page_title: Beaufort Sea
section_title: Hydrology and climate
hierarchical_section_title: Beaufort Sea / Hydrology and climate
caption_attribution_description: Ice ridges in the Beaufort Sea off the northern coast of Alaska
context_page_description: The Beaufort Sea is a marginal sea of the Arctic Ocean, located north of the Northwest Territories, the Yukon, and Alaska, and west of Canada's Arctic islands. 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.
  The sea, characterized by severe climate, is frozen over most of the year. Historically, only a narrow pass up to 100 km 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; 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 since the latter part of that period their exploration has become the major human activity in the area.
context_section_description: The Beaufort Sea is frozen over through the year, except for August and September when the ice breaks near the coast and opens what was once a 50–100 km (31–62 mi) wide strip of open water. During the 2000s, due to climate change in the Arctic, the ice-free area in late summer greatly enlarged. During the record minimum extent of Arctic sea ice in September, 2012, the sea ice boundary had retreated northward much farther than normal from the coast.
  The channels of the Mackenzie River thaw earlier, in late May–early June. This thawing increases the average water discharge from about 150,000 to 250,000 m³/s (5,300,000 to 8,800,000 cu ft/s).
  Hidden changes in the ice cover of the Beaufort Sea were discovered in 2009. Whereas the ice area remain stable, as detected by the observation satellites, so as the associated water temperature and salinity, the ice structure has changed recently. The new ice, called rotten ice, is thinner and much weaker structurally.
  The sea water has a stable temperature and is separated into four distinct layers as follows. The top 100 m (330 ft) are surface water which has a temperature of −1.4 °C (29.5 °F) in summer and −1.8 °C (28.8 °F) in winter. The next layer is formed by the inflows from the Pacific Ocean and Bering Sea coming through the Bering Strait; it extends up to the North Pole. The warmest, deep Atlantic layer has the temperatures between 0 and 1 °C (32 to 34 °F), and water at the bottom is a bit colder at −0.4 to −0.8 °C (31.3 to 30.6 °F). The average salinity varies between 28‰ and 32‰ (parts per thousand) from south to north. Typical air temperatures (at Tuktoyaktuk) are −27 °C (−17 °F) in January and 11 °C (52 °F) in July.
  The water currents form the clockwise-directed Beaufort Gyre, that results in south-westerly and westerly currents near the shores. The Mackenzie River partly affects this circulation inducing minor eastwards streams near its mouth. The river annually brings about 15 million tonnes of sediments which are rich in dolomite and calcium carbonate. Those deposits are spread over the sea and mixed with mud and gravel.
caption: Sea ice pressure ridges in the Beaufort Sea off the northern coast of Alaska (spring 1949).
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