The thickness of the ice is one thing, but it's the pressure. If you have thick ice and you can go around it, it's no problem. It's when you're between the archipelago and navigating through passages that you have to be careful.
On commercial shipping, Transport would be the one that would really answer this. My understanding is that commercial ships need to have an Arctic prevention certificate. They go in different zones and at different times in the Arctic, depending on their ice class. This would normally prevent ships from going places or areas where it's more severe.
The captain receives the ice charts, the ice information. Certainly I don't think any captain I know would willingly send their ship into a dangerous place.