There is a common myth that the Arctic is "opening up" because of...

There is a common myth that the Arctic is "opening up" because of melting ice and even that the "Northwest passage is now open".

I have even heard an admiral say this and refuse to listen to my gently correcting him.

It's nonsense. The Northwest passage is probably never going to be a reliable sea route this century.

Why? Because the passage refreezes every winter.

Yes, the Arctic ocean's ice cover has fallen slowly in the past half century - but mostly in late summer and fall, not significantly in winter or spring.

The minimum sea ice cover shows no downward trend in a decade now.

Besides, the Canadian Arctic, unlike the Russian Arctic (Northeast passage), is at the downstream end of the Arctic Ocean current, so the ice generally moves south in the passages between islands, clogging the NW passage for much of the year.

At best the NW passage is open for a couple of months in early fall each year and even then there is a risk of getting trapped in pack ice.

Unless you have an ice-breaker, of course. But that's not practical for routine trade.

Show me a shipping company, or an insurer, willing to set up to use a route that's only open for a couple of months, and has significant risks from pack ice.