Mk. So what happens is, the pipe there gets full of water. Then the weather cools down below freezing, and the water begins to solidify from the top down. Soon, the water freezing forces expansion to the point that the ice is being squeezes out of whatever holes are available, in this case a round hole. The ice extrudes out the hole to relieve the pressure as it freezes, the little tube gets longer and wobblier.

This usually happens as a ribbon, because there's usually a thin rectangular gap at the top of the railing pipe.