Sorry Northern Sea Passage which is the bit north of Russia. It is the route the German shipping firm made a lot of noise about in autmun claiming to be the first to travel that way. Which in turn was churned out as evidence of global warming by the newpapers etc.
Main reason it wasn't used much in the twentieth century was the cold war rather than ice. Russia was a bit prickly about ships travelling that way.
http://www.cnrs-scrn....ol03/tnm_3_2_1-17.pdf
Pictured above is the nuclear powered ice-capable transport Sevmorput, built specifically for the northeast passage and launched in 1988, whence it had been plying the route ever since, only recently having been withdrawn for conversion into a drilling ship.
Meanwhile, the Murmansk Shipping Company – which is the specialist operator in the northern sea route - is currently running a fleet of 303 vessels with a total deadweight of about 1.2 million tons. In 2006, the company shipped 2 million tons of cargo through the route. Pictures of some of the fleet are here, with some of the ships currently plying the northern sea route shown below.