Short answers, pulled from the story.
The Norwegian Sea formed about 250 million years ago when the Eurasian Plate and the North American Plate (which included Greenland) began separating. The narrow shelf sea between Norway and Greenland widened and deepened over geological time. The present continental slope marks where the two landmasses originally met.
The Norwegian Sea remains ice-free throughout the year because of the warm North Atlantic Current flowing in from the Atlantic Ocean. This current ensures relatively stable and elevated water temperatures compared to the Arctic seas. Research has found this large warm water mass is more important for Norway's mild winters than the Gulf Stream itself.
Norwegian Sea herring stocks collapsed dramatically between 1956 and 1970, with the biomass of young herring falling from 11,000,000 tonnes to nearly zero. The decline was caused at least partly by overfishing. Partial recovery began after 1987 following enforcement of fishing regulations, but the recovery disrupted capelin and cod populations.
The Moskenstraumen is a system of tidal eddies and a whirlpool located between the Lofoten islands of Moskenesoya and Vaeroya, near the small island of Mosken. It reaches speeds on the order of 15 kilometres per hour and has a diameter of 40 to 50 metres. Edgar Allan Poe introduced the word maelstrom into English through his 1841 story describing it.
The Norwegian Sea was the route for Allied convoys supplying Russia. Of 811 U.S. ships dispatched, 720 reached Russian ports, delivering roughly 4,000,000 tonnes of cargo including about 5,000 tanks and 7,000 aircraft. The Allies lost 89 merchant ships on the route to German naval operations including the attack on convoy PQ 17 in July 1942.
Norway began undersea oil production in the Norwegian Sea in 1993. The Ormen Lange gas field, at depths of 800 to 1,100 metres, started producing gas in 2007 and is connected to the Langeled pipeline, which at the time was the world's longest underwater pipeline. As of 2019, an estimated 6.5 cubic hectometres of crude oil remained in the Norwegian Sea.