Between 1807 and 1814, Denmark-Norway and Great Britain were in a state of war. The worst part of it, at least from a Norwegian point of view, was the British blockade of food supplies from Denmark to Norway, "leading to dire conditions and mass starvation", to quote Wikipedia. It was not only in 1812, however; already in the winter of 1809 there was widespread famine in Norway.
The Norwegians, on their side, engaged in privateering, and took a lot of trade ships on their route between Britain and the Baltic.
I haven't found much about the Norwegian participation in the Napoleonic wars on the Web, but if you're really interested in the history, I can recommend this book. It's insanely expensive, but you may be able to borrow it from a library.