A NASA-backed study published Oct. 12 found that a model of Antarctica's Thwaites Glacier fits decades of observed retreat more closely when it represents grounding zones as broad areas where seawater can reach beneath grounded ice. NASA says the updated model matched satellite records from the 1990s onward four times more closely than versions that treat the grounding zone as a sharp line. In some simulations, the glacier's contribution to global mean sea level by 2100 reached 30 millimeters, about twice some earlier projections. That is a modeled contribution from one glacier, not a forecast of total sea-level rise. The researchers say the results refine uncertainty around a difficult system; they do not remove it. Coastal planning still depends on many glaciers, ice sheets and emissions pathways.