The Beaufort Sea is a marginal sea of the Arctic Ocean, located north of the Northwest Territories, Yukon, and Alaska, and west of the Canadian Arctic Archipelago. The sea is named after Sir Francis Beaufort, a hydrographer. The Mackenzie River, the longest in Canada, empties into the Canadian part of the Beaufort Sea west of Tuktoyaktuk, which is one of the few permanent settlements on the sea's shores.