I vaguely remember reading that there were shipping routes that would be half the time and distance if the ice was melted... And some ships run during the summer months... Mostly from Russia to Europe... Iirc...
The route will become more popular, it's not a route the US can in anyway block.
If i'm not mistaken Russia can now ship 8~10 months of the year via the artic route, they want/are planning to create more nuclear ice breakers i'm sure the Chinese are more then willing to make sure the Artic route stays open the whole year.
Yes, Absolutely. A handful of years ago sailing through the North West Passage (around Alaska then across above Canada) was unheard of. Now it's quite routine, lots of people do it for fun every summer.
Also - totally unrealistic - but what if the ice freezed again, making the cables impermeable to spying and ushering in some kind of golden era of diplomacy and trust. I remember reading that in times when technology favored defense there were widespread moments of peace throughout Europe, like in the Middle Ages, so this could be something like that.
Spying by tapping into unencrypted traffic on undersea cables was done briefly during the Cold War. Now governments encrypt all their traffic so you won't get anything useful.