Seen here is wind-blown rime ice.
They look like ice shelves, but that’s not what’s happening in this photo. A wire fence stretches along the Cheviot Hills in Northumberland, UK. The wind blew straight at the fence from the right. Ice particles gradually built up along the wire.
There has to be a strong wind, temperatures have to be between plus one Celsius and minus one Celsius and there has to be plenty of moisture. This can either be from water vapour in the air, from snowfall or from freezing rain. The wind blows the moisture over the object, in this case the fence, and it freezes, building up a thick layer of ice on the windward side. Learn more here.