditions are held at their 1996 to 2023 average, so the authors call these lower bound figures.

Thwaites is now held in place by an undersea ridge, Mouginot Ridge. With a 4 to 6 km zone, the model puts the chance it breaks free by 2100 at about 60%, as early as 2038 in the widest runs. The 30 mm is not the 65 cm often quoted for Thwaites. That 65 cm is the glacier's total sea level equivalent, the rise if all its ice were lost, and this study does not project that for this century.

Thwaites sits in the Amundsen Sea sector, which accounts for about a third of the ice lost from the Antarctic Ice Sheet. For another large scale picture of the planet's changes, see our piece on 2025 deforestation.