The problem Cal with writing about a scene in a sonnet is when you come to the turn (the volta) in the third stanza. Your volta is very soft and hard to catch as a turn.It seems to be more a part of the same scene you mentioned in the first two stanza more like a narrowing of your field of vision from the general scene to an object in the scene. Its a beautiful work. I can see the problems though. How about: Though cold and dark the winters mark will bring; Sparkling ice flowers to recall the spring. Just be glad I didn't try for a heroic sonnet which is an 18 line form. Good job.