Sea, extension of the Arctic Ocean, northwestern Russia. Almost landlocked, it is connected to the more northerly Barents Sea by a long, narrow strait known as the Gorlo. It covers an area of approximately 35,000 sq mi (90,000 sq km) and has a maximum depth of 1,115 ft (340 m). Rivers, including the Northern Dvina and Onega, flow into it. An important transportation route, it remains navigable year-round with the help of icebreakers in winter. Arkhangelsk is one of the principal ports.