The last glacial inception (LGI) marks the transition from the interglacial warm climate to the glacial period with extensive Northern Hemisphere ice sheets and colder climate. This transition is initiated by decreasing summer insolation but requires positive feedbacks to stimulate the appearance of perennial snow. We perform simulations of LGI with climate model AWI-ESM-2.1, forced by the radiative and greenhouse gas forcing of 115,000 years before present. To compare with the preindustrial (PI) simulation, we use a consistent definition of the seasons during the LGI and the PI and evaluating model output on an angular astronomical calendar. Our study reveals a prominent role of sea ice in the albedo feedback to amplify the delayed climate siregnal at polar latitudes. Through a radiative budget analysis, we examine that the ice-albedo feedback exceeds the shortwave radiative forcing, contributing to the cooling and high latitude snow built-up during LGI.