Ice Wyverns are not found on the regular map on Fjordur, you have to travel to the Yoduheim realm. To travel to the Yodunheim Realm and get Ice Wyvern eggs you will need to use the Fjordur Portal Cave (40.6 57.5),or hold down the R key to get an options wheel. Once there you can travel to the coordinates below to find Ice Wyvern nests.
Ice Wyvern Cave
Once you locate the trench and the cave where the Ice Wyvern eggs and nest spawn on Fjordur Yodunheim Realm I find it best to attack the Ice Wyverns and clear out the area. So far, I found that there are few wyverns there, about four or five and I have used dire bears to clear them out. I think any number of tamed Ark creatures would work just fine for this job. Of course, your world may have many Ice Wyverns, and this could be a bad idea. The Ice Wyvern cave is very short, and I have only found two or three wyvern nests with eggs in them at one time.
Good luck stealing Ice Wyvern Eggs and hatching wyvern eggs on Fjordur!
Other Wyvern Locations on Fjordur