The study investigates the tipping point in ice-sheet grounding-zone melting due to ocean water intrusion. Marine ice sheets are highly sensitive to submarine melting in their grounding zones, where they transition from grounded to floating ice. Recent studies suggest that warm ocean water can intrude large distances beneath the ice sheet, significantly affecting ice dynamics. The authors develop a model to capture the feedback between intruded ocean water, the melting it induces, and the resulting changes in ice geometry. They find that as the grounding zone widens due to melting, both temperature and flow velocity increase, further enhancing melting. This can lead to a tipping point where ocean water intrudes unboundedly beneath the ice sheet, a process known as runaway melting. This tipping point may not be easily detected with early warning indicators. The study also considers the susceptibility of present-day Antarctic grounding zones to this process, finding that both warm and cold water cavity ice shelves may be vulnerable. The results suggest a stronger sensitivity of ice-sheet melting and higher sea-level-rise contributions in a warming climate than previously understood. The findings highlight the importance of including this feedback mechanism in ice-sheet models to better predict future sea-level rise.The study investigates the tipping point in ice-sheet grounding-zone melting due to ocean water intrusion. Marine ice sheets are highly sensitive to submarine melting in their grounding zones, where they transition from grounded to floating ice. Recent studies suggest that warm ocean water can intrude large distances beneath the ice sheet, significantly affecting ice dynamics. The authors develop a model to capture the feedback between intruded ocean water, the melting it induces, and the resulting changes in ice geometry. They find that as the grounding zone widens due to melting, both temperature and flow velocity increase, further enhancing melting. This can lead to a tipping point where ocean water intrudes unboundedly beneath the ice sheet, a process known as runaway melting. This tipping point may not be easily detected with early warning indicators. The study also considers the susceptibility of present-day Antarctic grounding zones to this process, finding that both warm and cold water cavity ice shelves may be vulnerable. The results suggest a stronger sensitivity of ice-sheet melting and higher sea-level-rise contributions in a warming climate than previously understood. The findings highlight the importance of including this feedback mechanism in ice-sheet models to better predict future sea-level rise.