Students will discover how conditions can become truly life-threatening in Antarctica when wind combines with cold, which happens frequently in Antarctica's coastal regions.
At the Cape Denison headquarters of the Australasian Antarctic Expedition of 1911-14, the average year-round wind speed was nearly 80 km/h, and in June and July the average speed was an astonishing 120 km/h. This earned the cape the name 'Home of the Blizzard'.
Such winds are caused by a combination of the cold of the interior, the domed shape of the continent and intense low pressure systems around the coast. For long periods - often many days - large amounts of dense, cold air slide at an accelerating rate down the coastal slopes of Antarctica's ice sheet, reaching hurricane force (around 120 km/h) by the time they reach the sea. Maximum gusts can be more than 250 km/h - equivalent in force to Tropical Cyclone Tracey which destroyed Darwin in 1974.
These winds, called 'katabatic' winds, are common throughout the world wherever there are high, cold places, but nowhere are they as ferocious as Antarctica's katabatics. So as well as being the coldest, Antarctica is also the world's windiest continent.
Following are two descriptions of a severe blizzard experienced at Mawson in 1960, which blew for 42 hours and wrecked both of the station's aircraft:
The blizzard was one of the worst ever experienced at Mawson, and was associated with a deep depression in the Southern Ocean. The barometer fell to 27.9 inches. Hurricane force winds bore down on Mawson and the ice plateau behind the station. Gusts at Mawson were as high as 116 mph, with the wind blowing for hours at about 80 mph. Up on the ice plateau nearby, at the airfield, they were estimated to be even higher. Some idea of the force of the hurricane is given by the fact that during the attempted rescue operations, men were lifted bodily into the air and thrown yards away to slide helplessly over the ice until rescued. Only the prompt action of men in holding on to each other prevented others being blown away with the wrecked parts of the Beaver aircraft which they were trying to save…
- Burke, D. Moments of Terror: The Story of Antarctic Aviation. Sydney, New South Wales University Press, 1994, pp. 206-207.
…drums of diesel fuel and petrol weighing 350 pounds [157.5 kilos] were moving at a fast walking pace along the ice standing on their ends. The caravan nearest us shift four feet [1.21 metres] sideways in one gust, stretching steel guy wires like rope.
- Bowden, T. The Silence Calling: Australians in Antarctica 1947-97. Sydney, Allen & Unwin, 1997, p. 240.
- Have students research the highest wind speeds ever recorded for their city. Compare this speed and its duration (usually these are brief gusts) with wind speeds and durations recorded in Antarctica. Use the Bureau of Meterology's detailed climate information.
- How do these speeds compare with the speeds of a car, train, aircraft?
- Get students to set up a wind sock and record the wind direction, and the weather that follows. Make a simple anemometer to record wind speed. Origin Energy has a simple project to build an anemometer [PDF].
- Have students create their own blizzard by blowing an electric fan over a tray of loose frosted ice. They can wet their face or hands and compare how much colder they feel when moisture is evaporating. Ask them to discuss why blizzards of strong wind and snow are so dangerous. Have them use a wind chill conversion calculator to estimate the way wind can effectively lower the air temperature to life-threatening levels.