The Beaufort Sea (French: mer de Beaufort) is a marginal sea of the Arctic Ocean, located north of the Northwest Territories, the Yukon, and Alaska, west of Canada's Arctic islands. The sea is named after hydrographer Sir Francis Beaufort. The major Mackenzie River empties into the Canadian part of the sea, west of Tuktoyaktuk, which is one of the few permanent settlements on the sea shores.The sea, characterized by severe climate, is frozen over most of the year. Historically, only a narrow pass up to 100 km (62 mi) opened in August–September near its shores, but recently due to climate change in the Arctic the ice-free area in late summer has greatly enlarged. Claims that the seacoast was populated about 30,000 years ago have been largely discredited (see below); present population density is very low. The sea contains significant resources of petroleum and natural gas under its shelf, such as the Amauligak field. They were discovered in the period between the 1950s and 1980s, and their exploration became the major human activity in the area since the 1980s. The traditional occupations of fishery and whale and seal hunting are practiced only locally, and have no commercial significance. As a result, the sea hosts one of the largest colonies of beluga whales, and there is no sign of overfishing. To prevent overfishing in its waters, the US adopted precautionary commercial fisheries management plan in August 2009. In April of 2011 the Canadian government signed a memorandum of understanding with the Inuvialuit as a first step in developing a larger ocean management plan. The Canadian government announced in October 2014 that no new commercial fisheries in the Beaufort Sea will be considered until research has shown sustainable stocks that would be made available to Inuvialuit first.