A study reveals widespread seawater intrusions beneath the grounded ice of Thwaites Glacier in West Antarctica, a major contributor to sea level rise. Using satellite data from the ICEYE constellation, researchers document a tidally controlled ice grounding zone, where seawater intrusions extend up to 6 km upstream. These intrusions, up to 5-10 cm thick, occur in bed depressions beyond a ridge, and align with subglacial hydrology models. Seawater intrusions are linked to high-pressure subglacial water systems and can cause significant ice melt, increasing the glacier's vulnerability to ocean warming. The study highlights that the ice grounding zone is 2-6 km wide, with variations in width depending on bed slope. The results challenge traditional models that assume a fixed transition between grounded and floating ice, suggesting a more dynamic process. The study also shows that seawater intrusions are more frequent at spring tides and less so at neap tides. The findings indicate that the glacier is retreating at a rate of 0.5 km/year, with potential for further retreat past key ridges. The study emphasizes the importance of incorporating these processes into ice sheet models to better predict future sea level rise. The research underscores the need for improved understanding of subglacial hydrology and its impact on ice sheet stability.A study reveals widespread seawater intrusions beneath the grounded ice of Thwaites Glacier in West Antarctica, a major contributor to sea level rise. Using satellite data from the ICEYE constellation, researchers document a tidally controlled ice grounding zone, where seawater intrusions extend up to 6 km upstream. These intrusions, up to 5-10 cm thick, occur in bed depressions beyond a ridge, and align with subglacial hydrology models. Seawater intrusions are linked to high-pressure subglacial water systems and can cause significant ice melt, increasing the glacier's vulnerability to ocean warming. The study highlights that the ice grounding zone is 2-6 km wide, with variations in width depending on bed slope. The results challenge traditional models that assume a fixed transition between grounded and floating ice, suggesting a more dynamic process. The study also shows that seawater intrusions are more frequent at spring tides and less so at neap tides. The findings indicate that the glacier is retreating at a rate of 0.5 km/year, with potential for further retreat past key ridges. The study emphasizes the importance of incorporating these processes into ice sheet models to better predict future sea level rise. The research underscores the need for improved understanding of subglacial hydrology and its impact on ice sheet stability.