No number means you don't get to remove an ice piece. Freezing Take the appropriate type and number of pieces and put them anywhere on the sea. Don't overlap pieces. Toward the end of winter, if there are not enough pieces, use as many as you can. If there are no pieces of the appropriate type left, you can do nothing this turn.
Same thing happens if there is no room to place the required piece.
Thawing As soon as all of the ice pieces are placed, or cannot longer be placed, Spring begins. You can only remove a piece with a container if there are no empty ice blocks remaining. Any containers on the ice fall into the water. You can never remove a piece holding a truck or the bear. It is vital to use containers to secure a path back to your camp with containers.