The July issue of Proceedings had a good article knocking down the notion that the melting of the polar ice cap means that merchant ships soon will be short-cutting through there.
The major reason offered by Stephen Carmel of Maersk Line is that the Arctic routes can only take ships with drafts of less than 40 feet, which excludes a lot of big carriers. Also, the Northern Sea route, across the top of Russia, has a beam restriction of 30 meters, as ships cannot be wider than the icebreakers supporting them.
His bottom line is that contrary to some assertions, "Arctic routes do not now offer an attractive alternative to the more traditional maritime avenues, and are highly unlikely to do so in the future."
My one quibble: If there were a major and long war at a significant chokepoint, such as the Suez Canal or Indonesia, that might encourage shipbuilders and shipping companies to adjust to the constraints of the Arctic.