The study by Rignot et al. documents widespread seawater intrusions beneath the grounded ice of Thwaites Glacier, a significant contributor to global sea level rise. Using daily repeat satellite synthetic aperture radar interferometry data from the ICEYE constellation, the researchers identify a 6 km-wide ice grounding zone in the central part of Thwaites and a 2 km-wide zone along its flanks. They also detect irregular seawater intrusions extending 6 km upstream at high tide in a bed depression beyond a bedrock ridge. These intrusions align with regions predicted by the GlaDS subglacial water model, indicating a high-pressure distributed subglacial hydrology system. The pressurized seawater intrusions will cause vigorous melt of the grounded ice over large distances, making the glacier more vulnerable to ocean warming and increasing projections of ice mass loss. The findings challenge traditional models that assume a fixed, abrupt transition from grounded ice to floating ice and suggest that kilometer-wide, widespread seawater intrusions may be a critical factor in the rapid changes observed in Antarctic ice sheets.The study by Rignot et al. documents widespread seawater intrusions beneath the grounded ice of Thwaites Glacier, a significant contributor to global sea level rise. Using daily repeat satellite synthetic aperture radar interferometry data from the ICEYE constellation, the researchers identify a 6 km-wide ice grounding zone in the central part of Thwaites and a 2 km-wide zone along its flanks. They also detect irregular seawater intrusions extending 6 km upstream at high tide in a bed depression beyond a bedrock ridge. These intrusions align with regions predicted by the GlaDS subglacial water model, indicating a high-pressure distributed subglacial hydrology system. The pressurized seawater intrusions will cause vigorous melt of the grounded ice over large distances, making the glacier more vulnerable to ocean warming and increasing projections of ice mass loss. The findings challenge traditional models that assume a fixed, abrupt transition from grounded ice to floating ice and suggest that kilometer-wide, widespread seawater intrusions may be a critical factor in the rapid changes observed in Antarctic ice sheets.