For any home owner who lives where it’s cold, this is not a good sight. I don’t know if you can tell scale from the picture but that ice dam is about one foot thick at least. So I finally borrowed a ladder from my Dad and climbed up there and chopped it off.
The best tool to use is an ice tool (ice axe used for ice climbing) mountaineering ice axes work pretty well, but a tool specifically designed for vertical ice climbing is prime. These things rock. Where I might be able to shatter a few inches off with a sledge hammer, or wood axe, I can break off chunks several feet wide and deep with my ice tools. And now we don’t need to worry about leaks.
Here is a picture of my tools in the backside of a waterfall: