Raven Latitude

Ulf Ironmouth is a skald - a poet who accompanies Viking expeditions to compose verses about their victories. He has done this work for twenty years. He is good at it. He writes what he sees, shapes it into the formal structures of Norse verse, and recites it at the evening meal. This is the job. On a twelve-ship voyage to the far north, Ulf writes a verse about a storm before the storm arrives. The details match: the sky-wall rising iron-ribbed, the clouds moving like cattle being driven, the wind from the northwest at the exact hour he named.
The crew notices. Ulf notices them noticing. Then he writes a verse about a safe passage through a strait the fleet has never navigated, including details about a specific rock formation and the depth of the channel - and the fleet finds exactly that passage, exactly those rocks, exactly that depth. The jarl notices. Ulf notices her noticing.*Raven Latitude* is Norse historical fantasy about a skald whose verses have started to shape events rather than merely describe them.
It follows Ulf across a three-month voyage into the far north, through uncharted waters and a series of raids that his verses seem to be composing rather than documenting.