Sea- salt
The sea salt is the main factor reaching the “Freezing point depression”; salt helps lowering the freezing point of the water, which is the main component of snow and consequently the melting point of it, and prevents the water from freezing or re-freezing.
When the salt is sprinkled on snow or ice, it makes a brine with the thin film of water covering snow and ice, leading to a start of melting process once the ice sprinkled on part is touched with.