Since the 1990s, Pine Island Glacier (PIG) has been a focal point of research due to its vulnerability within the West Antarctic Ice Sheet. Decades of research have interrogated this dynamic glacier system with a focus on its main trunk and the ice shelf section bordering and stabilizing PIG to the south (the ‘south shelf’), receiving comparatively less attention. Using satellite-derived observations from 2017 to 2023, we document marked dynamic changes on the south shelf, particularly following PIG’s 2018 calving event, which removed >60 km2 of ice from this section. Measurements of surface deformation, ice velocity and strain rates from synthetic aperture radar and optical imagery show localized acceleration and structural weakening of the south shelf near-coincident with this loss. Our findings, highlighting the role of peripheral ice shelves in glacier-system stability, suggest that PIG’s new configuration—characterized by weakening margins and a compromised south shelf—may result in a geometry that grows progressively unstable.