Well, the first thing we need is a far more robust underwater surveillance capability than we currently have. That'll give us a better sense of what's going on and who's where, and therefore what reactions we may or may not need to take.
We then need to increase the ability to respond and to be present. That means more submarines, and it means more submarines that are capable of operating in, or certainly on the edge of, the ice. That will drive us into a debate as to how much under-ice capability we may actually need for a next generation of submarine.