Snow is like a blanket for sea ice. In the winter, when the air is colder than the sea ice, snow keeps the sea ice warmer and slows its growth. In the summer, snow insulates the sea ice from the warmer air, keeping the ice cooler and melting more slowly. Snow is also brighter than sea ice, reflecting more energy into the atmosphere. In this project, we study the heating and cooling effects of snow on Antarctic sea ice using different data products (CASSIS, CryoSat2 CS2WFA, AMSR-E and AMSR-2) and an idealized snow-sea-ice model. Through data products, we find that snow depth is positively correlated with sea ice extent. In our idealized model that simulates snow depth, sea ice thickness and extent, we observed that snow insulation is the major effect snow has regarding the heating and cooling of sea ice. When snow accumulation increases across all seasons, the sea ice extent gets smaller. The model experiments suggest that although a longer sea ice season leads to more snow accumulation, snow accumulation provides a slight negative feedback to sea ice growth. These effects of snow on sea ice are important to consider when predicting sea ice conditions under climate change.