Beaufort Sea - Hydrology and Climate

Hydrology and Climate

The Beaufort Sea is frozen over through the year, except for August and September when the ice breaks near the coast and opens a 50–100 km (31–62 mi) wide strip of open water. 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.