ice bridge

noun3

1. •
   A type of ice road, a floating-bridge-like roadway made of floating ice atop a body of water.
2. •
   A type of ice road, a causeway-like road across a body of water, made of full-depth ice, where from the road surface to the lakebed or riverbed is solid ice.
3. •
   An ice control structure on a river, to control flowing river ice, that spans the breadth of the river, and may have a traversable roadway on top.