The simple answer to your question, from a mariner's point of view, and I've not taken ships into the Arctic, is that if your ship is designed for one metre of ice, and if it happens to be pack ice that's two metres thick, you don't go there. But the same effect applies to others who may be operating in the Arctic. If their ships are designed for one metre or less, or perhaps two metres, then they can go where they can go. But if the ice is such that it precludes that, then it makes no sense for those vessels to go there.
It's a very difficult thing to predict. The ice belongs to Mother Nature, and it goes where it goes. It's very difficult, and I think there's no clear prediction of what's going to happen in the Arctic at any given point in time in the future. But it's something that applies to both sides of the coin, so to speak.