SOLVED. Group of men go on an expedition to somewhere in the North/ Arctic (maybe Greenland). Slowly go mad because can’t sleep, also sort of a ghost story and I think sent in early 1900s? [s]

[Lobstergirl, au gratin]

Moving to Unsolved.

[Rainbowheart]

Maybe something by Jack London?

[Anna]

Antarctic rather than the Arctic, but has a historical setting, and a hunt for someone who may be alive or may be a ghost: Victim of the Aurora by Thomas Kenneally.

[Jamie]

This one is fairly recent, but it's about a group of men on an expedition through Alaska, and there are some mystical ghostly elements to it. To the Bright Edge of the World.

[Joseph]

Maybe Dark Matter by Michelle Paver.

[Joseph]

Or The Terror The Terror by Dan Simmons?