Antarctic fast ice is sea ice that stays attached to the coast. It helps stabilize ice shelves and supports deep ocean water formation—both crucial to Earth’s climate system. Yet, how fast ice changes over time is not well understood. This study shows that a major wind pattern called the Southern Annular Mode (SAM), especially in September, can influence how much fast ice exists six months later in March. When SAM is strongly positive, it pushes sea ice away from the Antarctic coast in regions like Dronning Maud Land and the Amundsen Sea. This leads to more sunlight being absorbed and stronger waves near the coast, which reduce fast ice by the end of summer. In the Australian sector, the connection is different. There, fast ice forms when pack ice is pushed westward by coastal currents. A positive SAM disrupts this westward drift, making fast ice formation harder. Our findings suggest that atmospheric patterns months earlier can shape regional fast ice conditions, but the effects depend on local ocean and coastline features. Understanding these connections is key to predicting future Antarctic ice behavior.