Lost at Sea circa 1870

My great-great grandfather was Carl JENSEN, a merchant seaman out of Christiania. He was lost at sea sometime after 1868 (when last child was born). In the late 1880s, the children, Karin Laurine and Carl, emigrated to the USA. How do I find records of Norwegian mariners lost at sea? Is there a list of merchant seamen who died while working? Thank you.