Gutorm/Guttorm is not very common, but it is not uncommon either.
When he was born in Norway in 1883 his name would be Gutorm Gutormson as he was son of Gutorm, not Tom. If he was son of Tom his name would be Thomson. But your source says that his father was also named Gutorm, so we are looking for Gutorm Gutormsen b. 1883 in Bergen.
(I do not know where the name Thomson came from - Tom was not very common in Norway and I would guess it was to pretend to be more english.)
In 1883-12-03 in Husnes, Hordaland (not very far from Bergen, but still not Bergen city) there was a Gutorm Gutormsen born. He was son of Gutorm Gutormsen (b. 1854) and Synniva Torgersdatter (b. 1851). See the church record here:
http://www.arkivverket.no/URN:NBN:no-a1450-kb20061229660254.jpg
This seems to fit, doesn't it?