The consequences of less refractive ice is a much more rapid heating of arctic waters. If you have watched any of the television programs like 'Yukon men' you might have noticed them making comments about how they have never seen ice conditions like this. There are several of these shows, like "Ice road truckers"( some of the more experienced drivers saying the season get shorter every year), "Deadliest catch"(pack ice breaking free in the dead of winter and moving south) and "Air Alaska"(landing on glaciers is no longer safe due to rapid unpredictable melting). Native peoples form these regions have all tried without avail to warn that a rapid change is underway.

You asked about crustal displacement, that is a forgone conclusion, on a massive level. Few buildings will be left standing, the cities laid to waste utterly. The actual position of the rotational axis might change significantly but the magnetic poles will definitely change in polarity and the change will be very rapid.