New modeling and satellite radar show Thwaites Glacier could add about 30 mm (1.2 in) to global sea level by 2100.
The revised estimate is roughly double earlier projections because warm seawater reaches 2 to 5 km under the ice with each tide.
Researchers say there is a 60% chance Thwaites slips past the Mouginot Ridge by 2100, possibly as soon as 2038.
If Thwaites contributes more sea rise, coastal flood planning, insurance and sea walls may need major updates worldwide.
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